FAO FOP ESTRY PAPER

f oisidtf#-. saw

39

ill manuals

7Fa) me) saw manual

FOOD AND AGRICULTURE ORGANIZATION OF THE UMTED NATIONSRome 1982

FAO FORESTRY PAPER 39

fao/ sida sawmill manuals

frame saw manual

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome 1982

The designations employed and the presentationof material in this publication do not imply theexpression of any opinion whatsoever on thepart of the Food and Agriculture Organizationof the United Nations concerning the legalstatus of any country, territory, city or area orof its authorities, or concerning the delimitationof its frontiers or boundaries.

M-30ISBN 92-5-101248-2

All rights reserved. No part of this publication rnay be reproduced,stored in a retrieval system, or transmitted in any form or by any means,electronic, mechanical, photocopying or otherwise, without the priorpermission of the copyright owner. Applications for such permission,with a statement of the purpose and extent of the reproduction, shoulcibe addressed to the Director, Publications Division, Food and AgricultureOrganization of the United Nations, Via delle Terme di Caracalla, 00100Rome, Italy.

FAO 1982

The designations employed and the presentation of material in this publ ication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

M-30 ISBN 92-5-101248-2

Al l rights reserved. No part of t his publication may be reproduced, stored in a retr ieval system , or transmitted in any form or by any means , electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.

© FAO 1982

CONTENTS

pg.e

Construction and operating principles ...... 2

FCrces and movements 38

Setldng sawblades into frame saw sash 68

How to feed logs into a frame saw .......... 79

Maintenance 00000 OOOOOO 000000004100,0000p00000 92

Revolutions, cog numbers and peripheral speeds 97

INTRODUCT ION

This manual deals with the construction and operatingprinciples of the frame saw. Many different kindsand makes of frame saws are in use. A very commontype of Swedish origin, originally made in 1946, has

been chosen as the example in this manual. Today'smodern frame saw has the same basic function, althoughcapacity, infeed and sawing accuracy is increased.Where frame saws of other makes differ considerably,this is pointed out.

FAO gratefully acknowledges its indebtedness tothe Government of Sweden whose financial aid made possiblethe publication of this manual and to the EmployersFederation of Swedish Industries, who provided the

original material.

- 1 -

INTRODUCTION

This manual deals with the construction and operating principles of the frame saw. Many different kinds and makes of frame saws are in use. A very common type of SWedish origin, originally made in 1946, has been chosen as the example in this manual. Today's modern frame saw has the same basic fUnction, although capaCity, infeed and sawing accuracy is increased. Where frame saws of other makes differ considerably, this is pointed out.

FAO gratefully acknowledges its indebtedness to the Government of Sweden whose financial aid made possible the publication of this manual and to the Employers Federation of Swedish Industries, who provided the original material.

1.

2.

3. 4.

5· 6.

CONTENTS

Construction and operating principles ••••••

Fbrces and movements •••••••••••••••••••••••

~

2

38

setting sawblades into frame saw sash ••••••• 68

How to feed logs into a frame saw.......... 79 Maintenance 92 Revolutions, cog numbers and peripheral speeds 97

................................

- 2-

PART I - CONSTRUCTION AND OPERATING PRINCIPLES

page

1. Foundation with base plate ................... 3

20 Crank section 00000000000000000000000000000000 7

Bottom frame 0000000,0000000000000000000000000 14

Upper frame 00,30000000e000000000000.70000p00o0o 15

Guide symtem ................................. 16

60 Sash 00000000000000000000000000000060000000000 19

70 Roll frame and feed rolls 000000000o00o0c0,3000 24

80 Feeding mechanism ............................ 31

Appendix 000000000000000000000000e000000000000 36

1.

2.

3.

4. 5· 6.

7.

- 2 -

3--

2

1

PART I CONSTRUCTION AND OPERATIm PR!NCIPLES

~ Foundation with base plate ................... Crank section ••••••••••••••••••••••••••••••••

Bottom frame . ................. ~ ............. . . ................................ . Upper frame

Guide system ••.••...•••..•.••..•..•.•••••••..

Sash ......................................... Roll frame and feed rolls . .................. .

3

8. Feeding mechanism ............................

7

14

15 16

19 24

31

36 Appendix •••••••••••••••••••••••••••••••••••••

1. Fbundation with Base Plate

The function of the foundation is:

The saw frame must be built on astrong foundation of reinforced concreteof about 60-803m3. Sometimes, however,up to 90-100 m is necessary to get astrong enough base for the saw frame whenground conditions are bad.

The foundation should be somewhatlonger in the longitudinal direction ofthe saw mill than in the transversedirection, since the principal directionof motion of the moving parts of the framecoincides with the direction of sawing.Accurate drawings shauldbe supplied bythe manufacturer.

to support the frame saw's weight andto absorb all the powerful forces thatare created and that cause strong vibra-tions when the saw frame is working.

The foundation must therefore beerected on solid ground. If there is nosuch ground available, pile driving mustbe done.

At the same time, the foundationsmust not be directly on solid rock, whichcan carry vibrations to adjoining areassome distance away.

- 3 -

1. Foundation with Base Plate

The saw frame must be built on a strong foundation of reinforced concrete of about 60-80

3m3• Sometimes, however,

up to 90-100 m is necessary to get a strong enough base for the saw frame when ground conditions are bad.

The foundation should be somewhat longer in the longitudinal direction of the saw mill than in the transverse direction, since the principal direction of motion of the moving parts of the fr~e coincides with the direction of sawing. Accurate drawings should be supplied by the manufacturer.

The function of the foundation is:

o support the frame saw's weight and o absorb all the powerful forces that re created and that cause strong vibr ions when the saw frame is working.

The foundation must therefore be erected on solid ground. If there is no such ground available, pile driving must be done.

At the same time, the foundations must not be directly on solid rock, which can carry vibrations to adjoining areas some distance away.

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A foundat ion on rock needs an inter-vening layer of a suppressing material, forexample, clay or sand. Sand especially isgood at absorbing vibrations.

It must be repeated that when the pre-liminary studies for anchoring the frame sawfoundation are done, a good solid ground basemust be found. If there is any doubt, alwaysconsult a specialist, because the consequencesof error could be serious.

It is also unwise to run all the sawframes within the mill at the same speed(number of revolutions). It is best to makethe frames work out of sequence in order tocounterbalance each other's motions, the sameas a group of soldiers breaking step when cross-ing a slender bridge. The ideal situation isto have the moving parts of one frame at theupper dead centre when the moving parts of theother frame are at the bottom dead centre. In

practice, however, this is not possible toachieve and instead one tries to vary the speedof each frame.

Usually the cant frame works four to fiverevolutions faster per minute than the log frame,which avoids harmonic peaks of vibration. In

addition, it also avoids the sympathetic vibra-tions in the surrounding ground which createsdisturbing shaking to buildings in the vicinity.

To obtain the necessary working height onthe ground floor of the sawing building, thefoundation should be built up to a suitableheight above the floor to make enough space fornecessary conveying machinery, etc.

In the past the cant frame has often beenmounted too low. The trend now is to raiseit to a better working height on the upperfloor.

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- 4 -

A foundation on rock needs an inter­vening layer of a suppressing material, for example, clay or sand. Sand especially is good at absorbing vibrations.

It must be repeated that, when the pre­liminary studies for anchoring the frame saw foundation are done, a good solid ground base must be found. If there is any doubt, always consult a specialist. because the consequences of error could be serious.

It is also unwise to run all the saw frames within the mill at the same speed (number of revolutions). It is best to make the frames work out of sequence in order to counterbalance each other's motions, the same as a group of soldiers breaking step when cross­ing a slender bridge. The ideal situation is to have the moving parts of one frame at the upper dead centre when the moving parts of the other frame are at the bottom dead centre . In practice, however, this is not possible to achieve and instead one tries to vary the speed of each frame.

Usually the cant frame works four to five revolutions faster per minute than the log frame, which avoids harmonic peaks of vibration. In addition, it also avoids the sympathetic vibra­tions in the surrounding ground which creates disturbing shaking to buildings in the vicinity.

To obtain the necessary working height on the ground floor of the sawing building, the foundation should be built up to a suitable height above the floor to make enough space for necessary conveying machinery, etc.

In the past the cant frame has often been mounted too low. The trend now is to raise it to a better working height on the upper floor.

5

When installing modern roll conveyersthe aim is to obtain a working height of700 mm.

On top of the foundation a BASE PLATEis fixed:

by embedding it in the concrete bed, and

by 8 anchor bolts (45 mm) embedded inthe concrete bed. These anchor boltsmust penetrate the whole foundation toget adequate anchorage.

The base plate consists of a deep Usection frame.

The Ushape is partly chosen becausethis design has very high "bending resistance",especially where the bearing housings arepositioned. (Fbr technical explanations ofthis see PART II FORCES AND MOVEMENTS.

This Ushape makes a strong plate, butother types of beams can also be used.

Another advantage of the Ushape is thatit can be filled with concrete, so that theanchorage of the plate to the foundation isstrongly reinforced.

In the base plate there are bearinghousings for the roller bearings of the crank-shaft.

The lower half of the housing is placedin the base plate itself.

The upper half (called the bearing cap)is fastened with bolts in the base plate.

There is one disadvantage with thissystem. If the outer ring of the crankshaftroll bearing, which is normally fixed in thebearing housing, starta to rotate in the baseplate, the whole base plate must be substitutedor reconstructed in situ.

- 5 -

When installing modern roll conveyers the aim is to obtain a working height of 700 mm.

On top of the foundation a BASE PLATE is fixed:

~ embedding it in the conorete bed, and

by 8 anchor belts (45 mm) embedded in the concrete bed. These anchor belts must penetrate the whole foundation to get adequate anchorage.

The base plate consists of a deep U section frame.

The U-shape is partly chosen because this design has very high "bending resistance", especially where the bearing housings are positioned. (For technical explanations of this see PART II - FORCES AND MOVEMENTS.

This U-shape makes a strong plate, but other types of beams can also be used.

Another advantage of the U-shape is that it can be filled with concrete, so that the anchorage of the plate to the foundation is strongly reinforced.

In the base plate there are bearing housings for the roller bearings of the crank­shaft.

The lower half of the housing is placed in the base plate itself.

The upper half (called the bearing cap) is fastened with belts in the base plate.

There is one disadvantage with this system. If the outer ring of the crankshaft roll bearing, which is normally fixed in the bearing housing, starter to rotate in the base plate, the whole base plate must be substituted or reconstructed in ~.

Therefore the most modern types of framesaws are fitted with detachable bearinghousinosmade of cast steel for the crankshaftroll bearing. Some older frame saws have"white metal" ring lubricated bearings.(Seeappendix.)

The function of the base plate is:

to hold the construction of theframe together;

to support the whole weight ofthe frame saw (about 10 tons);

to absorb and tranamit to thefoundation the powerful "inertiaforces" that arise during sawing.

The predominant forces that influence

the base plate are:

1. VERTICAL FORCES that arise due to:

the up and down movement of theupper end of the connecting rod.

the up and down movement of the sash.

2. HORIZONTAL FORCES that arise mostly due

to:

the flywheel counterweights which,incertain positions,have a horizontalcomponent of movement.

the lower end of the connecting rod

which, in certain positions, has ahorizontal component of movement.

the pressure of the log against the

saw blades.

3. SEDE FORCES from:

the belt tension.

the power from the motor.

These forces can vary considerably;depending on the size of the motor and how

the power is transmitted, i.e.

through direct drive, or

through transmission drive.

More detail on these stresses is explained

in Part 2 FORCES AND MOVEMENTS.

- 6 -

Therefore the most modern types of frame saws are fitted with detachable bearing housIDgs made of cast steel for the crankshaft roll bearing. Some older frame saws have "white metal" ring lubricated bearings.(See appendi~

The function of the base plate is:

to hold the construction of the frame together;

to support the whole weight of the frame saw (about 10 tons);

to absorb and transmit to the foundation the powerful "inertia forces" that arise during sawing.

The predominant forces that influence the base plate are:

1. VERTICAL RlRCES that arise due to:

_ the up and down movement of the upper end of the connecting rod.

_ the up and down movement of the sash.

2. HORIZONTAL FQRCES that arise mostly due to:

the flywheel counterweights whic~in certain position~ have a horizontal component of movement.

the lower end of the connecting rod which, in certain positions,has a horizontal component of movement.

the pressure of the log against the saw blades.

3. SIDE RlRCESfrom:

the belt tension.

the power from the motor.

These forces can vary considerably, depending on the size of the motor and how the power is transmitted, i.e.

_ through direct drive, or

_ through transmission drive.

Detachable bearing ·

More detail on these stresses is explained~--------------------------~--~ in Part 2 - FQRCES AND IDVEMENTS.

2. Crank Section

The crank section consists of:

a crank shaft of:

2 centre shafts

2 flywheels with counterweights

1 crank pin

a connecting rod.

A. Crankshaft with flywheel

The crankshaft is mounted in the baseplate by means of two spherical SKF rollerbearings (see appendix). (Some frame sawshave white metal ring lubricated bearingsinstead.)

It is a detachable type, which meansthat it is built up of several parts.

The crankshaft is divided into twosimilar halves. Each half consists of:

one centre shaft pressed intoan eccentric;

onto this eccentric has beenbolted a flywheel with a counter-weight.

The crankshaft halves are joined togetherby means of a crank pin. The connecting rodis attached to this pin by the lower connect-ing rod bearing.

The crank pin is fitted with mechanicaljoints in both the crankshaft halves, whichmake it easy to disassemble. (In some framesaws the eccentric and the flywheel are castin one piece).

When the two halves have been joinedtogether by the crank pin, the flywheels arepositioned on either side of the connectingrod, placed as close as possible to theconnecting rod bearing. This is done toreduce the strain in the shaft. The shorterthe crank pin, the more rigid it is and thebetter it resists strains. (In other modelsthe flywheels are located outside the baseplate and the counterweights are positionedon either side of the crank pin.)

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2. Crank Section

The crank section consists of:

a crank shaft of:

2 centre shafts

2 flywheels with oounterweights

1 crank pin

- a connecting rod.

A. Crankshaft with flywheel

- 7 -

The crankshaft is mounted in the base plate by means of two spherical SKF roller bearings (see appendix). (Some frame saws have white metal ring lubricated bearings instead.) .

It is a detachable type, which means that it is built up of several parts.

The crankshaft is divided into two similar halves. Each half consists of:

one centre shaft pressed int o an eccentric;

onto this eccentric has been bolted a flywheel with a counter­weight.

The crankshaft halves are joined together by means of a crank pin. The connecting rod . is attached to this pin by the lower connect­ing rod bearing.

Connecting

o-pulley Driving

Fl;yt-rheel Count er weight

The crank pin is fitted with mechanical axle joints in both the crankshaft halves, which make it easy to disassemble. (In some frame saws the eccentric and the flywheel are cast in one piece).

When the two halves have been joined together by the crank pin, the flywheels are positioned on either side of the connecting rod, placed as close as possible to the connecting rod bearing. This is done to reduce the strain in the shaft. The shorter the crank pin, the more rigid it is and the better it resists strains. (In other models the flywheels are located outside the base plate and the counterweights are positioned on either side of the crank pin.)

Eccent ric

Centre axle

On the ends of the crankshaft out-side the bearings in the base plate arefixed:

a crankshaft pulley on the feedingside which, in turn, drives thefriction disc or pulley for the logfeeding mechanism. A variabledrive mechanism (see page 33) can be

mounted. When this is done, thereis no need for a driving pulley,since log feeding is powered by aseparate electric motor.

a keyedon driving pulley on thedriving Bide to transmit thedriving power from the motor tothe crankshaft. The drivingpulley has a twopiece hub, whichmakes it easy to disassemble.

The above applies when each framesaw is direct driven from its ownseparate motor.

N

Brake lining

Drivingpulley

- 8 -

On the ends of the crankshaft out­side the bearings in the base plate are fixed:

a crankshaft pulley on the feeding side which, in turn, drives the friction disc or pulley for the log feeding mechanism. A variable drive mechanism (see page 33) can be mounted. When this is done, there is no need for a driving pulley, since log feeding is powered by a separate electric motor.

a keyed-on driving pulley on the driving side to transmit the driving power from the motor to the crankshaft. The driving pulley has a two-piece hub, which makes it easy to disassemble.

The above applies when each frame saw is direct - driven from its own separate motor .

9

If there is a system with one motordriving more than one saw through a trans-mission gear, it is necessary to have,inaddition,a free running pulley - an 0-pulley-running on strong double-row roller bearingsadjacent to the driven pulley, on an extensionof the crankshaft. The transmission beltfrom the motor pulley is connected to eitherthe driven pulley or to the adjacent freerunning 0-pulley. When the power is to bedisconnected, the belt is moved by means ofa belt guide from the driving pulley over tothe 0-pulley. When power is to be connected,the belt is moved back from the 0-pulley tothe driving pulley.

The belt guide consists of a clampthrough which the belt passes. A lever atthe operator's position on the infeed sideof the saws, close to the log feeding control,moves the belt sideways.

Braking the crankshaft rotation can bedone in two different ways,depending on whetherthe saw is powered by direct motor drive ortransmission gear:

- Direct driven saws.

The brake system consists of anordinary brake lining surrounding a brakedrum on the driving pulley. The lining istightened around the brake drum by means ofa lever placed at the operator's positionon the upper stand close to the infeedcontrols.

- Transmission gear driven saws.

The belt guidebar is connected with abrake lining that surrounds the brake drumof the fixed driving pulley. The brake isactuated when the belt guide lever is movedto its bottom position, which moves the beltover to the 0-pulley.

- 9 -

If there is a system with one motor driving more than one saw through a trans­mission gear, it is necessary to have,in additio~a free running pulley - an o-pulley­running on strong double-row roller bearings adjacent to the driven pulley, on an extension of the crankshaft. The transmission belt from the motor pulley is connected to either the driven pulley or to the adjacent free running o-pulley. I'lllen the power is to be disconnected, the belt is moved by means of a belt guide from the driving pulley over to the o-pulley. When power is to be connected, the belt is moved back from the o-pulley to the driving pulley.

The belt guide consists of a clamp through which the belt passes. A lever at the operator's position on the infeed side of the saws, close to the log feeding control, moves the belt Sideways .

Braking the crankshaft rotation can be done in two different ways, depending on whether the saw is powered by direct motor drive or transmission gear:

Direct driven saws.

The brake system consists of an ordinary brake lining surrounding a brake drum on the driving pulley. The lining is tightened around the brake drum by means of a lever placed at the operator 's position on the upper stand close to the infeed controls.

Transmission gear driven saws.

The belt guidebar is connected with a brake lining that surrounds the brake drum of the fixed driving pulley. The brake is actuated when the belt guide lever is moved to its bottom position, which moves the belt over to the o-pulley.

Direot IDOtor drive

Brake lining-

Transmission gear

The forces on the crankshaft and theconnecting rod are very complex.See PART2 - FORCES AND MOVEMENTS). It is there-fore not possible to fully balance a framesaw.

To enable the moving parts to work assmoothly and quietly as possible the crank-shaft is fitted with flywheels and fixedcounterweights, which together counterbalancesome of the rotating parts of the frame.

The parts that move up and down, however,cause high free vertical forces. By usingextra counterweights it is possible to reduceor eliminate these vertical forces. But,

in doing so, free horizontal forces willdevelop.

The difficulty is to find the degreeof balancing that is best for each individualmachine.

Even if total balancing is not achievable,at least by partial balancing, free forces arereduced and distributed more evenly both inthe vertical and horizontal directions.

To achieve the best balance, the fixedcounterweights are provided with cavities,where iron or lead weights can be insertedto fine-tune the balance.

Above all, it is essential to counter-balance:

the high force (+) on the lowerconnecting rod bearing in the n9 to 6o'oclock" section and the "3 to 12o'clock" section and, in addition,

the negative force (-) on the lowerconnecting rod bearing in the "12 to9 o'clock" section and the "6 to 3o'clock" section.

In addition, the counterweights helpto overcome:

forces at TDC and BDC, the "12 and 6o'clock" positions.

- 10 -

The forces on the crankshaft and the connecting rod are very complex. See PARI' 2 - FlJRCES AND MOVEMENTS). It is there­fore not possible to fully balance a frame saw.

To enable the moving parts to work as smoothly and quietly as possible the crank­shaft is fitted with flywheels and fixed counterweights, which together counterbalance some of the rotating parts of the frame.

The parts t hat move up and down, howev er, cause high free vertical forces. B,y using extra counter\o1eights it is possible to reduce or eliminate these vertical forces. But, in doing so, free horizontal forces will develop.

The difficulty is to find the degree of balancing that is best for each individual machine.

~ven if total balancing is not achievable, at least by partial balancing,free forc es are reduced and distributed more evenly both in the vertical and horizontal directions.

To achieve the best balance, the fixed counterweights are provided \o1ith cavities, where iron or lead weights can be inserted to fine-tune the balance.

Above all, it is essential to counter­balance:

the high force (+) on the lower connecting rod bearing in the "9 to 6 o'oclock" section and the "3 to 12 o'clock" section and, in addition,

the negative force (-) on the lower connecting rod bearing in the "12 to 9 0' clock" section and the "6 to 3 0' clock" sect ion.

In addition, the counterweights help to overcome:

forces at TDC and BDC, the "12 and 6 o'clock" positions.

• I t

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Count·er \-,eight

""'w--- Extra weights

The function of the flywheels and thecounterweights is therefore:

to balance the inertia caused bythe up and clown movement of thesash and the connecting rod.

Part 2 - FORCES AND MOVEMENTS explainsbalancing in detail.

B. The connecting rod

The connecting rod is made from onepiece of I-section steel 2 m. long.

The function of the connecting rod is:

to transmit the rotating movementof the crankshaft to the sash andto transform this rotating move-ment into a reciprocating movement.

This means that the connecting rod mustturn 700 times/Minute when the number ofrevolutions is 350 revolutions/minute.

The forces that act on the connectingrod depend on:

the weight of the sash (250-400 kgwith inserted blades).

- the weight of the connecting roditself, 250 kg.

the number of revolutions per minute.

In total, the connecting rod mustabsorb inertia forces of about 20 tons.

To enable the connecting rod to with-stand these strains it is necessary:

to make it of spe'cial steel.

to design it for strength.This is the reason why theI-section is chosen.

-11-

The fUnction of the flywhee'ls and the counterweights is therefore:

to balance the inertia caused by the up and down movement of the sash and the connecting rod.

Part 2 - FORCES AND IDVEMENTS explains balancing in detail.

B. The connecting rod

The connecting rod is made from one piece of I-section steel 2 m. long.

The fUnction of the connecting rod is:

to transmit the rotating movement of the crankshaft to the sash and to transform this rotating move­ment into a reciprocating movement.

This means that the connecting rod must turn 700 times/minute when the number of revolutions is 350 revolutions/minute.

The forces that act on the connecting rod depend on:

the weight of the sash (250-400 kg with inserted blades).

the weight of the connecting rod itself, 250 kg.

the number of revolutions per minute.

In total, the connecting rod must absorb inertia forces of about 20 tons.

To enable the connecting rod to with­stand these strains it is necessary:

to make it of spe'cial steel.

to design it for strength. This is the reason why the I-section is chosen.

/

The connecting rod is subject to bothcompression and tension. (See Part 2FORCES AND MOVEMENTS.) These are notconstant but alternate during each turn ofthe crankshaft. These stress variationscould cause the material of the connectingrod to weaken and failure might occur fromfatigue.

Fbr anything that is exposed torepetition of stress, there is a "fatiguelimit", which is the maximum repetion ofstress that the body in question can beexposed to without fracturing from fatigue.

The fatigue limit of the connectingrod depends on:

the type and structure of itsmaterial;

the surface condition of thematerial.

This means that the more even and smooththe connecting rod is, the more repetitionof stress it will stand before it fractuTesfrom fatigue.

Therefore, the connecting rod mustbe protected from any nicks. Underno conditions must it be hit againstany solid object or be tapped witha hard or sharp tool.

Every nick creates a concentrationof stress which gets bigger the deeper thenick is.

A relatively small nick on a connect-ing rod might, because of the strong con-centration of stress around it, eventuallyresult in an apparently inexplicable break-age.

Every nick on the connecting rodmust be ground down with an emeryor polishing cloth.

- 12 -

The connecting rod is subject to both compression and tension. (See Part 2 -FDRCES AND MOVEMENTS.) These are not constant but alternate during each turn of the crankshaft. These stress variations could cause the material of the connecting rod to weaken and failure might occur from fatigue.

For a.n;rthing that is exposed to repet it ion of stress, there is a "fat igue limit", which is the maximum repet ion of stress that the body in question can be exposed to without fracturing from fatigue.

The fatigue limit of the connecting rod depends on:

the type and struct=e of its material;

the surface condition of the material.

This means that the more even and smooth the connecting rod is, the more repet~tion of stress it will stand before it fract~es from fatigue.

Therefore, the connecting rod must be protected from any nicks. Under no conditions must it be hit against any solid object or be tapped ,lith a hard or sharp tool.

Every nick creates a concentration of stress which gets bigger the deeper the nick is.

A relatively small nick on a connect­ing rod might, because of the strong con­centration of stress around it, eventually result in an apparently inexplicable break­age.

Every nick on the connecting rod must be ground down with an emery or polishing cloth.

Undamaged connecting rod

One nick •.•.•

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'" might cause • breakage ••

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Another thing to note is that corrosion,e.g. formation of rust, reduces the fatiguelimit considerably and increases the riskof fatigue breakdown.

Saw mills situated near corrodingair or water should paint connect-ing rods with anti-corrosive pednt

The connecting rod has two bearings, onelower and one upper.

The lower connecting rod bearing is,mounted on the crankshaft journal. Aspherical SKF-roller bearing (see appendix)has been chosen for the lower end toeliminate:

- any alignment defects in the verticaldirection of the frame.

- any side forces working on the connect-ing rod, for instance, due to sash im-balance.

Such an imbalance might occur if the massof the frame is not symmetrically distri-buted around its centre; for example, ifthe blades are not perfectly centred.

The upper connecting rod bearing con-sists of a needle bearing (see appendix).There is a hole in the piston pin whichserves as a tank for lubricating oil.

A needle bearing is chosen to ensurethat all the parts above the crankshaftare as small and light as possible. Aneedle bearing is smaller and lighter thanother bearings.

- 13 -

VIZI

N mumw ...... A,A ;LOIL

- pA.i7e,7; ., eau AIMM,5

- 13 -

Another thing to note iS ,that corrosion, e.g. formation of rust, reduces the fatigue limit considerably and increases the risk of fatigue breakdown.

Saw mills situated near corroding air or water should paint connect­ing rods with anti-corrosive paint

The connecting rod has two bearings, one lower and one upper.

The lower connecting rod bearing is , mounted on the crankshaft journal. A spherical SKF-roller bearing (see appendix) has been chosen for the lower end to eliminate:

any alignment defects in the vertical direction of the frame.

any side forces working on the connect­ing rod, for instance, due to sash im­balance.

Such an imbalance might occur if the mass of the frame is not symmetrically distri­buted 'around its centre; for example, if the blades are not perfectly centred.

The upper connecting rod bearing con­sists of a needle bearing (see appendix). There is a hole in the piston pin which serves as a tank for lubricating oil.

A needle bearing is chosen to ensure that all the parts above the crankshaft are as small and light as possible. A needle bearing is smaller and lighter than other bearings.

lower connecting rod bearing

~)

upper connecting rod bearing

spherical roll er bearing

'i

I

needle bearing

3. Bottom Frame

The bottom frame is placed at thelower floor level of the sawmill building.It consists of:

two lower side frames whichare both fastened to thebase plate by

four bolts at the bottom,andjoined together by

two stay bolts at the top.

The function of the bottom frame is:

to extend the sash height to enableconnecting rod to be larger;

to support the two upper side frames;

to support the brake and belt guidesyBtems;

to serve as a support body for partsof the feeding mechanism and lubri-cator.

-14-

- - -----------------

- 14 -

3. Bottom Frame

The bottom frame iB placed at the lower floor level of the sawmill building. It oonsists ofl

A. two lower side frames whioh are both fastened to the base plate by

B. four bolts at the bottom,and joined together by

c. two stay bolts at the top.

The function of the bottom frame is:

to extend the sash heighi to enable oonneoting rod to be larger;

to support the two upper side frames;

to BUpport the brake and belt guide systems;

to serve as a support body for parts of the feeding meohanism and lubri­oator.

4- 11121,21222

The upper frame is attached to thelower frame by bolts. It consists of:

two upper side frames,

one top piece, and

two connecting plates at thebottom,one on each side.

The function of the upper frame is:

to support the system of guides;

to support the roll frame and thefeeding mechanism;

to transmit to the foundation,through the bottom frame, thevertical forces created whenthe sash presses against theguides.

To be able to support the rollframes attached to both the infeed andoutfeed sides of the upper frame thereare:

at the driving side a verticalcylindrical shaft, the attach-ment shaft, or the swingingshaft.

at the feeding side, a similarshaft called locking shaft.

15- 15 -

4. Upper hame

The upper frame is attached to the lower frame Qy bolts. It consists of:

A. two upper side frames,

B. one top piece, and

c. two connecting plates at the bottom, one on each side.

The function of the upper frame is:

to support the system of guides;

to support the roll frame and the feeding mechanism;

to transmit to the foundation, through the bottom frame, the vertical forces created when the sash presses against the guides.

To be able to support the roll frames attached to both the infeed and outfeed sides of the upper frame there are:

D. at the driving side a vertical cylindrical shaft, the attach­ment shaft, or the swingiIJg shaft.

E. at the feeding side, a similar shaft called locking shaft.

5. Guide System

To the side frames four guides, twoupper and two lower, are attached withbolts. A saw frame guide is describedas:

a guide rail having

a polished surface that is

- made of cast iron. This materialhas low friction for the wear platesto run on.

The function of the guides is:

to locate the sash in relation tothe centre line of the frame, andto guide the sash when it is movingvertically (up and down).

There are two different kinds ofguides:

A. Flat guides, which have completelystraight and plane slide faces.They are positioned on the infeedside.

- 16 -

B. V-Guides, which have slide facesshaped like a V. They are posi-tioned on the outfeed side.

Thus the sash is guided on both the infeedand outfeed side during its movement up-ward and downward. The front guides (asseen from the infeed side)are alwaysadjustable. The reason for this is thatthe tolerance between guide and frictionplate, (the "play"), must be adjustableto correct wear on guides and wear plates.

If the guide is too tight (the"play" made too small) overheating,and a risk of damage to guides andfriction plates could result.

If the guide is not tight enough(the "play" too big) the sashwill be loose and this could betramsmitted to the sawlines,resulting in poor sawing. Thereis also a risk that the guide,the friction plate and guide boltswill break,with the risk of furtherdamage.

OUT1IEED

- 16 -

5. Guide SYstem

To the side frames four guides, two upper and two lower, are attached with bolts. A saw frame guide is described as:

a guide rail having

- a polished surface that is

made of cast iron. This material has low friction for the wear plates to run on.

The function of the guides is:

to locate the sash in relation to the centre line of the frame, and to guide the sash when it is mov~ vertically (up and dOwn).

There are two different kinds of guides:

A. Flat guides, which have completely straight and plane slide faces. They are positioned on the infeed side.

B. V-Guides, which have slide faces shaped like a V. They are posi­tioned on the outfeed side.

Thus the sash is guided on both the infeed and outfeed side during its movement up­ward and downward. The front guides (as seen from the infeed side)are always adjustable. The reason for this is that the tolerance between guide and friction plate, (the "play"), must be adjustable to correct wear on guides and wear plates.

If the guide is too tight (the "play" made too small) overheating, and a risk of damage to guides and friction plates could result.

If the guide is not tight enough (the '~l~" too big) the sash will be loose and this could be transmitted to the sawlines, resulting in poor sawing. There is also a risk that the guide, the friction plate and guide belts will break, with the risk of f'urtheI damage.

Adjust­ing nut

OUTFEED

I

-+ t

Adjust- _,""rAI'l ing screw

Stay tighten r

17

Some frame saws have the guidesmounted, as shown in the figure alongside.

The guides are lubricated from a12tube grease pump, a high pressurelubricator. The lubrication is pro-portional to the speed of the saw frame,stopping when the saw frame stops. Thelubricant flows with a pressure of up to100 atmospheres (10 mPa). The lubricatoris mounted on one of the side frames. It

is driven by an eccentric directly fromthe crankshaft.

To each Vguide two lubricationtubes are connected, and

to each flat guide one lubricationtube is connected.

Feedi4gmechanism

side

>1>

Driving side

LUBRICATING SYSTEM

Flat guide VguideI lubrication 2 lubricationtube tubes

Lever for eccentric

- 17 -

Some frame saws have the guides mounted, as s hown in the figure alongside.

The guides are lubricated from a 12-tube grease pump, a high pressure lubricator. The lubrication is pro­portional to the speed of the saw frame, stopping when the saw frame stops. The lubricant flows with a pressure of up to 100 atmospheres (10 mPa). The lubricator is mounted on one of the side frames. It is driven by an eccentric directly from the crankshaft.

To each V-guide two lubrication tubes are connected, and

to each flat guide one lubrication tube is connected.

Feeding mechanism

side

'" • .'! .. , I" g

[5

LUBRICATING SYSTUI

Flat guide 1 lubrication tube

V-guide 2 lubrication tubes

Lever for e"';entrj.c

The load on the lower guides isheaviest as they are mounted closest tothe upper end of the connecting rod.Therefore, they take the horizontal forcescreated by the upper end of the connectingrod at certain positions of movement.

Because of this high pressure theseguides are provided with water cooling,making it easier to carry away the heatcaused by the high pressure.

This makes it possible to adjust theguides of the sash With minimum tolerance,which markedly improves the efficiency ofsawing.

The water cooling device is a closedsystem where the water is continuouslypumped. It consists of:

a system of radiator cells,

an electric fan, and

a pump.

This selfcontained equipment can beplaced beside the frame, or on the bottomfloorlor, in any other suitable place.Water is led through tubes to the guideswhich are hollow, so that the water canpass through them.

18- 18 -

The load on the lower guides is heaviest as they are mounted closest to the upper end of the connecting rod. Therefore, they take the horizontal forces created by the upper end of the connecting rod at certain positions of movement .

Because of this h~h pressure these guides are provided with water cooling, making it easier to carry away the heat caused by the h~h pressure .

This makes it possible to adjust the guides of the sash with minimum tolerance , which markedly improves the efficiency of sawing.

The water cooling device is a closed system where the water is continuously pumped. It consists of :

a system of radiator cells,

an electric fan, and

a pump.

This self-contained equipment can be placed beside the frame, or on the bottom floor, or in any other suitable place . Water is led through tubes to the guides which are hollow, so that the water can pass through them.

Expans i on

Fan

Pump

6. Paah

The sash consists of four parts:

one upper cross beam

one lower cross beam

two columns,one on each side.

The lower cross beam has a bracket onits under side in the form of two wings.Attached to these is the upper crank pinwhich connects the sash with the connectingrod.

The distance between the upper and thelower cross beam is adjusted, so that theupper blocks in the lowest position of theframe and the lower blocks in the highestposition of the frame do not touch the log.

The columns are made of steel tubingto keep weight down. In relation to itsweight tubing has high resistance to com-pression and tension stress.

The two columns and the two beamsmake up the sash into which the saw bladesare inserted.

To hold the sawblades each cross beamis provided with a slot, i.e. a clearanceinto which are inserted:

top hangers at.the top, and

bottom hangers at the bottom

The saw blades are fitted into thesehangers when the saw blades are set.

-19-- 19 -

6. ~ The sash consists of four parts:

A. one upper cross beam

B. one lower cross beam

C. two columns, one on each side.

The lower cross beam has a bracket on its under side in the form of two wings. Attached to these is the upper crank pin which connects the sash with the connecting rod.

The distance between the upper and the lower cross beam is adjusted, so that the upper blocks in the lowest position of the frame and the lo~r blocks in the highest position of the frame do not touch the log.

The columns are made of . steel tubing to keep weight down. In relation to its weight tubing has high resistance to com­pression and tension stress.

The two columns and the two beams make up the sash into which the saw blades are inserted.

To hold the sawblades each cress beam is provided with a slot, i.e. a clearance into which are inserted:

D. top hangers at . the top, and

E. bottom hangers at the bottom.

The saw blades are fitted into these hangers when the saw blades are set.

Bottom hangers

3

Top hangers

The sash is constructed:

to withstand the stresses createdwhen the blades are fitted. Eachblade is fitted with a tension of7-9 tons. If seven blades arefitted, the total tension will be50-65 tons.

- 20 -

to enable, in particular, the lowercross beam to absorb forces from themoving connecting rod. Theseforces are of a magnitude of 15-20tons and they alternately put thebeam under bending stress upwardsand downwards.

At the top dead centre, where thewhole sash must slow down, stop andchange direction, the connecting rod willbend the beam down.

At bottom dead centre, where thesash once again must slow down, stopand change direction, the force fromthe connecting rod will bend the beam up.

The cross beam, seen in a crosssection, is in principle like two U-beamsback to back.

The U-beam is chosen because it givesadvantage both in manufacturing and instrain distribution, such as:

the U-form is easy to manufacturein the foundry.

in resisting stress, the U-form hasan advantage because this shape givesa high bending resistance (i.e. resis-tance against bending stress).

if 11 1 II i

rrinar

Fitt ing5665TON

15-20 TON

- 20 -

The sash is constructed:

to withstand the stresses created when the blades are fitted. Each blade is fitted with a tension of 7-9 tons. fi tted, the 50-65 tons.

If seven blades are total tension will be

to enable, in particular, the lower cross beam to absorb forces from the moving connecting rod. These forces are of a magnitude of 15-20 tons and they alternately put the beam under bending stress upwards and downwards.

At the top dead centre, where the whole sash must slow down, stop and change direction, the connecting rod will bend the beam down.

At bottom dead centre, where the sash once again must slow down, stop and change direction, the force from the connecting rod will bend the beam up.

The cross beam, seen in a cross section, is in principle like two U-beams back to back.

The U-beam is chosen because it gives advantage both in manufacturing and in strain distribution, such as:

the U-form is easy to manufacture in the foundry.

in resisting stress, the U-form has an advantage because this shape gives a high bending resistance (i.e. resis­tance against bending stress).

Too 10,[ Correct

~.~

t Centre of bending

LoHer cross beam

Centr e of bending

Too high

In the centre of the cross beam thereare two strongly dimensioned angularstiffeners or ribs, the function of whichis to steady the beam against the forcesmentioned above.

The tension stress acting on the sashthrough the set of blades depends on, andvaries with, the number of blades and howtight each blade has been fitted.

The stress that the connecting rodtransmits to the sash, mainly the lowercross beam, primarily depends upon:

the weight of the sash, and

the number of revolutions per minute.

The sash must be dimensioned accordingto the diameter timber to be sawn. Thebigger the timber, the bigger the sash andthe higher the weight.

The width of the sash can vary between18" and 34", which is the inside dimensionand also the diameter limit of any logthat can pass through the frame.

The weight of the sash varies between

about 250 kg for a 15" frame withinserted blades, and

about 400 kg for a 34" frame withinserted blades.

The stress transmitted by the connect-ing rod to the lower cross beam of the sashwill increase:

with increased weight of the sash;

with increased speed (rev./Min.)

There is a limit to the stress placedon any piece of machinery and, in this case,the manufacturers place restrictions on theweight and speed as under:

for a 18" frame ... 380-390 rev./Min.

for a 24" frame ... 360-365 rev./Min.

for a 30" frame around 320 rev.hlin.

21

Weight ofthe connecling rod

- 21 -

In the centre of the cross beam there are two strongly dimensioned angular stiffeners or ribs, the function of which is to steady the beam against the forces mentioned above.

The tension stress acting on the sash t .hrough the set of blades depends on, and varies with, the number of blades and how tight each blade has been fitted.

The stress that the connecting rod transmits to the sash, mainly the lower cross beam, primarily depends upon:

the weight of the sash, and

the number of revolutions per minute.

The sash must be dimensioned according to the diameter timber to be sawn. The bigger the timber, the bigger the sash and the higher the weight.

The width of the sash can vary between 18" and 34", which is the inside dimension and also the diameter limit of any log that can pass through the frame.

The weight of the sash varies bet,Teen

about 250 kg for a 15" frame with inserted blades, and

about 400 kg for a 34" frame with inserted blades.

The stress transmitted by the connect­ing rod to the lower cross beam of the sash will increase:

"ith increased weight of the sash;

with increased speed (rev./min.)

There is a limit to the stress placed on any piece of machinery and, in this case, the manufacturers place restrictions on the weight and speed as under:

for a 18" frame

for a 24" frame

for a 30" frame

... 380-390 rev./min.

360-365 rev./min.

around 320 rev.}nin.

,

To the columns of the sash four gaugeattachments are fastened, one in eachcorner. Between these and the outer bladeson either side, blocks or gauges (measuringbodies located between adjacent blades todetermine the thickness of the sawn timber)are located. This makes it possible toalign the whole set of blades with screwsfixed in the gauge attachments.

In the four corners of the sash, theends of the cross beams are provided withbrackets for the sliding blocks.

The function of the sliding blocks isto guide the sash into the guides of theupper frame.

The surface of the blocks is mad..) upof interchangeable friction plates made ofa low friction, low wear material such asaluminium blocks with a special bakelitefinish, npockenholz" or other low frictionmaterial. The aluminium blocks are pre-ferred for weight and maintenance reasons.

The aim is to get friction as low aspossible between the friction plates andthe guides, in order to prevent overheating,because overheating can cause the guides tobuckle.

The sliding blocks on both sides ofthe sash are made in the same way:

on the infeed side as flat blocks, and

on the outfeed side, as pointed blocksto steer the sash in the guides.

So the sash is guided both on thefeeding mechanism side and the drivingside of the frame.

The system with flat blocks and flatguides makes adjustment of the sash easierand the number of surfaces requiring care-ful clearance adjustment is reduced.

- 22 -

To the columns of the sash four gauge attachments are fastened, one in each corner. Between these and the outer blades on either side, blocks or gauges (measuring bodies located between adjacent blades to determine the thickness of the sawn timber) are located. This makes it possible to align ' the whole set of blades with screWS fixed in the gauge attachments.

In the four corners of the sash, the ends of the cross beams are provided with brackets for the sliding blocks.

The function of the sliding blocks is to guide the sash into the guides of the upper frame.

The surface of t he blocks is mad., up of interohangeable friction plates made of a low friction, low wear material such as aluminium blocks with a special bakelite finish, "pockenholz" or other low friction material. The aluminium blocks are pre­ferred for weight and maintenance reasons.

The aim is to get friction as l ow as possible between the friction plates and the guides, in order to prevent overheating, because overheating can cause the guides t o buckle.

The sliding blocks on both sides of the sash are made in the same way:

on the infeed side as flat blocks, and

on the outfeed side, as pointed blocks to steer the sash in the guides.

So the sash is guided bot h on the feeding mechanism side and the driving side of the frame.

The system with flat blocks and flat guides makes adjuetment of the sash easier and the number of surfaces requiring care­ful clearance adjuStment is reduced.

Blades must be fitted into the sashwith an overhang setting, to make theblade at the upward stroke move awayfrom the cutting line in the log, whichis continuously fed.

Overhang setting means that thetooth line is set away from thevertical and has a slope awayfrom the log at the bottom.

This overhang must be obtained withoutfitting the blades so that the tensionline falls diagonally through the blades.

To get a correct overhang, the twocross beams are not vertically one abovethe other. In relation to a verticalplumb line through the centre of the sawsthe upper sliding blocks are displacedtowards the front (log infeed) and thelower sliding blocks towards the rear(log outfeed). The overhang is about50 mm from vertical.

- 23 -

Blades must be fitted into the sash with an overhang setting, to make the blade at the upward stroke move away from the cutting line in the log, which is continuously fed.

Overhang setting means that the tooth line is set away from the vertical and has a slope away from the log at the bottom.

This overhang must be obtained without fitting the blades so that the tension line falls diagonally through the blades.

To get a correct overhang, the two cross beams are not vertically one above the other. In relation to a vertical plumb line through the centre of the saws the upper sliding blocks are displaced towards the front (log infeed) and the lower sliding blocks towards the rear (log outfeed). The overhang is about 50 mm from vertical.

7. Roll Frame ad Fiaed rolls/NM

The function of the roll frame is:

to support the upper and lowerfeed rolls;

to create a roll pressurebetween the feed rolls

It consists oft

the upper roll frames, one in frontand one at the back. (Seen from the

infeed side).

the lower roll frames, one in frontand one at the back. (Seen from the

infeed side).

The upper roll frame

The frame is supported on both theinfeed and outfeed sides by shaftsattached to the upper frame:

on the feeding mechanism side of

the frame by locking shafts.

on the driving side of the frame,

by vertical holding swinging shafts;

Each upper roll frame is fixed on and canswing out on the swinging shaft to giveaccess to the sash (e.g. when changing

blades). Rach roll frame carries an

upper feeding roll.

Lockishafts

- 24 -

7. Roll :r'rame and Feed rolls

The fUnction of the roll frame is:

to support the upper and lower feed rolls;

to create a roll pressure between the feed rolls

It consists cf:

the upper roll frames, one in front and one at the back. (Seen from the infeed side).

the lower roll frames, one in front and one at the back. (Seen from the infeed side).

The upper roll frame

The frame is supported on both t he infeed and outfeed sides by shafts attached to the upper frame:

on the driving side of the frame, by vertical holding swinging shafts;

on the feeding mechanism side of the frame by locking shafts.

Each upper roll frame is fixed on and can swing out on the swinging shaft to give access to the sash (e.g. when changing blades). Each roll frame carries an upper feeding roll.

FRONT

Upper roll frame

Lower roll

Swing" shafts "

' "

]

Lower roll

Lock" shafts

VII : 1

The roll frame is cast and providedwith:

a vertical hole A for the holdingshaft on the driving side.

a vertical notch B for the lockand the locking shaft on the feedingmechanism side.

two vertical holes B'for the clamps.

a horizontal hole C for one sprocketshaft on the driving side.

two horizontal holes D and D' forthe supporting shaft to the upperroll clamps.

Each roll frame can be raised andlowered along the vertical swinging shaftto make it possible to adjust it todifferent diameter logs. This is donemanually by means of the handwheel.

The handwheel acts on a toothed trans-mission gear F of which the teeth are mesh-ing with the corresponding rack of teethof the swinging shaft G.

The toothed transmission gear isprovided with a locking device in the formof a catch H which meshes a ratchet wheel I.

This is placed on the shaft betweenthe handwheel and the gear.

With this device the gear and the rollframe can be locked in the correct positionfor any given log diameter. When raisingand lowering the frame the catch must be inthe raised position.

with:

- 25 -

The roll frame is cast and provided

a vertical hole A for the holding shaft on the driving side.

a vertical notch B for the lock and the locking shaft on the feeding mechanism side.

two vertical holes B'for the clamps.

a horizontal hole C for one sprocket shaft on the driving side.

two horizontal holes D and Dr for the supporting shaft to the upper roll clamps.

Each roll frame can be raised and lowered along the vertical .swinging shaft to make it possible to adjust it to different diameter logs. This is done manually by means of the hand-wheel.

The hand-wheel acts on a toothed trans­mission gear F of which the teeth are mesh­ing with the corresponding rack of teeth of the swinging shaft G.

The toothed transmission gear is provided with a locking device in the form of a catch H which meshes a ratchet wheel I.

This is placed on the shaft between the hand-wheel and the gear.

With · this device the gear and the roll frame can .be locked in the correct position for any given log diameter. When raising and lowering the frame the catch must be in the raised position.

G--';-"

C F H

D

F

8'

8

D'

Clamps

~open ~r

The lower roll frame

The lower roll frames are constructedon the same principle as the upper ones.Since they must give firm support to thelog during sawing, they are fixed vertically.

Like the upper roll frames theyswing outwards. Nowadays they are made ofcast steel for strength.

Each roll frame supports a lower feedroll. Both the upper and lower roll framecan be locked inwards, (i.e. the operatingposition) by a simple catch on the feedingmechanism side of the stand which is thenturned so that it totally encloses thelocking shaft. This also eliminates anyplay in the roll frame. The lock isinaccessible when the saw is working.

The feed rolls

The feed rolls are called:

upper feed rolls

lower feed rolls.

26

The function of the feed roll is tofeed the log through the frame saw in thesmoothest possible way.

The upper rolls consist of one frontand one rear roll which:

rotate on shafts mounted in risingand falling clamps (roll clamps) onthe upper roll frame. Such a roll isalso called a pendular roller.

(In some models the roll shaft ismounted directly on the rising andfalling roll frame a fixed roll.The roll frames are adjusted verti-cally with a handwheel and then theyare automatically selfadjusting fromthe bottom position.)

- 26 -

The lower roll frame

The lower roll frames are constructed on the same principle as the upper ones. Since they must give firm support to the log during sawing, they are fixed vertically.

Like the upper roll frames they swing outwards. Nowadays they are made of cast steel for strength.

Each roll ·frame supports a lower feed roll. Both the upper and lower roll frame oan be locked inwards, (i.e . the operating position) by a simple catch on the feeding mechanism side of the stand which is then turned so that it totally encloses the locking shaft . This also eliminates any play in the roll frame. The lock is inaccessible when the saw is working .

The feed rclls

The feed rolls ar e called:

f Closed

upper feed rolls ~ Open

lower feed r olls . ~J The function of the feed roll is to

feed the log through the frame saw in the smoothest possible way.

The upper rolls consist of cne front and one rear roll which:

rotate on shafts mounted in r1s1ng and falling clamps (roll clamps) on the upper roll frame. Such a roll is also called a pendular roller.

(In some models the roll shaft is mounted directly on the rising and falling roll frame - a fixed roll. The roll frames are adjusted verti­cally with a hand-wheel and then they are automatically self-adjusting from the bottom position.)

Roll stan

£" -...:----

27

are selfadjusting vertically (becauseof the rising and falling clamps) tosmall variations in the diameter of thelog. If, however, sawing is done buttend first, the rolls have to be liftedby a special device because they cannotopen themselves up from the small endof one log to the butt end of the nextone.

This lifting is one by means of ahydraulic cylinder which the sawyercan control from the log carriage. Thecylinder has a piston mounted betweenthe pendular roll clamp and the rollframe. The pressure comes from ahydraulic pump on the upper side ofthe side frame.

(In some frame saws the lifting is doneby pneumatic valves operated by thesawyer from the log carriage. Thelifting device consists of a pneumaticcylinder with a piston which is mountedon the roll frame. The air pressurecomes from a separate motor drivencompressor.)

are driven from the feeding mechanismby means of a chain. A sprocket ismounted on the roll shaft on the sideof the feeding mechanism. When therevolving frame is recessed, this chainwheel will mesh with a correspondingchain driven from the feeding mechanism.

The lower feed rolls, one front and onerear:

consist of roller sections that aremounted on a cylinder of cast steel.These centre cylinders are mountedvertically, fixed in interchangeablemetal bushes in the lower roll frame.Because the bushes are interchangeablethere is no risk of the rolls pullingsideways because of wear in the bearingboxes.

are driven from the feed mechanism bymeans of a cog wheel transmission. Onthe side of the feeding mechanism theshaft journal of the roll is providedwith chain wheels that mesh with a cogwheel of the feeding medhanism whenthe swinging roll frame is engaged.

-,

4841ï

,..

dr

1111r1i-ItN

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Oil tub

Yoke

Hydraulic.sbonpi

Hydrauliccylinder

'oil stand'endularroller

111111!

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aoR

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ltrie,v4,Or, Appipw--*VIM?:'*-0; It% 4% f 0

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- 27 -

are self-adjusting vertically (because of the rising and falling clamps) to small variations in the diameter of the log. If, however, sawing is done butt· end first, the rolls have to be lifted by a special device because they cannot open themselves up from the small end of one log to the butt end of the next one.

This lifting is one by means of a hydraulic cylinder which the sawyer can control from the log carriage. The cylinder has a piston mounted between the pendular roll clamp and the roll frame. The pressure comes from a hydraulic pump on the upper side of the side frame.

(In some frame saws the lifting is done by pneumatic valves operated by the sawyer from the log carriage. The lifting device consists of a pneumatic cylinder with a piston which is mounted on the roll frame. The air pressure comes from a separate motor driven compressor.)

are driven from the feeding mechanism by means of a chain. A sprocket is mounted on the roll shaft on the side of the feeding mechanism. When the revolving frame is recessed, this chain wheel will mesh with a corresponding chain driven from the feeding mechanism.

The lower feed rolls, one front and one rear:

consist of roller sections that are mounted on a cylinder of cast steel. These centre cylinders are mounted vertically, fixed in interchangeable metal bushes in the lo"er roll frame. Because the bushes are interchangeable there is no risk of the rolls pulling sideways because of wear in the bearing boxes.

are driven from the feed mechanism by means of a cog wheel t~ansmission. On the side of the feeding mechanism the shaft journal of the roll is provided with chain wheels that mesh with a cog wheel of the feeding mechanism when the swinging roll frame is engaged.

Pattern of feed rolls

The function of the feed rolls hasearlier been described as:

to feed the log through theframe by rotating,and also

to restrain the log while be-ing fed to prevent it turningor moving sideways.

This task must be done under verydifferent conditiOns dependent upon:

- the form of the material

- the hardness and surface of thematerial, for example, logs withbark on or off, frozen or un-frozen timber.

The demands on the function of thefeed rolls are:

- that the timber is not damaged bypressures that leave marks on thesawn surface.

- that the log is fed evenly andsteadily without slipping. Slippingresults in the wrong relationshipbetween feeding and overhang settingwhich results in poorer sawing andmore strain on the blades.

- 28 -

LOG or CANT

that is roundand has smallcontact sus,-faces againstthe feed rolls

that has twoflat sawn sill,-

faces againstthe feed rolls

- 28 -

Pattern of feed rolls

The function of the feed rolls has earlier been described as:

to feed the log through the frame by rotat ing, and also

to restrain the log while be­ing fed to prevent it turning or moving sideways.

This task IIlIl8t be done under very different conditions dependent upon:

- the form of the material

LOG or CANT

that is round that has two and has small flat sawn SU!'-

contact SUI'- faces against faces against the feed rolls the feed rolls

the hardness and surface of the material; for example, logs with bark on or off, frozen or un­frozen timber.

The demands on the function of the feed rolls are:

that the timber is not damaged by pressures that leave marks on the sawn surface.

that the log is fed evenly and steadily without slipping. Slipping results in the wrong relationship between feeding and overhang setting which results in poorer sawing and more strain on the blades.

For the feed rolls to functionproperly two things are required:

The right pattern for differentconditions.

Satisfactory maintenance (as partof the preventive maintenance syntem)of the pattern of the feed rolls.

The roll pattern is made in oneof two different wayn:

a roll core is provided withpatterned rings, or

the pattern is cut directly intothe roll.

The roll pattern can, in principle,be of two different kinds:

spiked or toothed, i.e. the contactpoints have been made pointed togrip the log better and reduceslipping between log and feed rollsto a minimum.

flat or grooved, i.e. the contactpoints have been made smooth so asnot to damage soft timber.

In the log frame the spiked pattern isusually used both for the upper and lowerfeed rolls.

Since the stresses are biggest on thelower feed rolls, these are usually pro-vided with replaceable spiked rings, oftenwith cleaning irons between them.

In the cant frame only feed rolls witha smooth pattern are used to prevent anyroll marks on the surfaces of the sawnblock. These surfaces are normally thefinal product surface.

Fbr the feed rolls to function properly two things are required:

1. The right pattern for different conditions.

2. Satisfactory maintenance (as part

- 29 -

of the preventive maintenance system) of the pattern of the feed rolls.

The roll pattern is made in one of two different ways:

A. a roll core is provided with patterned rings, or

B. the pattern is cut directly into the roll.

The roll pattern can, in principle, be of two different kinds:

spiked or toothed, i.e. the contact points have been made point ed to grip the log better and reduce slipping between log and feed rolls to a minimum.

flat or grooved, i.e. the contact points have been made smooth so as not to damage soft timber.

In the log frame the spiked pattern is usually used both for the upper and 10l1er feed rolls.

Since the stresses are biggest on the lower feed rolls, these are usually pro­vided with replaceable spiked rings, often with cleaning irons bet'oJeen them.

In the cant frame only feed rolls with a smooth pattern ar e used to prevent any roll marks on the surfaces of the sa,m block. These surfaces are normally the final product surface.

Log frame

B

In frames that are used for both logand cant cutting, the lower feed rolls areoften provided with:

one centre part consisting of spikedrings.

side parts consisting of flat rings.

The spiked rings in the centre arepositioned a little lower than the flatrings on the sides.

The form and pattern of the rollsdepend upon what logs are to be cut andthe clima-tic conditions, etc., duringwhich sawing takes place.

2. The maintenance of the feed rollsmust, regardless of their form and pattern,aim

to keep the pattern of the feedrolls in good condition.

This is done either by exchangingworn rings or by recutting or grindingfeed rolls of fixed pattern.

30

In frames that are used for both log and cant cutting, the lOl-ler feed rolls are often provided Hith:

one centre part consisting of spiked rings.

side parts consisting of flat rings.

The spiked rings in the centre are positioned a little lower than the flat rings on the sides.

The form and pattern of the rolls depend upon Hhat logs are to be cut and the climatic conditions, etc., during Hhich sal<ing takes place.

2. The maintenance of the feed rolls must, regardless of their form and pattern, aim

to keep the pattern of the feed rolls in good condition.

This is done either by exchanging Horn rings or by re-cutt ing or grinding feed rolls of fixed pattern.

8. Feed Mechanism

The feed mechanism is made for con-tinuous feeding. This means that thelog is fed when the blades are movingup as well as when they are moving down.It is done, as has been said before, bythe lower and upper feed rolls.

The feed mechanism consists of agear box with a friction drive mountedon one side stand.

The frame is said to be a right-hand or left-hand frame, depending onwhich side of the stand, right or left,the feeding mechanism is mounted.

The function of the feedingmechanism is to transmit a rotating move-ment from the crankshaft to the feedrolls.

The friction drive consists of:

a friction wheel A mounted on ahorizontal shaft, and

two fibre rollers, one upper B andone lower B', mounted on verticalshafts.

Both rollers can be moved against thecommon friction wheel.

The upper roller B is movablealong a splined shaft and is used forthe feeding. It is automatically pressedagainst the friction wheel by a springdevice with a force that increases withthe resistance to feeding. Contactbetween the roller and the friction wheelis made by means of a knob D close tothe frame.

The lower roller B', mounted on itsshaft, is only used for return feeding andis otherwise lifted from the frictionwheel. It starts to work when a wheel-handle C is turned, thereby releasing astrong spring. This spring is mountedin such a way that it will press thefriction roller against the wheel.

31- 31 -

8. Feed Mechanism

The feed mechanism is made for con­tinuous feeding. This means that the log is fed when the blades are moving up as Hell as when they are moving down. It is done, as has been said before, qy the lower and upper feed rolls.

The feed mechanism consists of a gear box with a friction drive mounted on one side stand.

The frame is said to be a right­hand or left-hand frame, depending on which side of the stand, right or left, the feeding mechanism is mounted.

The function of the feeding mechanism is to transmit a rotating move­ment from the crankshaft to the feed rolls.

The friction drive consists of:

a friction wheel A mount ed on a horizontal shaft, and

two fibre rollers, one upper Band one lower B', mounted on vertical shafts.

Both rollers can be moved against the common frict ion ~Iheel.

The upper roller B is movable along a splined shaft and is used for the feeding. It is automatically pressed against the friction ~Iheel by a spring device with a force that increases >lith the resistance to feeding. Contact between the roller and the friction wheel is made by means of a knob D close to the frame.

The lower roller B', mounted on its shaft, is only used for return feeding and is otherwise lifted fro~ the friction wheel. It starts to work when a wheel­handle C is turned, thereby releasing a strong spring. This spring is mounted in such a way that it will press the friction roller against the wheel.

The function of the friction driveis to enable the feed rolls to turn atdifferent speeds.

The speed can be varied from 10 to40 mm/stroke (with special arrangementsup to 50 mm/stroke).

The speed of the friction roller Bcan be adjusted by contact with a longeror shorter radius of the friction wheel A.

The speed is increased as thefriction roller B moves towards theperiphery of the friction wheel.

The transmission of power is doneas follows:

A belt from a driving wheelmounted on the crankshaft drivesthe friction wheel A.

The wheel drives the frictionroller B, which then starts torotate together with its verticalshaft E.

A mitrewheel gearing F transmitsthe rotation from the verticalshaft E to a horizontal shaft G.

On this horizontal shaft G aremounted both a cog wheel H thatmeshes with the cog wheels I ofthe lower feed rolls and asprockelJ that transmits the move-ment to the upper feed rollsthrough a driving chain K, the out-sides of which mesh with sprocketsL and L'. These sprockets aremounted on horizontal shafts in theupper feed frame.

The feed rolls are finally set towork by a driving chain M that runsover a sprocketN, on one of the hori-zontal shafts and also over asprocket 0 mounted on the shaft ofthe feeding mechanism.

- 32 -

The function of the friction drive is to enable the feed rolls to turn at different speeds.

The speed can be varied from 10 to 40 rnrn/stroke (with special arrangement's up to 50 rnrn/stroke).

The speed of the friction roller B can be adjusted by 'contact with a longer or shorter radius of the friction wheel A.

The speed is increased as the friction roller B moves towards the periphery of the friction wheel.

The transmission of power is done as follows:

A belt from a driving wheel mounted on the crankshaft drives the friction wheel A.

The wheel drives the friction roller B, which then starts to rotate together with its vertical shaft E.

A mitre-wheel gearing F transmits the rotation from the vertical shaft E to a horizontal shaft G.

On this horizontal shaft G are mounted both a cog wheel H that meshes with the cog wheels I of the lower feed' rolls and a sprocket J that transmits the move­ment to the upper feed rolls through a driving chain K, the out­sides of which mesh ,lith sprockets Land L'. These sprockets are mounted on horizontal shafts in the upper feed frame.

The feed rolls are finally set to work by a driving chain M that runs over a sprocket N, on one of the hori­zontal shafts and also over a sprocket 0 mounted on the shaft of the feeding mechanism.

Feeding mechanism m/Variator

The main parts of this feed mechanismare:

7.5 hp motor A which drives by meansof V-belts.

the variable drive consisting of twotapered discs (Band C). These discstransmit the movement through a V-beltD to two other tapered discs (E and F).These latter discs are mounted on ashaft G, which is connected to:

the gear drive H which, in turn,drives the feed rolls I of theframe saw.

the 0.25 hp motor J which changesthe feed speed.

the stand K on which the parts ofthe feed mechanism are mounted andwhich is fixed to the frame byfour bolts.

Both,motors are controlled by a con-trol panel placed on the log carriage oron a special stand.

It works as follows:

The motor of the feed mechanism drives,with V-belts, a shaft L. Po tapered discs(B and C) are mounted on this shaft. Theinside disc B is fixed on the frame andcannot be moved sideways.

The outside disc C, however, is mounteddirectly on a movable shaft. By movingthe shaft L the position of the outsidedisc C can be changed Ln the longitudinaldirection of the shaft.

Between these two discs runs the wide

V-belt D. The other end of the belt drivespulleys E and F on driven shaft G.

-

Thli

111E1111 IP-a ar

are:

- 33 -

Feeding mechanism m/Variator

The main parts of this feed mechanism

7.5 hp motor A whi ch drives by means of It-belts.

the variable drive consisting of two tapered discs (B and C). These discs transmit the movement through a V-belt D to two other tapered discs (E and F). These latter discs are mounted on a shaft G, which is connected to:

the gear drive H which, in turn, drives the feed rolls I of the frame saw.

the 0.25 hp motor J which changes the feed speed.

the stand K on which the parts of the feed mechanism are mounted and which is fixed to the frame by four bolts.

Both-motors are controlled by a con­trol panel placed on the log carriage or on a special stand.

It works as follows:

The motor of the feed mechanism drives, with V_belts, a shaft L. Two tapered discs (B and C) are mounted on this shaft. The inside disc B is fixed on the frame and cannot be moved sideways.

The outside disc C, however, is mounted directly on a movable shaft. By moving the shaft L the position of the outside disc C can be changed in the longitudinal direction of the shaft.

Between these two discs runs the wide V-belt D. The other end of the belt drives pulleys E and F on driven shaft G.

34

The inner of these discs E is movablealong the shaft. In the longitudinaldirection of the shaft (as seen outwardsfrom the frame) this disc is spring-loadedby a coil spring inside the hub and istherefore always pressed against the out-side disc. Through this the belt isstretched.

The driven axle G is in driving contactwith the lower feed rolls I through a spurgear unit H. The upper feed rolls M aredriven by a chain transmission N from thefeeding mechanism.

The feed speed is varied by changingthe position of the outside disc C inrelation to the inside disc on the shaft.

Through this the belt will run on abigger or smaller diameter between thetwo tapered discs E and F. Since thelength of the belt and the distance betweenthe axles G and L are unchanged, the tapereddiscs E and F on the driven axle will auto-matically adjust themselves to new conditionsby the spring load that acts on the insidedisc.

If the discs B and C are pressed closertogether the belt will run on a biggerdiameter between discs E and F on the drivenshaft. Through this the &riven shaft Gwill rotate faster than the shaft L.

Since it is the driven shaft G thatis connected with the feed rolls

the rotation speed of the feedrolls will increase when the out-side disc C is moved closer tothe inside disc B.

10

20

30

- 40

50

60

70

- 34 -

The inner of these discs E is movable along the shaft. In the longitudinal direction of the shaft (as seen outwards from the frame) this disc is spring-loaded b,y a coil spring inside the hub and is therefore always pressed against the out­side disc. Through this the belt is stretched.

The driven axle G is in driving contaot with the lower feed rolls I through a spur gear unit H. The upper feed rolls M are driven by a chain transmission N from the feeding mechanism.

The feed speed is varied b,y changing the position of the outside disc C in relation to the inside disc on the shaft.

Through this the belt will run on a bigger or smaller diameter between the two tapered discs E and F. Since the length of the belt and the distance between the axles G and L are unchanged, the tapered discs E and F on the driven axle will auto­matically adjust themselves to new conditions by the spring load that aots on the inside disc.

If the discs B and C are pressed closer together the belt will run on a bigger diameter between discs E and F on the driven shaft. Through this the driven shaft G will rotate faster than the shaft L.

Since it is the driven shaft G that is connected with the feed rolls

the rotation speed of the feed rolls will increase when the out­side disc C is moved closer to the inside disc B.

On the other hand, the belt willrun on a smaller diameter if the discs Band C are moved away from each other. Atthe same time, the belt is running on abigger diameter between the tapered disc-s Eand F on the driven aTie.

Since it is the driven axle G that isconnected with the feed rolls

the rotation speed of the feedrolls will decrease when thediscs B and C on the axle shaftare moved away from each other.

In this way the gear ratio between theengine of the feed mechanism and the gearbox can be varied infinitely in the ratioof 1:7. This means that the feeding canbe infinitely varied from 10 to 70 mmistroke.

The adjustment of the feed speed isread on an indicating device placed abovethe feed mechanism.

- 35 -

On the other hand, the belt will run on a smaller diameter if the disos B and C are moved away from each other. At the same time, the belt is running on a bigger diameter between the tapered discs E and F on the driven CL%le.

Sinoe it is the driven ule G that is connected with the feed rolls

the rotation speed of the feed rolls will decrease when the discs B and C on the ule shaft are moved away from each other.

In this way the gear ratio between the engine of the feed meohanism and the gear box oan be varied infinitely in the ratio of 1:7. This means that the feeding can be infinitely varied from 10 to 70 mm/stroke.

The adjustment of the feed speed is read on an indicating devioe placed above the feed mechanism.

.. "II

10 20 30 40 50 60 70

9. Appendix

Bearings

The bearings dealt with in this manual, viz:

- white metal bearings

- needle bearings, and

- spherical roller bearings

are all radial bearings, which means that theymainly take up stress working in the radialdirection.

White metal bearings consist of:

- a bearing housing, made of one piece;

a lining in the shape of a bush ortwo-oup halves;

a lubrication device.

The bearing cups are made of bronze, whichcan stand a high bearing pressure and a highnuMber of revolutions.

They are mounted in the bearing housingwith a round fit. Taps and collars preventthem from turning with the axle

The lining cast into these bearing cupsis made of tint antimony, copper and lead.This composition metal is called white metalor babbit.

To fix the white metal properly on thebearing cup face a few shallow holes aredrilled into the surface, alternatively, itis provided with a few dovetail slots.

Because white metal has a low meltingpoint, any overheating means that only themetal lining is damaged and not the bearing.It is easy to cast a new metal lining.

The movement in a slide bearing is madewhile the shaft journal is sliding against thebearing cups. Friction then occurs but it isvery much reduced by an oil film created betweenthe two bearing surfaces by means of special oil-ways.

When the shaft starts to rotate in thatbearing it brings with it an oil layer that ispressed in under the shaft like a wedge, whiohlifts the ¡shaft from the lower bearing cup. Thefaster the axle rotates, the thicker the oilwedge. Therefore, it is important that bearing"play" is big enough to make it possible forthe oil wedge to grow and lift the shaft.

- 36 -

White metal bearing

'4,,,,

halves'

device

bush

lubricating

bearinghousing

or cup

,..,,.,

oil

It1.1... e, ....-L

_

- cup halves

1

bush

\oil

I

--'''

e' metal

oilwa

- o

1

II whitNs=

dovetailslot

Amil

. ll composi-t ion

$1.

//IF rr'''.-

\"',_:-7.

- ...

MII:Mr

oilfilm

9. Appendix

Bearillgs

- 36 -

The bearings dealt with in this manual, vizl

white metal bearings

needle bearings, and

spherioal roller bearings

are all radial bearings, which means mainly take up stress working in the direction.

White metal bearings consist 01'1

that they radial

a bearing hOUSing, made of one pieoe;

a lining in the shape of a bush or two-oup halves;

a lubrioation devioe.

The bearing cups are made of bronze, whioh oan stand a high bearing pressure and a high number of revolutions.

They are mounted in the bearing housing with a round fit. Taps and collars prevent them from turning with the axle

The lining oast into these bearing cups is made of tin, antimony, copper and lead. This oomposition metal is called white metal or babbit.

To fix the white metal properly on the bearing cup face a few shallow holes are drilled into the surface, alternatively, it is provided with a few dovetail slots •

. Beoause white metal has a low melting point, any overheating means that only the metal lining is damaged and not the bearing. It is easy to cast a new metal lining.

The movement in a dide bearing is made while the shaft journal is sliding against the bearing cups. Friction then ooours but it is very muoh reduoed by an oil film oreated between the two bearing surfaces by means of special 011-wayB.

When the shaft starts to rotate in that bearing it brings with it an oil layer that is pressed in under the shaft like a wedge, whioh lifts the shaft from the lower bearing cup. The faster the axle rotates, the thioker the oil wedge. Therefore, it is important that bearing "play" is big enough to make it possible for the 011 wedge to grow and lift the shaft.

White metal be.arl.ll2

oil

oil

oil

dovetail slot

lubricating device

cup

tion

oilfilm

- 37 -

Roller bearings is the comprehensive termfor cylinder bearings and needle bearings.

These types of bearings conaist of

outer ring

inner ring

rollers, and

holders for the rollers, which keep themapart and in position.

The bearing pressure is absorbed by therollers, positioned between the two rings.Roller bearings offer less rolling resistancethan ordinary bearings and resistance isnearly independent of velocity.

These two types of bearings aleo requireless lubrication and, at the same time, therisk of overheating is smaller. Contraryto white metal bearings, these bearings arelubricated with grease.

The lower connecting rod bearing and thebearings of the orankmhaft pins consist ofspherical double row roller bearings. The

two rows of rollers have a common sphericalroll conveyer in the outer ring, which makesthem selfcontrolling and able to adjustthemselves to the taper of the shaft.

The upper connecting rod bearing con-siste of a type of needle bearing calledgudgeon pin bearing.

The reason for having a needle bearinghere is that this type of bearing is suitablewhen the movements are to and fro, which isthe case for the upper end of the connectingrod. Needle bearings also have good resis-tance against shock loads.

Since the friction in a needle bearingis three times bigger than in a roller bear-ing, it is not suitable for the lowerconnecting rod bearing, where speed andfriction are high.

Instead of rollers the needle bearinghas two rows of needles, each needle being70 mm long and 6 mm in diameter. The

gudgeon pin is holed and serves as a tankfor the lubricant.

Needlebearing

Grease ways

Needles

N.1111.21111My.6

,-:1314401A46.141b14..":\ -,11.1414*.7

' Ili=It Lubrica-ting tank

- 37 -

Roller bearings is the oomprehensive term for oy1inder bearings and needle bearings.

These types of bearings consist ofs

outer ring

inner ring

rollers, and

holders for the rollers, which keep them apart and in position.

The bearing pressure is absorbed by the rollers, positioned between the two rings. Roller bearings offer less rolling resistance than ordinary bearings and resistance is nearly independent of velocity.

These two types of bearings also require less lubrication and, at the same time, the risk of overheating is smaller. Contrary to white metal bearings, these bearings are lubricated with grease.

The lower connecting rod bearing and the bearings of the oraIlkshaft pins consist of spherical double row roller bearings. The two rows of rollers have a common spherioal roll conveyer in the outer ring, which makes them self-oontrolling and able to adjust themselves to the taper of the shaft.

The upper connecting rod bearing con­sists of a type of needle bearing oalled gudgeon pin bearing.

The reason for having a needle bearing here is that this type of bearing is suitable when the lIIOVements are to and fro, whioh is the case for the upper end of the conneoting rod. Needle bearings also have good resis­tance against shook loads.

Since the friction in a needle bearing is three times bigger then in a roller beal'­ing, it is not suitable for the lower conneoting rod bearing, where speed and friction are high.

Instead of rollers the needle bearing has two rows of needles, each needle being 70 II1II long and 6 DID in diameter. The gudgeon pin is holed and serves as a tank for the lubricant.

Spheric roller bearing

Inner

ring

wer connecting rod bearj..ng and . s of the crankshaft pins

Needle bearing

Grease ways

- 38 -

PART II FORCES AND MOVEMENTS

Bodies , Mot ions and Forces 01,00000000000 39

Stress and Strain............................... 43

Primary Stress: Compression o.oeooeeopeetegeoey 44Tension 00000000DOO.0.00000000

45Secondary Stress: Shear 00000000000,7000000900000 46

Torsion OGOOOODOOGOODOCOOO0000 47

Combined Stress: Bending ...................... 48Compression and Bending ...... 51

Static and Dynamic Stress OOOOO ......... 0000000 53

Factors that influence struotural strength ..... 55

Concentrated strains ......... 55Surface cpaality .00000000000 56COTTOSiOn 09000.001,005,0000440 56Heat treatment ...o.n.o....." 57Checks oesoec0000m0000p000gao 58

The Movement Mechanism of the Frame Saw 59

Pierces acting on the sash, the connecting rodand crankshaft journal 00000 ........ ......... 61

The cutting conditions of the Sash ..........o.. 66

Appendix ........... ec000000comeoaag0000000ragoo 67

- 38 -

PART II RlRCES AND IDVEMENTS

~

1. Bodies, Motions and PUrees ••••••••••••••••••••• 39

2. Stress and Strain............................... 43 PriJDar;r Stress,

Seoondar,r StreBs:

Combined Stress.

Compression •••••••••••••••••• Tension ••••••••••••••••••••••

Shear •••••••••••••••••••••••• Torsion ...................... Bending ...................... . Compression and. Bending •..•.•

44

45 46 47 48 51

3. Static and n,n&mio Stress •••••••••••••••••••••• 53

4. Factors that influence struotural strellgth ••••• 55

Conoentrated strains ••••••••• Surface quality ••••• • •••••••• Corrosion ••••••••••••••••••• Heat treatment ••••••••••••••• Cheeks •••••••••••••••••••••••

55 56 56 57 58

5. The Movement Meohanism of the Frame Saw •••••••• 59

6. Force. act ing on the sash, the conneot ing rod and crankshaft journal......................... 61

7. The outt ing oondi t ions of the Sash ••••••••••••• 66

Append1%: ••••••••••••••••••••••••••••••••••••••• 67

1. Bodies, Motions and Diorces

In mechanics a car or the sash of agangsaw is called a body.

- The weight of a body or, morecorrectly, its mass, is givenin kilograms.

A moving body has a certainvelocity which is defined inmetres per second (or minute)or in kilometres per hour.

A change in velocity is called:

Acceleration, if the velocityis increasd, and

Retardation, if the velocityis reduced.

The acceleration or retardation is thechange in velocity (e.g. m/sec) over acertain unit of time (each second). It is,therefore, measured in a unit that ismetres per second, every second; so itconsists of:

a length unit, and

a squared time unit. There isa unit for acceleration called"kuetres per second squarRd",written as m/sec2 or m/S.

- 39 -

Mass

L4,4*.6, -4....,.r .-?At

_...I I

'

Velocity

I 1

,-4 ./ -̂ ' , ..__.)'111111.1 1 I I

*:-. W

Acceleration

= -_,A-T-=T== ===

f----

__,C-7-

,_, A -.A 0.. .. .t ..W.-

--7'.., i

-.:( -_-_0

=-

Ret ardat ion

..

"f\I w I I.

III -

.

... 4. A ''''- 4 .., ,. . If 4WP ,.74 1--;--- A b

. . _'A`VV

- P

- 39 -

1. :Bodies, Mot ions and Forces

In mechanics a car or the sash of a gangsaw is called a body.

The weight of a body or, more correotly, its mass, is given in kilograms.

A moving body has a certain velooity which is defined in metres per second (or minute) or in kilometres per hour.

A change in velocity is called:

Acceleration, if the velooity is increasd, and

Retardation, if the velocity is reduced.

The acceleration or retardation is the change in velocity (e.g. m/sec) over a oertain 1.Dlit of time (each second). It is, therefore, measured in a unit that is metres per seoond, every second; so it consists of:

a length unit, and

a squared time unit. There is a 1.Dlit for acceleration called 'metres per second squar!'!d", written as m/seo2 or m/s2•

J>!ass

Velocity

Accel erat ion

Retardation

To make a body (a mass) accelerateor retard (acoelerate negatively) a forceis needed. The relationship between force,mass and acceleration iss

FORCE . MASS x ACCELERATION

which is written: F.mxa

where: F . the force affectingthe body or the mass;

m . the mass of the body;

a . the acoeleration.

The unit for masa of a body iskilogram (kg).

The unit of force is the Newton.

1 N . the force that gives2a mass of1 kg an acceleration of 1 misec .

The unit for force used to be thepoundal, which was the force required togive an llb mass an acceleration of1 footieec2. This text uses the metricNewton.

Algy force that acts on a body alwayscreates a resisting force inside the body.

A body is reluctant to change itsstate, whether it is at rest or in motion.If it is moving, it is also reluctant tochnnge its direction.

Fbr instance, if the movement of acar or a gangsaw sash is to be changed inspeed or direction, these bodies will tryto maintain their existing velocity ordirection. These resisting and internalforces are called inertia forces. Theyare given in Newtons.

If one tries to change the velocity orthe direction of, for instance, a car or asash, such bodies will resist with forcescalled inertia forces, that are measured inNewtons.

..,

2

LI "

4' =

A cold winter morning the

high force ised to accelerateit from ,stand.stillto motion.

r

Then a higher force id r. guirecr to-bring it to a standstill.

_°_,--. .6llj

- 40 -

To make a body (a mass) acoelerate or retard (acoelerate negatively) a force is needed. The relationship between force, mass and acceleration iSI

FORCE - MASS x ACCELERATION

whioh is writtenl F _ m x a

where 1 F - the force affecting the body or the mass;

m - the mass of the body;

a - the acoeleration.

The unit for mass of a body is kilogram (k€).

The unit of force is the Newton.

1 N - the force that gives2a mass of 1 k€ an acoeleration of 1 m/seo •

The unit for force used to be the poundal, which was the force required to give an lIb mass an acceleration of 1 foot/seo2• This text uses the metric Newton.

Any force that acts on a body always creates a resisting force inside the body.

A body is reluotant to ohange its state, whether it is at rest or in motion. If it is moving, it is also reluctant to change its direction.

For instanoe, if the movement of a car or a gaogsaw sash is to be changed in speed or direction, these bodies trill try to maintain their existing velocity or direotion. These resisting and internal forces are oalled inertia forces. They are given in Newtons.

If one tries to change the velocity or

A cold .,inter morning the car "ill not o • • ~ ()" oJ start. . .

Once it moves, less force is needed keep it . going until one wants to stop

•

.. ' ~ • 0 ' .. .. . ,

~,.. " .... J 1'1 .. '/ .. . ..

o

3

Then a 'bring i"t .l.t;;ll"a

r 15""'-I1ClB'L

the direction of, for instance, a oar or a "'"~:~~::=:::'~~~~~!:'!~~ sash, such bodies will resist with forces ~ ~~

called inertia forces, that are maasured in~----------=~ __ ~==~ __ ~~~~~~~=1 Newtons.

What we have dealt with so far arebodies with inertia forces in linear move-ment: i.e. trying to move straight aheadwith unchanged velocity.

If a body, for instance, a weightattaohed to a rope, is swung in a circleit will, due to inertia forces, try tomove straight ahead, i.e. to move awayfrom the centre. This type of inertiaforce is called centrifugal force.

The magnitude of the centrifugal forcedepends on the mass of the moving body, theradius of the circle and the velocity ofthe body. If the velocity is unchanged,but its weight or the radius of the circleis made two, three or four times bigger,the centrifugal force will also become two,three or four times bigger. On the otherhand, if the velocity (for instance thenumber of revolutions per minute) isdoubled, trebled, etc., the centrifugalforce will increase with the square of thevelocity, i.e. it will become 2 i 2, 3 x 3or 4 x 4 times greater.

This means in practice that, for framesaws, it is the rotational velocity, i.e.the number of revolutions, that has thegreatest influence on the magnitude of thecentrifugal force, If the number of revolu-tions is doubled, the centrifugal force isincreased four times.

- 41 -

What we have dealt with so far are bodies with inertia foroes in linear move­ment: i.e. trying to move strai€ht ahead with unchanged velooity.

If a body, for instence, a wei€ht attached to a rope, is BW1lllg in a circle it will, due to inertia foroes, try to move straight ahead, i.e. to move away from the centre. This type of inertia force is called centrifugal foroe.

The magnitude of the centrif'ugal force depends on the maBS of the moving body, the radius of the oircle and the velocity of the body. If the velocity is unchanged, but its weight or the radius of the circle is made two, three or four times bigger, the centrif'ugal force will also become two, three or four times b~er. On the other hand, if the velocity (for instance the number of revolutions per minute) is doubled, trebled, etc., the centrifUgal force will increase with the square of the velocity, i.e. it will become 2 x 2, 3 x 3 or 4 x 4 times greater.

This means in practice that, for frame saws, it is the rotational velOCity, i.e. the number of revolutions, that has the greatest influence on the magnitude of the centrif'ugal force. If the number of revolu­tions is doubled, the centrifugal force is increased four times.

A car has a weight of 1000 kg. We want to accelerate the car from standstillto a velocity of 72 km/hour in 10 seconds. What magnitude of mass force i-B requiredfor this aooeleration (presuming that the acceleration is uniform)?

The mass . 1000 kg

The velocity = 72 km/h . 20 m/sec.

The acceleration is:

Velocity 20Time = 10 =

The required force is then: F.mxa

F = 1 000 (mass) x 2 (acceleration . 2 000 Newton.

Fbr comparison we can find out what forceis required to accelerate a moving gangsaw sashweighing 345 kg from bottom dead centre whereit is stationary (at 6 o'clock) to maximumvelocity, which at 330 revolutions/Min is equalto 10.3 m/éec and takes place at the 3 o'clockposition.

The acceleration of a sash is not uniformas the acceleration of the car in the aboveexample. This makes OUT calculations some-what more complicated. Without going intodetails of how the calculations are made, themaximum acceleration at the upper turning point(at 12 o'clock) iB 412 m/sec2 (see figure along-side).

The required force is then: 345 (the ma's's)x 412 (the acceleration) = 142 140 Newton.This is the force that is transmitted by theupper crankshaft bear5rg. The magnitude of thisforce oan be compared with the lesser forcerequired in the car example.

2 m/sec2

10

9

Inert ja142 140Newton

=11 '. 14 . 1

. '

,

411111i0''

Accel erat ion of the Sash

mng ...m

'12 11 10 2 1.-emammwKL

12KL

-NEEff-,x7.7_!!_

- 42 -

A car has a wei8ht of 1000 kg. We want to aocelerate the car from standstill to a velocity of 72 Ian/hour in 10 seconds. What magnitude of mass force is required for this acoeleration (presuming that the acceleration is uniform)?

The mass - 1000 kg

The velocity a 72 Ian/h a 20 m/sec.

The acoeleration is:

Velooity _ 20 Time 'iO

The required force is then: F _ m x a

2 2 m/sec

F a 1 000 (mass) X 2 (acceleration a 2 000 Newton.

72 Ian/hour

2000 Newton

For comparison we can find out what foroe is required to accelerate a moving gangsaw sash wei8hing 345 kg from bottom dead centre where it is stationary (at 6 o'clock) to maximum velocity, Which at 330 revoluticns/min is equal to 10.3 m/sec and takes place at the 3 o'clock position.

The acoeleration of a sash is not uniform as the acceleration of the car in the above example. This makes our calculations some­what more complicated. Without going into details of how the calculations are made, the maximum acceleration at the upper turning point (at 12 o'clock) is 412 m/sec2 (see figure nlong­side).

The required force is thenl 345 (the mass) x 412 (the acceleration) - 142 140 Newton. This is the force that is transmitted by the upper crankshaft bearing. The magnitude of this force can be compared w,ith the lesser force required in the car eX!llllpl e.

Standstill

Inertia 142 140

: Newton .

Acceleration of the Sash

2. Stress and Strain

All bodies oonsist of very small particles called molecules. These areattached to eaoh other by certain internal forces in the material itself, so-called cohesive forces.

When a mechanical part is influenced by outside forces it undergoes a changeof form or shape, usually so small that it cannot be seen or measured. Theseoutside forces strive to change the location of the molecules (and so the shape).At the same time the cohesive forces inside the material resist to prevent thesechanges of location.

The external force is called a stress: it is the force on a body exertedover a given area. The internal force resisting the change of shape is calledstrain, and is measured in the same way, a force over a given area.

If the external forces are bigger than the internal ones, a change of formof the material takes place.

If the body recovers its original form completely when the stress is removed,the change of form is called elastic.

Depending on the material of the body and the magnitude of the force, apermanent deformation sometimes occurs. This change of form is then said to beplastic.

If the external forces are even greater, the change of form can go so far thatthe material will break. TIAB is called fracture.

BOTH STRESS AND STRAIN ARE FORCES THAT ACT ON A GIVEN AREA OF THE MATERIAL,i.e. THE RELATIONSHIP F, WHERE F IS THE FORCE THAT ACTS ON THE CROSS SECTION A.

They are measured in Newton/Mm2 or Newton/Cm2.

Note: Strain is a force induced as a reaction to stress: it is independent of thematerial under stress. This is distinct from structural strength, which is:THE ABILITY OF A BODY TO RESIST BREAKAGE OR DEFORMATION (CHANGE OF FORM) CAUSEDBY P_ATERNAL FORCES.

The structural strength properties of a material are usually given as limitsthat result in permanent changes of form or breakage. A given body has differentstructural strength for different kinds of stress, viz0 tension, compression,lending, etc.

There are three main groups of stresses:

Primary stress, i.e. compression andtension.

Secondary stress, i.e. shear, wherethe stress is tangential to the stress(see figure alongside). Twistingstress torsion is an example of shear.

Combined stresses occur when more thanone stress acts at the same time. Thisgroup incorporates bending.

- 43 -

2. Stress and Strain

All bodies oonsist of very small particles called molecules. These are attached to eaoh other by oertain internal foroes in the material itself, so­called oohesive foroes.

When a mechanical part is influenced by outside foroes it undergoes a ohange of form or shape, usually so small that it cannot be seen or measured. These outside foroes strive to change the location of the molecules (and so the shape). At the same time the cohesive foroes inside the material resist to prevent these changes of location.

The external force is called a stress: it is the force on a body exerted over a given area. The internal foroe resisting the change of shape is called strain, and is measured in the same way, a foroe over a given area.

If the erlernal forces are bjgger than the internal ones, a ohange of form of the material takes place.

If the body recovers its original form completely when the stress is removed, the change of form is called elastic.

Depending on the material of the body and the magnitude of the foroe, a permanent deformation sometimes occurs. This change of form is then said to be plastic.

If the erlernal forces are even greater, the change of form can go so far that the material will break. This is called fracture.

roTH STRESS AND STRAIN ARE FORCES THAT ACT ON A GIVEN AREA OF THE MATERIAL, i.e. THE RELATIONSHIP 1:, WHERE F IS THE FORCE THAT ACTS ON THE CROSS SECTION A.

A

They are measured in Newton/mm2

or Newton/om2•

NOte: Strain is a force ~rial under stress. THE ABILITY OF A BODY TO BY EXTERNAL FDRCES.

induced as a reaction to stress: it is independent cf the This is distinct from structural strength, which is: RESIST BREAKAGE OR DEFORMATION ( CHANGE OF FDRM) CAUSED

The structural strength properties of a material are usually given as limits that result in permanent changes of form or breakage. A given body has different structural strength for different kinds of stress, viz. tension, compression, bending, et c •

There are three main groups of stresses:

1. Prime.r,y stress, i.e. compression and tension.

2. Secondary stress, i.e. shear, where the stress is tangential to the stress (see figure alongside). Twisting stress - torsion is an example of shear.

3. Combined stresses oocur when more than one stress acts at the same time. This group incorporates bending.

, SF, - A

1 ~ our£oco of ,',

, ... '"'''' F

2 ~/_ .. _ A ... , - ","

, A. ~:~{l.~ F

Primary stress: Compression

The figure to the right shows a partunder compression.

A compression in any material iscalculated by the following formula:

The compressive forceCompression .

Sectional area of rod

Compression occurs in a saw framein the following places:

In the columns of the sash due tothe tension from the inserted saw-blades.

In the connecting rod when itreduces the downward movement ofthe sash, roughly between 9 and6 o'clock, where compression isgreatest. (See figure andappendix).

In the connecting rod when itaccelerates the sash upwards,roughly between 6 and 3 o'clock.

44

0"

- 44 -

Primary stress: Compression

The figure to the right shows a part under oompression.

A compression in any material is calculated by the following formula:

Com ression _ The ?ompressive force p Sect l.onal a.I:ea of rod

Compression occurs in a saw frame in the following places:

In the columns of the sash due to the tension from the inserted saw­blades.

In the oonnect ing rod when it reduces the downward movement of the sash, roughly between 9 and 6 o'clock, where compression is greatest. (See figure and appendix).

In the oonnecting rod when it aocelerates the sash upwards, roughly between 6 and 3 o'olock.

~ - -

strain 500.000-650.000

" i: ,"

Prima- stress: Tension

The figure to the right shows a partunder tension.

The tension in any material is cal-culated by the following formula:

The stretching forceTension .Sectional area of the rod

Applied to the above example:

1 NewtonT = 1N/cm2

Fbr a saw frame the biggest tensionstress is in the connecting rod:

when the velooity of the sash goingup is being reduced (retarded), whichis ringhly between 3 and 12 o'clockas it heads for the upper dead centre,where the tension in the connectingrod is greatest. (See figure andappendix.)

when the connecting rod pulls thesash downwards, roughly between 12and 9 o'clock.

45- 45 -

Primary stress: Tension

The figure to the r~ht shows a part under tension.

The tension in any material is cal­culated u.r the following formula:

Tension E The stretching force Sectional area of the rod

Applied to the above example:

T 1 Newton - 1 cm2

2 1 N/cm

Fbr a saw frame the biggest tension stress is in the connecting rod:

when the velooity of the sash going up is being reduced (retarded), which is roughly between 3 and 12 o'clock as it heads for the upper dead centre, where the tension in the connecting rod is greatest. (See figure and appendi:z:. )

when the conneoting rod pulls the sash downwards, roughly between 12 and 9 o'olock.

IZJ 1 em

Secondary stress: Shear

The figure to the right shows a partunder shear stress.

These stresses arise when the actingforces occur in the planes of the surfacesconcerned, so that two adjoining surfacesare pressed past each other, as when apair of scissors are cutting.

This is often the case in rivetedjoints. In frame saws shear stressoccurs in the rivets at the base of thesawblades.

Shear stress is calculated by the

formula below:

The shear forceShear 1=

Area of theshearing material

- 46 -

Secondary stressl Shear

The figure to the right shows a part under shear stress.

These stresses arise when the acting forces occur in the planes of the surfaces concerned, so that two adjoining surfaces are pressed past each other, as when a pair of scissors are cutting.

This is often the case in riveted joints. In frame saws shear stress occurs in the rivets at the base of the sawblades.

Shear stress is calculated b,y the fomula belowl

Shear -The shear force

Area of the shearing material

rivet

açcada_a- stress: Torsion

A special form of shear is twistingusually called torsion.

This stress occure when, forinstance, a shaft is subjected to aturning movement, for example, when ascrew or bolt is tightened.

Imagine a shaft consisting of aninfinite number of thin discs.

If such a shaft is turned, allthese discs will turn slightly, whichresults in shear stress between thediscs.

This type of shear is called torsion,The figure shows how torsion increasesfrom the centre of shaft towards theperiphery.

Because of this, shafts can bemade hollow without significantlyreducing torsional strength, yetmarkedly reducine weight.

Torsional strength is proportionalto the cube of the diameter of the shaft.If we double the diameter, the torsionalstrength will increase eight times, whichmeans that we can increase the twistingforce eight times without increasing thestress on the shaft.

47

iii---..1AOMUMORAMVXMONSUIMMNI

1111=11111111111111.1111rifiti

NENNINEN MON"

- 47 -

Secondary stress: Torsion

A special fonn of shear is twisting usually called torsion.

This stress occurs when, for instance, a shaft is subjected to a turning movement, for example, when a screw or bolt is tightened.

Imagine a shaft consisting of an infinite number of thin discs.

If such a shaft is turned, all these discs will turn slightly, which results in shear stress between the discs.

This type of shear is called torsion. The figure shows how torsion increases from the centre of shaft towards the periphery.

Because of thiS, shafts can be made hollow without significantly reducing torsional strength, yet markedly reducing weight,

Torsional strength is proportional to the cube of the diameter of the shaft. If we double the diameter, the torsional strength will increase eight times, which means that we can increase the twisting force eight times without increasing the stress on the shaft.

D=l

G • • D=2

Combined stress: Bending

Bending stresses occur if, forinstance, a bar iB under pressureperpendicular to its centre lineeBending stresses are composed of bothtension and compression.

At the centre line the stress iszero.

Above the centre line there iscompression.

Below the centre line there istension.

To calculate the magnitude of thebending stress is complicated and itis not pursued in this manual.

A practical example, however, canassist our understanding.

It is much easier to bend a ruleras shown in version A in the figure,than as shown in version B.

We can see that the measure H(taken in the same direction as thebending force) is more important tobending resistance than the measure B.

These two factors, i.e.:

the relationship of stressaround the axle beam centre;

the influence of the measure Hon the resistance to bending,

are behind the design of the Isectionbeam, or Igirder.

48- 48 -

.Combined stress: Bending

Bending stresses oocur if, for instanoe, a bar is under pressure perpendicular to its oentre line. Bending stresses are oomposed of both tension and oompression.

At the oentre line the stress is zero.

Above the oentre line there is oompression.

Below the oentre line there is tension.

To oaloulate the magnitude of the bending stress is oomplioated and it is not pursued in this manual.

• I

I I

I

A praotioal example, however, oan?=====================================~ assist our understanding.

It is muoh easier to bend a ruler as shown in version A in the figure, than as shown in version B.

We oan see that the measure H (taken in the same direotion as the bending force) is more important to bending resistanoe than the measure B.

These two faotors, i.e.:

the relationship of stress around the axle beam centre;

the influence of the measure H on the resistance to bending,

are behind the design of the I-secticn beam, or I-girder.

Version A

Version B

B

.------.

When constructing the I-girder theaim is to make the waist-line:

'narrow (measure B) to reduce theamount of material in thosesections where it is not needed(the stress is minimal in thecentre line), and

high (measure H) to concentratethe mass of material as far awayas possible from the beam centre,thereby locating as much materialas possible to sections where themagnitude of tension and corn-pression is strongest.

A given cross sectional area (seefigure) of differing distribution,illustrates in this series of drawingshow the structural strength of girders

can vary. We have obtained a bending

strength in d) more than three timesstronger than the original one in a).

2000

125-1

130

175 75

50

12550

a) breakload

26 000 KG

N7.

breakload

45 000 KG

Weight KG/CM

1,275

150 50

O

250 150

15025

12525

in all alternatives

b) breakload

40 000 KG

IIU

d) breakl.oad

5080 000 KG

- 49 -

When construct ing the I-girder the aim is to make the waist-line:

"narrow (measure B) to reduce the amount of material in those sections where it is not needed (the stress is minimal in the centre line), and

_ high (measure H) to concentrate the mass of material as far away as possible from the beam centre, there~ locating as much material as possible to sections where the magnitude of tension and com­pression is strongest.

A given cross sectional area (see figure) of differing distribution, illustrates in this series of drawings how the structural strength of girders can vary. We have obtained a bending strength in d) more than three times stronger than the original one in a).

2000

:Q: , j

a) brealcload

26000 KG

c) breakload

45000 KG

Weight KG/eM I in all alternatives

1.275

b) breakload

40000 KG

d) breakload

80000 KG

In a saw frame bending stressesoccur in the conecting rod due toinertia that origina-tes when the lowerpart of the connecting rod is foroed tofollow the rotating movements of thecrank shaft journal. These stressesare strongest at the upward stroke at3 o'clock and at the downward stroke at9 o'clock. (See figure and appendix.)

The connecting rod must thereforebe:

as light as possible to reduceinertia.

as strong as possible to resistbending stress.

Fbr these reasons connecting rodsare I-shaped in the cross-beams due tostress from sawblade tension (about70-90 000 N/blade) and also from theinertia of the sash and the connectingrod (about 150-200 000 N).

Fbr the same reasom, applied tothe construction of Ingirders, cross-beamsare made deep (measure H) in order toobtain the greatest bending rigidity.

- 50 -- 50 -

In a saw frame bending stresses occur in the conecting rod due to inertia that originates when the lower part of the connecting rod is foroed to follow the rotating movements of the crank shaft journal. These stresses are strongest at the upward stroke at 3 o'clock and at the downward stroke at 9 o'clock. (See figure and appendix.)

bel The connecting rod must therefore

as light as possible to reduce inertia.

as strong as possible to resist bending stress.

For these reasons connecting rode are I-shaped in the crose-beams due to stress from sawblade tension (about 7~90 000 N/blade) and also from the inertia of the sash and the connecting rod (about 15~200 000 N).

For the same reasons, applied to the construction of I-girders, orose-beams are made deep (measure H) in order to obtain the greatest bending rigidity.

3~

6

Combined stress: Compressionand Bending

Another example of multiple stressesis that which exposes a body to both com-pression and bending strains.

If a bar (for instance, a connectingrod) is long in relation to its cross-section and comes under influence of acompressional strain, the direction ofwhich is not completely in line with thecentre line of the bar, the bar will bow.If the stress is high enough, the barmight finally break.

Strains in a Connecting Rod due to Tension, Compression and Bending

50

30

ÉE 1

5 /2

z I MIN WAIFo

E 1

Beaul

I11Total

60

51

11 10 \ 9

Compr

7 N, 6

:L94»

111,

Iota

NMOAF 111011111

IffillifellIES11111\ MIEN

NM/A

- 51 -

Combined stress: Compressionand Bending

Another example of multiple stresses is that which exposes a bod3 to both pression and bending strains.

If a bar (for instance, a conneoting rod) is long in relation to its cross­section and comes under influenoe of a oompressional strain, the direction of which is not oompletely in line with the oentre line of the bar, the bar will bow. r-------------.::=~-..::::::===~_l If the stress is high enough, the bar might finally break.

F F

F

Strains in a Connecting Rod due to Tension, Compress-ion and Bendil!g

N

E E

~ o "i ~ z

<l

"

3Dr-~ ~ '~ 9 o~ J

2D-'~ .:J 1 '

6 5 4 0

"-1

Bend;"

" " " "', 3

, f.~;

Comp

--t-- /

5

6

I I

/ 3

I 1 / /

II / /

/ ...,. 7 ./ /'

[h"tal

------~, 1,,\ Tota

/'j " Tensi ~ II \

/ 1'\ '\ ......... . Bend .ng / \

II i'" \

1\/ \8 "-1 11 10 \ 9 ] "- 6

/ ,

1\ , , " ,

l ~ mfr ', l~

In a saw frame the greatest risk ofthis stress is in the connecting rod.

The risk of damage occurring isincreased if, at the same time, bendingforces are present in the connecting rod.As previously explained (see also appendix)in certain positions the connecting rodis subject to bending stress.

As can be seen from the figure, themaximum compression occurs at B.D.C.(6 o'clock), and decreases to zero at3 o'clock. Maximum bending occursbetween 3 o'clock and 2 o'clock.

The greatest risk of the combinationis between 5 o'clock and 4 o'clock on theupstroke.(Figure and appendix.)

- 52 -

In a saw frame the greatest risk of this stress is in the connecting rod.

The risk of damage occurring is increased if, at the same time, bending forces are present in the connecting rod. As previously explained (see also appendix) in certain positions the connecting rod is subject to bending stress.

As can be seen from the figure , the maximum compression occurs at B.D.C. (6 o'clook), and decreases to zero at 3 0' clock. Maximum bending oocurs between 3 o'clock and 2 o'clock.

The greatest risk of the oombination is between 5 o'clock and 4 o'clock on the upstroke. (Pigure and appendix. )

Compression Bending

9 39 3

6 6

3. Static and Dynamic Stress,

The force creating stress on a bodycan be of two different kinds, static or

dynamic.

A static force maintains the same

magnitude independent of time. If the

force is increased, breakage willeventually occur. The actual force at

which the material will fracture iscalled the breaking force and it occurs

at breaking point.

A dynamic force is characterised bythe fact that the magnitude of the forcevaries (pulsates) between two extremes,which means that the strains within thebody also vary (pulsate) in the same way.

If a mechanical part comes under the

continuous influence of a force that

pulsates repeatedly, fracture might occur

in spite of the fact that the magnitude

of the force may be conniderably belowthe static breaking point of the parti-cular mechanical part. The pulsatingstress finally strains the mechanicalpast so that it reaches the fatigue limit

of that material.

53- 53 -

3. Static and DynamiC Stress

The force creating strsss on a bod3" can be of two different kinde, static or dynamiO.

A stat ic force maintains the same magnitude independent of time. If the force is increased, breakage will eventually occur. The actual force at which the material will fracture is called the breaking force and it ooours at breaking point.

A dynamic force is charaoterised by the fact that the magnitude of the foroe varies (pulsates) between two extremes, whioh means that the strains within the body also vary (pulsate) in the same way.

If a mechanical part oomes under the continuous influence of a force that pulsates repeatedly, fraoture might occur in spite of the fact that the magnitude of the force may be considerably belotl the static breaking point of the parti­cular mechanical part. The pulsating stress finally strains the meohanioal part so that it reaches the fatigue limit of that material.

Statical Constraint

Breaking C)

Dynamical Constraint

~.7?t

Fatigue limitO r:::>

- 54 -

The fatigue limit of a material isthe maximum static and dynamic stressthat can be put on a material withoutan unlimited number of pulsating stressesmusing breRkage.

The fatigue limit of any material isalways well below its breaking point.

For materials frequently used inmechanies the magnitude of permittedstress es are known and tabulated.

One of the best examples to be foundis the alternating tension/compression inthe connecting rod and the lower cross-beam that is alternatively pushed andpulled.

The design of mechanical componentsunder dynamic stress is always muchheavier than corresponding parts understatic stress only.

This is the reason why the lowercross beam is so heavily dimensioned.

Another example of a component subjectto fatigue is the crankshaft, which, inaddition to torsion, is also under bendingstress occurring each upward and downwardmovement of the sash and the connecting

rod.

Referring back to bending stress,the upper half of the crankshaft is intension and the lower half in compression.(See figure). Bit, as the crankshsftrotates, the part that was in tension willdevelop compression half a turn later.

Fer any given point of the crankshaft

the stresses are constantly alternatingfrom tension to compression: a typioalexample of a component subject to fatigue.

- 54 -

The fati,gue limit of a material is the maximum static and dynamic stress that can be put on a material without an unlimited number of pulsating stresses causing breakage.

The fati.gue limit of F;Y material is always well below its break1ng point.

Fbr materials frequently used in meohanios the magnitude of permitted stresses are known and tabulated.

One of the best examples to be found is the alternating tension/compression in the connectinJ rod and the lower croSll­beam that is alternatively pushed and pulled.

The design of mechanical oompcnents under dynamic stress is always much heavier than corresponding parts under statio stress only.

This is the reason why the lower cross beam is so heavily dimensioned.

Another example of a compcnent subject to fat i,gue is the crallkshaft, which, in addition to torsion, is also under bending stress oocurring each upward and downward movement of the sash and the connecting rod.

Referring back to bending stress, the upper half of the crallkshaft is in tension and the lower half in compression. (See figure). But, as the crankshaft rotates, the part that was in tension will develop oompression half a turn later.

Fbr a:t13 given point of the crankshaft the stresses are constantly alternating from tension to compressions a typioal example of a component subjeot to fati,gue.

4. Factors that influence StructuralMreRgth

There are many different factorsthat influence the structural strengthof a component, particularly againstfatigue.

Some of the most important are:

Concentrated strains

Sharp corners, holes not properlydrilled, different types of nicks, hackand uneven surfaces result in strainslocally concentrated.

These cause abrupt restrictions inthe transmission of force through thecomponent. This leads to stressesgreater than those only due to thereduced sectional area of the nick.

The surface of machine parts underdynamic strain must therefore have allcorners and edgers well rounder, i.e.with large radius. (See figure.)

-55-

4. Factors that in:fluenoe Structurel Strength

There are many di~erent factors that influence the structurel strength of a component, particularly against fatigue.

Some of the most important are:

Concentrated strains

- 55 -

Sharp oorners, holes not properly drilled, different types of nioks, haok and uneven surfaoes result in strains looally ooncentrated.

These cause abrupt restriotions in the transmission of force through the oomponent. This leads to stresses greater than those only due to the reduced seotional area of the niok.

The surfaoe of maohine parts under dynamio strain must therefore have all oorners and edgers well rounder, i.e. with large radius. (See figure.)

Bodies with polished and groundsurfaces demonstrate more resistanceand strength than bodies with rough,uneven surfaces.

Corrosion

Rust and other chemical corrosionreduces structural strength considerably

This is corrected by surfaceconditioning, painting and the use ofrust proof materials.

-56-- 56 -

Surfaoe quality

Bodies with polished and ground surfaces demonstrate more resistance and strength thaJl bodies with rough, uneven surfaces.

Corrosion

Rust and other ohemioal oorrosion reduoes struotural strength oonsiderably

This is correoted by surface oonditioning, painting and the use of rust proof materials .

Heat treatment

A metal part that has been repairedthrough welding unually has a lowerfatigue limit due to:

unfavourable structure ofthe weld material.

builtin heat stress in thematerial, following the welding.

Firstly, (figure a) the weld material Aas well as the surrounding originalmaterial B, are heated up during thewelding procedure above the temperatureat which a structural change takes placein the materials.

In thisifollowed by uncontrolledcooling of A and BI a zone C unuallyresults which is stiffer and more brittlethan the original material B9 whichreduces its fatigue limit (figure b).

In order to retain the structure andimprove the strength of the material inthe weld joint, annealing is practised.This meann that zones A and B are heatedup to 750 850'C (depending on carboncontent) for half to one hour, followedby cooling in normal air. (Electricwelding, however, does not normallyrequire this procedure.)

Secondly, when welding a given part(see figure c) the material heated atpoint C tends: to expand. The rest of thematerial B is still cool and does notexpand, but rather prevents expansion andstrives to press together the material ofthe C zone which is plastic and workabledue to high temperature and thereforecauses bulging (figure d). Expanding andcompressive forces more or less eliminateeach other and the frame remainn rectangularas long as C material is hot.

-57-

An example of how heatstress can occur when amachine foundation iswelded together atroint c.

- 57 -

Heat treatment

A metal part that has been repaired through welding usually has a lower fatigue limit due to:

unfavourable structure of the weld material.

built-in heat stress in the material, following the welding.

Firstly, (ngurea) the weld material A as well as the surrounding original material B, are heated up during the welding procedure above the temperature at which a structural change takes place in the materials.

In this, followed by uncontrolled cooling of A and B, a zone C usually results which is stiffer and UNre brittle than the original material B, which reduces its fatigue limit (figure b).

In order to retain the structure and improve the strength of the material in the weld joint, annealing is practised. This means that zones A and B are heated up to 750 - 850'C (depending on carbon content) for half to one hour, followed by cooling in normal air. (Electric welding, however, does not normally require this procedure.)

Seccndly, when welding a given part (see figure c) the material heated at point C tends to expand. The rest of the material B is still cool and does not expand, but rather prevents expansion and strives to press together the material of the C zone which is plastio and workable due to high temperature and therefore causee bulging (figure d). Expanding and compressive forces more or less eliminate eaoh other and the frame remains rectangular as long as C material is hot.

B A B

\] / 11 I

a

c

d

An exampl e of how heat stress can occur when a machine foundation is welded together at !Oint c.

- 58 -

But then the component cools off, thematerial around C oontracts, whioh resultsin stress and shape change. To eliminatethis, the component must be heated up inone of the following three different ways:

The material at G is heated up toapprolimately the same temperatureas the material at point C. Thiscreates a uniform expansion andoompression.

The whole part is heated up to 5-600°Cduring the welding, which makes thematerial plastic so that stress iseliminated, so-called hot welding.

The whole part is stress-reliefannealed at 5-6000C within a fewhoure after the completion of thewelding.

Nbte: Welding of more complicated partsshould be left to experiencedworkshops.

Checks

As we have seen, the sash is undersignificant stresses and some componentsare more subject to fatigue than others.Tb ensure proper functioning of the framesaw, these vulnerable parts:

the lower cross-beam

the connecting rod

the crank pin

the cranks

must be checked regularly and givenmaintenance.

Incorporate checks into the preventivemaintenance programme

- 58 -

&.t then the coJDpOnent cools off, the material around C contracts, whioh results in stress and shape ohange. To eliminate this, the component must be heated up in one of the following three different Waysl

1. The material at G is heated up to approximately the same temperature as the material at point C. This creates a uniform expansion and oompression.

2. The whole part is heated up to 5-600"C during the welding, whioh makes the material plastio so that stress is eliminated, so-called hot welding.

3. The whole part is stress-relief annealed at 5-600·C within a few hours after the completion of the welding.

lbte: Welding of more complioated parts should be left to experienced workshops.

Cheoks

As we have seen, the sash is under significant stresses and some oomponents are JIlOre subject to fatigue than others. To ensure proper functioning of the frame saw, these vulnerable partsl

the lower crose-beam

the connecting rod

the crank pin

the cranks

must be cheoked regularly and given maintenanoe.

c

" I i ! "' I I I i • I I I

I I I I I I I I I I ' . I I , I

B

Incorporate oheoks into the preventive maintenance progr8Jlllle

5. The Movement Mechanism of the FrameSaw

The oscillating movement mechanismof the frame saw is based on crank motion,i.e. a rotating movement is convertedthrough a connecting rod into a to-and-fro movement.

The figure is an explanatory sketchof the moving parts of a frame saw where:

A . the centre of the crankshaft

B . the centre of the crank pin

C = the centre of the sash pin.

Pbint A rotates at an even speed which isthe number of revolutions of the framesaw, for instance 350 r/min.

Point B will then describe a circle aroundpoint A. This is done at an even speed,as B is directly linked to A.

Point C is given a movement that isidentical to the movement of the sash asit can be regarded as a part of the sash.

At the same time it can be regardedas a part of the upper connecting rodbearing and the distance that it travels .the length of the stroke of the sash .(in our case) 600 mm. As the sash issteered in its guides, the rotating move-ment of A and B is transformed to a move-ment up and down.

- 59 -

Upperturningpoint

Upperguides

Lowerguides

- 59 -

The II'JOvement Meohanism of the Prmne Saw

The osoillating movement meohanism of the frmne saw is based on orank motion, i.e. a rotating movement is oonverted through a oonnecting rod into a to-and­fro movement.

The figure is an explanatory sketoh of the moving parts of a frame saw where:

A c the o entre of the orankshaft

B c the oentre of the orank pin

C - the oentre of the sash pin.

Point A rotates at an even speed whioh is the number of revolutions of the frame saw, for instanoe 350 r/min.

Point B will then desoribe a oircle around point A. This is done at an evan speed, as B is direotly linked to A.

Point C is given a movement that is idantioal to the movemant of the sash as it oan be regarded as a part of the sash.

At the same time it oan be regarded as a part of the upper oonneoting rod bearing and the distanoe that it travels a

the length of the stroke of the sash _ (in our case) 600 I11III. As the sash is steered in its guides, the rotating move­ment of A and B is transformed to a move­ment up and down.

Upper guides

Lo"Ter guides Lower

turning • . -.J_

Upper turning point

'H'H o 0

.<:: Q)

j-g~ Q).p cd ...:lllllll -.-

During the movement of point C thespeed at which it travels and its directionvary.

The figure shows the speed of point C.The horizontal axis has been divided intothe 12 points of the clock face. Thevertical axis shows the speed of C at acertain clock face position of B.

The speed is at its lowest, i.e.0 m/min at:

top dead centre (TDC), i.e. when B isat the 12 o'clock position and at:

bottom dead centre (BDC), i.e. whenB is at the 6 o'clock position.

The speed is at its highest during:

the downward movement when B is atthe 9 o'clock position and during

the upward movement when B is atthe 3 o'clock position.

As the speed of movement of the sashchanges during one revolution of thecrankshaft, this means that the sash isalternatively accelerated and retarded.

The figure shows the acoeleration ofpoint C. It indicates that theacceleration

is greater at the TDC and BDC, orthe turning points, when point Bis at 12 and 6 o'clock positionsand that

acceleration is greater at theupper dead centre (point B at12 o'clock) than at the lowerdead oentre (B at 6 o'clock).

Acceleration of Sash

- 60 -

During the movement of point C the speed at which it travels and its direction vary.

The figure shows the speed of point C. The horizontal axis has been divided into the 12 points of the clock face. The vert ical axis shows the speed of C at a certain clock face position of B.

The speed is at its lowest, i.e. Om/min atl

top dead centre (TOC), i.e. when B is at the 12 o'clock position and at:

bottom dead centre (BDC), i.e. when B is at the 6 o'clock position.

The speed is at its highest during:

the downward movement when B is at the 9 o'clock position and during

the upward movement when B is at the 3 o'clock position.

As the speed of movement of the sash changes during one revolution of the crankshaft, this means that the sash is alternatively accelerated and retarded.

The figure shows the acoeleration of point C. It indicates that the acceleration

is greater at the TDC and BDC, or the turning points, when point B

c--;--

A -T----7'ii B---,->-_,.

Velocity of Sash

is at 12 and 6 o'clock positions Acceleration of Sash and that

acoeleration is greater at the upper dead centre (point B at 12 o'clock) than at the lower dead oentre (B at 6 o'clock).

6. Forces acting on the Sash, theConnecting Rod and the Crankshaftjournal

The sash and the lower cross-beam inparticular are under forces that originatefrom:

the moving parts of the frame saw(sash, sawblades and parts of theconnecting rod), particularly theacceleration and retardation of thesash

- the cutting force at sawing.

With inserted blades an 18" sashweighs around 245 kg, a 26" sash weighs345 kg and a 34" Bash 400 kg.

The upper end of the connecting rodmoves up and down like the sash. There-fore a certain part of the maas of theconnecting rod (around 55 kg) can beadded to the mass that moves upward anddownward.

We have seen earlier that:

Fbrce = Maas x Acceleration.

In this case, the total forces canbe calculated by multiplying theacceleration of the sash at differentpositions by the weight of the sash plusthe weight of the sawblades and thehangers plus 55 kg of the connecting rod.

6. Forces acting on the Sash, the Connecting Rod and the Cl'anksha:f't Journal

- 61 -

The sash and the lower cross-beam in particular are under forces that originate from:

the moving parts of the frame saw (sash, sawblades and parts of the connecting red), particularly the acceleration and retardation of the sash

the cutting force at sawing.

With inserted blades an 18" sash weighs around 245 kg, a 26" sash weighs 345 kg and a 34" ,sash 400 kg.

The upper end of the connect ing red moves up and down like the sash. Ther&-fore a certain part of the mass of the connecting rod (around 55 kg) can be added to the mass that moves upward and downward.

We have seen earlier that:

Force c Mass x Acceleration.

In this case, the total forces can be calculated by multiplying the acceleration of the sash at different positions by the weight of the sash plus the weight of the sawblades and the hangers plus 55 "kg of the connecting rod.

By their weight the fitted sawbladesincrease the forces but they also influencethe sash because of the fitting tensionwhich can be 70,000 N or more for eachblade. A frame saw that holds 9 bladesthus has a fitting tension of 630 000 Nin total. Apart from these forces, thesash is also subject to cutting forcesthat arise from sawing.

These forces, at least the ones thatact at right angles to the sawblades,increase with the square of the feedspeed. The stress on the blades is,strangely enough, greater while return-ing than while sawing.

When sawing a 40 cm cant at a feedspeed of 33 mm stroke, the force thatorigirates from feeding is 2 000 N atreturn sawing just after the turn of thestroke at the BDC.

Under the very same cant size andfeed speed, the force at the cuttingmovement is biggest just before the BDCand reaches 1 400 N/blade.

The connecting rod is subject toforces that consist of:

forces from the upward and down-ward moving parts (sash, bladesand part of the connecting rod).

cutting forces at sawing.

inertia forces.

The first two of these inertiaforces have already been dealt with.Here we discuss the third group ofinfluencing forces.

- 62 -

B.y their weight the fitted sawblades inorease the foroes but they also influenoe the sash because of the fitting tension whioh can be 10,000 N or more for each blade. A frame saw that holds 9 blades thus has a fitting tension of 630 000 N in total. Apart from these forces, the sash is also subjeot to outting forces that arise from sawing.

These foroes, at least the ones that act at right angles to the sawblades, inorease with the square of the feed speed. The stress on the blades is, strangely enough, greater while return­ing than while sawing.

When sawi1'lJ5 a 40 om cant at a feed speed of 33 mm/strcke, the foroe that originates from feeding is 2 000 N at return sawing just after the turn of the stroke at the ROC.

Under the very same oant size and feed speed, the force at the outting movement is biggest just before the ROC and reaches 1 400 N/blade.

The oonneoting rod is subjeot to forces that oonsist of:

foroes from the upward and down­ward moving parts (sash, blades and part of the oonneot ing rod).

outting foroes at sawing.

inertia forces.

The first two of these inertia forces have alrea~ been dealt with. Here we disouss the third group of influenoing forces.

2 000

strain 630.000 NEWTON

6

When the lower end of the connectingrod is rotating it is influenced by forcesof inertia that strive to bend it.

These forces are spread along theconneoting rod but, to make it simple,we can assume that they act from onepoint only,situated one-third down thelength of the connecting rod from thecentre of the crank pin.

The connecting rod is under maximumbending stress at this point. How theinertia forces that act on the connectingrod change their size and direction atdifferent positions of the crank pin isgiven in the figure alongside.

From this figure we can see thatthese forces are zero at the turningpoints (12 and 6 o'clock), while theyreach their greatest at a point situatedroughly where the connecting rod andthe radius of the flywheel form a rightangle, which occurs just before the3 o'clock and just after the 9 o'clockpositions.

As indicated in the appendix, theother stresses on the connecting rod,tension and compression are smallestwhen the bending stress is largest.But on the other hand, tension and com,-pression increase when bending decreasestowards the dead centres.

- 63 -- 63 -

When the lower end of the oonneot ing rod is rotating it is influenoed by" foroes of' inertia that strive to bend it.

These foroes are spread along the oonneoting rod but, to make it simple, we oan aeeume that they act from one point only, situated on_third down the length of the oonneoting rod from the oentre of the orank pin.

The oonneoting rod is under maximum bending stress at this pOint. How the inertia foroes that act on the oonneoting rod ohange their size and direotion at different positions of the orank pin is given in the figure alongside.

From this figure we oan see that these foroes are zero at the turning points (12 and 6 o'olook), while they reach their greatest at a point situated roughly where the oonneoting rod and the radius of the flywheel form a right angle, whioh oocurs just bef'ore the 3 o'olook and just after the 9 o'olook positions.

As indioated in the appendix, the other stresses on the oonneoting rod, tension and oompression are smallest when the bending stress is largest. But on the other hand, tension and 001&­

pression inorease when bending deoreases towards the dead oentres.

9 3 9

6

9

6

Bending strains

Stretching su'aulS

The crankshaft journal is subjectto all these forces, transmitted to thecrank pin through the lower connectingrod bearing. The biggest force actingon the connecting rod bearing occurs atthe upper dead centre, i.e. the 12 o'clockposition.

The whole of this force is not trans-mitted through the crankshaft bearing tothe base plate and the foundation but isreduced through counter balancing of theflywheel.

Flywheels are made with permanentcounterweights placed on the oppositeside of the crankshAft from the crankpin, which shifts the centre of masstowards that side. The distance fromthe centre of mass to the centre ofrotation is thus modified so that allthe rotating mass forces eliminate eachother as much as possible.

As shown in the figures:

Cl is the centrifugal forceof the rotating part of theconnecting rod, the connect-ing rod bearing and the crankpin, while

C2 is the centrifugal forceof the eccentrically placedcounterweights of the twoflywheels.

If these two centrifugal forces(C1 and C2) have the same magnitude,C2 will counterbalance Cl.

When the crank pin is at the 6and 12 o'clock positions, the upwardand downward moving inertia forces ofthe sash and part of the connecting rodalternatively put compression andtension on the lower connecting rodbearing. (Appendix.)

- 64 -

The crankshaft journal is subject to all these forces, tl'8llBmitted to the crank pin through the lower oonnecting rod bearing. The biggest force acting on the connecting rod bearing oocurs at the upper dead oentre, i.e. the 12 o'clook position.

The whole of this force is not trans­mitted through the crankshaft bearing to the base plate and the foundation bIlt is reduoed through oounter balancing of the flywheel.

Flywheels are made with permanent counterweights placed on the opposite side of the crankshaft from the crank pin, which shifts the centre of mass towards that side. The distance from the centre of mass to the centre of rotation is thus modified so that all the rotating mass forces eliminate each other as much as possible.

As shown in the figures:

01 is the centrifugal force of the rotating part of the connecting rod, the connect­ing rod bearing and the crank pin, while

02 is the centrifugal force of the eccentrically placed counterwsights of the two flywheels.

It these two oentrifugal foroes (01 and 02) have the same magnitude, 02 will counterbalance 01.

When the orank pin is at the 6 and 12 o'clock positions, the upward and downward moving inert ia forces of the sash and part of the connecting rod alternatively put compression and tension on the lower connecting rod bearing. (Appendix.)

Ertra Countenle ight

Tension

CompreBsion

These up and downward actinginertia forces can be reduced, however,if the force C2 iB made bigger thanthe force Cl.

Part of the up and downward force Fwhich is transmitted through the connect-ing rod from the sash and the up anddownward moving part of the connectingrod will then be counterbalanced verti-cally. The force F, however, is zeroat the 3 and 9 o'clock positions.

C2 can be increased by melting leadinto specially provided holes in the fly-wheel.

To obtain the best results from thecounterbalance, the size of the leadweight must be tested individually foreach frame saw,

The outofbalance that this createsin the flywheel will cause forces thatdo not counterbalance when the crank tapis in the 3 and 9 o'clock positionswhere F O. This will cause somehorizontal vibration but these are lessthan those that would occur if no balanc-ing was done of the flywheel. The upand downward forces would then createvery strong vertical vibration.

-65-- 65 -

These up and downward acting inertia forces can be reduced, however, if the force 02 is made bigger than the force 01.

Part of the up and downward force F whioh is transmitted through the connect­ing rod from the sash and the up and downward moving part of the connecting rod will then be oounterbalanoed verti­oally. The force F, however, is zero at the 3 and 9 o'clock positions.

02 can be increased by melting lead into specially provided holes in the fly­wheel.

To obtain the best results from the oounterbalance, the size of the lead weight must be tested individually for each frame saw.

The out-of-balance that this creates in the flywheel will cause forces that do not counterbalance ~lhen the crank tap is in the 3 and 9 o'clock positions where F a O. This will cause some

C2 Cl

Cl C2

horizontal vibration but these are less ~::::::::::::::::;:::::::::::::::::::~ than those that would occur if no balanc- r ing was done of the flywheel. The up and downward forces would then create very strong vertical vibration.

/:

Cl.r . \ \ \',\ ,

'\\, \

)~C2 r !.

7. The Cutting Conditions of the Sash

The working stroke (cutting)

The return stroke (free. wheeling)

Direction of feedäo

1 2 4

5 6

Efficient cuttingLess efficieilt cuttingWood crushingReturn sawingFree wheelingMiddle of the strokei.e. where cuttingpotential cannot bemaximized.

- 66 -

7. The Cutting Conditions of the Sash

The working stroke (cutting)

Bi

Bj

~. ~ 1 2 3 4

OD Direction of feed 0

The r eturn stroke (fre.e .. Wb!l!llixlg)

~ 5 6

A. B. c. D. E. F.

Efficient cu ing Less efficient cutting Wood crushing Return sawing Free wheeling Middle of the stroke -i.e. where outting potential cannot be marimiz ed.

Appendix

Tension and Compression

0

I0I

i

0I

I

00

/

i

The forces in the connect ingrod at different positionsduring one turn of flywheel

0

/ .i.

...

0

o o 21I

.

ir11039 lii9 o 03 o

. s

39 0 3

s

(49,

04110_,I

.39 0 i-,

9 0

fi

0

6

3 i 011 i gkiNi6 E.

30° 60* 900 120* 150° 180* 210° 240° 270° 300° 330°

150 000

100000-- -

; 50 000 Tension

e-0

50 000HCompress100 000

150 000

Lending 0 00 I I

00 WI

0 0 I VW

SS .Ilie

I1

1I

Il

iwit1

01oel 0 0

NII IIiII

1 11404, 9 0 1k'I , 9

.

-):I 2 1

11(

0 0

I

0II

99 39 o

SI

1I

III

" I/ 01 39 --0

1

_Tension and Compression

1500 1000

" '500 ~ ,. W 500

10001 1500,

0" 30 •

I I I I '

;-I-Tension ! I + eompressJ 0

I

Bending

:0:

:0:

60' 90 ' 110' 150' I I I I ; i --I I ...- I

I ..-I -- I J

I I , I I

180 ' 110 ' 140' I I ~ I ..........

.......... 1 I

I I I

:o~ :O~

Append1%

The f orces in t he cormeet ing rod at different positions during one turn of flywheel

170 ' 300' 330 ' I I I I I I

I I I I I -,.......,

I I I T

, l.

'" ->

-68-

Tools of Operat Tools of Helper

er withextension

PART III SETTING SAWBLADES IND° FRAME SAW SASH

Removing blades from the sash ..... ....... ....... .......... 70

Setting blades into the sash 009.00DOODOO00000001,0"0000.0010 71

Inserting hangers 00p000000000000.000000000000000000000108 71

Inserting sawblades 000000.00000000000c00000002.00000000Beco 72

Tnrierting blocks 00000m000m000.o0000000s000eopooloom0000d 73

Adjustment of overhang setting Oe0004103O000001,00000o00001110-0 74

Setting right angle of a set of sawblades 75

Plumbing in a set of sawblades ..... ....................... 76

Adjustment of splitters. (Knife guides.) ........... ...... 77

Safety equipment 78

MO.

- 68 -

Tools of Helper

F+renCb

er . ."..--," ~

Hamner

~f with

PART III - SFl'TIOO SAWllLADES INTO FRAME SAW SASH

1. Removing blades from the sash ............................. 2. Setting blades into the sash •••••••••••••••••••••••••••••• 71

Insert i.rJg hal'lg'ers ••••••••••••••••••••••••••••••••••••••.•• 71 Inserting sawblades ••••••••••••••••••••••••••••••••••••••• 72

In.sertizlg blocks ••.•••••••••••••••.•••••••••••••.•••••.•.. 73 Adjustment of overhang setting •••••••••••••••••••••••••••• 74 Setting right angle of a set of sawblades ••••••••••••••••• 15 Plumbing in a set o£ sawblades •••••••••••••••••••••••••••• 76

Adjustment of splitters. (Knife guides.) ••••••••••••••••• 77 Safety equipment •••••••••••••••••••••••••••••••••••••••••• 78

- 69 -

The setting of blades can be divided into two main parts:

Removing blades from the sash.

Setting blades into the sash.

Here the two jobs are described in sequence, as performed by an Operator(usually the sawyer or sawdoctor) and a Helper.

The sash must be securely locked in its upper position. Front upperand lower roll frames must be open. Switch off the current.

OPERATOR

stands in front of the

sash.

HELPER

is on the outfeed sideof the frame elevatedon a board that hasbeen placed between theknife guides to enablehim to loosen the tophanger.

- 69 -

The setting of blades can be divided into two main parts:

Removing blades from the sash.

Setting blades into the sash.

Here the two jobs are described in sequence, as performed by an Operator (usually the sawyer or sawdoctor) and a Helper.

The sash must be securely locked in its upper position. Front upper and lower roll frames must be open. SI-litch off the current.

OPERATOR

stands in front of the sash.

Operator r"'"""~

feeding.~

Helper HELPER

is on the out-feed side of the frame elevated on a board that hae been placed between the knife euides to enable him to loosen the top hanger.

OPERATOR

1. Loosens upper and lowerblock attachments on therighthand side, the upperones just enough for blocksto remain in place.

2. Knocks away right lowersupport block. Thentakesaway other blocksone by one from right toleft, so that the bladesare completely free.

REMOVING BLADES FROM THE SASH

The blades have now been removed from the sash.

HELPER

2. Loosens each hanger inthree steps (otherwisethere is a risk ofbreaking the hanger onthe last blade). Startswith centre blade. Con-tinueson alternatesides with each step.

Step Right order of

---/

each step

53 1 242

1

Knocks away left uppersupport (seen from theHelper's position).Takesaway the blocksone by one from leftto right. Meanwhile,keepsremaining blocksin position by push-ing side of lastblade against them.

Collects two or three 3. Collects the tops ofblades together and pulls two or three bladesthem out of the bottom together (the same ashangers. the Operator) and

pus he the blades outfrom top hangers.

Takes the blades and puts 4. Checks blockn. Discardsthem in the sawdoctor's if damaged. Cleans un-box. broken blocks and puts

them in their respectiveboxes.

OPERATOR

1. Loosens upper and lower blook attachments on the right-hand side, the upper ones just enough for blocks to remain in place.

2. Knocks away right lower support block. Then takes away other blocks one by one from right to left, so that the blades are completely free.

3. Collects two or three blades together and pulls them out of the bottom hangers.

4. Takes the blades and puts them in the sawdoctor's box.

- 70 -

REOOVING BLADES FROM THE SASH

HELPER

2. Loosens each hanger in three steps (otherwise there is a risk of breaking the hanger on the last blade). Starts with centre blade. Con­tinueson alternate sides with each step.

Step 3 ?l 2

"' . .\ 1 . 3- .1

Right order 0

each step

5 3 1 24

ffl~ffl ;:'. Knocks away left upper

support (seen from the Helper's position). Takes away the blocks one by one from left to right. Meanwhile, keeps remaining blocks in position by push­ing side of last blade against them.

3. Collects the tops of two or three blades together (the same as the Operator) and pushes the blades out from top hangers.

4. Checks blocks. Discards if damaged. Cleans un­broken blocks and puts them in their respeotive boxes.

The blades have now been removed from the sash.

OPERADOR

2. Checks hangers and makessure the contact surfacesand the blade hooks arestraight and parallel,the rivet is fixed, theopening between theblades corresponds tothe thickness of theblades and that thereare no indications offractures.

3. Puts the bottom hangersthrough the lower crossbeams from the top down,-wards (with the attach-ments first). Thenturns them one-quarterof a turn to make theattachments come intocontact with the lowerside of the beam andlock into position.

SETTILU BLADES INTO THE SASH

Inserting the hangers

Problems in a Hanger

non,Tarall 1bladerhóókA

IndicationsDf fractUrel

HELF'ER

Cleans the cross beamsfrom sawdust, etc.Brushes carefully, orpreferably uses com-pressed air. If a wear-ing plate is used on topof the upper cross beam,checks that it is inthe right position.

Checks the hangers andmakes sure the contactsurfaces and bladehooks are straight andparallel, the rivet isfixed, the opening bet-ween the blades corres-ponds to the thicknessof blades and that therethere are no indicationsof fractures.

Puts the top hangersthrough the cross beamfrom the top downwards.Then turns them one-quarter of a turn BO

that the hanger wedgesare straight acrossthe beam. Turns theeccentric lever alittle more than half-way down to make iteasier to slip on thespanner.

- 71 -

SEl'TIID BLAllES IN'ro THE SASH

Inserting the hangers

OPERA'roR

2. Checks hangers and makes Problems in a Hanger sure the contact surfaces and the blade hooks are straight and parallel, the rivet is fixed, the opening between the blades corresponds to the thickness of the blades and that there are no indicatione of dications fractures. f fractur~ '~

3. Pute the bottom hangers through the lower cross beams from the top down­wards (with the attach­ments first). Then turns them one-quarter of a turn to make the attachments come into contact with the lower side of the beam and lock into position.

HELPER

1. Cleans the cross beams from sawdust, etc. Brushes carefully, or preferably uses oom­preeeed air. If a wear­ing plate ie used on top of the upper croee beam, checks that it ie in the right position.

2. Checks the hangers and makee eure the contact surfacee and blade hooks are straight and parallel, the rivet is fixed, the opening bet­ween the blades corree­ponds to the thickness of blades and that there there are no indicatwna of fractures.

3. Puts the top hangers through the cross beam from the top downwards. Then turns them one­quarter of a turn so that the hanger wedges are straight across the beam. Turns the ecoentric lever a little more than half­way down to make it eaeier to slip on the spanner.

OPERAR

1. Takes the blades one at atime carrying the blade atthe back with the lefthand and balancing it withthe right hand, holdingthe front at the bottom,(the teeth facing Operator).Passes upper end to theHelper.

2. Inserts the bottom end ofthe blade into the leftbottom hanger. Then con-tinues with the rest ofthe blades.

Insert from left to right. When all the bladesblades (the hangers) sideways to the approximatewhen the blocks are inserted.

3. Adjust the blades in thebottom hangers in thedirection of sawing sothat

the outside bladesare a little for-ward of the centreblades, i.e. theywill cut first.

- the blades areplaced symmetricail.y.

- the whole set ofblades is perpendi-cular to thedirection of sawing.

the fitting tensionwill be correct inthe blades.

Since blades are positioned as abovewidth a rule on positioning ispossible oentre of hangers shouldin figure, or the front of the hanger

- 72 -

Inserting the sawblades

Outer blades Lowerput forward cross

be

samedistance

Feeding

and are often of differentdifficult to state. As far ascoincide with a line as shownbe in line with gullets.

HELPER

1. Takes the blade bygrasping upper endwith the right hand.Holds the hanger withthe left hand.

2. Inserts upper end ofthe blade into thecorresponding tophanger. Adjusts thewedge in the tophanger so that theblade is located inthe hanger. (If theblade is "standing"free it could fallforward onto Operator.)

are inserted, position theposition they will have later

3. Adjust the blades intothe top hangers in thesame way as theOperator does with thebottom.

- 72 -

Inserting the sawblades

OPERA'roR

1. Takes the blades one at a time carr,yillg the blade at the back with the left hand and balancillg it with the r~ht hand, holdillg the :!'rent at the bottom, (the teeth faoillg Operator). Passes upper end to the Helper.

2. Inserts the bottom end of the blade into the left bottom llm1ger. Then con­tinues with the rest of the blades.

HELPER

1. Takes the blade by graspillg upper end with the ri8ht hand. Holds the hallger with the left hand.

2. Inserts upper end of the blade into the corresponding top llm1ger. Adjusts the we<18e in the top hallger so that the blade is located in the hallger. (If the blade is nstanding" tree it oould fall forward onto Operator.)

Insert :!'rem left to r~ht. When all the blades are inserted, position the blades (the hallgers) sideways to the approximate poSition they will have later when the blocks are inserted.

3. Adjust the blades in the bottom hallgers in the direction of sawing 80 tmt

r----------------------, 3. Adjust the blades into

outer blades Lower the top hangers in the Bame way as the Operator does with the bottom.

the outaide blades are a little fo~ ward of the centre blades, i.e. they will cut first.

the blades are ~ same placed symmetriCally.

the whole Bet of blades is perpendi-cular to the direction of sawing.

- the fittillg tension will be correot in the blades.

Since blades are posit ioned as above width a rule on positioning is possible oentre of hallgers should in f~e, or the :!'rent of the hallger

.. distanc Feedillg

and are often of different diffioul t to state. As far as coincide with a line as shown be in line with gullet ••

1. Inserts with the left handthe lower left supportblock (i.e. on that sidewhere the block attachmentEhave not been touched andare therefore at rightangles).

With the right hand pressevthe free blade against theblock so that the bottomhanger is correctly posi-tioned and the block isheld in place.

Continues until all theblades and blocks are in-serted. Finally insertsthe last support block.

2. Tightensthe upper blockattachment a little whenall the blocks are in-serted so that they donot fall out.

At the same time, adjuststhe blocks so that theyare all in a horizontalline together.

Inserting of blocks

1. With the right handinserts the uppersupport block corres-ponding to that ofthe sawyer. Pressesthe blade with theleft hand against theblock to keep it inplace. Taps thewedge with the hammerBO that the blade isstretched a littlethe block is thenfixed and stays inposition by itself.(The top hangers arenow positioned alittle to one side.)Continues like thisuntil all the bladesand blocks are in-serted. Finally,inserts the supportblock.

The last support block is often a bit bigger than the distance allows. If thedifference is small the support block can be tapped down (the Helper drives hisblock upwards). If the difference is big, the block attachment must be un-screwed. Never force the last support block with heavy blows. The supportblock could become deformed and be pressed so hard that later adjustment willbe more difficult.

2. Loosens the eccentricsof the top hanger alittle and adjusts theposition of the tophangers sideways sothat they are directlyin line with the blade.Then completes thefirst step in the ten-sioning of the blades.At this stage alsoadjusts the hangerwedges. Startswiththe outside bladesand works alternatelyfrom left to righttowards the centre.

OPERATOR HELPEROPERATOR

1. Inserts with the left hand the lower left support block (i.e. on that side where the block attaclunentE; have not been touched and are therefore at right angles ).

With the right hand presseE; the free blade against the block so that the bottom hanger is correctly posi­tioned and the block is held in plaoe.

Continues until all the blades and blocks are in­serted. Finally inserts the last support block.

- 73 -

Insertillg of blocks

HELPER

1. With the right hand inserts the upper support block corres­ponding to that of the sawyer. Presses the blade with the left hand against the block to keep it in place. Taps the wedge with the hammer so that the blade is stretched a little -the block is then fixed and stays in position by itself. (The top hangers are now positioned a little to one side.) Continues like this until all the blades and blocks are in­serted. Finally, inserts the support block.

The last support block is often a bit bigger than the distance allows. If the difference is small the support block oan be tapped down (the Helper drives his block upwards). If the difference is big, the blook attachment must be un­sorewed.. Never force the last support block with heavy blows. The support block could become deformed and be pressed so hard that later adjustment will be more difficult.

2. Tightensthe upper block attachment a little when all the blocks are in­serted so that they do not fall out.

At the same time, adjusts the blocks so that they are all in a horizontal line together.

Stet1_ 2 Right order .~ - '~in each step

. -~ 3ffl~ffl

2. Loosens the eccentrics of the top hanger a little and adjusts the position of the top hangers sidevlays so that they are directly in line with the blade. Then completes the first step in the ten­sioning of the blades. At this stage also adjusts the hanger wedges. Star1swith the outside blades and works alternately frcm left to right towards the centre.

OPERATOR

1. Adjusts the right overhangsetting on the overhangsetting board. Holds theboard against one blade ata time, presses againsttooth line and taps withthe hammer at upper end ofblade in the direction ofsawing, so that the rightoverhang setting isobtained.

- 74 -

Adjustment of overhang Bettina

HELPER

If the overhangsetting alreadyadjusted is toosmall, gently tapsout the blade atupper end.

At this stage the blades must not be stretched so much that they risk damageor that the stretching plates of the blades get jolted.

2. Taps top hangerwedges to achievea slight stretch-ing of the blades.

- 74 -

Adjustment of overhang setting

OPERA'roR HELPER

1. Adjusts the right overhang -r------------------, If the overhang setting on the overhang setting already setting board. Holds the adjusted is too board against one blade at small, gently taps a time, presses against out the blade at tooth line and taps with upper end •

.<: the hammer at upper end of blade in the direction of saWing, so that the right overhang setting is obtained.

;,

::l III

.... 0 .,

.!04 2 +> [Q

In£eed

Overhallg I-~

UDirection of sash movement

1/

Ii \;

At this stage the blades must not be stretohed so much that they risk claJuage or that the stretching plates of the blades get jolted.

2. Taps top hanger wedges to achieve a slight stretch­ing of the blades.

OPERATOR

Puts the aligning edge on thebearing pivot of the frame sawstand. Puts the aligning Tsquare on the aligning edge.Checks by moving it againstthe sides of the blades that thethe blades are at right anglesto the edge (i.e. parallelto the T square).

If the set of sawblades is notat right angles, adjusts theangles by tightening the frontand back screws of the blockattachments differentially.Do not use any force whichmight result in a deformationof the blocks without theblades reaching the rightposition. Then it would bedifficult to continue settingtheangles ofthe rest of the blades.

When all the blades are atright angles, tightens theright-hand side block attach-ment but makes sure that thesetting does not changeduring tightening.

4. Checks the angle of the bladesin the same way as in 1 and 2above, when the sash has reachedthe lower position. The adjust-ment is made with the upper lineof blocks.

- 75 -

Setting right angle of a set of sawblades

BELPER

3. Loosens the sashand pushes it tobottom deadcentre.

- 75 -

Setting right angle of a set of sawblades

OPERA'roR

1. Puts the aligning edge on the bearing pivot of the frame saw stand. Puts the aligning T square on the al igning edge. Checks by moving it against the sides of the blades that the the blades are at right angles to the edge (i.e. parallel to the T square).

If the set of sawblades is not at right angles, adjusts the angles by tightening the front and back screws of the block attachments differentially. Do not use ~y force which might result in a deformation of the blocks without the blades reaching the right position. Then it would be difficul t to continue setting ihe r"!..--."'-,------;--,--;--.,-, angles of the rest of t11e blades.

2. When all the blades are at right angles, tightens the right- hand side block attach­ment but makes sure that the setting does not change during tightening.

4. Checks the angle of the blades in the same way as in 1 and 2 above, when the sash has reached the lower position. The adjust­ment is made with the upper line of blocks.

HELPER

3. Loosens the sash and pushes it to bottom dead centre.

1. Holdsthe T squareagainst the aligningedge with one edgeof the square closeto one side of a blade.The set of sawbladeswill be vertical ifthe side of the blade,when making its move-ment up and down, isalways at the same dis-tance from the fixedmeasuring point. Ifthe distance to theside of the blade isnot the same going upas going down, theupper block row mustbe adjusted sideways.Loosens both screwsequally on that sideof the block attach-ment where the setof sawblades needsadjusting and corres-pondingly tightensboth screws at theother block attach-ment. The set ofblades will move inthe right way.

PluMbing in a set of Efawblades

OPERATOR HELPER

..-4-11111

pop

Ordningsfoltdvarje steg

13 5 4

Pushes the frame tomake the sash moveslowly up and down:

Tightens the set ofblades in stages.(Steps 2 and 3). Startswith the outside IflPries

and works alternativelytowards centre.Tightens centre bladelast in every step. Ifsawing does not startuntil following day,delay tightening untilsawing is to start,thus avoiding cross-beams and blades beingunder pressure for anunnecessarily longidme.It is essential thatall blades are equallytightened or load oncross beams will be un-evenly distributed andresult in curved sawing.Checks strain in bladesby pressing each bladehard with hand.

miummmommmillapp.

ill- move-ine

Tighten--1 Loosenboth scr both

OPERATOR

1. Boldsthe T square against the aligning edge with one edge of the square close to one e ide of a blade. The Bet of sawblades will be vertical if the side of the blade, when making its move­ment up and down, is always at the Bame dis­tance from the fixed measuring po int • If the distance to the side of the blade is not the Barne go ing up as going down, the upper block row must be adjusted sideways. Loosens both screws equally on that side of the block attach­ment where the Bet of sawblades needs adjust ing and corres­pondingly tightens both screws at the other bl ock attach­ment. The Bet of blades will move in the right way.

- 76 -

Pl._bill+; in a set of .... wblades

Tighten-. l Loosen both scrf's .both

\~ ~UU u . ~~ l' ... ", 1111 II • ~

.uecliion. move-=

Steg 1 Ordnirgsf61jd .-oi~ I vaqe steg

~3M~M

HELPER

1. Pushes the frame to make the sash move slowly up and down'.

2. Tightens t he set of blades in stages.

(steps 2 and 3). Starts with the outside ~B and works alternatively towards centre. Tightens centre blade last in every step. If sawing does not start until following day, delay tightening until sawing is to start t thus avoiding cross­beams and blades being under pressure for an unneoessarily long time. It is essent ial that all blades are equally tightened or load on oross beams will be un­evenly distributed and result in curved sawing. Checks strain in blades by preSSing each blade hard with hand.

Puts-the aligning edgeagainst inside of one ofthe bladessawing themain yield. (Note: Fbrcant frames put the edgealong the inside of oneof the outside bladesof the cant boards).

Indicatesby signsalreadyagreed upon how Helpermust move ihe splitterso that it bears againstthe inside of the align,ing edge.

4. Repeats this procedurewith the othereplitter.

5. Checks adjustment oncemore, see above.

Adjustment of splitters (knife guides)

Loosens thesplitters andmoves them alittle together.

Moves thesplitter as

directed byOperator sothatit bears against

inside edge ofaligning edge.

Fixes and lockssplitter.

Repeats thisprocedure withthe othersplitter.

OPERATOR HELPER

-77-

Adjustment of splitters (knife guides)

OPERATOR

1. Pu1sthe aligning edge against inside of one of the blades sawing the main yield. (Note: For cant :frames put the edge along the inside of one of the outside blades of the cant boards).

2. Indicatesby signs already agreed upon how Helper IllUSt move "the splitter so that it bears against the inside of the align­ing edge.

4. Repeats this procedure with the othersplitter.

5. Checks adjustment once more, see above .

HELPER

1. Loosene the splitters and moves them a little together.

2. Moves the splitter as directed by Operator so tmt it bears against ins ide edge of aligning edge.

3. Fixes and locks splitter.

4. Repeats this procedure with the other splitter.

A newly sharpened blade is easilydamaged even by gentle nudges and bumps.Contact with other objects can damageboth edges and teeth setting.

To avoid damage, the edge can beprotected by strips of plastic that areplaced over the teeth.

Even more easily damaged are thehands of the Operator, which can be cutwhen blades are handled, especially whenthe Operator is inserting blades, blocksor tightening the block attachments.

By using the plastic strips theOperator is protected during the wholeprocedure, except when the overhangsetting is adjusted. The strips areeasy to put on and take off.

Safety equiEment

- 78 -

Safety equipment

A newly sharpened blade is easily damaged even by gentle nudges and bumps. Contact with other objects can damage beth edges and teeth setting.

To avoid damage, the edge can be proteoted by strips of plastio that are plaoed over the teeth.

Even more easily damaged are the hands of the Operator, which can be cut

, ., I

, .;'

when blades are handled, espeoially whenL-~' ~" ~ ____ ~~~~ __ -L ____________ ~

the Operator is inserting blades, blooks 'r-_ or tightening the block attachments.

By using the plastic strips the Operator is protected during the whole procedure, except when the overhang setting is adjusted. The strips are easy to put on and take off.

II'

-79

ROW TO FEED LOGS INTO A FRA10E SAW

PART IV HOW TO FEEM LOGS INTO A FRAME SAW

122E2

Cant Sawing Principles ..... 0.000..000000000 *0000.0000 ....... O 80

Sawing Symmetrical Logs .... 00000.0.000.000000 OOOOOOOO 00000. 82

sawing Logs with Form Defects ...... ...................... OOOOO o 84

3.1 Crooked Logs ......... ........... .... 00000,000000.000 84

3.1.1 Straight Sawing .................................. 85

3.1.2 Curve Sawing *****000000000000 ................. 000 86

3.1.3 A Comparison of Straight Sawing or Curve Sawing .. 86

3.1.3.1 Straightness 00000009eavey.************* 87

301.302 Positioning of the Pith 0000.00000000000 87

3.1.3.3 Wane eb000**000.00000000"00.00***00 87

3.1.3.4 Practical Performance 0000.m000cac0000po 87

3.2 Logs with Irregular Cross Sections ...........,........... 87

3.3 oval Logs 0000000000000000000000000000000000000.9*****900* 88

Sawing Logs with Bole Defects 00***0.00000.50060.0*****800000*Go 90

Sawing Logs with Heart Shakes s000pcloocapooseep00000.00acoopeoe 91

6. Sawing Loge with Quality Defects ............ 00300000000.00000 91

1.

2.

3.

4.

5· 6.

_ 79 _

HOW TO FEE:D LOGS Im'O A FRANE SAW

PART IV HOW TO FEED LOGS INl'O A FRAME SAW

Cant Sawing Principles .... " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " Sawing Symmetrical Logs ••••••••••••.•••••••••••••••••••••••••••

Sal'ling Logs with Form Defects """,,"""""""""""""""""""""""""""""" 3.1 Crooked Logs " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " "

3.1.1

3.1.2

3.1.3

" " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " Straight Sawing

Curve Sawing " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " A Comparison of Straight Sawing or Curve Sawing ••

3.1.3.1

3.1.3.2

3.1.3.3

3.1.3.4

" " " " " " " " " " " " " " " " " " " " " " " " " " " Straightness

Positioning of the Pith " " " " " " " " " " " " " " " " Wane " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " Practical Performance " " " " " " " " " " " " " " " " " "

Logs with Irregular Cress Sections " " " " " " " " " " " " " " " " " " " " " " "

Ov"al Logs """""""""""""""""""""""""""""""""""""""""""""""" Sawing Logs with Bole Defects " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " Sawing Logs with Heart Shakes " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " " Sawing Logs with Quality Defects ................................

~ 80

82

84

84

85 86

86

87 87 87 87 87 88

90 91 91

-8o-

1. Cant Sawing Principles

The principles of cant sawing consist of two steps (figure 1).

Step I. The log is edged in the log frame, which givesa cant and one or more boards on each side.

Step II. The cant is resawn in the cant frame which gives amain yield of planks, and a number of boards oneach side.

The main yield has now been block sawn, i.e. the sawblades havetouched all four sides and normally can be marketed as they are.

The boards from both steps are further processed in one or more edgers.

- 80 -

1. Cant Sawing Prinoiples

The prinoiples of oant sawing oonsist of two steps (figure 1).

Step I. The log is edged in the log frame, whioh gives a ~ and one or more boards on eaoh side.

Step II. The oant is resawn in the oant frame whioh gives a main yield of planks, and a number of boards on each side.

The main yield has now been blook sawn, i.e. the sawblades have touohed all four sides and normally oan be marketed as they are.

The boards from both steps are further prooessed in one or more edgers.

I

Edgesa~Iing

LOB L-----Blab8s------~

The oant to ~ resawing

V --. I ~ ..•

Fig.l

Planks ~lain yi Id

:II

Resawing

The sawing is usually done in two frames, one log frame saw and one aantframe saw, which operate one after the other.

The sawing, however, can be done in junt one frame that is set upperiodically for edging or resawing. In this case, the cante must be piledup between the two operations.

When processing the logs, the purpose is to achieve:

a good result both as regards quality and quantity.

the highest possible economic yield.

The logs must, therefore, be correctly fed into the frame saw.

The log can be of:

different size and tree species

different form and quality, (see ,figure 3)and must be treated accordingly.

When the log sawyer or cant sawyerhas each log or cant before him, he mustmake an assessment quickly and positionthe log, or the cant, for the sawingprocedure, to ensure the best resultpossible.

Once the sawblades have startedto cut into the log, there is nopossibility of making any adjustment.Such action might very well cause abreakdown. (See figure 2 and 3.1.2Curve Sawing).

Fig.2

Repositioniof log

Centre linof log

'Jammed against the---'steering knives

Wrenched setof blades

'Centre line of'set of blades

Result of trying to move log sidewaysafter sawing has started.

- 81 -

The sawing is usually done in two frames, one log frame saw and one cant frame saw, which operate one after the other.

The sa~ling, however, can be done periodically for edging or resawing. up between the two operations.

in just one frame that is set up In this case, the cants must be piled

lfuen processing the logs, the purpose is to achieve:

a good result beth as regards quality and quantity.

the highest possible economic yield.

The logs must, therefore, be correctly fed into the frame saw.

The log can be of:

different size and tree species

different form and qualit~, (see ~igure 3) and must be treated accordingly.

lfuen the log sawyer or oant sawyer has each log or cant before him, he must make an assessment quickly and position the log, or the cant, for the sawing procedure, to ensure the best result possible.

Once the sawblades have started to cut into the log, there is no possibility of making any adjustment. Such action might very well cause a breakdown. (See figure 2 and 3.1.2 -Curve Sawing).

Fig.2

Repositioni of log

.' "'/

I

', ., o

0,

I';,

,',I" ,I:, ' 1\ , '.

Result of.trying to move log sideways after saW1ng haS started.

Symmetrical log Logs with form defec . Irregularcrosssec

Log with quality defect

1. Crooked log

Fig.3

4. Log wiboleSc

5. Log withheart che

I

2. Sawing Symmetrical Logs (Figure 3)

A symmetrical log

is round and straight without anyform defects;

has quality faults in the form ofknots distributed evenly in numberand size.

Infeed Rule for Symmetrical Logsin Log and Cant Frame:

Centre line of log or the cantshall coincide with centre lineof the set of blades. (Figure 4).

Exception to rule: If, for instance,too small a log for the actualsetting has been included, the sawnsurface of the cant may be too smallfor the main yield-

-82

o

et ofblades

Centreline ofblades

Centre lineof log

Fig.4

Centreline ofcant

Logsawing Cant resawire

- 82 -

SyDllletrical

3. Oval log

Lo~th quality defect

Fig.3

Logsawing 2. Sawing Symmetrical Loge (Figure 3)

A symmetrical log

is round and straight without any fonn defeotsl

has quality faults in the fonn of knots distributed evenly in number and size.

Infeed Rule for Symmetrioal Logs in Log and Cant Frame I

Centre line of log or the oant shall ooinoide with oentre line of the set of blades. (Figure 4).

Exoeption to rulel If, for instanoe, too small a log for the actual setting has been inoluded, the sawn surfa.oe of the oant may be too small for the main yield •.

il C"nicre 1 ine

Fig.4

Cant resaw

Centre line of

Figure 5a shows this case where thesawing procedure has followed the rule,i.e. the centre line of the cant follows_the centre line of the set of blades.Both plankm have got wane.

Figure 5b shows a side movement ofthe cant so that the two centre linesdo not coincide.

This has resulted in one of the two

planks being fully edged. The other

one has got more wane but, due to thenatural taper of the log, not markedly

longer.

One drawback here, however, is that-the full eaged plank has become "-pith-

included". In some species distortion

on drying is often worst in pith,included planks, therefore their value

may be reduced. (See figure 5c)0

Before aligning a straight cantwith a sawn surface which is too small,one should bear in mind that:

in some species the sideways move-

ment (figure 5b) must not become

so big that excessive distortion

or pith cracks: appear when the log

is dried;

alignment following the basic

rule (figure 5a) is recommendedwhen the log is of such a qualitythat knots, decay, blue stain, etc,make wane acceptable.

83- 83 -

Figure 5a shows this oase where the sawing prooedure has followed the rule, i.e. the oentre line of the cant folloWB_ the centre line of the set of blades. Both planks have got wane.

Figure 5b shows a side movement of the cant so that the two centre lines do not coinoide.

This has resulted in one of the two planks being fully edged. The other one has got more wane but, due to the natural taper of the log, not markedly longer.

One drawback here, however, is that· the full edged plank has beoome '~ith­inoluded". In some species distortion on drying is often worst in pith­inoluded planks, therefore their value may be reduced. (See figure 5c).

Before aligning a straight cant with a sawn surface which is too small, one should bear in mind that I

in some species the sideways move­ment (figure 5b) IllUst not become so big that excessive distortion or pith cracks appear when the log is dried;

alignment following the basio rule (figure 5a) is reconmended when the log is of such a quality that knots, decay, blue stain, etc. make wane acceptable.

Wane

Wane

Pith plank Heart checks amddis . l=l.Oll.-~~~..::

\\ ,.,...--_-Cedge

Fig.5 c

3. Sawing Logs with Form Defects

3.1 Crooked Logs

The most common form of crookednessis "sweep" or "long crook". The sweepmay not, according to previous Swedishlog quality standards, exceed 25 mm foreach 1.5 m. A 4.5 m long log couldtherefore have a maximum-even sweep notexceeding 75 mm. (See figure 6).

Infeed Rule for Crooked Log, Log Ftame:

Turn log so that the sweep is ondownward side. (Seen from sidein figure 7a). Then align logso that its centre line coincideswith centre line of the set ofblades. (Seen from above infigure 7b).

The cant from a crooked log sawn inthis way is crooked but the surfaces areevenly sawn. (See figure 8)

Infeed Rule for Crooked Cant, Cant Fi-ame:

Align the cant and saw it sothat main yield just fallswithin sawn surface on insideof the sweep. (See figure 9a).

Gant boards withinsawn surface ofblock

- 84 -

Sawing Logs with Form Defects

3.1 Crooked Logs

The most common form of crookedness is "sweep" or "long crook". The sweep may not, according to previous Swedish log quality standards, exceed 25 IIID for each 1.5 m. A 4.5 m long log could therefore have a maximum ·even sweep not exceeding 75 IIID. (See figure 6).

Infeed Rule for Crooked loS'. Log Frame:

4.5 IIID

I t

''.. .. :; :_'._ .-..... : -.. :,>-~ .. k .. . _>.. ' .• . ".;"0.;"

I 75 mm

Fig.6

b

Turn log so that the sweep is on downward side. (Seen from side in figure 7a). Then al~ log so that its centre line coincides with centre line of the set of blades. (Seen from above in figure 7b).

-b.:~· -_-. :.:. , ~,' , --j I I: 1

The cant from a crooked log sawn in this way is crooked but the surfaces are evenly sawn. (See figure 8)

Infeed Rule for Crooked Cant, Cant Frame:

Align the cant and saw it so that main yield just falls within sawn surface on inside of the sweep. (See figure 9a).

Sa .. cuts

Fig. 7

Fig.8

Cant boards within

Fig.9 a

If one does not follow the rule and saws instead in accordance with figure 9b:

wane will appear in the middle of one of the main planks but

at the same time the amount of wane at the ends of the otherplank will decrease.

If the quality of the log is low because of knots, blue stain, etc., such asawing approach may be recommenf,ed. (See figure 10).

Sawlines

Fig.9b

Normallynot likethis

3.1.1 Straight Sawing

The cant is sawn straight, i.e. itis fed through the frame so that theblades make straight cuts. The align-ment is then made as indicated infigure 11.

The main yield should then fallwithin the sawn surface of the block,at the points A and B, and the middlecut should fall within the sawn surfacein point C.

Fig.10

The rule is that the main yield should fall within the sawn surface in theinner sweep. If this rule is followed, resawing in the cant frame can be donein accordance with either of two principles:

Fig.11

- 85 -

If one does not follow the rule and sa~IS instead in aocordance with figure 9b:

wane will appear in the middle of one of the main planks but

at the same time the amount of wane at the ends of the other plank will decrease.

If the quality of the log is low because of knots, blue stain, etc., such a sawing approach may be recollUJleni',ed. (See figure 10).

Fig.9b Fig.10

The rule is that the main yield should fall within the sawn surface in the inner sweep. If this rule is followed, resawing in the cant frame can be done in accordance ~lith either of two principles:

3.1.1 S"tra i ght Sawil1ff

The cant is sa~m st raight, i . e. it is fed through the frame so that the blades make straight cuts. ~'he align­ment is then made as indicated in figure 11.

The main yield should then fall within the sa~m surface of the block, at the points A and B, and the middle cut should fall 'lithin the sawn surface in point C.

c

Fig. 11

- 86 -

3.1.2 Curve SawinR

The cant is sawn curved, i.e. itis fed so that the saw cuts follow thesweep of the cant as in figure 12.

The possibility of doing this in acant frame is limited depending on:

the distance between the knifeguides and the blades. (Thecloser they are, the greater thepossibility.)

the length of the knife guides;

the distance between the separatingplatee for the main yield.

Position 1 - InfeedBlade A cuts within sawnsurface of cant so mainyield becomes fnay edged.

Direction of cant: lart-tend

of block is moved sidewaysso centre line through topand butt ends is off-linecompared to centre linethrough set of blades.

Sawing offirst half.Butt end ofcant isshifted side-ways so thatblade A foDowsedge of sawnsurface afcant

Fig.13 - Procedure for Curve Sawing

Position 2Blade A now at edgeof sawn cant. Centreline through topardbutt ende of blockis inline butehiftedin comparison withcentre line of setof blades.

Middle section issawn with slightshift of the cant.

Position 3

Sawing of butt endis done without anyshifting of cant.The cuts becomestraight. Sawn sur-face is wider heredue to log taper, sostraight sawingshould not resultin timber with wane.

3.1.3 A Comparison of Straight Sawing or Curve Sawina of cante from logs withsweep is made below.

- 86 -

3.1.2 Curve Sawing

The cant is sawn curved, i.e. it is fed so that the saw cuts follow the sweep of the cant as in figu:re 12.

The possibUity of doing this in a cant frame is limited depending on:

the distance between the knife guides and the blades. (The closer they are, the greater the possibility. )

the length of the knife guides;

the distance between the separating plates for the main yield.

Fig.I) - Procedure for Curve Sawing

Position 1 - Infeed Blade A cuts ~ sawn surface of cant 80 main yield becomes fUlly edged. Direction of cants b,l'tt end of block is moved sideways so centre 1 ine through top and butt ends is off-l ine compared to centre line through set of blades.

Sawing of first half. Butt end of cant is shifted sid~ way!! so that blade A fo11ows edge of sawn surface of cant

Position 2 Blade A now at edge of sawn cant. Centre line through topand butt ende of block is in line but Iilifted in comparison with centre line of set of blades.

Middle section is sawn with slight shift of the cant.

Fig.12

Position 3

Sawing of butt end is done without ~ shift ing of cant. The cuts become straight. Sawn IIlU'­

faoe is wider here due to log taper, so straight sawing should not result in timber with wane.

3.1.3 A Comparison of Straight Sawing or Curve Sawing of cants from logs with sweep is made below.

3.1.3.1 Straightness

Straight sawing results in straight main ydeld.

Curve sawing gives main yield with bow.

The thicker the plank or board, the more important a defect bow becomes.During drying, restraint in a stack will tend to straighten bowed pieces.

3.1.3.2 Pbsitioning of the pith

Straight sawing results in spreadand therefore poor positioning of thepith in the main plahks as it fallsinside both planks, which can lead todistortion and cracks during drying.

Curve sawing can more favourablyposition the pith, which reduces riskof distortion and checks.

3.1.3.3 Wane

Straight sawing usually results inmore wane on one of the main planks.

Curve sawing reduces the wane and,if the sweep is not too great, wane canbe eliminated, resulting in full edgedmain yield,

3.1.3.4 Practical performance

Straight sawing is simpler thancurve sawing. Curve sawing may, there-fore, slow production levels unless thereis special infeed equipment to simplifythe procedure. Whether crooked cantsare straight or curve sawn at the cantframe is up to the individual sawmill.By applying curve sawing, however, it ispossible to increase the sawn timberrecovery.

3.2 Logs with Irregular CrossSections

In figure 15a logs with irregularcross sections are shown, one being oval,the other irregular.

If these logs are positioned in theway that is shown in figure 15b, whereeach is resting against points on theupper and lower rollers that are not ina vertical line, the log will turn duringsawing, resulting in a twisted cant.

lafeed Rule for Log with Irregular CrossSection, Log Frame:

Align log so that contact pointsbetween log and upper and lowerrollers foro vertical line. (Seefigure 150

This gives the log the safest steeringthrough the frame.

87

Oval Cross section

Fig: 15

- 87 -

Straightness

Straight sawing results in Btra~ht main yield.

CUrve saw~ gives main yield with bow.

The thicker the plank or board, the more important a defect bow becomes. Dur~ drying, restraint in a stack will tend to 8tra~hten bowed pieces.

3.1.3.2 Fbsitioning of the pith

Straight sa>1ing results in spread and therefore poor positioning of the pith in the main planks as it falls inside both planks, which can lead to distortion and cracks during drying.

.-- , I Direct ion of po. th IV '-,

Curve sawing can more favourably position the pith, which reduces risk of distortion and checks. I~

\J Heart shra,nks

3.1.3.3 wane

straight sawing usually results in more wane on one of the main planks.

Curve sawing reduces the wane and, if the Bweep is ~ot too great, wane can be eliminated, resulting in full edged main yield.

3.1.3.4 Practical performance

Straight sawing is simpler than curve sawing. Curve sawing may, there-fore, slow production levels unless there is special infeed equipment to simplify the proCedu:r6. rlhether crooked cants are straight or curve sawn at the cant frame is up to the individual sawmill. B,y applying curve sawing, however, it is possible to increase the sawn timber recovery.

3.2 Logs with Irregular Cross Sections

In figure 15« logs with irregular CroBS sections are shown, one be~ oval, the other irregular.

If these logs are positioned in the way that is sho>1D in figure 15b, where each is resting against points on the upper and lower rollers that are not in a vertical line, the log will turn during sawing, resulting in a twisted cant.

rnreed Rule for Log with Irregular eross Section, Log Frame:

Align log so that contact points I between log and upper and lower rollers form vertical line. (See figure 15c)

This gives the log the safest steering through the frame.

f:--~i

-- il , I , , , I<-

~ Fig: 14

!'" "1

Cross sectio

3.3 Oval Logs

When measuring an oval log,different diameters can be recordeddepending on how the measurement isdone. (See figure 16). The logcan therefore be designated fordifferent size classes.

To avoid this, oval logs mustbe measured by cross measurement.In practice, one measurement is madeof the maximum diameter and one of theminimum diameter, following which themean value is calculated and used.

To prevent an oval log from turn-ing during the sawing process, accordingto the infeed rule for logs withirregular cross-sections, it can onlybe positioned resting either on itsflat or high side. (See figure 17).

In figure 18 the top side of anoval log is shown:

positioned on its high side,

positioned on its flat side.

In the figure lines have been drawnthat indicate 125, 150 and 175 mm wideplanks, as well as 50, 63 and 75 mm plankthickness. The intersection between anyof these two lines shows.how the cornerof a cant board will fall in relation tothe top area of the log.

3.3 Oval Logs

When measuring an oval log, different diameters can be recorded depend~ on how the measurement is done. (See figure 16). The log can therefore be designated for different size classes.

To avoid this, oval logs must be measured by cross measurement.

- 88 -

In practice; one measurement is made of the maximum diameter and one of the minimum diameter, following which the mean value is calculated and used.

To prevent an oval log from turn­ing during the sawing process, according to the infeed rule for logs with irregular cross-sections, it can only be positioned resting either on its flat or high side . (See figure 17).

In figure 18 the top side of an oval log is shown:

positioned on its high side,

positioned on its flat side.

In the figure lines have been drawn that indicate 125, 150 'and 175 rom wide planks, as well as 50, 63 and 75 rom plank thickness. The intersection between any of these two lines shows ' how the corner of a cant board will fall in relation to the top area of the log.

Measurement

Flat side (min.measure)

Mean value

High side (max.measure)

F; g: 16

Size Class

B

9

Positioning on higJLside

Positioning on flat side

fi 9: 17

The table in figure 18 indicates:

the different ways to measure logs, and

to which size class the log would have been assigned depending on theresults from these. In addition, we can see:

alternative dimensions for the different size classes and a descriptionof the edge of the main yield.

We can draw the following conclusions from the tablee

Measuring the maximum diameter results in the highest amount of waneno matter how the log is positioned.

Measuring the minimum diameter gives the greatest certainty of fulledged main yield.

Positioning the log on its flat side gives an advantage in one case only,when cutting 50 x 175 mm.

To position the log on its flat side, however, necessitates that the logis straight if any benefit is to be gained.

Fig.18

Alignment on highCant width

side for log frame125 150 175 mm

Fl ank 751thick 63'ness mm 50' met¡ir

89

25

ego

Alignment on flatside for log frame

Plank 75

thick- 63ness mm50

Gant width12 1 0 175 mm

Way ofmeasuring

Sizeclassmm

Alternativedimension

Edge of planks when

Sawing onhigh side

Sawing onflat side

Minimumdiameter

200 75 x 12563 x 150

Pull edgeIt it

full edgeII II

Meandiameter

212.5 50 x 17563 x 163

_

wane,little?I It

full edgewane,little

Maximumdiameter

225

_

63 x 17575 x 150

wane, muchH il

wane,muchu t,

- 89 -

The table in figure 18 indicates:

the different ways to measure logs, and

to which size olass the log would have been assigned depending on the results from these. In addition, we can see:

alternative dimensions for the different size classes and a description of the edge of the main yield.

We can draw the following conclusions from the table:

Measuring the maximum diameter results in the highest amount of wane no matter how the log is positioned.

Measuring the minimum diameter gives the greatest certainty of full edged main yield.

Positioning the log on its flat side gives an advantage in one case only, when cutting 50 x 175 IIID.

To position the log on its flat side, however, necessitates that the log is straight if any benefit is to be gained.

Fig. 18

A~ignment on high Cant width B1de for 1f fr~5 150 175 II1II

Plank 75 t-------".I""'p.'0<H-+--­thick- 63+' -----F~M-__TI1" ness DID 50._' ~ _____ t--Pf\.r\-M_~fiiirlD1 @;g

Way of Size Alternative measuring class dimension

mm

Minimum 200 75 x 125 diameter 63 x 150

Mean 212.5 50 x 175 diameter 63 % 163

Maximum 225 63 x 175 diameter 75 x 150

Alignment on flat side for 10g

1 frame Cant width

12, 1 0 175 III

~-........... Plank 75 ""-thick- 631-----l'-.;:!-+\--

ness mm50~ ____ -+-++1~_

\ ~>~-

Edge of planks when

Sawing on Sawing on high side flat side

:f'ul1 edge :f'ul1 edge " " " "

wane, 1i tt1e :f'ul1 edge " " wane, li1tle

wane, much wane, much " " " "

It is, however, common that ovallogs also have sweep. A softwood treethat grows crooked forms "compressionwood", on the low side of the log,resulting in an oval stem. Figure 19shows how crookedness and ovality occurat the same time in a log. If thecrook is placed downwards, the oval ison its high side.

Infeed Rule for Oval Log, Log Frame:

The log is normally positioned onits high side. In addition,adjust log so that resting pointsbetween rollers and log are in avertical line. (Figure 15.)

4, Sawing Logs with Bole Defects

A bole scar will occur on a standingtree following external damage and sub-sequent healing.

The bole scar usually takes theform of a depression in the log whichcan be so deep that the main yield isaffected.

Infeed Rule for Lo with Bole ScarFrame:

Turn log so that the bole scar is onthe top side. (See figure 20.)

If the log is positioned with thebole scar on the side, both planks canbe affected so that they need cutting.(Figure 21.)

90

Plane of crookHigh side oflqg

- 90 -

It is, however, common that oval loge also have sweep. A soft\food tree that grows crooked forme "compression ~Iood", on the low side of the log, resulting in an oval stem. Figure 19 shows how crookedness and ovaJ.ity occur at the same time in a log. If the crook is placed downwards, the oval is on its high side.

Infeed Rule for Oval Log, Log Frame:

The log is normally positioned on its high side. In addition, adjust log so that resting points between rollers and log are in a vertical line. (Figure 15.)

4. Sawing Logs l~ith Bole Defects

A bole soar \fill occur on a standing tree following external damage and sub­sequent healing.

The bole scar usually takes the form of a depression in the log which can be so deep that the main yield is affected.

Infeed Rule for Log with Bole Scar, Log Frame:

Turn log so that the .bole scar is on the top side. (See figure 20.)

If the log is positioned with the bole scar on the side, both planks can be affected so that they need cutting. (Figure 21.)

High si of log

Sawing Logs with Heart Shakes

Heart shakes occur mostly in largediameter logs. They originate in thestanding tree. As the heartwood getsolder and dries, it may shrink to thestage of checking. If such 1gs arestored in water, the cracks will swellup and disappear, only to widen againwhen the sawn timber is dried.

Infeed Rule for Log with Heart Shakes,Log Frame:

Position the log so that the biggest

Icrack

lies horizontally. (See Fig.22.)

If the log is positioned with theheart shake vertically, it will affectboth planks after resawing. (Fig.23.)

Sawing Logs with Quality Defects

A log with knots distributed evenlyover the surface must be positionedprimarily according to its form.

Very often, however, a log has mostof its knots concentrated on one side.This can be due to the fact that the treehas been growing next to an open space sothat the branches have developed more onthat side. Or the tree might have beencrooked and the branches have developedmore on the opposite side in order toeven out the load distribution.

Tnfeed Rule for Log with most knots onone side, Log Frame:

Turn the log so that the worst sideis upwards, (Figure 24.)

91

The smaller cross section of the knotswill then appear on the face of the planks.If the log is positioned with the worstknots to one side, larger cross sectionknots (or wing knots) will appear on theface of the cant boards, depressingquality more.

The above rules describe the procedure for aligning logs with only one defectat a time. But a log can have many different defects at the same time, so it isnecessary to determine which of these defects will have the greatest influence onthe sawn yield.

Pr.'

\ "-; V7} ///7

Heart shake

i

.,

s

( _-- ;

,,--'

Fi g: 22

Heart shake

. ----...

,--"

_ i , 2,-- e. --

-"--'" ,---,""<.- e.';''I _:) e.

- ' 11

'.-.... _ -_-_-%1

/Fi g: 23

i..otty

upwardssid: eg,

.\ N e knot on

.flat sideo 0 ..I , ' ,#, 0 .. ' O :: i 9 90 .. , -: 4 co 0

o

- ?,-;-- o if,-,-s-).-1 .-;,.,./. 0 ,..,

1 -,-- .-

.1...* ,"-----1--'-

o

o #ei

B.Mr MIY1 Fig: 24

Fi g: 25s\ .'?'.;

,_..:-. 49 , ,,,,,

.I I otty , .

...

,..../

side ,41111.414otsMt/ MO an edges

- 91 -

5. Sawing Logs with Heart Shakes

Heart shakes occur mostly in large diameter logs. They originate in the standing tree . Al3 the heartwood gets older and dries, it ~ shrink to the stage of checking. If' suoh hgs are stored in water, the craoks will swell up and disappear, only to widen again when the sawn timber is dried.

Infeed Rule for Log with Heart Shakes, Log Frame,

Position the log so that the biggest crack lies horizontally. (See Fig.22.)

If the log is positioned with the heart shake vertically, it will affect both planks after resawing . (Fig.23 . )

6. Sawing Logs with Quality Derects

A log with knots distributed evenly over the ~ace must be positioned pr~i1y according to its form.

Ver,y often, however, a log has most of its knots concentrated on one side . This can be due to the fact that the tree has been growing next to an open space BO that the branohes have developed more on that side. Or the tree might have been crooked and the branohes have developed more on the OPPOSite side in order to even out the load distribution .

Infeed Rule for Log with most knots on one side! Log Frame:

Turn the log so that the worst side is upwards, (Figure 24.)

F"i 9: 22

Fleart shake

Fi 9: 23

The smaller cross section of the knots~======================~~============; will then appear on the faoe of the planks . If the log is positioned with the worst knots to one Bide, larger CroSB section knots (or wing knots) will appear on the face of the cant "boards, depressing quality more .

The above rules describe the procedure for aligning logs with only one defect at a time. But a log can have many different defects at the Bame time, so it is necessary to determine which of these defects will have the greatest influenoe on the sawn yield.

PART V - MAINTENANCE

Check-ups Paat

1. DailY 0000000000000000000000000 00000 00 93

20 WeeklY 00000000000500000004000000000000 93

Monthly OOOOOOOO 000000000000000000000 94Every three months 000000000000000000 94Twice a year 0o0000000000000000000000 94Once a year 0000000000006000000000000 94Lower connecting rod bearing 94Upper connecting rod bearing 95

Guide control 95

Control of sash movement 95

Guide cooling system _____0000. 96

In order to achieve an effective production the frame saw has to bemaintained regularly: daily check-ups should be carried out and repairs madeby skilled personnel and with original spare parts.

Detailed maintenance and greasing instructionsmust be provided by each frame saw manufacturer.Below are some more general statements on framesaw maintenance.

There are two kinds of maintenance:

- pre-maintenance, such as greasing, oiling,controls and adjustments.

- minor repairs or services to eliminateprevious disturbances in production.

Pre-maintenance is of the utmost importance in order to reduce the rate ofbreakdown.

- 92 -- 92 -

PART V - MAINTENANCE

Check-ups

1.

2.

3.

4.

5· 6.

7. 8.

9. 10.

11.

Daily ................................ Weekly •••••••••••••••••••••••••••••••

Monthly ............................. Every three months

Twice a year ..................

........................ Once a year ......................... LeMer connecting rod bearing

Upper connecting rod bearing

......... ........

Guide oontrol ....................... ............ Control of sash movement

Guide cooling system ........ " ...... .

93 93

94 94 94 94 94 95 95 95 96

In order to achieve an effective production the frame saw has to be maintained regularly: daily check-ups should be carried out and repairs made by skilled personnel and with original spare parts .

Detailed maintenance and greasing instructions must be provided by each frame saH manufacturer. BeloH are some more general statements on frame saw maintenance.

There are two kinds of maintenance:

pre-maintenance, such as greasing, oiling, controls and adjustments.

minor repairs or services to eliminate previous disturbances in production.

Pre-maintenance is of the utmost importance in order to reduce the rate of breakdown.

- 93 -

Check,-ups

1. Dailz

a) Before starting the machine, check:

the lubricating system, ensuring that grease flowsinto the sash guides.

the water cooling device, fan and pump.

the play between guides and sliding blocks.

that the sawdust evacuation slope is open.

that the roll frames are locked into position.

that the opening between upper and lower roll framesis set according to log dimensions.

that the blade setting is correct.

that greasing has been done following grease instructions.

b) While sawing:

adjust feeding speed according to instructions.

if the speed of the sash is reduced when feedirg logsthrough, infeed has to be stopped and the reasons forthe disturbance found.

if a piece of wood is wedged between blades or betweenblades and sash columns, the frame must be stopped andthe piece removed; ignorance of this might causeaccidents or overheating of blades.

if greasing or cooling of the guides is not satisfactory,a certain smell from the sliding blocks can be noticed;if this happens, the reason has to be found and rectified.Cooling water must not be passed through overheated slidingblocks until they have cooled off.

2. Weekly

The temperature of the lower connecting rod bearing should be measured andregistered.

The cross beams, columns and connecting rod should be cleaned and checkedfor damage. To achieve the best result an electric or pneumatic brush shouldbe used. The connecting rod should be brushed lengthwise. Damages or nickson the cross beams are easier to discover when the blades in the sash aretightened.

Smaller nicks should be grounded down with an emery or a polishing cloth.

- 93 -

Check-ups

a) Before starting the machine, check:

the lubricating system, ensuring that grease flol<s into the sash guides.

the water cooling device, fan and pump.

the play between guides and sliding blocks .

that the sawdust evacuation slope is open.

that the roll frames are locked into position.

that the opening between upper and lOl<er roll frames is set according to log dimensions.

that the blade setting is correct.

that greaSing has been done following grease instructions.

b) While sawing:

adjust feeding speed according to instructions.

if the speed of the sash is reduced when feeding logs through, infeed has to be stopped and the reasons for the disturbance found.

if a piece of wood is ;;edged bet;;een blades or between blades and sash columns, the frame must be stopped and the piece removed; ignorance of this might cause accidents or overheating of blades .

if greasing or cooling of the guides is not satisfactory, a certain smell from the sliding blocks can be noticed; if this happens, the reason has to be found and rectified. Cooling water must not be passed through overheated sliding blocks until they have cooled off.

2. Weekly

The temperature of the lower connecting rod bearing should be measured and registered.

The cross beams, columns and connecting rod should be cleaned and checked for damage. To achieve the best result an electric or pneumatic brush should be used. The connecting rod should be brushed lengthwise. Dameges or nicks on the cross beams are easier to discover 'lhen the blades in the sash are tightened.

Smaller nicks should be grounded dO>ln with an emery or a polishing cloth.

Monthly

Adjust all chains and check for wear and tear.

Check shafts and bearings of the feed rolls.

Check the wear of the sliding blocks.

Check and tighten all bolts, including anchor bolts.

Every Three Months

The lower connecting rod bearings should be washed and cleaned.

Twice a Year

The bearing play of the upper and lower connecting rod bearings shouldbe measured. If it exceeds the recommended limits, the bearing must be replaced.

Once a Year

The frame saw should be thoroughly checked; all worn parts should bereplaced; bolts should be tightened and bearings cleaned.

The connecting rod bearings should be washed.

The guides should be cleaned and checked.

The movement of the sash should be controlled.

The alignment of the frame saw should be checked so that any changes infoundation or base plate may be noted.

Lower Connecting Rod Bearing

This bearing is one of the most important and has to be maintained care-fully. Grease types and working/greasing intervals can be found in the manufacturer's recommendations.

Imurtant to note when greasing:

Before greasing, grease nipples,and the grease pump muzzle should becleaned to avoid dirt getting into the bearing. Greasing should be doneimmediately after the frame has been stopped. The temperature of theconnecting rod and the bearing caps should be checked. Maximum allowedtemperature is 60°C. At least once a week the inside temperature of thebearing should be measured. This temperature and the temperature in thesawmill should be registered. Increased temperature is normally anindication of bearing pollution or of wear and tear. By studying theregistered temperature variations it is possible to maintain or repairdetails before complete breakdown.

Increased temperature can also be caused by faulty mounting of the guidesresulting in abnormal sash movement or vibrations. If the reason for increasedtemperature cannot be detected, the bearing has to be washed and greased severaltimes before the result is satisfactory.

- 94 -

3. Monthly

Adjust all chains and check for wear and tear.

Check shafts and bearings of the feed rolls.

Check the wear of the sliding blocks.

Check and tighten all belts, including anchor belts.

4. Every Three Months

The lower connecting rod bearings should be washed and cleaned.

5. Twice a Year

The bearing play of the upper and lower connecting rod bearings should be measured. If it exceeds the recommended limits, the bearing must be replaced.

6. Once a Year

The frame saw should be thoroughly checked; all worn parts should be replaced; belts should be tightened and bearings cleaned.

The connecting rod bearings should be washed.

The guides should be cleaned and checked.

The movement of the sash should be controlled.

The alignment of the frame saw should be checked so that any changes in foundation or base plate may be noted.

7. Lower Connecting Rod Bearing

This bearing is one of the most important and has to be maintained care­fully. Grease types and working/greasing intervals can be found in the manu­facturer's recommendations.

Important to note when greaSing:

Before greaSing, grease nipples, and the grease pump muzzle should be cleaned to avoid dirt getting into the bearing. Greasing should be done immediately after the frame has been stopped. The temperature of the connecting rod and the bearing caps should be checked. Maximum allowed temperature is 60°C. At least once a week the inside temperature of the bearing should be measured. This temperature and the temperature in the sawmill should De registered. Increased temperature is normally an indication of bearing pollution or of wear and tear. By stu~ing the registered temperature variations it is possible to maintain or repair details oefore complete breakdown.

Increased temperature can also be caused by faulty mounting of the guides resulting in abnormal sash movement or vibrations. If the reason for increased temperature cannot be detected, the bearing has to be washed and greased several times before the result is satisfactory.

Upper Connecting Rod Bearing

The gudgeon pin of this needle bearing should be checked and cleaned oncea year.

The brake should be locked when the sash is in its top position.

The sash should be fixed in its upper position by using a pulley.

The infeed guide bolts should be loosened and the guides pulled back asfar as possible.

The bolts in the crank pin brackets of the lower cross beams should beloosened.

The slots in the pin brackets should be widened to release the pin.

Using the pulley, the sash should be adjusted so that the pin can beremoved.

To prevent the bearing needles from falling out a provisional pin shouldbe inserted when removing the original pin.

Guide Control

The guides should be controled and aligned once a year.

The infeed guides are checked by using a straight edge at least as longas the guide and an insert knife measuring device. If the play exceedsrecommendations, the guide must be exchanged or repaired.

The outfeed guides should be checked using a straight edge long enoughto cover upper and lower guides simultaneously. The checkup should be madehaving the guides mounted in the frame. For maximum play allowed betweenstraight edge and guide, see manufacturer's recommendations.

To align the guides when mounted in the frame, use a plumb line from theupper to the lower guides and compare with allowed deviation. If this controlindicates that the base line of the frame, for any reason, has been changed,correction should be made by adjusting the base plate.

Control of Sash Movement

This should be carried out once a year but also if abnormal vibrationsin the frame are noticed.

There are two ways of controlling this:

Open the caps of the lower connecting rod bearing and measurethe distance between the rollers and the outer ring. The dis-tance should be the same for any position of the sash.

A more accurate result is achieved using two plumb lines andtwo metal sheets with a hole in the centre. See figure below.

- 95 -

8. Upper Conneoting Rod Bearing

The gudgeon pin of this needle bearing should be oheoked and oleaned onoe a year.

The brake should be locked when the sash is in its top position.

The sash should be fixed in its upper position by using a pulley.

~e infeed guide bolts should be loosened and the guides pulled back as far as possible.

The bolts in the crank pin brackets of the lower cross beams should be loosened.

The slots in the pin brackets should be widened to release the pin.

Using the pulley, the sash should be adjusted so that the pin can be removed.

To prevent the bearing needles from falling out a provisional pin should be inserted ~Ihen removing the original pin.

9. Guide Control

The guides should be controled and aligned once a year.

The infeed guides are checked by using a straight edge at least as long as the guide and an insert knife measuring device. If the play exceeds recommendations, the guide must be exchanged or repaired.

The outfeed guides should be checked using a straight edge long enough to cover upper and lower guides simultaneously. The check-up should be made having the guides mounted in the frame. For maximum play allowed between straight edge and guide, see manufacturer's r ecommendations.

To align the guides when mounted in the frame, use a plumb line from the upper to the lower guides and compare with allowed deviation. If this control indicates that the base line of the frame, for any reason, has been ohanged, correction should be made by adjusting the base plate.

10 . Control of Sash Movement

~is should be carried out once a year but also if abnormal vibrations in the frame are noticed.

~lere are two ways of oontrolling this:

1. Open the caps of t he lower connecting rod bearing and measure the distance between t he rollers and the outer ring. The dis­tance should be the same for any position of t he sash.

2. A more accurate result is aohieved using two plumb lines and two metal sheets with a hole in the centre. See figure below.

96

1 Good2-1 Accepted4-6 Correction required

Attach the two metal pieces to the crahk shaft bearinghousing as shown in figure.

Pull the plumb lines through the holes in the metal piecesand attach the line to the lower cross beams of the sashand vertical to the holes. The sash should be in its topposition.

Adjust the metal pieces to centre the plumb line in the hole.

Using a file, mark the position of the plumb lines of thelower cross beam.

Lower the sash to its bottom position and attach the plumblines to their previous position, using the file.marks.

If the movement of the sash is incorrect this can be seenfrom the position of the plumb line in the hole. The figureshows some typical faults of whiCh some can be accepted andsome have to be corrected.

11. Cuide Cooling System

Regular control of the cooling system efficiency it3 recommended. It

is easily carried out by measuring in and outgoing water temperature.Maximum allowed outgoing.temperature is 65°C and maximum alloweddifference between in and outgoing water temperature is 15°C.

- 96 -

Good Accepted

~ I o

1 2-3 4--6 Correction required

- Attach the two metal pieces to the crank: shaft bearing housing as shown in :figure.

Pull the plumb lines through the holes in the metal pieces and attach the line to the lower cross beams o:f the sash and vertical to the holes. The sash should be in its top position.

- Adjust the metal pieces to centre the plumb line in the hole.

Using a :file, mark the position o:f the plumb lines o:f the lower cross beam.

Lower the sash to its bottom position and attach the plumb lines to their previous position, using the :file. marks.

I:f the movement o:f the sash is incorrect this can be seen :from the position o:f the plumb line in the hole. The :figure shows some typical :faults o:f which some can be accepted and some have to be corrected.

11. Guide Cooling System

5

Regular control o:f the cooling system e:f:ficiency is recommended. It is easily carried out by measuring in and outgoing water temperature. Maximum allowed outgoing-temperature is 65°0 and maximum allowed di:f:ference between in and outgOing water temperature is 15°0.

-97-

REVOLUTIONS,

COG NUMBERS

AND PERIPHERAL

SPEED.(FORMULAS AND CALCULATIONS )

PART VI REVOLUTIONS, COG NUMBERS AND PERIPHERAL SFEEDS

2ad2

Introduction 00000000000000000060000110000000000 98

Abbreviations used in text 00000000000000000000000DO 98

How to calculate the number of revolutions of a shaft 99

How to calculate the diameter of a pulley .......... 100

How to calculate the number of teeth required on asprocket DO ******** 00000041.00a00000ODOooDOOD000o0O00. 101

Hbw to calculate the number of revolutions of a shaftwhen power is trannmitted over several intermediateshafts 0000000000000000060"0000000000000000000000et 102

How to calculate peripheral speeds ............... 103

8. Some practical examples 0600000000000000000O00000000 104

- 97 -

R Jl VOL UTI 0 N 5,

COO BUKBERS

AND PERIPHERAL

S PEE D.

(roRlHlLAS AND CALCULATIOIE)

PART VI - REVOLUTIONS, COG NUMBERS AND PERIPHERAL SPEEDS

1. Introduotion ••••••••••••••••••••••••••••••••••••••• 98

2. Abbreviations used in text ••••••••••••••••••••••••• 98

3. How to calculate the number of revolutions of a shaft 99

4. How to calculate the diameter of a pulley •••••••••• 100

5. How to caloulate the number of teeth required on a sprooket ••••••••••••••••••••••••••••••••••••••••••• 101

6. How to calculate the number of revolutions of a shaft when power is transmitted over several intermediate shafts .............................................. 102

7. HOw to calculate peripheral speeds ••••••••••••••••• 103

8. Some praotioal examples •••••••••••••••••••••••••••• 104

1. Introduction

Within the saw milling industry it is often necessary to be able to calculate,for instance:

the number of revolutions of a shaft in order to be able tofit a matching blade or grinding disc.

the required diameter of a pulley to obtain a certain numberof revolutions.

the necessary number of teeth of a driven sprocket, in orderto match it to the desired number of revolutions of, forinstance, driving sprockets.

the peripheral speed of a revolving circular sawblade inorder to determine the correct speed to feed the saw.

This manual uses practical examples to show how answers to these types ofquestions can be obtained.

2. Abbreviations used in Text

Circumference ... 0 0 0

The Constant Pi (= the'number 3,1416) which is used tocalculate the circumference of a circle ...

Metres per second 0 .. 0 0 0 0 m/Sec

Peripheral sreed (Velocity)

Number of cogs or teeth

Number of revolutions (revs

expressed as

- 98 -

000 0 0 0

V

r/Min orr/sec

Diameter ... 0 0 0 0 n 0 0 0 O 0 0 O 0 0

9 0

0 0 0 0 O

- 98 -

1. Introduction

Within the saw milling industry it is often necessary to be able to calculate, for instance I

the number of revolutions of a shaft in order to be able to fit a matching blade or grinding disc.

the required diameter of a pulley to obtain a certain number of revolutions.

the necessary number of teeth of a driven sprocket, in order to match it to the desired number of revolutions of, for instance, driving sprockets.

the peripheral speed of a revolving ciroular sawblade ·in order to determine the correct speed to feed the saw.

This manual uses practical examples to show how answers to these types of questions can be obtained.

2. Abbreviations used in Text

Diameter ... . .. . .. . .. Circumference ... ~~e Constant Pi (= the · number 3.1416) which calculate the circumference of a circle •••

Met res per second ... Peripheral speed (Velocity)

Number of cogs or teeth

Number of revolutions (revs) ••

expressed as

... . ..

. .. · ... d

· .. . c

is used to J1 · ...

. .. m/sec

V

Z

n

rjmin or rlsec

Row to Calculate the number of Revolutions of a Shaft

i) TASK: To find the number of revolutions of the driven shaft Ain the figure below

300 mm 450 mm

ii INITIAL POINTS: We start from what we know:

that the engine B runs at 1440 r/Min.

that the pulley C has a diameter of 300 mm.

that the pulley D has a diameter of 450 mm.

iii) CALCULATIONS: To find out the unknown number of revolutions thefollowing calculations are made:

The number of revolutions of the engine is multipliedby the diameter, in mm, of the pulley of the engine.

In this case it is 1440 x 300.

This figure is divided by the diameter of the drivenpulley, which gives the unknown number of revolutions, i.e.

engine speed x diameter of driving pulley unknown num,diameter of driven piney ber of revs.

In this case the answer is:

1440 x 300. 960 r/Min

= 450

99 -

3. How to Calculate the number of Revolutions of a Shaft

i) TASK: To find the number of revolutions of the driven shaft A in the figure below

300mm

n~ 1440 rj min

ii) TIIITIAL POINTS: Ive start from what we know:

that the engine B runs at 1440 r/min.

that the pulley C has a diameter of 300 Mm.

that the pulley D has a diameter of 450 mm.

450 mm

iii) CALCULATIONS: To find out the unknown number of revolutions the following calculations are made:

The number of revolutions of the engine is multiplied by the diameter, in mm, of the pulley of the engine.

In this case it is 1440 x 300.

This figure is divided by the diameter of the driven pulley, which gives the unknown number of revolutions, i.e.

n ~ engine speed x diameter of driving pulley _ unknown num-

diameter of driven pulley ber of revs.

In this case the answer is:

n 1440 x 300 450

~ 960 r/min

4. How to Calculate the Diameter of a Pulley

i) TASK: To find the suitable diameter of pulley Ain the figure below.

INITIAL POINTS: We start from what we know:

that the driven shaft B has a pulley C,the diameter of which is 400 mm.

- that this shaft needs to rotate at 1200 r/Min.

that the engine D runs at 970 r/Min.

iii) CALCULATIONS: To find the unknown diameter the followingcalculations are made:

- To start with, we calculate the gear ratio between thepulley and the engine. This is done by dividing thenumber of revolutions of the pulley by the number ofrevolutions of the engine, i.e.

number of revolutions of pulley/Min . 1200

number of revolutions of engine/min 970

Then, this ratio is multiplied by the diameter of thedriven pulley C, i.e.

1200d = 757 x 400 = 495 mm.

This result can be rounded off to the higher figure of 500 mmwhich is a standard diameter.

- 100 -

4- How to Calculate the Diameter of a Pulley

i) TASK: To find the suitable diameter of pulley A in the figure below.

n= 970 rjmin 1200 rj min

ii) INITIAL PO INTS: We start from what we know:

that the driven shaft B has a pulley C, the diameter of which is 400 mm.

- that this shaft needs to rotate at 1200 r/min.

that the engine D runs at 970 r/min.

400mm

iii) CALCULATIONS: To find the unknown diameter the follol~ing calculations are made:

To start with, we calculate the gear ratio between the pulley and the engine. This is done by dividing the number of revolutions of the pulley by the number of revolutions of the engine, i.e.

number of revolutions of ulle min c ]1QQ number of revolutions of engine min 970

- Then, this ratio is multiplied by the diameter of the driven pulley C, i.e.

d c 495 nun.

This result can be rounded off to the higher figure of 500 DID

whioh is a standard diameter.

101

5. How to Calculate the Number of Teeth re ired on a S roket

To calculate the gear ratio for chain drives or cog transmission, i.e. therelationship between the number of teeth or cogs of the driving and the drivensprocket, the same procedure can be used as in the previous example. The onlydifference is that instead of using the diameter of a wheel, the number of teethor cogs is used.

i) TASK: To find the necessary nuMber of teeth of the driven sprocket Ain the figure below.

ii) INITIAL POINTS: We start from what we know:

that the conveyer roller B will do 100 r/6in.

that its sprocket has 20 teeth

that the engine C does 60 r/6in.

iii) CALCULATIONS: The following calculations are made according to thegeneral formula:

speed of cog wheel Aspeed of cog wheel B

x the number of teeth of cog wheel B

. the unknown number of teeth of cog wheel A.

Applied to our example:

divide the speed of engine A by the speed of conveyor roller B, and

multiply the result by the number of teeth of the chain wheel By i.e.

...2Egine speed A/Min

conveyor speed B/min x number of teeth of wheel B

. unknown number of teeth of wheel A.

With figures inserted

.10062

x 20 . 12 teeth

- 101 -

5. How to Calculate the Number of Teeth required on a Sproket

To calculate the gear ratio for chain drives or cog transmission, i.e. the relationship between the number of teeth or ooge of the driving and the driven sprocket, the same prooedure can be used as in the previous example. The only difference is that instead of using the diameter of a wheel, the number of teeth or cogs is used.

i) TASK: To find the necessary number of teeth of the driven sprocket A in the figure below.

n=60 r/min

z=1 •

n= 100 r/min z= 20

ii) INITIAL POINTS: We start from what we know:

that the conveyer roller B will do 100 r/min.

that its sprocket has 20 teeth

that the engine C does 60 r/min.

iii) CALCULATIONS: The following calculations are made according to the general formula:

speed of cog wheel A x the number of teeth of cog wheel B speed of cog wheel B

~ the unknown number of teeth of cog wheel A.

Applied to our example:

- divide the speed of engine A by the speed of conveyor roller B, and

- multiply the result blf the number of teeth of the chain wheel B, i.e.

e ine seed A/min conveyor speed B min x number of teeth of wheel B

- unknown number of teeth of wheel A.

With figures inserted

z 60 a 100 X 20 a 12 teeth

- 102 -

6. How to Calculate the number of Revolutions of a Shaft when Power istransmitted over several intermediate Shafts

i) TA: To determine the rotation speed of machine C when power istransmitted through an intermediate shaft B from the drivingwheel A, as illustrated in figure below.

ii) INITIAL POINTS: We start from what we know:

that the speed of the driving wheel A is 600 r/Min.

that the diameter of the driving wheel A is 400 mm.

that the driven wheel of the intermediate shaft B has adiameter of 300 mm.

- that the driving wheel of the intermediate shaft B has adiameter of 600 mm.

that the diameter of the disc of machine C is 300 mm.

iii) CALCULATIONS: To find the unknownfollowing calculations are made:

the number of revolutions of thefirst calculated as follows:

diameter of driving wheel number of revs of driven wheeldiameter of driven wheel - number of revs of driving wheel

Note: Make sure which wheel is driven and which is driving.

With figures inserted

492 number of revolutions of Bn =300 600

the number of revolutions of B600 x 400- 800 r/Min.

300

- the number of revolutions of C can be calculated using the sameformula:

600 number of revolutions of C3oo 800

600 x 800the number of revolutions of C . =

3001600 r/Min

number of revolutions, the

intermediate shaft B is

- 102 -

6. How to Calculate the number of Revolutions of a Shaft when Power is transmitted ovsr several intermediate Shafts

i) TASK: To determine the rotation speed of machine C when power is transmitted through an intermediate shaft B from the driving wheel A, as illustrated in figure below.

d=600mm d=400mm

d=3:X)mm

d =300 mm

ii) JJHTIAL POINTS: He start from what we kncw:

- that the speed of the driving wheel A is 600 r/min.

- that the diameter of the driving wheel A is 400 rom .

- that the driven wheel of the intermediate shaft B has a diameter of 300 rom.

- that the driving wheel of the intermediate shaft B has a diameter of 600 mm.

that the diameter of the disc of machine C is 300 mm.

iii) CALCULATIONS: To find the unknown number of revclutions, the following calculations are made:

the number of revolutions of the intermediate shaft B is first calculated as follows:

diameter of driving wheel c

diameter of driven wheel number of revs of driven wheel number of revs of driving wheel

~: Make sure which wheel is driven and which is driving.

With figures inserted:

number of revolutions of B 600

the number of revolutions of B = 600 x 400 = 800 r Imin. 300 I'

the number of revolutions of C can be calculated using the same :fonnula:

n 600 = - = 300

number of revolutions of C 800 600 x 800 !. the number of revolutions of C c 300 c 1600 rlmin

7-

103

How to Calculate Peri heral S eeds

Peripheral speed (henceforth marked with the letter V) is the speed of animagined rotating point situated on the circumference of the rotating shaft. It

is usually expressed as metres per second (m/sec).

i) TASK: To find the peripheral speed (V) of the toothpoints of a circular sawblade. (See figure below).

ii) INITIAL POINTS: We start from what we know:

that the diameter of the sawblade is 1200 mm.

that the sawblade does 900 r/Min.

iii) CALCULATIONS: To find the unknown peripheral speed, thefollowing general formula is used:

The circumference of the sawblade (c) (in metres) is multipliedby the number of revolutions of the sawblade (in r/sec).

Using the formula for the circumference of a circle (c =n- xd)we calculate the circumference of the sawblade:

=11rx 1.2 = 3.14 x 1.2 m = 3.77 m.

The circumference, c, is then multiplied by the number ofrevolutions per second of the sawblade, i.e.

= 3.77 x 900 r/Min . 3.77 x0 r/sec 57 m/sec.6

revs/minute N

(Note revs/second =60

- 103 -

7. How to Calculate Peripheral Speeds

Peripheral speed (henceforth marked with the letter V) is the speed of an imagined rotating point situated on the circumference of the rotating shaft. It is usually expressed as metres per second (m/sec).

i) TASK: To find the peripheral speed (V) of the tooth points of a circular sawb1ade. (See figure below).

d=1200mm

ii) INITIAL POINTS: We start from ~lhat we know:

that the diameter of the sawb1ade is 1200 mm.

that the sawblade does 900 r/min.

iii) CALCULATIONS: To find the unknown peripheral speed, the following general formula is used:

The circumference of the sawb1ade (c) (in metres) is multiplied by the number of revolutions of the sawblade (in r/sec).

Using the formula for the circumference of a circle (c =~ x d), we calculate the circumference of the sawblade:

c =JTx 1.2 ' = 3.14 x 1.2 m = 3.77 m.

The circumference, c, is then multiplied b,y the number of revolutions per second of the sa~lblade, i.e.

V = 3.77 x 900 r/min = 3.77 x 9~ r/sec = 57 m/sec.

(Note revs/second = revs£~inute )

104

8. Some Practical Examples

A. How to calculate the maximum number of revolutions of a grinding disc.

i) TASK: To install a new grinding disc in a grinder mountedon a circular saw we need to know the maximum numberof revolutions of a disc of a given diameter. (See

figure below.)

ii INTTIAL PACTS: We start from what we know:

that when grinding freehand with a ceramic disc, as in thiscase, a maximum peripheral speed of 28 m/sec is allowed.

that the diameter of the disc is 305 mm.

iii) CALCULATIONS: The unknown number of revolutions (n) can becalculated from the formula:

number of revolutions (rjmin)peripheral speed V . circumference c x

60

In this example V . 28 m/sec

c 51. x diameter of disc . 3.14 x 0.305 = 0.96 m

Inserted into the above formula we find:

28 x 60n = 0.9d-- . 1750 r/min.

- 104 -

8. Some Practical Examples

A. How to calculate the maximum number of revolutions of a grinding disc.

i) TASK I To install a new grinding disc in a grinder mounted on a circular saw we need to know the maximum number of revolutions of a disc of a given diameter. (See figure below.)

ii)

d=305mm

V=max

INITIAL POINTS: \,e start from what we knoWI

that when grinding free-hand with a ceramic disc, as in this case, a maximum peripheral speed of 28 m/sec is allowed.

that the diameter of the disc is 305 mm.

iii) CALCULAT IONS I The unknown number of revolutions (n) can be calculated from the formula I

number of revolutions (r/min) peripheral speed V c circumference c x 60 - -

In this example V D 28 m/sec

c a:rr x diameter of disc a 3.14 X 0.305 a 0.96 m

Inserted into the above formula we find:

n -28 x 60

0.96 1750 r/min.

-105

B. How to calculate the necessary number of teeth of a sprocket.

i) TASK: To calculate the required number of teeth on the sprocketof motor A (in figure below) to make the roll conveyer workat a desired speed.

n = 90 r/rninZE3= toeth

INITIAL POINTS: We start from what we know:

that the required speed of the roll conveyer is about 75 m/Min.

that the sprocket on motor A does 90 r/Min.that the driven sprocket B has 20 teeth (ZB) and diameter of 175 mm.

CALCULATIONS: This problem is solved by using the formula

number of revolutions of sprocket A2:number afteeth of sprocket B =

number of revolutions of sprocket B

. the unknown number of teeth of sprocket A.

To be able to use this formula we must first calculate the number ofrevolutions of sprocket B.

We know that the peripheral speed of B must correspond to the desiredperipheral speed of the roll conveyer, i.e. 75 m/Min. By using the formulabelow we can therefore calculate the number of revolutions of B:

Peripheral speed )Ir x diameter x nuMber of revolutions.

With figures inserted:

75 =iT x x n

n 21..E.1222175 = 136 r/Mino (Note: 175mm = lilt m)

We can now calculate the necessary nuMber of teeth of drivingsprocket A by using the first formula:

Unknown number of teeth (ZA) is

zA.4x 20 = 13.25 . 13 teeth (rounded off to nearest13

whole number)

By checking this example for ZA = 13 teeth we find that roll conveyor

willwork a little faster than 75 m/Min.

- 105 -

B. How to calculate the necessary number of teeth of a sprocket.

i)

ii)

iii)

TASK: To calculate the required number of teeth on the sprocket of motor A (in figure below) to make the roll conveyer work at a desired speed.

INITIAL POINI'S:

- that the required

- that the sprocket

d =175mm 75m/ m in --

n=90 r / min

'E-7 tooth •

d=175mm

We start from what we know:

speed of the roll conveyer

on motor A does 90 r/min.

- that the driven sprocket B has 20 teeth (~)

is about 75 m/min.

and diameter of 175 mm.

CALCULATIONS: This problem is solved Qy using the formula

numoer of revolut~ons of sprocket A x number of teeth of sprocket B = number of revolut10ns of sprocket B

~ the unknown number of teeth of sprocket A.

To be able to use this formula we must first calculate the number of revolutions of sprocket B.

We know that the peripheral speed of B must correspond to the desired peripheral speed of the roll conveyer, i.e. 75 m/min. By usiDg the formula below we can therefore calculate the number of revolutions of B:

Peripheral speed JT x diameter x number of revolutions.

With figures inserted:

75 a JT X .ill x n 1000

n a 75 X 1000 ~ 136 r/min. (Notel 175= ~ 1000175 m) JT x 175

We can now calculate the necessary number of teeth of driving sprocket A Qy using the first formula:

Unknown number of teeth (ZA) is

a 13 teeth (rounded off to nearest whole number)

By checking this example fcr ZA - 13 teeth we find that roll conveyor will work a little faster than 75 m/mm.