Frame Saw Manual 1902

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AT MICROFlCHEREFERENCELIBRARYA project of Volunteers in AsiaBy: FAO Forestry Paper

Published by: Food and Agriculture Organization of the United NationsPublications DivisionVia della Terme di Caracaiia00100 HomeITALY

Available from: Food and Agriculture Organization of the United NationsPublications DivisionVia deiie Terme di Caracalia00100 RomeITALY

Reproduced with permission.Reproduction of this microfiche document in any form is subject to the samerestrictions as those of the original document.


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FAO FORESTRY PAPER

fao/sida sa

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSRome 1982


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

M-30ISBN 92-5-l 01248-2All rights reserved. No part of this publication may be reproduced ,stored in a retrieval system, or transmitted in any form or by any means,electronic, mechanical, photocopy ing or otherwise, without th 3 priorpermiss ion of the copyright owner. Applications for such perr,lission,with a statement of the purpose and extent of the reproduction, shouldbe addressed to the Director, Publications Division, Food and Agricultu reOrganization of the United Nations, Via delle Terme di Caracalla, 00100Rome, Italy.

0 FAO 1982


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IRTRODUCTION

This manual deals with the construction and operatingprinoiples of the frame saw. Many different kindsand makes of frame saws are in use. A very oomontype of Swedish origin, originally made in 1946, hasbeen chosen as the example in this manual. Today'smodern frame saw has the same basic funotion, althoughcapacity, infeed and sawing acouracy is increased.Where frsme 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 Employers&deration of Smdish Ihhatries, who povided theoriginal material.

coNTEms

1. Construction aud operating principles ...... 22. Forces and movements ....................... 383. Setting sawblades into frame saw sash ....... 684. Row to feed logs into a frame saw .......... 795. Main-t enance ................................ 926. Revolutions, cog numbers and peripheral speeds 97


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PART1 - CO~~IO~ARDOpERAT~F'R'IRCI[pLw&!!iE

1. Foundation with base plate ................... 32. Crank section ................................ 73. Bottom frame ................................. 144. Upper frame .................................. 155. Guide system ................................. 166. Sash ......................................... 197. Roll frame and feed rolls .................... 248. Feeding mechanism ............................ 31

Appendix ..................................... 36


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1. Foundation with Base mateThe eaw freme must be built on aetrong foundation of reinforced concreteof about60-80 m3. Sometimes, however,

up to ~100 m3 is necessary to get aetrong enough base for the eaw frame whenground conditions are bad.The foundation should be Bornewhatlonger in the longitudinal direction ofthe 8aw mill than in the transversedirection, since the prinoipal directionof motion of the moving part8 of the framecoinoides with the direction of sawing.Accurate drawings shouldbe supplied bythe manufaoturer.The ftanction of the foundation is:

The foundation must therefore beerected on eolid mund. If there ia nosuch ground available, pile driving mustbe done.At the same time, the foundationsmust not be directly on solid rock, which

can carry vibrations to adjoining areassome distance away.


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A foundation on rock needs an intervening layer of a suppressing material, forexample, clsy 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 soecialist. because the consequencesof error could be serious.It is also unwise to run all the sawfrsmes 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 same

as 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. Inpractice, however, this is not possible toachieve and instead one tries to vary the speedof each frsme.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 vibr-tions in the surrounding ground which createsdisturbing shaking to buildings in the vicini ty.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 upper

floor.


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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 conorete 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 U-shape is partly chosen becausethis design has very high '"bending resistance",especially where the bearirg housings arepositioned. (For technical explanations ofthis see PART II - FORCXSANDMU~S.This &shape makes a strong plate, butother types of beams can also be used.

Another advantage of the U-shape 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 be;rri.ng, which is normally fixed in thebearing housing, starts to rotate in the baseplate, the who1 e base plate must be substitutedor reconstructed in si-tu.--


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Therefore the most modern types of framesaws are fitted with detachable bearinghousin@made of cast steel for the crankshaftroll bearing. Some older frsme saws haveWhite metal" ring lubricated bearings,(SeeappendiThe flunction of the base plate istto hold the construction of theframe together;to support the whole weight ofthe frame saw (about 10 tons);to absorb and transmit to thefoundation the powerful "-inertiaforcesVV that arise during sawing.The predominant forces that influencethe base plate aret

1. VERTICAL IQRCXS 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 FCRCES that arise mostly dueto:- the flywheel counterweights which,incertain positions,have a horizontalcomponent of movement*- the lower end of the connecting rodwhich, in certain positions,has ahorizontal component of movement.- the pressure of the log against thesaw blades.

3. SIDEFQRCRS from:- the belt tension.- the power from the motor.These forces can vary considerably,depend* on the size of the motor and howthe power is transmitted, i.e.- through direot drive, or- through transmission drive.More detail on these stresses is explainedinFart2- ~RCESARDMDVENENTS.

Detachable bearing housinga!!!3


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2. Crank SectionThe crank section consists of:- a crank shaft of:

2 centre shafts2 flywheels with counterweightslorankpin

- a connecting rod.A. Crankshaft with flywheelThe crankshaft is mounted in the baseplate by means of two spherical SKY rollerbearings (see appendix). (Some frame saws

have 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 been

bolted a flywheel with a counte-weight.The crankshaft halves are joined togetherby means of a crank pin. The connecting .vdis 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 strati. (In 0th er modelsthe flywheels are located outside the baseplate and the counterweights are positionedon either side of the orank pin.)

weight


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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 meohanism (see page 33 can bemounted. When this is done, thereis no need for a driving pulley,since log feeding is powered by aseparate electric motor.- a keyed-on driving pulley on thedriving side to trsnsmit thedriving power from the motor tothe crankshaft. The drivingjxlley has a two-piece hub, whiohmakes it easy to disassemble.

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


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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 O-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 O-pulley. When the power is to bedisconnected, the belt is moved by means ofa belt guide from the driving pulley over tothe O-pulley. When power is to be connected,the belt is moved back from the O-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 wayqdepending on whetherthe saw is powered by direct motor dr ive 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 a

brake 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 C&pulley.

IIireotmotordrive

Transmissiongem


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The forces on the crankshaft and theconnecting rod are very complex.See PAFIT2 - FORCFS AND MOVEMENTS). It is there-fore not possible to fully balance a frsmesaw.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 'arts of the frame.The parts that move up and down, however,cause high free vertical forces. By using

extra counterweights it is possible to reduceor eliminate these vertical forces. But,in doing so, free horizontal forces willdevelop.The difficul ty is to find the degreeof balancing that is best for each individualmachine.bven 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 imn 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 9 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'clocks section and the 16 to 3oVclockl* section .In addition, the counterweights helpto overcome:forces at TDC and EDC, the "12 and 6olclockW positions.

CounterweightE3ctraweights


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The Action of the flywheels and thecounterweights is therefore:

Past2 - FQRCES AND MX%XCNTS explainsbalancing in detail.B. The connecting rodThe connecting rod is made from onepiece of I-section steel 2 m. long.The function of the connecting rod is:

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


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The conneoting rod is subject to bothcompression and tension. (See Part 2 -lQRCESARDMOVEMENTS.) 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.

Far anything that is exposed torepetition of stress, there is a *fatiguelimit,,, which is the maximum repetion ofstress that the body in question can beesqosed to without fracturing from fatigue.The fatigue limi t of the connecting

rod depends on:- the type and structure of itsmaterial;- the surfaoe condition of thematerial.

This means that the more even and smooththe connecting rod is, the more repetitionof stress it will stand before it fracturesfrom fatigue.Therefore, the connecting rod mustbe protected from any nicks. Underno conditions must it be hit agains;any 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.

____. ..-.Undamaged connecting rod I

One nick. . 0

*1 ,I 1


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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.

C] ir or water should paint connect-

The connecting rod has two bearings, onelower and one u&per.The lower connecting rod bearing ismounted on the crankshaft journal. Aspherical SK&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 oonneot-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 oentred.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 lubricLting oil.A needle bearing is chasm to ensurethat all the parts above the crankshaftarz as small and light as possible. Anelzdle bearing is smaller and lighter thanotI!er bearings.

lower connectingrod bearing


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3. Bottom Rwne!Cha bottom fkame is plwed at theiower floor level of the a&mill buildiag.It oonaiete of:

A. two lower aide frame8 whiohare both fastened to thebrree plate byB. four bolts at the bottom,andjoined together byC. two stay bolts at the top.The ,funotion of the bottom frame iet

tri extend the each height to enableoonnecting rod to be larger;to eupport the two upper side W&es;to mapport the brake and belt guideeye*-;to serve aa a eupport body for partaof the feeding meQhaz&nn and lubri-oator.


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4. Upper RwneThe upper frame is attached to thelower frame by bolts. It consists of:A. two upper side frames,B. one top pieoe, andC. two oonnecting 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, thevertica l 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 therea3-0:

D. at the driving side a verticalcylindrical shaft, the attach-ment shaft, or the swingingshaft.E. at the feeding side, a similarshaft called locking shaft.

B


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59 Guide SystemTo the side frames four guides, twoupper and two lower, are attached withbo' -6. A saw frame guide is described

as: - 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 to;j

There are two different kinds ofguides:A. Flat guides, which have completelystraight aad plane slide faoes.They are positioned on the infeedside.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-wardanddownward. The front guides (asseen from the Weed side)are alwaysadjustable. The reason for this is thatthe tolerance between guide and friotionplate, (the "playV1), rmrst be adjustableto oorreot wear on guides and wear plates.

If the guide is too tight (thenpleye made too small) overheating,and a risk of damege to guides andfriction plates could result.If the guide is not tight enough(the "plays too big) the sashwill be loose and this could betransmitted 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 fur-the:df=dse*

Adjust-ing nutAdjust-ing scr

Staytightel


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

The guides are lubricated from a12-tube 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. Itis driven by an eccentric directly fromthe crankshaft.- To each V-guide two lubricationtubes are connected, and- to each flat guide one lubricationtube is connected.

fi:rriving WieI LUBRICATING SYSTEM

blat guide V-guide1 lubrication 2 lubrication. tubes,

Lever for m/centric


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The load on the lower guides isheaviest as they are mounted closest tothe upper end of the oonnecting rod.Therefore, they take the horizontal forcescreated by the upper end of the oonnectingrod 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 h&h 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-aPump.

This self-contamed equipment oan beplaced beside the frame, or on the bottomfloor,or in any other suitable place.Water is led through tubes to the guideswhich are hollow, so that the water canpass through them.

Expansion tankI


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The sash consists of four parts:A. one upper cross beamB. one lower cross beamc. two columus,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 lowpr 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 oom-pression and tension stress.The two columns and the two beamsmake up the sash into which the saw blades

are inserted.To hold the sawblades each cross beamis provided with a slot, i.e. a clearanceinto which are inserted:D. top hangers at the top, andE. bottom hangers at the bottom.The saw blades are fitted into thesehangers when the saw blades are set.

I -A

Bottom hangers I Top hangers


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The sash is constructed:- to withstand the stresses createdwhen the blades are fitted. Eachblade is fitted with a tension of7-g tons. If seven blades arefitted, the total tension will be5CL6'j tons.- 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 csntre, 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-beams

back 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).

1&20TONLower crotx beam

Centre of bending

6

Too low Correct Too high


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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 w 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;

i -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 . . . X&365 rev./mkfor a 30,' frame . . . around 320 rev&in.

Weight ofthe sash

fumberbevolut


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To the columns of the sash four gaugeattachments are fastened, one in eaohcorner. Between these and the outer bladeson either side, blocks or gauges (measuringbodies located between adjaaent blades todetermine the thickness of the sawn timber)are looated. This makes it possible toalign the whole set of blades with sorewsfixed in the gauge attachments.In the four oorners of the sash, theends of the cross beams are provided withbra&&s for the sliding blocks.The function of the sliding blocks is

to guide the sash into the guides of theupper frame.The surface of the blocks is made upof interchangeable friction plates made ofa low friction, low wear materia l such asaluminium blocks with a special bakelitefinish, 'pockenholeVV or other low friction7tat erial . The aluminium blocks are pre-ferred for weight and maintenance reasons.The aim is to get friction as low as .possible between the friction plates and

the guides, in order to prevent overheating,because overheating can cause the guides tobuck1 e .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 syatsm with fla t blocke and flatguides makes adjustment of the sash easierand the number of surfaces requiring care-ful clearance adjustment is reduced.


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Blades must be fitted into the sashwith an overhang eetting, 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 thewrtical and has a slope awayfrom the log at the bottom. 1This owrhang must be obtained withoutfitting the blades 60 that the tensionline falls diagonally through the blades.

To gst a correct overhang, the twocram besms 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 infesd) and thelower elidin blocks towards the rear(log outfeed 7 . The overhang is about50 mm from vertical.


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7. Roli Frame and Feed rollsThe function of the roll frame is:

It consists of:- the upper roll frames, one in front

and one at the back. (Seen from theinfeed side).- the lower roll frames, one in frontand one at the back. (Seen from theinfeed side).

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

- on the driving side of the frame,by vertical holding swinging shafts;- on the feeding mechanism side ofthe frame by locking shafts.

Each upper roll frame is fixed on and canswing out on the swinging shaft to giveaccess to the sash (e.g. when changingblades). Each roll frame carries anupper feeding roll.


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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.

Eaoh 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 hand-wheel.The hand-wheel acts on a toothed trans-mission gear F of which the teeth are mesh-ing with the corresponding rack of teeth

of the swinging shaft G.The toothed transmission gear isprovided with a locking devioe in the formcf a catch H which meshes a ratchet wheel I.This is placed on the shaft betweenthe hand-wheel and the gear.With this device the gear and the rollframe can be locked in the correct positionfor any given log diameter. When raising

and lowering the frame the catch must be inthe raised position.


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The lower roll frameThe lower roll frames are constructedon the same principle as the upper ones.Since they must give fina support to thelog during sawing, they are fixed vertiually.Like the upper roll frames theyswing outwards, Nowadays they are made ofcast steel for strength.E&h roll frame supports a lower feedroll. Both the upper and lower roll framecan be locked inwards, (i.e. the operatingposition) by a simple catoh on the feedi%mechanism side of the stand which is thenturned 60 that i t totally encloses thelocking shaft. This also eliminates anyplay in the roll frame. The lock isinaccessible when the saw is working.The feed rollsThe feed rolls are called:

- upper feed rolls- lower feed rolls.

The diction 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 hand-wheel and then theyare automatically self-adjusting fromthe bottom position.)

Close

Open


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- are self-adjusting 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 pneumatl;.c valves operated by thesawyer from the log carriage. Thelifting devfoe consists of a pneumaticcylinder with a piston which is mountedon the roll freme. 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 meohanism.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 when

the swinging roll frame is engaged.

Oil tut

YokeIFIHvdraulicpistonI Hydraulic

I-TJ cyl incle

I:1--r

endular4 roller


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Pattern of feed rollsThe function of the feed rolls hasearlier been described as:

to feed the log through theframe by rotating,and alsoto restrain the log while be-ing fed to prevent it turningor moving sideways.

This task must be done under verydifferent conditions dependent upont- the form of the material

I MC I Ir CANT Ithat is roundand has smallcontact sur-faoes againstthe feed rolls

that has twofaces egainst

- the hardness and surface of thematerial; for exsmple, logs withbark on or off, frozen or un-frozen timber.The demands on the funotion 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.


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For the feed rolls to f'unctionproperly two things are required:1. The right pattern for differentconditions.2. Satisfactory maintenance (as partof the preventive maintenance system)of the pattern of the feed rolls.

The roll pattern is made in oneof two different ways:A. a roll core is provided withpatterned rings, orB. 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 betwben log and feed rollsto aminimum.- 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.


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In frames that are used for both logand cant cutting, the lower feed rolls areoften provided with:- one oentre 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. IThe form and pattern of the rollsdepend upon what logs are to be cut andthe climatic 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.tThis is done either by exohang'ingworn rings or by re-cutting or grindingfeed rolls of fixed pattern.


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8. Feed MechanismThe 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 on

which 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 feedl-OllS.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 frict-ion wheel by a springdevice with a force that increases with

the 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.

>,.!:..:i,i:;;,,


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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 mitre-wheel 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 iower feed rolls and asprccketJ that transm= 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 spzcoketN, on one of the hori-zontal shafts and also over asprocket 0 mounted on the shaft ofthe feeding mechanism.


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Feeding mechanism m/VariatorThe main parts of this feed mechanism

are:- 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 &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. Two 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 cutsidedisc C can be charged in the longitudinaldirection of the shaft.Between these two discs runs the wide-belt D. The other end of the belt drivespulleys E and F on driven shaft G.

i-4

-dlL I

Bt J


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The inner of these discs E is movablealong the shaft. In the longitudinaldirection of the shaft (as seen outwardsfrcm the frsme) this disc is epring-loadedby a aoil spring inside the hub and istherefore always preesed against the out-aide disc. Through this the belt isstretched.

The driven axle 0 ia in driving contactwith the lower feed rolls I through a spurgearunitH. The upper feed rolls I aredriven by a chain transmission I frcm thefeeding mechanism.The feed speed is varied by ohanging

the position of the outside diet C inrelation to the inside disc on the shaft.!Fhrowh 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 &es (3 and L are unchanged, the tapereddiece E and F on the driven axle will auto-matically adjust themselves to new conditionsby the spriag load that acts on the insidedisa.If the discs B and C are pressed closertogether the belt will run on a biggerdiameter between discs E and F on the drivenSbft. Through this the driven ehaft Bwill rotate faster than the shaft L.Since it is the driven ehaft Q thatis connected with the feed rolls

J-


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On the other hand, the belt willrun on a qmailer diameter if the discs Band C are proved away fkom each other. Atthe same time, the belt is rurming on abigger diameter between the tapered discs Eand F on the driven a&e.

Since it ia the driven axle (3 that isconnected with the feed rclle

the rotation speed of the feedrolls will decrease when thedisos B and C on the axle shaftare moved away from each other.In thie way the gear ratio between theengine of the feed meohanism and the gearbar can be varied infinitely in the ratioof 1x7. This means that the feeding canbe infinitely varied frcm 10 to 70 mm/stroke.The ad$ustment of the feed speed isread on an indicating devioe placed abovethe feed mechanism.

_ - -*....

@o0 I 0 0\ -4.-.-


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The bearings dealt with in this manual, viet- white metal bearinga- needlebearings, and- epherical roller bearings

axe all radial bear-, which means that theymainly take up strese wcrking in the radialdirection.White metal bearings ccnsiet oft- 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 brcnse, whichoanstandahighbea~ing~e~eandahighnumber of revolutions.They are mounted in the bearing housingwith a rcund fi t. Taps and acllsrs preventthem tim turning with the axleThe lining wt into these bearing cupsis deaf tin, antimony, copper andlead.This composition metal is called white metalor berbbit.To fir the white metal prcperly on thebearingcupface afewehallowhcles aredrilled into the eurface, alternatively, itis provided with a few dovetail slots.Because white metal has a low meltiqgpoint, any overheating means that only themetallinizsgia damsgedandnct thebearizg.It it3 eaayto castanewmetallin~.The mcvement in a slide bearing is made

while the shaft journal is sliding against thebearing cups. Friction then occurs but it isvery much reduced by an oil film oreated betweenthe twc bearing surfaces by means of special cil-m.

oil halves

mHhen the shaft starts to rotate in thatbearing it brings with it an oil lqer that is Ipressed in under the shaft like a we-, whichlifta the shaft frcm the lower bearing cup. The 1faster the tie rctates, the thicker the oilwedge. Therefore, it is impcrtantthatbearing?playn is big enough to srake it possible forthe oilwedgeto grcwandliftthe ahaft.


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Roller bearings ie the ccmprehensive termfor cylinder bearin@ and needle [email protected] types of bearings ccasiet of:

- outer ring- inner ring- rcllem, and- hcldere for the rollers, which keep themapart and in position.

The bearing pressure ie absorbed by therollers, positioned between the two rings.Rcller berrringf~ offer lee6 rolling resistancethan ordinary bearings end resistance isnearly independent of velocity.

These two types of bearings also requireless lubrication and, at the same time, therisk of overheating is smaller. Contraryto white metal bearings, these bearings arelubricated with grease.The lower connecting red bearing and thebearings of the crankshaft pins consist ofspherical double row roller bear-s. The

two rows of rollers have a common sphericalroll conveyer in the outer ring, which makesthem self-ccntmlling and able to adjustthemselvee to the taper of the shaft.The upper connecting rod bear- ocn-siste of a type of needle bearing calledgudgeonpinbearing.The reason for havinga needle bear*here ie that this type of bearing is suitablewhen the movements are to and fm, which isthe case for the upper end of the connecting

red. Needle bearings also have good resis-tance against shook loads.Since the friction in a needle bear-is three times bigger than in a roller bssr-ing, it is not suitable for the lowerconnecting rod bearing, where speed andfriction are high.Instead of rollers the needle bearinghaa two rcwa of needles, each needle being70 raa long and 6 mp in dismeter. Thegudgecnpinis hcledandserves as atsnkfor the lubricant.

Needleeedlebearingearing Grease waysrease waysNeedles. F:hT\


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. :TENSION AND . :- ,...,>::


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1. Bodies, Motions and &roesIn mechanics a car or the sash of agsagsa~ is called a body.

- The weight of a body or, morecorreotly, its mass, is givenin kilograms.- Amovingbodyhas acertainvelooity which is defined inmetree per second (or minute)or in kilometres per hour.

A change in velocity is calledt- Acceleration, if the velooityis increasd, and- Rettudation, if the velooityis reduced.

The acceleration or retardation is thechange in veloaity (e,g. m/se,) over aoertain unit of time (each second). It is,therefore, measured in a unit that ismetree per seoond, every second; 80 itconsist8 of:- alengthunit,and- a squared time unit. There isa unit for aooeleration oalled%etree per aecowritten a8 m/aeo9 8squer dl*,or m/0 .

Mass

Velocity

Acceleration

Retardation


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To make a body (a mass) aooelerateor retard (aooelerate negatively) a foroeis needed. The relationship between foroe,mass and aoceleration is:lUNl3 =NASSxAC(JEXERATIONwhich is written: F - m I awhere: F-the foroe sffeotingthe body or the mass;

m = the mass of the body;a - the aooeleration.

The unit for mass of a body is~logram ~431.The unit of foroe is the Newton.1 N I the foroe that gives2a mass of1 kg an aooeleration of 1 m/se0 .The unit for foroe used to be thepoundal, whioh was the foroe required togive an llb mass an aooeleration of1 foot/seo2. This text uses the metricN&on.Anyforcethat aots onabodyalwapcreates a resisting foroe inside the body.A body is reluotant to change itestate, whether it is at rest or in motion.V it ie moving, it is also reluotant tochange its direction.For instanoe, if the movement of acar or a gangsaw sash is to be changed inspeed or direction, these bodies will tryto maintain their existing velocity or

direotion. Theee reeieting and internalforces are oalled inertia fames. Theyare given in Newtons.If one tries to chaage the velocity orthe direction of, for instance, a oar or asash, such bodies will resist with foroesoalled inertia foroee, that are measured irNew-tones

A cold winter morning the car rqill notstart l

,To etpt it movimg a high force ised to accelerate

it moves, less force is needed toitsgoing until one wants to star,

. .e J,. .:JIG: .,.::,.I!.$0 40

3

Fhen a hi'br* it herf 0 a ZGGZll:


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What we have dealt with ao far arebodies with inertia foroea in linear movementt i.e. tryiq to move straight aheadwith unchanged velooity.

Ef a body, for instsnce, a weightattaohed to a rope, is swung in a ciroleit will, due to inertia fomes, try tomove etraight ahead, i.e. to move awfrom the centre. This type of inertiaforce is called oentrifuual force.The magnitude of the oentrifugal foroedepends on the maes of the moving body, theradius of the circle and the velocity ofthe body. If the velooity is unchanged,but itswsightor the radius of the oiroleis made two, three or four times bigger,the centrifugal foroe will also become two,three or four-times b Y I. On the otherhand, if the velocity for instance thema&er of revolutions per minute) isdoubled, trebled, eto., the oentrifugalforue will increase with the square of thevelocity, i.e. it will beoome 2 x 2, 3 x 3or 4 x 4 times greater.!l%ie means in practioe that, for frsmesaws, it is the rotational veloaity, i.e.the number of revolutions, that has thegreatest influence on the magnitude of thecentrifugal forue, If the number of revolu-tions ie doubled, the oentrifugal foroe ieincreased four timee.


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A oar hm a weight of1OOOkg. We want to aooelerate the oar f'rom standstillto a velocity of 72 km/hour in 10 eeoonds. What magnitude of mass force is requiredfor thie acaoeleration (presuming that the acceleration is uniform)?The ma8e - 1aOOkgThe veloaity o 72 km/h - 20 m/see.The aoaeleration iet

Velooi* 20Time =i6= 2 m/eeo2The required fome is then: F I m x a

F = 1 000 (mass) I: 2 (aoceleration = 2 000 Newton.

72 lan/ho~ Sta.ndstill

Fbr aomparison we can find out what foroeis required to aocelerate a moving Bsageaw sashweighing 345 kg from bottom dead oentre whereit is stationary (at 6 o'clock) to maximumvelooity, which at 330 revolutione/min ie equalto 10.3 m/sea and takes plaoe at the 3 o'clookposition.The auoeleration of a sash is not uniformas the acceleration of the car in the aboveemmple. Thie makes our oalculations some-what mre complioated. Without goiq intodetails of how the caloulations are made, thenmximum acoeleration at the upper turning point(at 12 o'clook) is 4l2 m/sea2 (aee figure along-side).The required force is then: 345 (the marre)x 412 (the acceleration) = 142 140 Newton.Thie is the force that is transmitted by theupper crankshaft bearing. The magnitude of thieforoe oan be compared with the lesser forcerequired in the car example.

Accolemtion of the Sash


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2. Stressand StrainAll bodies oonsist of very small particles oalled moleoules. These areattaohedto eaoh other b aertain internal foroes in the material itself, so-oalled cohesive forces.When a meohaniaal part is influenced by outside foams it undergoes a ohangeof form or shape, usually so -1 that it cannot be seen or measured. Theseoutside forces strive to ohaage the looation of the moleoules (and so the shape).At the ssme time the oohesive foroes inside the material resist to prevent thesechanges of location.The external force is oalled a stress: it is the force on a body exertedover a given area. The internal foroe resistiag the change of ehape is oalledstrain, and is measure d in the ssme way, a foroe over a given area.If the external foroes are bi&ger than the internal ones, a ohange of formof the material takes plaoe.If the body reoovers its original form completely when the e-tress is removed,the change of folm is oallsd elastio.Depending on the material of the body and the magnitude of the foroe, apermanent deformation sometimes ooours. This chrrage of form is then said to bep1aatia.If the external foroes are sven greater, the chargeoffonncango so fsrthatthe material will break. This is aalled fracture.~SrmESSAM)STRAINARE~RCESTIIBTACTONA~NENAIZEBOFTAEWATERIBL,i.e. TRE RELATIONSHIP ,F, MERF, F IS THE mRCE TRAT ACTS ON THE CROSSSECTION A.A

They are rmasure d in Newton/rise2 or Newton/om2.Rote: Strain is a force induoed as a reaotion to stress: it is independent of thexrial under straw. This is distinot from structural strength, whiah is,rTHEBBafTPOFA~~TORESIST~~OR~R2BBTION(CHBNIZEOF~~)CAUSEDBpEXTERNALliDRCEZ

The structural strength properties of a material are usually given as limitsthat result inpenusnent changes offormorbreakage. A given body has differentetruotural strength for different kinds of stress, v iz. tension, compression,knding, etc. -

There are three main groups of streseesr1. Primary stress, i.e. compression andtension.2. Seaondaq stress, i.e. shear, wherethe stress is tangential to the stress(see figure alongside). Twistingstress - torsion is an emple of shear.3. Combined stresses ooour when more thanone stress ants at the same time. Thisgroup incorporates bending.


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Risu3ry stress: CompressionThe figure to the right shows a partunder oompression.A aompression in any material iscalculated by the following formula:

Compression - The compressive forceSectional area of rodCompreesion ocoura in a saw framein the following places:

- In the columns of the sash due tothe tension from the inserted eaw-bladee.- In the oonnecting rod when itreduces the downward movement ofthe sash, roughly between 9 and6 o'olock, where compression isgreatest. (See figure andappendix).- In the oonnecting rod when itaocelerates the sash upwards,roughly between 6 and 3 o'olook. 1


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Rimaxy stresst TensionThe figure to the right shows a partunder tension.The teamion in any material is cal-culated by the following formula:Tension II The strstohinR forceSeotional area of the rodApplied to the above example:T -w P 1 N/om2Fir a saw frame the biggest tensionetrees is in the oonnecting rod:

- when the velooity of the sash goingup is being reduced (retarded), whichie rou&ly between 3 and 12 o'clockas it heads for the upper dead centre,where the tension in the conneotingrod is greatest.appendix.) (See figure and- when the conneoting md pulls thesashdownwards, roughlybetween 12and 9 o'clock.


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Seoondary etresst ShearThe figuretothe right shows a partunder shear stress.Theee stresses arise when the actingfames occur in the planes of the surfaoesoonoerned, so that two adjoining surfaceaare pressed past each other, as when apair of soissors are outting.This is often the case in rivetedjoints. In frame saws shear stressoocum in the rivets at the base of thesawblades.Shear stress is oalculated by theformula belowtshsar - The shear forceArea of theshearing material


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Secondary stress: TorsionA special form of shear is twistingusually called torsion.This stress occurs 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, whiohresults in shear stress between thediscs.This type of shear is called torsion,The figure shows how torsion inoreasesfrom the centre of shaft towards theperiphery.Because of this, shafts can bemade hollow without significantly

reducing torsional strength, yetmarkedly reducing weight.!Forsionalstrengthis 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.

D=l

D=2


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.Combined stress: BendingRending stresses occur if, forinstanoe, a bar is under pressureperpendioular to its centre line.Bending stresses are oomposed of bothtension and compression.

- At the centre line the stress iseero.- Above the centre line there isoompression.- Below the centre line there istension.

To calculate the msgnitude of thebending stress is oomplicated and itis not pursued in this manual.A praotical example, however, oanassist our understanding.It is much easier to bend a ruler

aa shown in version A in the figure,than as ahcwn in version B.We can see that the measure H(taken in the same direction as thebending foroe) is more important tobending resistance than the measure B.These two faotors, i.e.:

- the relationship of stresssround the Bile beam centre;- the influence of the measure Hon the resistanoe to bending,

sre behind the design of the I-secticnbeam, or I-girder.

Version A

Version B


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When constructing the I-girder theaim is to make the waist-liner- -narmw (measure B) to reduoe theamount of material in thosesections where it is not needed(the stress is minimal in theoentre line), and- high (measure H) to concentratethe mass of material as far awayas possible from the beam oentre,thereby looating as much s&erialas possible to sections where theetude of tension and com-pression is strongest.

A given cross sectional area (seefigure) of differing distribution,illustrates in this series of drawingshow the structural strength of girders-V81Pg= We have obtained a bendingstrength in d)more than three timesstronger than the original one in a).

t- 2000 F

a) brealload

in all alternativeseight KG/CM1,275

breakload

80000 KG


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In a saw frame bend*q stressesoccur in the conecting rod dua toinertia that originates when the lowerpart of the oonneoting rod is foroed tofollow the rotating movements of theorakshaf% journal. These stressesare strongest at the upward stroke at3 oclock and at the downward stroke at9 oclock. (See figure and appendix.)

The oonneoting rod must thereforebe:- as light as possible to reduceinertia.- as strong ss possible to resistbend@ stress.

For these reasons connecting rodsare I-shaped in the oross-beams due tostress from sawblade tension (about7bgO 000 N/Made) and also from theinertia of the sash and the conneotingrod (about 15Cb2OC? 00 N).Fbr the same reasons, applied tothe oonstruotion of I-girders, oxss-beams

me made deep (measure H) in order toobtain the greatest bending rigidity.

6--


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Combined stressr Compreesionatld BendinqAnother example of multiple stressesis that which erpoees a body to both oolppreseion and bendiq strains.If a bar (for instance, a connectingrod) is long in relation to its oross-section and comes under influence of aoompressional 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.

)J \./

3-

c FStrains in a Cormeating Rod due to Tension, Compression and Bending


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In a saw frame the greatest risk ofthis stress ie in the conneoting rod.The risk of we ooaurring isincreased if, at the same time, bendirgforcee are preeent in the oonneoting rod.Ba previously explained (see also appendix)in certain posit ions the oonneoting rodis sub jeot to bending etrees.Be can be eeen from the figure, the

maximum compression oooum at B.D.C.(6 oolook), and decreaaee to zero at3 oolock. Maximum banding oooursbetween 3 ololock and 2 oclook.The greatest riek of the combinationie between 5 ololook and 4 oolook on theupstroke. (SSgure and appendix. )

Compress ion Bending

3


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3. Static and Dynamic StreeeThe fame creating etrees on a bodyoan be of two d.ifferent kind, etatio ordpamio.A static foroe maintains the 8-emagnitude independent of time. If theforoe ie increased, breakage willeventually ooour. The actual foroe atwhich the material will fraoture ieaalled the 'breaking: fame and it OO~LWBat breaking point.A dynamio force is oharaoterieed bythe faot that the magnitude of the fomevaries (pulsatee) between two ertremee,whioh 11188118hat the etraine within thebody aleo vary (puleate) in the came way.If a meohanioal part oomes under thecontinuous influence of a fome thatpuleatee repeatedly, fraoture might oocurin epite of the faot that the magnitudeof the force mey be considerably belowthe etatio breaking point of the parti-oularmeohanioal part. The puleatingstreee finally etraina the meohanioal

part 80 that it reaohee the fatigue limi tof that material.

--= Constraint

Constraint

Fatiguelimit rS


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The fatigue limit of a material iethe nmximum etatio and dynamic etreesthat oan be put on a material withoutan unlimited number of puleati~ sltreeseeoaut3ing hreerkage.

The fatigue limit of any material isal- well below ite break* point*Fbr materials ikequently ueed inmeohauioa the magnitude of permittedstreeeee are Imown and tabulated.One of the beet examples to be foundie the alternating tezmion/compreseion in

the conneoting sod and the lower oroef~-beam that is alteruatively pushed andpulled.The design of meahanical oomponenteunder dymmio streee is alraye muchheavier than oorreepondiug part6 underetatio stress only.!l%ie ie the reason why the loweromes beam ie so heavily dimensioned.Another example of a oomponent subject

to fatigue is the ommk~haf't, whioh, inaddition to torsion, ia al60 under bendingetreee ooourring eaohupwardmddownwardmovement of the sash and the oonueotingrod.Referriag baak to bending atrerre,the upper half of the crankshaft ie intermion and the lower half in aompreesion.(See figure), Bat, aa the crankahaf'trotatee, the part that wae in tension willdevelop compression half (L turn later.R.IT any given point of the cra~~?~hsf'tthe etreeaee are oomtantly alteruatiu&from texmion to compreesion~ a typioalexample of a oomponent mabjeot to fatigue,

r

II -7-I..S/I

!!I!

/!l/llB/j/ ;;.1::.:..-,.._, ,.( .,. ...: . ..,.. __., .*,. . .. .


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4. Factora that influence StructuralStrengthThere are many different faotomthat influence the etructural etreugthof a oomponent, particularly againstfatigue.Some of the most important are:Concentrated strainsSharp oornera, holee not properlydrilled, different typee of niokm, hackand uneven surfaoes result in stratilooally ooncentrated.Theee cause abrupt restriotione inthe tranamieeion of foroe through theoomponent. Thie lada to etreeseegreater than those only due to thereduced eectional area of the niok.The surface of maohine paHe underdynamio &rain must therefore have alloornem and edgera well rounder, i.e.with large radius. (See figure.)

- 55 -

--


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Surfaoe qualityBodice with polished and groundmxrfaoea demonstrate more reairrtanoeand strength than bodiear with rough,uneven 8wfaoe8.

CorroraionF&st and other chemical corrosionreduces etructural strength aonsidersblyThis ie oorrected I~T surfaceconditioning, painting and the uBe ofrust proof materiala.


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Heat treatmentA metal pa;rt that has been repairedthrough welding usually has a lowerfatigue limit due to:

- unfavouzsble struoture ofthe weld material.- built-in heat stress in themateria l, following the welding.

Firstly, (figure,a) the weld meteria l Aas well as the auxrounding originalmateria l B, are heated up during thewelding procedure above the temperatureat which a structural change takes placein the materials.

In thiqfollowed by uncontrolledcooling of A and B, a zone C usuallyresults which is stiffer and more brittlethan the original materia l B, whichreduces its fatigue limi t (figure b).In order to retain the structure andimprove the strength of the material inthe weld joint, annealing is practiced,This means that zones A and B are heatedup to 750 - 850C (depading on carboncontent) for half to one hour, followedby cooling in normal air. (Electricwelding, however, does not normallyrequire this procedure.)Seoondly, when welding a given part(eee figure c) th e materia l heated atpoint C tends to expand. The rest of themateria l B is still cool and does notexpand, but rather prevents e-ion and

strives to pea together the materia l ofthe C zone which is plastio and workabledue to high temperature and thereforeuauaea bulging(figure d). Ekpandingandcompressive foroea more or leas eliminateeach other end the frame remains rectangularas long as C materia l is hot.

B A B

b

d

An example o f how heatstress can occur when amachine foundation iswelded together &pint c.


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But then the oomponent cools off, thematerial around C oontreote, which remltein BtF866 and Shape OhA@. % elilUiJWtethis, the component muat be heated up inone of the following three different wayat

1. The materia l at (1 ia heated up toapproxin&ely the same temperatuream the material at point C. Thiecreates a uniform expansion andoompreerrion.2. The whole part is heated up to +&XI%during the welding, whioh makes thelpaterial pleat io 80 that stress iseliminated, so-oalled hot welding.3. The whole part ia streaa-reliefannealed at +6OOC within a fewhoum &ter the oompletion of thewelding.

IMe: Welding of more complicated pa&sshould be left to experienoedworkehope.

CheokmAS we have seen, the eaah 3.6 undersignificant etreesea and some componentsare more subject to fatigue than others.lb ensure proper fumtioning of the framesaw, these vulnerable parte:the lower aroea-beamthe connecting mdthe crank pinthe orank~

muat be checked regularly and givennurintenanoe.Incorporate ohecb into the preventivemaintenance progrmrne


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5* The Eovement Mechanism of the FrameSawThe oscillating movement meohaniamof the frame saw is bslred on orank mot ion,i.e. a rotating movement is convertedthrough a connecting rod into a t-d-fro movement.The figure is an explanatory aketohof the moving perks of a frame Eaw where:A c the centre of the oxankahsftB R the centre of the crank pinC I the centre of the aaah pin.

Point A rotates at an even speed which isthe number of revolutions of the framesaw, for inatanoe 350 r/min.Faint B will then describe a oirole aroundpoint A. This ie done at an even epeed,as B is direotly linked to A.Fbint C is given a movement that isidentical to the movement of the eaah aait oan be regarded aa a part of the sash.

At the same time it oan be regardeda.a a part of the upper conneoting rodbearing and the diatanoe that It travela -the lemgth of the stroke of the aaah I(in our oaee) 600 mu. AE the aaah issteered in its guidea, the rotating move-ment of A and B is transformed to a mov-metnt up and down.

11 ~Upper f --Lower

B-


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6. Fbrcea actiw on the Smh, theConnectiq Rod and the CrankshaftJournalThe Bash and the lower CmB8-beam inparticular are under forces that originatefrom:

- the moviq parka of the frame saw(each, sawbladee and parts of theconnecting rod), particularly theaooeleration and reterdation of thesa6h- the cutting fome at sawing.

With inserted blades an 18 sashweighs mound 245 kg, a 26 Bash weigha345 kg and a ~ll,BaBh 400 kg.The upper end of the connecting rodmoves up and down 1 ke the eaah. Therwfore a certain part of the maas of thecanneoting rod (around 55 kg) can beadded to the ma86 that moves upward anddownward.We have seen earlier that:Fbrce - Mass x Acceleration.In this maeI the total forces canbe calculated by multiplying theacceleration of the Bash at differentpositions by the weight of the Bash pluathe weight of the sawblades and thehanger8 plus 55 Q of the connecting rod.


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By their weight the fitted BaWbladBBinoreaae the foroea but they also influencethe each beoauae of the fitting tensionwhioh oan be 70,000 N or more for eaohblade. A frame Baw that holds 9 bladesthue has a fitting tension of 630 000 Nin total. Apart from these foroee, theaaah is also subject to gutting foroeathat ariee From sawing.

These foruea, at leaat the ones thatact at right aaglea to the W~wbladee,increase with the equare of the feedspeed. The streee on the blades is,atrsagely enough, greater while ret-ing than while sawing.When eawi ')" a 40 am cant at a feedspeed of 33 mm stroke, the fome thatoriginatea from feeding is 2 000 lV atreturn sawing just &er the turn of thestroke at the HOC.Under the very same oant aize andfeed speed, the foroe at the outtingmovement ie biggest just before the BDCand reaohee 1400 N/blade.The oonnecting rod ia subject toforces that oonaiat of:

- forces from the upward and do-ward nmving parts (eaah, bladeaand part of the connecting rod).- outtlng foroee at sawing.- inertia forces.

The firat two of these inertiaforces have already been dealt with.Here we disouse the third group ofinfluenoing foroee.

2 000


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The orankehaft jourrvrl ie aubjeotto all theme foraea, tmtted to thecrank pin through the lower oonneotingrodbearing. The biggemt Some aotingon the aonneating rod bearing oaaura atthe upper dead oentre, i.e. the 12 oolookposition.

The whole of this forae is not trams-mittedthrowhthe crankshaft bearing tothe barse plate and the foundat ion but iereduoed through oounter balancing of theflywheel.Flywheele are made with permranent

aoamterweighte plaoed on the oppoeiteaide of the CrankBhaft from the Caulkpin, which Bhif'te the oentre of -6towards that side. The distanae fromthe aentre of maam to the aentre ofrotation ie thue modified BO that allthe rotating maea fames eliminate eaohother 811 muoh as poesible.Aa ehown in the figure68

- Cl is the aentrifugal fomeof the rotating part of theconnecting rod, the conneot-ingradbearingandthearankpin, while

- C2 ie the centrifugal foraeof the eccentrically plaaedaounterwe@hte of the twoflywheels.If these two oentrifugal foroee(Cl and C2) have the same magnitude,C2 will oounterbalanoe Cl.When the orank pin is at the 6and 12 olaloak positione, the upwardand downward lpoving inertia fames ofthe aash and part of the conneoting rodalternatively put oompreeeion andt-ion on the lower connecting rodming. (Appends)

EktraCounterweib# Counterweight

I II Tension 1

I Compression I


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These up and downwerd actinginertia forces can be reduced, however,if the foroe C2 ia made bigger thanthe foroe Cl.Fkrt of the up and downward foroe Fwhioh is transmitted through the connect-ing rod from the s&ah and the up anddownward moving part of the connectingrod will then be counterbalanoed verti-cally. The force F, however, is zeroat the 3 and 9 ololock positions.C2 can be increased by melting leadinto apeaially provided holes in the fly-wheel.To obtain the beat results from thecounterbalance, the size of the leadwaht muat be tested individually foreaoh frame saw.The out-of-balance that this createsin the flywheel will oauae forces thatdo not counterbalance when the orank tapis in the 3 and 9 oolock positionawhere F = 0. This will cause Borne

horizontal vibration but these are leesthan those that would occur if ne balanc-ing was done of the flgrJhee1, The upand downward forces would then treat every strong vertical vibration,

c2


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7. The Cutting Condition6 of the Saeh

The working stroke (outtimg) ..__... ._............... ....-....... - -,

2 3 4Direction of feed

A. EXficient cuttingI B. Less efficie& cuttingc. Wood crushingD. Return eawingE. Free wheelingL F. Middle of the stroke -5 6 i.e. where cutting

potential cannot beIlEd.UlmiZed.


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n0S-

-.__

\--

1EiEf


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PART III - SETTIEX3SAWBLADESmFaehaESAWSASH

1. Rensoving blades from the sash .............................2. Setting blade6 into the sash ..............................

Inserting hangers .........................................Inserting eawbladee .......................................Inserting blocks ..........................................Adjustment of overhaq setting ......................... ...Setting right angle of a eet of sawbladee .................Plumbing in a eet of sawblades ............................Adjustment of eplitters. (ICnife guides.) .................Safety equipment ..........................................

70717172737475767778


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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 looked in its upper position. Front upperand lower 1~11 frames must be open. Switoh off the current.

OPERATORstands in front of thesash.

Operator HelperHELPER

is on the out-feed sideof the frame elevatedon a board that hasbeen placed between theknife guides to enablehim to loosen the tophanger.


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OFEXATOR1. tiosene upper and lowerblook attachments on theright-hand side, the upperones just enough for bloclato remain in place.

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REMDVIMGBLADESF'ROMTIESASH

HELPER

2. Knocks away right lowersupport blook. Thentakesaway other blocksone by one from right toleft, so that the blade6are completely free.

3. Colleots two or threeblades together and pullsthem out of the bottomhangers.

4. Tekee the blades and putsthem in the Bawdoctor'Bbox.

2. Loosena each hanger inthree steps (otherwisethere ie a risk ofbreaking the hanger onthe last blade). Startswith centre blade. Con-tinuEeon alternatesides with eaah step.I Step Rignt order ofeach step

I

Knock8 away left uppersupport (seen from theINper's position).Takasaway the blocksone by one from leftto right. Meanwhile,kewremaining blooksin position by push-ing side of lastblade against them.

3. Collects the *spa cftwo or three bladestogether (the same asthe Operator) andpushee the blades outfrom top hangers.

4. Checks blooka. D~BCE&Eif damaged. Cleana un-broken blooks and putethem in their respeotivebox%6 l

The blades have now been removed from the sash.


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SEZTINBLAI)ESIrJTOTRESASHInsert-the hangers

OPEZWlQR

2. Checlm wers and makessure the contaot surfacesand the blade hooks arestraight and parallel,-the rivet is fixed, theopening between theblades corresponds tothe thickness of theblades and that thereare no indiaations offraatures.

3. Puts the bottom hangerethrough the lower crossbeams from the top down-wards (with the attach-ments first). Thenturm them one-quarterof a turn to m&e theattaohments oome intocontact with the lowerside of the beam andlook into position. II

t

Problems in a Hanger

I

HEXPER1. Cleans the cross besmsfrom sawdust, eto.Brushes carefully, orpreferably uses oom-pressed air. If a wear-ing plate is used on topof the upper oross beam,cheeks that it is in

the right position.

2. Cheeks the hangers andmakes sure the uontaatsurfaces and bladehooks are straight andparallel, the rivet is ~fixed, the opening bet-ween the blades corres-ponds to the thicknessof blades and that therethere are no indicationsof fraotures.

3. Puts the topthrough the cross beamfrom the top downwexds.Then turns them one-quarter of a turn sothat the hanger wedgesare straight acrossthe beam. Turns theeccentric lever alittle more than half-way down to make iteasier to slip on thespanner.


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Inmrting the aawbladseOPERAlQR

1. Takea the blader one et 8time oarrying ths blade atthe baok with the laithand and aalanoing it withthe right hand, holwthe front at the bottom>(the teeth faoing Opsrstor).&IIE~S upper end to theHfilpar.

2. Iiurerte the bottom end ofthe blade into the l&tbottom hanger. Then oon-tinuerr with the reet ofthe blades.

1. Wee the blade byglwping upper endwith the right hand.Rolds the hanger withthe left hand.

2. limerts upper end ofthe blade into the00rrespmlin.g tophangsr. Adjust0 thewedge in the tophanger 80 that theblade is looated inthe hanger. (If theblade ia standingfree it oould fallforuazd onto Operator.)Ineert f!rom lsft to right. Ifhen all the blades are inserted, position theblades (the hEIllgere) 6idewaye to the approate poBitiOn they will have laterwhen the blooks-are'inserted.

3. Adjust the blades in the 1 13.bottom hangere in thedireot ion of 6ewing aoth& Outer blade8 LowerOX066- the outRide blade6-8 a little for-ward of the oentrebladee, i.e. theywill out first.- the blades areplaoed evetriofC&- the whole set of

Adjust the blsdea intothe top hangere in thesane way 88 theOperator &es with thebottom.

blades ie perpendi-oular to thedirection of eawing.- the fitting tensionwill be oorreot inthe blades.

Sinoe blades are poeitioned aa abovewidth a rule on poeitioning iepoesible oentre of hangers ehouldin figure, or the tint of the hangerand are often of diffeirentdiffioult to state. Aa far aaooinoide with a line 88 shownbe j.n line with gullets.


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Insert* of blocks

1. Ineerts with the left handthe lower left supportblock (i.e. on that sidewhere the block attachmentshave not been touched andare therefore at rightangles).With the right hand pressesthe free blade agaFnst theblock so that the bottomhanger is correotly posi-tioned and the block isheld in plaoe,Continues until all theblades and blocks are in-serted. Finally insertsthe last support blook.

2.

1. With the right handinserts the uppersupport block oorres-pending to that ofthe sawyer, Pressesthe blade with theleft hand against theblock to keep it inplace. Taps thewedge with the hsmmerso that the blade isstretched a little --the blook is thenfixed and stays inposition by itself.(The top hangers arenow posxtioned alittle to one side.)Continues like thisuntil all the bladesand blooks are in-serted. Finally,inserts the supportblock.

The last support blook is often a bit bigger than the distance allows. If thedifference is small the support blook can be tapped down (the Helper drives hisblock upwsrds). If the difference is big, the blook attaohment must be un-sorewed. N&er force the last support b&ok with heavy blows. The supportblook could beoome deformed and be pressed so hard that later adjustment willbe more difficult.Tightensthe upper blookattaohment a little whenall the blooks are in-serted so that they donot fall out,At the ssme time, adjuststhe blocks so that theyare all in a horizontalline together.

2, Loosens the eooentriosof 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. Star4swiththe outside bladesand works alternatelyfrom left to righttowards the oentre.


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Adjustment of overhang eettis

HELPERAdjusts the right overharsetting on the overhangsetting board. Holds theboard against one blade Ea time, preesee againsttooth line and taps withthe haPPmerat upper end cblade in the direction oisawing, so that the righloverhang setting isobtained.

Directionof sashmovement

1 L

If the overhangsetting alreadyadjusted is toomall, gently tapsout the blade atupper end.

---

II-iii:At this stage the blades must not be stretohed eo much that they risk damsgeor that the etretohing plats6 of the blades get jolted.

2. Taps top hangerwedges to achievea slight stretoh-ing of the blades.


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Setting right angle of a set of sawblades

1. Puts the aligning edge on thebe~kg PiVet OP the frsme sawstand. Arts the aligning Tsquare on the aligning edge.Checks by moving it sgainstthe eides 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 baok screws of the blockattachments differentially.Do not use any foroe whichmight result in a deformationof-the blooks without theblades reaching the rightposition. Then it would bedifficu lt to continue settingthesngles ofthe rest of the blades.

2. When all the blades are atright angles, tightens theright-hand side block attach-ment but makes sure that thesetting does not changeduring tightening.

3. Loosens the sashand pushes it tobottom deadcentre,4. Checks the angle of the bladesin the esmewayas inland 2above, when the sash has reachedthe lower position. The adjust-ment is made with the upper lineof blocks.


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Phmbing in a set of ouwbladeeOF'ERAToh REILFm

1. Holdsthe T equsreagainst the aligningedge with one edgea 1.i bfie QYwe Gif&;to one side of 8 blade.The Bet of eawbladeswill be vertioel ifthe side of the blade,when making ite IUOVB-meat up and down, isalways at the same die-tanoe from the fixedmeasuring point. Ifthe distance to theeiae of the blade ienot the a8me going upaa going down, theupper block row mustbe adjusted eidewaye.Laoeena both aorewmequ8lly on that eideof the blook Bttaoh-ment where the eetof aawbladee needeedjuating ana correa-poondingly tightensboth screw0 at theother block attach-ment. The set ofbledee will move inthe right w(4~r.

1. Pushem the frappe tomake the each moveelowly up 8nd down-.

2. Tighten8 the set ofblades in etagee.(Steps 2 snd 3). startswith the outside 'Liladeeand worlca alternativelytowarde oentre.Tightena centre bladelaet in every etep. IfsawI does not startuntil following day,delay tightening untilS8Wiw ie to etart,thus avoiding oro~e-hwea a-& hlarlna hainnM....WW --a-c,under pressure for anunneoeeesrily longtie.It ie esaentisl thatall blades are equallytightened or load onomes beama will be WI-evenly dietributed andresult in curved S8Wing.Checks strain in blade8by preesing each bladeh8rd with hand.


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Ol?EXKPOR1. Puts the aligning edgeagainst inside of one ofthe bladessawing themain yield. (Notet firoant frames put the edgealong the inside of oneof the outside bladesof the cant boards).2. Indioatmby signsalreadyagreed upon how Helper

must move ti splitterso that it bears againstthe inside of the align-ing edge.

Adjustment of splitters (hife guides)

4. Repeats this procedurewith the othersplitter.

?

I-HELPER1. hoeens thesplitters andmoves them alittle together.

2. Moves thesplitter asdirected byOperator so tbstit bears againstirside edge ofaligning edge.

3. Fixes and lookssplitter.4. Repeats thisprocedure withthe othersplitter.

5. Cheeks adjustment onoemore, see above.


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Safety equipmentA newly sharpened blade is easilydmaged even by gentle nudges and Insups.Coztaot with other objeote oau damsgeboth edges and teeth setting.To avoid dsmsge, the edge can beprotected by strips of plastio that areplaced over the teeth.Even more easily dmsged are the

hands of the Operator, which can be cutwhen blades are handled, espeoially whenthe Operator is inserting blades, blooksor tightening the blook attachments.m using the plastio strips theOperator is protected during the wholeprocedure, except when the overhaugsetting is adjusted. The strips areeasy to put on and take off.


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- 79 I

PARTIV - HOWTO FEED LOGS IMI'O A FRAIE SAWlE!%!z

1. Cat Sawing Principles ......................................... 802. Sawing Symmetrical Logs ...................... .................. 823. Sawing Lngs with Rum Defects .................................. 84

3.1 Crooked Logs ............................................. 843.1.1 Straight Sawing .................................. 853.1.2 Curve Sawing ..................................... 863.1.3 A Comparison of Straight Sawing or Curve Sawing . . 86

3.1.3.1 Straightness ..................... ...... 873.1.3.2 Positioning of the Pith ................ 873.1.3.3 Wane ................................... 873.1.3.4 Practical Performance .................. 87

3.2 Logs with &regular Cross Sections ....................... 873.3 oval Logs ................................................ 88

4. Sawing I.qs with Bole Defects ...................... ............ 905. Sawing bgs with Heart Shakes .................................. 916. Sawing Logs with Quality Defects ............................... 91


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1. Cant Sawing PrinoipleeThe principles of aant cawing ooneist of two steps (figure 1).Step I. The log ie eked in the log frsme, whieh givesa oant and one or more boards on eaoh side.Step II. The oant is reeawn in the oant fYsme whioh gives amain yield of planks, and a number of boards oneach side.The msin yield has now been blook sawn, i.e. the eawblades havetouched all four sides and normally can be marketed as they are.The boarda from both steps are further processed in one or more edgers.

EdgesawingThe cant to Resawing

Fig,1


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The Hawing ie usually done in two framee, one log frame eaw and one oantframe saw, which operate one after the other.The sawing, however, oan be done in juet one frame that ie set upperiodioally for edging or reaawing. In thie oaae, the cants mu& be piledup between the two operations.When prooeeeing the lo@, the purpose ie to aohievez

- a good result both ~EI regards quality and quantity.- the highest poeeible economio yield.

The log8 must, therefore, be correotly fed into the frame maw.The log oan be ofr

- different siee and tree speoies- different form and quality, (rJee figure 3)and must be treated acoordingly.

When the log sawyer or oant eawyerhaa eaoh log or oant before him, he mustm&e an aaseewnent quiokly and positionthe log, or the cant, for the sawingprocedure, to ensure the beet resultpoeeible.Once the sswbladee have etartedto cut into the log, there is nopossibility of making any adjustment.Such action might very well oame abreakdown. (See figure 2 and 3.1.2 -Curve Sawing).

:eeult of tryi% to move log eidewqmtier =wing hae barted.


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Logs with fom d

Fig.3

2. Sawing Symmetrical Lo609 (Figure 3)A eymmetrioal log

- ie round and etraight without arsyfow defeota;- haa quality faulta in the foxm ofknots dietributed evenly in numberand eiee.

Infeed Rule for Symetrioal I4xBinbRand Cant&amer-..----.-I___I Centre line of log or the oamt&all coincide with oentre lineof the eet of blades.Ezoeption to rule8 If, for instams,too emall a log for the aotualsetting haa be& inoluded, the aawnmrfaue of the ca& msy be too mullfor the laain yield..

hgsawing Cant resew*

tIIIIIIIIIIIIIL

Centreline of.bladesI

kntre line !I'IIf log %1I

Centre I4ineof ,oantFig.4

Frame Saw Manual 1902

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Transcript of Frame Saw Manual 1902