DESIGN AND FABRICATION OF PARKINSON GEAR TESTER

A PROJECT REPORT

Submitted by

J.KIRUBASON EDWIN

A.KANNAN

S.JAYAPRAKASH

S.IYYAPPAN

In partial fulfillment for the award of the degree

Of

MECHANICAL ENGINEERING

GOVERNMENT COLLEGE OF ENGINEERING

TIRUNELVELI-07

ACKNOWLEDGEMENT

Our first and foremost thanks to THE ALMIGHTY for presenting this opportunity to complete this project.

We also wish to express our sincere thanks to our beloved principal Dr.D.SHALINIPUNITHAVATHANI,M.E.,Ph.D.,MISTE., for her kind patronage.

With great pride and pleasure we express our deep sense of gratitude and profound thanks to Dr.T.CHRISTOPHER,M.E.,Ph.D., Professor & Head of the Department, Mechanical Engineering, Government College of Engineering, Tirunelveli for encouraging us to undertake this project.

We are indebted to our project supervisor, Dr.T.CHRISTOPHER,M.E.,Ph.D., Assistant Professor in Mechanical Engineering Department for her kind guidance, advice and encouragement throughout the project.

Our special thanks to our faculty adviser,

Mr. T. PREM SINGH INBARAJ. ME., Assistant Professor in Mechanical Engineering for his profound and valuable insight and comments on our project.

We express our sincere thanks to all the faculty & staff members of the Department of Mechanical Engineering for helping and guiding us to complete this project with great success.

We also express our special thanks to our parents who have sacrificed greatly in our education and welfare. We thank all those who have helped directly and indirectly in this doing project and bringing out this successful report.

ABSTRACT

Parkinson gear tester is used to test the error in the gear. Here the carriage has two spindle. One main gear is fixed in one spindle and another testing gear is fixed in the second spindle. The can slide both side and these gears are mounted in mesh by spring pressure. When the gear are rotated, the moment of sliding carriage can be measured by the dial indicator. This values are recorded in

the recorder. The spindles can be adjusted so that axial distance is equal and scale is attached to one side and vernier to the other side for measure the centre distance. If errors occur in the tooth form moment of carriage due to the error in the pitch and tooth thickness. This moment is indicated in the dial gauge. The maximum gear diameter 150 mm can be tested.

CONTENTS Chapter 1: Introduction 1.1 Parkinson gear tester

1.2 Gear

1.3 Shaft

1.4 Ball bearing

Chapter 2: Construction & working

2.1 Construction

2.2 Working Chapter 3: Design & Calculations

3.1 Helical gear calculation

3.2 Bevel gear calculation

3.3 Spring calculation

3.4 Bearing calculation

Chapter 4: Fabrication process

4.1 Bevel gear

4.2 Helical gear

4.3 Shaft

4.4 Ball bearing

4.5 Rail setup and assembly

Chapter 5: Cost Estimation

Chapter 6: Conclusion

CHAPTER 1

INTRODUCTION

1.1 PARKINSON GEAR TESTER

Parkinson gear tester is used to test the error in the gear. principle of this gear tester is to mount a standard gear on a fixed vertical spindle and gear to be tested on another similar spindle mounted on a sliding carriage, maintaining the gears in mesh by spring pressure. Movement of the sliding carriage as the gear rotated are indicated by a dial indicator. This dial indicator gives the reading ofmovement of gears or it may be said that dial gauge gives the measurement of gear variations. These variations are a measure of any irregularities in the gear under test.

Here the carriage has two spindle. One main gear is fixed in one spindle and another testing gear is fixed in the second spindle.The can slide both side and these gears are maintained in mesh by spring pressure. When the gear are rotated, the moment of sliding carriage can be measured by the dial indicator. This values are recorded in the recorder. The spindles can be adjusted so that axial distance is equal and scale is attached to one side and vernier to the other side for measure the centre distance. If errors occur in the tooth form moment of carriage due to the error in the pitch and tooth thickness. This moment is indicated in the dial gauge. The maximum gear diameter 150mm can be tested

1.2 GEAR

• Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work

• A gear is a component within a transmission device that transmits rotational force to another gear or device .

1.2.1 TYPES OF GEAR

1. According to the position of axes of the shafts.

• Parallel

1.Spur Gear

2.Helical Gear

3.Rack and Pinion

b. Intersecting

Bevel Gear

c. Non-intersecting and Non-parallel

worm and worm gears

1.2.2 Spur

Spur gears or straight-cut gears are the simplest type of gear. They consist of a cylinder or disk with the teeth projecting radically, and although they are not straight-sided in form(they are usually of special form to achieve constant drive

ratio, mainly involute), the edge of each tooth is straight and aligned parallel to the axis of rotation.

1.2.3 Helical

Helical or “dry fixed” gears offer a refinement over spur gears. The leading edges of the teeth are not parallel to the axis of rotation, but are set at an angle.

• The teeth on helical gears are cut at an angle to the face of the gear

• This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears

• ne interesting thing about helical gears is that if the angles of the gear teeth are correct, they can be mounted on perpendicular shafts, adjusting the rotation angle by 90 degrees

1.2.4 Double helical

Double helical gears, or herringbone gears, overcome the problem of axial thrust presented by "single" helical gears, by having two sets of teeth that are set in a V shape. A double helical gear can be thought of as two mirrored helical gears joined together. This arrangement cancels out the net axial thrust, since each half of the gear thrusts in the opposite direction resulting in a net axial force of zero. This arrangement can remove the need for thrust bearings. However, double helical gears are more difficult to manufacture due to their more complicated shape.

For both possible rotational directions, there exist two possible arrangements for the oppositely-oriented helical gears or gear faces. One arrangement is stable, and

the other is unstable. In a stable orientation, the helical gear faces are oriented so that each axial force is directed toward the center of the gear. In an unstable orientation, both axial forces are directed away from the center of the gear. In both arrangements, the total (or net) axial force on each gear is zero when the gears are aligned correctly. If the gears become misaligned in the axial direction, the unstable arrangement generates a net force that may lead to disassembly of the gear train, while the stable arrangement generates a net corrective force. If the direction of rotation is reversed, the direction of the axial

thrusts is also reversed, so a stable configuration becomes unstable, and vice versa.

Stable double helical gears can be directly interchanged with spur gears without any need for different bearings.

1.2.5 Bevel gear

A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevel gears mesh, their imaginary vertices must occupy the same point. Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts. The angle between the shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and shaft axes at 90 degrees are called miter gears.

Types of Bevel Gears

Bevel gears are classified in different types according to geometry:

Straight bevel gears have conical pitch surface and teeth are straight and tapering towards apex. Straight bevel gears are shown in Figure 1.6.

Figure 1.6. Straight Bevel gears

Spiral bevel gears have curved teeth at an angle allowing tooth contact to be gradual and smooth. Spiral bevel gears are illustrated in Figure 1.7.

Figure. Spiral Bevel gears

Zero bevel gears are very similar to a bevel gear only exception is the teeth are curved: the ends of each tooth are coplanar with the axis, but the middle of each tooth is swept circumferentially around the gear. Zero bevel gears can be thought of as spiral bevel gears (which also have curved teeth) but with a spiral angle of zero (so the ends of the teeth align with the axis).

Hypoid bevel gears are similar to spiral bevel but the pitch surfaces are hyperbolic and not conical. Pinion can be offset above, or below, the gear centre, thus allowing larger pinion diameter, and longer life and smoother mesh, with additional ratios

1.2.7 Worm gear

The worm gears are widely used for transmitting power at high velocity ratios between non-intersecting shafts that are generally, but not necessarily, at right angles. It can give velocity ratios as high as 300:1 or more in a single step in a minimum of space, but it has lower efficiency. The worm gear is widely used to speed reducer and a worm wheel or gear. The worm(which is the driving member) is usually of a cylindrical form having threads of the same shape as that of an involute rack. The threads of the worm may be left handed or right handed and single or multiple threads.

Worm wheel or gear (which is the driven member) is similar to a helical gear with a face curved to conform to the shape of the worm gear is made of bronze or cast iron for light service.

The worm gearing is classified as non-interchangeable, because a worm wheel cut with a hop of one diameter will not operate satisfactorily with a worm of different diameter, even if the thread pitch is same.

TYPES OF WORMS

The following are the two types of worms:

• Cylinder or straight worm, and

• Cone or double enveloping worm.

The cylinder or straight worm is most commonly used. The shape of the thread is involute helicoid of pressure angle 14 0 for single and double threaded worms and 200 for single and double threaded worms and 200 for triple and quadruple threaded worms. The worm thread are cut by a straight sided milling cutter having its diameter not less then the outside diameter of worm or greater than 1.25 times the outside diameter of worm.

The cone or double enveloping worm is used to some extent, but it requires extremely accurate alignment.

TYPES OF WORM GEARS

The following three types of worm gears are important from the subject point of view:

• Straight face worm gear,

• Hobbed straight face,

• Concave face worm gear.

The Straight face worm gear is like a helical gear in which the straight teeth are cut with a form cutter. Since it has only point contact with the worm thread, therefore it is used for light service.

The Hobbed straightt face worm gear is also used for light service but its

teeth are cut with a hob, after which the outer surface is turned.

The Concave face worm gear is the accepted standard form and is used for all heavy service and general industrial uses. The teeth of this gear are cut

Fig:worm gear

1.2.8 Rack and pinion

A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Torque can be converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii are then derived from that. The rack and pinion gear type is employed in a rack railway.

1.3 Terminology

1.2.9 NOMENCLATURE

• Addendum circle: A circle bounding the ends of the teeth, in a right section of the gear.

• Root (or dedendum) circle: The circle bounding the spaces between the teeth, in a right section of the gear.

• Addendum: The radial distance between the pitch circle and the addendum

circle.

• Dedendum: The radial distance between the pitch circle and the root circle.

• Clearance: The difference between the dedendum of one gear and the addendum of the mating gear.

• Face of a tooth: That part of the tooth surface lying outside the pitch surface.

• Flank of a tooth: The part of the tooth surface lying inside the pitch surface.

• Circular thickness (also called the tooth thickness): The thickness of the tooth measured on the pitch circle. It is the length of an arc and not the length of a straight line.

• Circular pitch (Pc) : The width of a tooth and a space, measured on the pitch circle.

• Diametral pitch (Pd): The number of teeth of a gear unit pitch diameter. The diametral pitch is, by definition, the number of teeth divided by the pitch diameter. That is,

Where

Pd = diametral pitch

N = number of teeth

D = pitch diameter

• Module (m): Pitch diameter divided by number of teeth. The pitch diameter is usually specified in inches or millimeters; in the former case the module is the inverse of diametral pitch.

m = D/N

1.3 SHAFT

A shaft is a rotating machine element which is used to transmit power from one place to other place.

Carbon steels of grade 40C8, 45C8, 50C4, 50C12 are normally used as shaft materials.

Material properties

• It should have high strength

• It should have good machinability.

• It should have low notch sensitivity factor. iv. It should have good heat treatment properties.

v. It should have high wear resistance.

1.3.1 TYPES OF SHAFT

• Transmission shaft:

These shafts transmit power between the source and machines absorbing power. The counter shafts, line shafts, overhead shafts all shafts are transmission shafts.

• Machine shafts:

These shafts from an integral part of the machine itself.

1.4 BALL BEARING

The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this by using at least two races to contain the balls and transmit the loads through the balls. In most applications, one race is stationary and the other is attached to the rotating assembly (e.g., a hub or shaft). As one of the bearing races rotates it causes the balls to rotate as well. Because the balls are rolling they have a much lower coefficient of friction  than if two flat surfaces were sliding against each other.

Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element bearings due to the smaller contact area between the balls and races. However, they can tolerate some misalignment of the inner and outer races.

Single-direction thrust ball bearings are separable and the mounting is simple as the components can be mounted individually. There are three separable parts of this bearing known as shaft washer, a housing washer and the ball and cage assembly. The mounting of thrust bearing is shown in the Figure 1.8.

Figure 1.8. Thrust Bearing The inner diameter of the shaft washer is press fitted in the screw body.

The outer diameter of the housing washer is press fitted in the cup. These two components are separately mounted before final assembly. The life of thrust bearing is assumed to be 3000 hours.

CHAPTER 2 CONSTRUCTION AND WORKING

2.1 PRINCIPLE:

The principle of this is to mount a standard gear on a fixed vertical spindle and the gear to be tested on another similar spindle mounted on a sliding carriage,maintaining the gears in mesh by spring pressure.

2.2 PARTS:

1) Master gear

2) Gear under test

3) Fixed part

4) Movable part

5) Railing arrangement

6) Hub

7) Bearing

8) Spur gear

9) Bevel gear

10) spring

11) dial indicator

2.3 CONSTRUCTION OF PARKINSON:

It consists of gears, dial indicator, fixed and movable part, bearing and spring. The gears are mounted on the two mandrels so that they are free to rotate without measurable clearance. The left spindle can be moved along the table clamped in any desired position.

The right mandrel slide is free to move running on steel balls ,against spring pressure and it has a limited movement.The two mandrels can be adjusted so that their axial distance is equal to the designed gear center distance.

The spring pressure can be regulated.There are also screws for limiting the movement of the sliding carriage. A scale is attached to one carriage and a vernier to the othor.This enable center distance to be measured to with in 0.025 mm.

The dial indicator on the right contacts the right end of the sliding and therefore indicates any radial viriations of the gear under test as the gears are rotated.The waxed paper recorder is fitted ,the chart makes a revolution for each one of the gears mounted on the sliding carriage.As the chart moves or rotates,the line traced records the movement of the floating carriage a circle is drawn at the same time as the record.

The fig is reproduction of a few typical charts with a reduced scale and radial errors magnified about 50 times.The gear shown by No.1 record is a fully satisfactory one,that at No.2 is a moderate gear at No.3 is an unsatisfactory one.

2.4 WORKING OF A PARKINSON:

The working of the Parkinson gear tester is the movement of the sliding carriage as the gears are rotated are indicated by a dial indicator and these variations are a measure of any irregularities in the gear under test;alternatively a recorder can be fitted in the form of a waxed circular charts and records made of the gear variation in accuracy of mesh.

The correct method of testing is single-flank method in which instead of measuring center distance variation the angular variation is measured.The tester is a complex system and more costly.

An indicator is used to measure angular variation between the gear and disc on this shaft.In use ,the two discs are brought into frictional contact so that one can drive the other without slip.

This method is not popular because it requires the manufacture of two very accurate pitch discs for every gear pair of differentsize

CHAPTER 3 DESIGN CALCULATION:

3.1. HELICAL GEAR CALCULATION

• DETERMINATION OF MATERIAL PROPERTIES

From design data book for material C45 Steel

Ultimate yield stress σy = 3600 kg/cm3

Allowable yield stress [σy] = 1800 kg/cm3

Allowable shear stress [τ] = 1080 kg/cm3

Allowable bending stress [σb] = 2160 kg/cm3

• DETERMINATION OF MINIMUM CENTRE DISTANCE:

Minimum center distance amin = (i+1) Speed ratio i = 1.58

Ψ = 0.1

Young’s Modulus E = 2.15 106 kgf/cm2

Design torque [Mt] = Mt Kd K

Nominal torque Mt = 97420× = 36.53 kgfcm

Design torque [Mt] = Mt Kd K

= 36.53×1.3 =49 kgfcm

Allowable compressive stress [σc] = Cb HB KCl

= 25×229×0.9 =5152.5 kgf/cm2

Compare the above value with allowable [σc] value in step 1 value and

take the least value for further calculations.

[σc] = 2160 kgf/cm2

Minimum centre distance = (1+1)

amin = 5.956 cm

• DETERMINATION OF MODULE: Module Mav = 1.15 cosβ

Minimum No. of teeth to avoid interference

Z1 = 20

Virtual no. of teeth Zv = = = 24

Form factor Yv = 0.413 from PSG DDB Pg no. 8.18

Life factor for bending Kbl = 0.7

Endurance stress σ-1 = 0.22(σu+ σy)+500

= 0.22(3600+1600)+500 = 1424 kgf/cm2

Factor of safety n = 2

Fillet factor Kσ = 1.2

Allowable bending stress

[σb] = 479.5 kgf/cm2

Compare the above value with [σb] value in step 1 and take the least value for further

mav=1.15 cos25

mav = 0.299cm

standard module mav = 0.3 cm

• DETERMINATION OF ACTUAL CENTRE DISTANCE:

Actual centre distance a = =

a = 8.6 cm

Compare the above value with a value in step 2 and take the greater value for further calculations

Actual centre distance a = 8.6 cm

• DETERMINATION OF ACTUAL NUMBER OF TEETH

No. of teeth on pinion Z = =

Z1 = 25.14 =29 Z2 = 1.48×29 =43

• DETERMINATION OF DIAMETER OF GEARS

Pitch circle diameter of pinion d1= z1= = 6.62 cm

Pitch circle diameter of wheel d2 = z2 = = 14.23 cm

• DETERMINATION OF WIDTH OF GEARS

Ψ = = 0.1 = 0.86 cm

Width b = 1.13 cm

ψm

Width b = 0.3×10

b = 3 cm

Compare the above values and take the greater value as width for further calculations

b = 3 cm

CHECKING

• CHECK FOR INDUCED COMPRESSIVE STRESS

=

= = 0.19

Load concentration factor K = 1.13 from PSG DDB Pg no. 8.15

Velocity of drive V =0.1159 m/s

Preferred IS quality = 6 from PSG DDB Pg no. 8.3

Dynamic load factor kd= 1.3

[Mt]= 49×1.13×1.3 = 71.98 kgf/cm2

Compressive stress σc =

= 2071.97 kgf/cm2

For safe design

σc ≤ [σc]

2071.97 ≤ 2160

Design Is Safe

• CHECK FOR INDUCED BENDING STRESS

[σb] = 39.146 kgf/cm2

For design safe

σb ≤ [σb] Design Is Safe

3.2. BEVEL GEAR CALCULATION

• DETERMINATION OF MATERIAL PROPERTIES

From design data book for material C45 Steel

Ultimate yield stress σy = 3600 kg/cm3

Allowable yield stress [σy] = 1800 kg/cm3

Allowable shear stress [τ] = 1080 kg/cm3

Allowable bending stress [σb] = 2160 kg/cm3

• DETERMINATION OF MINIMUM CONE RADIUS

Radius of cone R = Ψy

Speed ratio i = 1 Ψy = = 3

Young’s Modulus E = 2.15 106 kgf/cm2

Design torque [Mt] = Mt Kd K

Nominal torque Mt = 97420× = 36.53 kgf/cm2

Design torque [Mt] = Mt Kd K

= 36.53×1.5 =54.79 kgf/cm2

Allowable compressive stress [σc] = Cb HB KCl

= 25×229×0.9 =5152.5 kgf/cm2

Compare the above value with allowable [σc] value in step 1 value and take

the least value for further calculations.

[σc] = 2160 kgf/cm2

Minimum cone radius R= 3

Rmin = 3.04 cm

• DETERMINATION OF MODULE: Module Mav = 1.28

Minimum No. of teeth to avoid interference

Z1 = 20

Reference angle δ = 14o

Virtual no. of teeth Zv = = 21

Form factor Yv = 0.396 from PSG DDB Pg no. 8.18

Life factor for bending Kbl = 0.7

Endurance stress σ-1 = 0.22(σu+ σy)+500

= 0.22(3600+1600)+500 = 1424 kgf/cm2

Factor of safety n = 2

Fillet factor Kσ = 1.2

Allowable bending stress

[σb] = 479.5 kgf/cm2

Compare the above value with [σb] value in step 1 and take the least value for further

Mav=1.28

mav = 0.158cm

standard module mav = 0.2 cm

• DETERMINATION OF ACTUAL CONE RADIUS

Transverse module mt = mt = 0.24 cm

Actual cone radius R = 0.5z

R = 0.5×0.24×20

R = 3.4 cm

Compare the above value with R value in step 2 and take the greater value for further calculations

Actual cone radius R = 3.4 cm

• DETERMINATION OF ACTUAL NUMBER OF TEETH

No. of teeth on pinion Z = =

Z1 = 16.58 16 Z2 = 1×16 =16

• DETERMINATION OF DIAMETER OF GEARS

Pitch circle diameter of pinion d1= mtz1 = 0.36×16 = 5.76 cm

Pitch circle diameter of wheel d2 = mtz2 = 0.36×48 = 5.76 cm

• DETERMINATION OF WIDTH OF GEARS

Ψy

Width b = 1.13 cm

ψm

Width b = 0.2×10

b = 2 cm

Compare the above values and take the greater value as width for further calculations

b = 2 cm

CHECKING

• CHECK FOR INDUCED COMPRESSIVE STRESS

=

= = 0.19

Load concentration factor K = 1 from PSG DDB Pg no. 8.15

Velocity of drive V =0.12 m/s

Preferred IS quality = 10 from PSG DDB Pg no. 8.3

Dynamic load factor kd= 1

[Mt]= 36.53×1×1 = 36.53 kgf/cm2

Compressive stress σc =

σc = 2107.8 kgf/cm2 For safe design

σc ≤ [σc]

2107.8 ≤ 2160

Design Is Safe

• CHECK FOR INDUCED BENDING STRESS

[σb] = 247.94 kgf/cm2

For design safe

σb ≤ [σb] Design Is Safe

3.3. SPRING CALCULATION

C = 0.2 KW

P = 7 N

• DETERMINATION OF MATERIAL PROPERTIES

The chosen shaft material is (C15 steel)

Ultimate Yield stress σy = 500 N/mm2

Allowable Yield stress [σy] = 250 N/mm2

Allowable Shear stress [τ] = 150 N/mm2

Assume factor of safety = 2

• DETERMINATION OF DIMENSION OF SPRING:

Shear stress τ =

Whal stress factor =

Ks = 1.1448

150 =

coil diameter = 1.14 mm = 1mm

Mean wire diameter = 10 mm

• DETERMINATION OF NUMBER OF TURNS:

Deflection of spring y =

36 =

Number of coils = 58

• DETERMINATION OF SOLID HEIGHT, FREE LENTH AND PITCH:

Free length = pn+d

Solid length = dn+d = 1×58+1 = 59 mm

Free length = solid length + maximum expansion

= 59 + 36 = 95 mm

Free length = pn+d = 95

Pitch = 1.6 mm

3.4. BEARING CALCULATION

Radial load = 100 N = 10 kgf

Axial load = 75 N = 7.5 kgf

Life = 2 years

Speed = 40 rpm

I. DETERMINATION OF EQUIVALENT LOAD

Assume the bearing as deep groove ball bearing PSG DDB Pg No. 4.2

Equivalent Load P = [(XFr)+(YFa)]S =

Service factor S = 1.3

From PSG DDB Pg.No. 4.4 > (0.22-0.44)

X= 0.56 Y= 1

P = [(0.56×100)+(1×75)]×1.3

Equivalent Load P = 170.3 N = 17.03 kgf

II. DETERMINATION OF DYNAMIC LOAD

Dynamic Load C ×P From PSG DDB pg no. 4.2 L10 = 1 mr

K = 3 for ball bearings

Life L = 2×365×12×60×40

= 21.024 mr C =

Dynamic load C = 470.02 N

= 47 kgf

III.SELECTION OF BEARING

For equivalent Shaft diameter = 22 mm

Dynami capacity =47 kgf

SKF 6004 can be selected from PSG DDB Pg.No. 4.2

Shaft diameter d

= 22 mm

Bearing diameter D

= 42 mm

Width of bearing B

= 12 mm

Dynamic load C

= 735 kgf

Static load C0 = 450 kgf

IV.TOLERANCE ANALYSIS

from PSG DDB Pg.No. 4.8

for shaft, type of condition is light and variable load j6

for housing, type of condition is normal and light load J7

from PSG DDB Pg.No. 3.8

Shaft diameter= 22 mm

Bearing outside diameter= 42 () mm

Chapter 4 : FABRICATION

4.1. BEVEL GEAR

Bevel gears are used for 90º power transmission. Some materials chosen for bevel gear are Cast Iron, Steel, Cast Steel, Carbon Steel, Alloy Steel and Non-Metallic Materials. Bevel gears are manufactured on precision generating machines by indexing method ensuring that the teeth should be of tapered depth and thickness. Teeth are cut on the outside of the cone. They have a straight tooth geometry, which if extends, passes through the intersection of their axes. Bevel gears are generally known as straight bevel gears. Straight bevel angles can also be with one gear flat with a pitch angle of 90º. They have conical pitch surfaces that operate on intersecting axes. They can be designed and cut to operate on any shaft angle. In bevel gears when each tooth engages it impacts the corresponding tooth and simply curving the gear teeth can solve the problem. These gears are recommended at less speed and when loads are light. At higher speed they makes noise. The most preeminent function of these gears is in a bevel gear differential. Bevel gears are also used in steel plant, material handling system and cooling towers etc.

4.2. HELICAL GEAR

Helical or dry fixed gears offers a refinement over spur gears. They are generally made up of Carbon Steel, Cast Iron, Alloy steel and Non-Metallic Materials. These gears are manufactured by various processes. These are, casting, stamping, rolling, extruding, and machining. Gears can also be produced by powder metallurgy. Among the above said process, machining process in most commonly used. It is an accurate method. Basically gears are produced by machining by a) Forming method. b) Generating method.

4.2.1. GEAR FORMING

In this method a form cutter is used. The formed cutter may be single point cutting tool or a multipoint milling cutter. The cutting edges formed cutter has been finished to the shapebetween the gear teeth being cut. Forming method is used for producing very small numberof gears. Gears produced by forming are less accurate. Forming process is simple

and cheaper.This method is takes more time.

4.2.2. Gear Generating

This method of gear manufacturing is based on the fact that any two involute gears of the same module will mesh together. Here one of the meshing gears is made as the cutter. The other gear rotates and also reciprocates along the width of the gear blank. Because of the relative rolling motion between cutter and the blank, gear teeth are generated on the gear blank. The gear may be generated by rack cutter, pinion cutter or a hob. Using the generated method, profile of the gear teeth can be very accurately produced. The following generating methods used for gear production are Gear shaping, Gear planning, Gear hobbing.4.2.2.1. Gear Hobbing

It is a process of generating a gear by means of a rotating cutter called hob. The hob has helical threads. Grooves are cut in the threads parallel to the axis. This will provide the edges. Proper rake and clearance angle are ground on these cutting edges. The rotating hob acts like a continuously moving rack as it cuts. The blank is mounted on a vertical arbour. The hob is mounted in a

rotating arbour. The hob axis is tilted the hob lead angle so that its teeth are parallel to the axis of the gear blank.

4.3. SHAFTS

Shafts are usually made up of Cast Iron. A higher diameter rod is reduced into required dimensions by conducting facing and turning operations on lathe machine. Facing is the operation which is used to reduce the length of the shaft. Facing usually carried out on both sides of the shafts. Turning is one of the most common of metal cutting operations. In turning, a workpiece is rotated about its axis as single-point cutting tools are fed into it, shearing away unwanted material and creating the desired part. Turning can occur on both external and internal surfaces to produce an axially-symmetrical contoured part.

4.4 Ball Bearings

Ball bearings are at the heart of almost every product with a rotating shaft. Ball bearings are generally made up of high carbon steel. The varios processes involves in the fabrication of ball bearings are turning operation, centerless grinding, heat treatment, hardness testing rough grinding, finish

grinding, honing and super finishing. The rings, balls and cages are manufactured in different sections and finally assembled together.

4.5 Rail Setup and Assembly

The rail setup is used for the to and fro motion of the movable gear assembly. Welding and drilling operations are used for the assembly of rail setup and the whole setup. There are many welding processes used in modern metal fabrication and repair. The primary differences between the various welding processes are the methods by which heat is generated to melt the metal. The most common types of welding are oxy-fuel gas welding (OFW), arc welding (AW), and resistance welding (RW). Here OFW and AW are used. One of the most popular welding methods uses a gas flame as a source of heat. In the oxy-fuel gas welding process heat is produced by burning a combustible gas, such as acetylene, mixed with oxygen. Gas welding is widely used in maintenance and repair work because of the ease in transporting oxygen and fuel cylinders. Using gas welding metal plate of nearly 10mm can be cut. Arc welding is a process that uses an lectric arc to join the metals being welded. A distinct advantage of arc welding over gas welding is the concentration of heat. Arc welding is generally used for join two metal parts.

Drilling is the operation used for producing a small hole for the assembly of whole parts using bolt and nut. This operation is simply carried out by drilling machine and drill bit. Due to high speed of rotation of the drill bit a hole can be generated on the metal plete. Usually the drill bit is made up of high carbon steel.