1. Unit 1
Machine Elements
9/20/2018

2. Introduction to Machine
A machine is device, consisting of various elements arranged
together, so as to perform the prescribed task to satisfy
human needs.
INPUT
(Source of Energy)
MACHINE (Arrangement of elements)
OUTPUT (Prescribed task)
A machine is capable of doing some useful work. It converts
and transfers energy.
Examples:- pump set, I.C. engines, turbine, screw jack etc.
9/20/2018

3. Introduction to machine
9/20/2018

4. Machine elements
Any machine is made up of number of different components.
An individual component of the machine is known as
machine element.
Each component performs a specific function.
The functions of machine elements:-
Holding the different components of machine.
Supporting the different components of machine.
Transmitting the power from one machine component to
another.
9/20/2018

5. Types of machine elements
Holding Type Element
Supporting Type Element
Power transmitting element
Keys
Nuts and bolts
Cotters
Rivets
Axles
Bearings
Brackets
Body or Frame
Shafts
Pulleys and belts
Sprockets and chains
Gears
9/20/2018

6. Machine Elements The machine elements which we are studying: Shaft
Axle
Key
Couplings
Bearings
Clutches
Brakes
Belts
Gears
9/20/2018

7. Shaft A shaft is a rotating member which transmits power from
one point to another.
The shaft is rotated by application of tangential force which is
applied through pulleys and gears mounted on the shaft.
As tangential force is acting on shaft, they are generally made
round in cross section.
Types of shaft:-
A. Transmission Shaft: B. Machine shaft:
i. Line shaft i. Spindle.
ii. Counter shaft ii.Crank shaft
9/20/2018

8. Types of shaft Transmission shaft :-
A shaft which is used to transmit the power between the
machine generating power and absorbing power.
e.g: Fire Pump, Portable Agriculture Pump.
The transmission shafts supports transmission elements like,
gears, pulleys, sprockets etc.
The transmission shaft are subjected to torque, bending
moment and axial force.
The examples of transmission shaft are line shaft and counter
shaft.
9/20/2018

9. Explain here with Diagram
Sr.
Line Shaft
Counter Shaft 1
It’s a Primary Shaft which is directly driven by Prime mover and from which power is supplied to different machines by using gear, belt etc.
It is a secondary shaft driven by main shaft through belt, chain or gear drive and from which power is supplied to different machines.
Explain here with Diagram
9/20/2018

10. Types of shaft 2. Machine shaft :-
A machine shaft is the short rotating shaft which is an
integral part of machine itself.
The machine shaft are also subjected to torque, bending
moment and axial force.
The examples of transmission shaft are spindle and crankshaft.
e.g: Spindle, crank shaft
9/20/2018

11. Types of Shaft A) Solid shaft B) Hollow shaft C) Stepped shaft
Solid shaft are used in all types of
machines.
Hollow shafts are lighter in weight than
solid shafts.
Hollow shafts provide more strength per
kg weight of the shaft.
The shaft is also made stepped for fixing
transmitting elements like pulleys, gears
and bearings.
B) Hollow shaft
C) Stepped shaft
9/20/2018

12. Shaft material and their properties
The material used for shaft should have following properties:-
It should have high strength and good machinability.
It should have high wear resistance and good heat treatment
properties.
iii. It must be hard enough and posses good corrosive resistance.
iv. It should be ductile.
The material used for shaft are:-
i. The common material used for shaft is mild steel.
The Plain Carbon steel (containing 0.4 to 0.6 % carbon) is preferred where
high strength and wear resistant is required. e.g: 40C8,45C8,55C8
iii. Alloy steels such as nickel, chromium and molybdenum steels are used
where very high strength and corrosive resistance are needed. e.g: 40Cr1.
Manganese = Improving Hardenability
9/20/2018

13. Axle Axle is an non rotating machine element which is used to
support rotating machine elements like wheels, pulleys etc.
An axle does not transmit torque. It is subjected to bending
moment and axial force.
The purpose of axle is to secure the wheels or gears to specific
locations relative to other wheels or gears.
There are three different kinds of axles in vehicles:-
Straight axle
Split axle
Tandem axle
9/20/2018

14. Axle
9/20/2018

15. Difference Between shaft and axle
Sr.
Shaft
Axle 1
It is a rotating element of a machine.
It is stationary element of a machine. 2
Bending, torsional and axial stresses are acting on shaft.
Only bending and axial stresses are acting on axle. 3
Specially used to transmit the power.
Specially used for support for rotating members such as bearings, wheels, idler gears, etc. 4
Application :
Propeller shaft in four wheel drives Crank shaft in engine.
Front wheel axle in 4 wheelers
9/20/2018

16. Keys
Key is an element used to prevent relative motion between a shaft and the part mounted on it, such as pulley and gear wheel.
A groove/recess/slot is cut on surface of the shaft, parallel to its axes and in the hub of the part to be mounted. They are called keyways.
The material used for keys are plain carbon steels and alloy steels.
The material used for key are is of lesser strength than the shaft material.
Function of keys:-
Prevent the relative motion between the shaft and hub of
rotating element like gear, pulley or sprocket.
To transmit the torque from the shaft to rotating elements.
9/20/2018

17. Keys
9/20/2018

18. Types of keys The keys are broadly classified into six types:-
Sunk Key
Square sunk key
Rectangle sunk key
Parallel sunk key
Gib-head sunk key
Feather sunk key
Woodruff key.
2. Saddle key
Flat saddle key
Hollow saddle key
3. Round key and taper pins
4. Kennedy key
5. Tangent key
6. Splines
9/20/2018

19. Types of keys Sunk Key :-
The sunk keys are provided half in the keyway of the shaft and half in the
keyway of the hub or boss of the rotating element.
Square sunk Key:-
w = t = d/4
Taper of 1:100 is provided on hub side.
Square sunk key
Rectangular sunk key:-
w = d/4, t = d/6 or 2/3 w.
Taper of 1:100 is provided on hub side.
Parallel sunk key:-
No taper is provided.
Application: Gearbox
Rectangular sunk key
9/20/2018

20. Types of Keys d) Gib-Headed sunk Key:-
Rectangular tapered sunk key with gib head
provided at one end.
Easy removal and installation of key.
Flywheel, pulley, gear, overhaging shaft
Gib-Headed Key
e) Feathered sunk key:-
It is parallel key fasten either to shaft
or hub.
It prevents relative rotary motion
but Permits axial relative motion between
shaft and hub. e.g: clutch & gear shifting device.
Feathered Key
f) Woodruff key:-
The key is a piece of cylindrical disc segment of
uniform strength.
Used to transmit small torques.
Woodruff Key
9/20/2018

21. Types of keys 2. Saddle Key :-
The saddle key is a tapered key which completely fits in the keyway
provided in the hub of rotating element.
The torque is transmitting due to the friction between the key and the
shaft. Hence the torque transmitting capacity of saddle is low.
The different saddle keys are:
Flat saddle key:-
It is a taperless key which sits on a flat
surface provided on shaft and fits
in a keyway provided in the hub.
Hollow saddle key:-
It is a tapered key which fits in a
keyway provided in the hub.
The key is hollow so as to sit on the
curved surface of the shaft.
9/20/2018

22. Types of keys Round Keys:- Circular in cross section.
Fitted into the partly drilled holes in shaft
and hub.
Used for low power transmission.
Round Key
Tapered pins:-
Taper of 1:50 is provided.
Used for low power transmission.
Tapered pin
Splined shaft:-
Consist of multiple integral keys in 4,6,10
or 16 in number.
Strength is more than single keyway shaft.
Used for large power transmission.
Used in automobile gear box.
Splines
9/20/2018

23. Types of keys Tangent key:- Consist of two tapered rectangular keys
placed at 900 apart.
Each key withstands torque in one direction.
Used in heavy duty industrial application.
Tangent Key
Kennedy Key:-
Consist of two tapered square keys placed
at 900 apart.
Used in heavy duty industrial application.
Kennedy Key
9/20/2018

24. Couplings
Coupling is an important mechanical element used to connect two shafts or to couple driver shaft with driven shaft.
Shafts are usually available up to 7 meters length due to inconvenience in transport.
Inorder to have greater length, it is necessary to join two or more pieces of shaft by means of couplings.
So a coupling is a device used to connect two shafts permanently so that necessary power and torque can be transmitted.
The coupling can be used when,
- When axes of shaft are collinear.
- When two shafts are intersecting.
- When two shafts are parallel and some distance apart.
9/20/2018

25. Requirements of Couplings
The requirements of good couplings are,
It must transmit full power of the driving shaft.
It should keep the shaft in perfect alignment or it should absorb the slight mis-alignment between the shaft.
It should be easy to connect and disconnect the coupling.
It should be able to operate in any type of operating condition.
It should not transmit shock loads.
vi It should be easily available at low cost.
vii. It should not have any projected part.
9/20/2018

26. Types of shaft couplings
The shaft couplings are classified into two types:-
Rigid coupling:-
Rigid couplings are used to connect two shafts which are perfectly aligned.
These couplings has no flexibility hence the shafts need to be in good alignment, in order to avoid excessive loads on coupling or shaft bearing.
Following are types of rigid couplings:-
Flange coupling
Sleeve or Muff coupling
Clamp or compression coupling
9/20/2018

27. Types of shaft couplings
Flexible coupling:-
Flexible coupling used to connect two shafts consisting of small amount of mis-alignment which may be lateral or angular.
The shock and vibration absorption capacity of these couplings is more.
Following are types of flexible couplings:-
Bushed pin type flexible coupling
Oldham’s coupling
Universal coupling or Hook’s joint
9/20/2018

28. Types of Rigid coupling
Rigid flange coupling:-
It consist of two separate cast iron flanges, which are mounted on shaft with the help of key.
The two flanges are coupled together by means of nut and bolts.
Advantages:
It is simple in construction.
It is easy to assemble and disassemble.
It has high torque transmitting capacity.
Disadvantage:
If there is small misalignment between shafts, then flange coupling can not be used.
This coupling is used when the motion is free from shocks and vibrations.
9/20/2018

29. Types of Rigid coupling
Applications:
Used to connect electric motor to pump or electric motor to compressor.
Flange coupling is generally used for heavy loads and in long shafts.
Rigid flange Coupling
9/20/2018

30. Types of Rigid coupling
2. Sleeve or muff coupling: Clamp or compression spring
9/20/2018

31. Types of flexible coupling
Bush pin type coupling:-
In bush pin type flexible
coupling, rubber bushes are
used which are inserted into
the flanges.
It can tolerate very small
amount of lateral or angular
misalignment.
9/20/2018

32. Types of flexible couplings
2. Oldham coupling:-
Used for connecting two shafts whose axes are parallel and at a small distance(lateral) apart.
There is a relative sliding motion between flanges and intermediate circular disk.
9/20/2018

33. Types of flexible coupling
3. Universal coupling or Hook Joint:-
Used for connecting two non parallel and intersecting shafts having small angle between them.
It consist of two U shaped yokes or forks and a cross or connecting link.
This is used to transmit power from the gear box of automobile engine to the rear axle.
9/20/2018

34. Bearing
Bearing is a machine element used for supporting rotating shaft and carry loads applied to them.
It permits relative motion between bearing surface and shaft surface and facilitate smooth running.
Relative motion, sets up frictional force and certain amount of power loss to overcome this frictional force.
The frictional force generates heat.
So lubrication is provided between two surfaces to avoid wear, power loss and heat generation.
9/20/2018

35. Types of Bearings
The bearings are generally classified into sliding contact bearings and rolling contact (antifriction) bearings.
Sliding Contact bearings
The bearing in which the contacting surface makes sliding contact or are seperated by a film of lubricant are known as sliding contact bearings.
a. Journal Bearing
b. Thrust Bearing
Rolling contact bearings
The bearings in which the contacting surfaces make a rolling contact are known as rolling contact bearings.
a. Ball bearing
b. Roller bearing
9/20/2018

36. Sliding contact bearings
The Sliding contact bearings are:
Journal Bearing
The relative sliding motion between the two parts is rotary.
The load is acting perpendicular to axis of the shaft.
Journal bearing supports radial loads.
Load
Journal Bearing
Thrust Bearing
The relative sliding motion between the two parts is rotary.
The load is acting parallel to axis of the shaft.
Thrust bearing supports axial (Thrust) loads.
Thrust Bearing
9/20/2018

37. Rolling contact bearing
The rolling contact bearings are ball bearing and roller bearings.
The ball and roller contact bearing consist of an inner race which is mounted on shaft or journal and an outer race which is carried out by the housing or casing.
In between inner and outer race there are balls or rollers, these are held at proper distances so that they will not touch each other.
In ball bearings the contact between balls and inner & outer race is point contact.
Where as in roller bearings the contact between rollers and inner & outer race is line contact.
9/20/2018

38. Rolling contact type Ball Bearing
Balls
Outer Race
Cage
Inner Race
Ball Bearing
9/20/2018

39. Rolling contact type Roller Bearing
Rollers
Outer Race
Cage
Inner Race
Roller Bearing
9/20/2018

40. Types of Ball Bearing The different types of ball bearings are:
Single row deep groove ball bearing:-
Take radial as well as thrust load.
Carry high radial load and moderate
thrust (axial) load.
Double row deep groove ball bearing:-
Carries heavier radial and axial loads.
Used instead of using two single row deep groove
ball bearings.
Angular contact ball bearing:-
Carries substantial thrust (axial) load in
addition to radial load.
Thrust ball bearing:-
Used to take pure thrust (axial) loads.
9/20/2018

41. Types of Roller Bearing
The different types of roller bearings are:
Cylindrical roller bearing:-
Take greater radial load.
Cannot take thrust (axial) load.
Needle roller bearing:-
Carries heavier radial loads.
Used where radial space is limited.
Taper roller bearing:-
Carries high radial and thrust (axial) load.
Taper roller Thrust roller bearing:-
Used to take pure thrust (axial) loads.
9/20/2018

42. Comparison between Ball & Roller bearing
Sr. No.
Comparison parameter
Ball Bearing
Roller Bearing 1
Rolling Element
Spherical balls
Cylindrical rollers, Taper rollers or spherical rollers. 2
Nature of contact
Point contact
Line contact 3
Load carrying capacity
Due to point contact load carrying capacity is low
Due to line contact load carrying capacity is high 4
Radial dimensions
Radial dimensions are more
Radial dimension is less 5
Axial Dimensions
Axial dimensions is less
Axial dimension is more
9/20/2018

43. Clutch
9/20/2018

44. CLUTCH Clutch Introduction
A Clutch is a machine member used to connect the driving shaft to a driven shaft, so that the driven shaft may be started or stopped at will, without stopping the driving shaft.
A clutch thus provides an interruptible connection between two rotating shafts
Clutches allow a high inertia load to be stated with a small power.
A popularly known application of clutch is in automotive vehicles where it is used to connect the engine and the gear box.

45. Clutch
Clutch is mechanical device used to connect or disconnect driving shaft from the driven shaft at the will of operator.
It is mounted between driving shaft and driven shaft.
Mostly clutch is used in
Automobiles.
9/20/2018

46. Classification of clutch
The clutch is classified into general two types:
Positive clutch
Positive clutch are used when positive drive is required.
a. Square jaw clutch
Friction clutch
Friction clutch is a non positive drive clutch.
a. Disc or plate clutch
i. Single plate clutch
ii. Multi plate clutch
b. Cone clutch
c. Centrifugal clutch
9/20/2018

47. Classification of clutch

48. Positive clutch Positive clutches are used when
positive drive is required.
The Jaw clutch is the simplest type
of positive clutch.
It permits one shaft to drive another
shaft through a direct contact of
interlocking jaws.
Square jaw toothed clutch
9/20/2018

49. Positive clutch Advantages of positive clutch 1) They do not slip.
2) No heat is generated.
3) Requires little or no maintenance.
4) Design is simple.
Disadvantages of positive clutch
1) They cannot be engaged at high speeds.
2) Sometimes, they cannot be engaged when both shafts are at rest unless the jaws are aligned.
3) Engagement at any speed is accompanied by shock.
4) Frequent engagement and disengagement cause wearing of jaws, which affects their performances.
Applications of positive clutch :
Automotive transmission, presses, punches and household
appliances like kitchen grinding machine.
9/20/2018

50. Friction clutch
Transmit power or motion by friction between contacting surfaces.
Uses:
Transmission of power of shaft and machines which must be started and stopped frequently.
When power is to be delivered to machines partially or fully loaded.
Requirements:
The contact surface should develop sufficient frictional force that may pick up and hold the load.
The heat of friction should be rapidly dissipated and tendency to grab should be minimum.
The surface should be backed by a material stiff enough to ensure a reasonably uniform distribution of pressure.
9/20/2018

51. Friction clutch
9/20/2018

52. Friction single plate clutch
Construction:
A single plate clutch consist of one driving plate and driven plate (Friction plate).
The driving plate is rigidly keyed to the driving shaft, while driven plate is free to slide axially on the splined driven shaft.
The friction lining, made of friction material like asbestos is either riveted or pasted to the driven plate.
The helical compression spring exerts the axial force on the driven plate or friction plate.
Single plate clutch
The disengagement sleeve, lever and
clutch pedal is used for disengaging the
clutch.
9/20/2018

53. Friction single plate clutch
Working:
The helical compression spring presses the driven plate (friction plate) against the driving plate.
The spring creates an axial force between the driven plate (friction plate) and driving plate.
The frictional force between the two plates is responsible for transmitting the torque or power.
In engaged condition, the torque is transmitted from driving shaft through key to driving plate, from driving plate to driven plate due to frictional force and
Single plate clutch
finally from driven plate through the
splines to the driven shaft.
9/20/2018

54. Friction single plate clutch
Working:
Due to force exerted by the helical spring, the clutch is normally in engaged position.
The friction clutch is not positive type and hence can slip under certain conditions.
In order to disengage the clutch, the clutch pedal is pressed downward. Due to this, the liver displaces the disengagement sleeve to the right.
Due to sufficient area is available for heat dissipation in single plate clutches, no cooling oil is required.
Single plate clutch
The single plate clutch are of dry type.
Applications:
Truck, Buses, Cars
9/20/2018

55. 9/20/2018

56. Multi-plate Clutch

57. Cone clutch
They are usually now confined to very specialist transmissions in racing cars and power boats.
This is because the clutch does not have to be pushed in all the way and the gears will be changed quicker.

58. Centrifugal clutch
As engine revolutions per minute increase, weighted arms in the clutch swing outward and force the clutch to engage
Centrifugal clutches are often used in
 mopeds,mini bikes.

59. Brakes
A Brake is a device used to apply frictional resistance to moving member to retard or stop the motion.
In this process it absorb kinetic energy of moving member and which is dissipated in the form of heat.
Requirements: It should have
High coefficient of friction and heat dissipation capacity.
Low wear rate.
Adequate mechanical strength.
No effect of moisture or oil.
9/20/2018

60. Classification of Brakes
Drum Brake
Disc Brake
Mechanical
Brakes
Band Brake
Hydraulic
Block Brake
Electric
Magnetic
9/20/2018

61. Disc Brake Disc brake is a wheel brake which
slows rotation of the wheel by
friction.
Most of modern car have disc brake
on front wheel and some have disc
brake on all wheels.
The main component of disc brake
are:
The brake pads
The caliper which contains piston.
The rotter which is mounted on
hub
9/20/2018

62. Disc Brake The brake pads are pushed against
the rotor to stops the rotation of
wheel.
The actuation of brake pad is done
with the help of piston and caliper
arrangement.
The piston is forced either
mechanically, hydraulically,
pneumatically or electromagnetically.
The friction causes the disc and
attaches wheel to slow and stops.
9/20/2018

63. Block or shoe Brakes Double block shoe brake Single block shoe brake
Application: Trains, tram cars etc.
Application: Hoisting machineries,
trains etc.
9/20/2018

64. Internal expanding shoe brake
Application: Used in automobile vehicles trucks, cars, motorcycles, scooters etc.
9/20/2018

65. Band and Band – block brake
Band and block Brake
Band Brake
Application: Used in material handling instruments.
9/20/2018

66. Power Transmission Devices
Why to use ?
Many times power generated cannot be used at point of generation and it is to be
taken at point of use.
The device used for this purpose is known as Mechanical drive or power
transmitting devices.
Ex:- The power produced by engine shaft is to be transmitted to propeller shaft and
is done by power transmitting devices.
The requirements of good power transmitting devices are:
The drive should be efficient and reliable.
The capital and maintenance cost should be low.
It must be able to change the speed in steps as per the requirements.
The drive should be compact and weight/power ratio should be as minimum as
possible.
9/20/2018

67. Power Transmission Devices
The different types of power transmission devices are:-
Belt Drive
Chain Drive
Gear Drive
9/20/2018

68. Power Transmission Devices
The belts and ropes are flexible members which are used
where distances two shaft is large. The belts and ropes
transmit power due to the friction between the belt or rope
and pulley. The belt drive are non positive drive.
The chain also have flexibility but they are preferred for
intermediate distances. The chain drive is positive drive.
The gears are used when the shafts are very close with each
other. This type of drive is called as positive drive because
there is no slip. If distance is slightly larger, chain drive can
be used for making it a positive drive.
9/20/2018

69. Belt Drive
Belts are flexible machine elements which are used to transmit power from one
shaft to another between two parallel shafts.
The power is transmitted due to friction between belt and pulley.
The belt drive basically consist of three elements, driving pulley on driving shaft,
driven pulley on driven shaft and belt.
Application:- Transportation of coal, mineral ores over a long distances.
9/20/2018

70. Types of Belt Drive The belt drives mainly are of the common types:
Open Belt Drive
Cross Belt Drive
Compound Belt Drive
Open Belt Drive:
In open belt drive direction of rotation of
both the pulleys are same.
This is used when shafts are parallel.
9/20/2018

71. Types of Belt Drive 2. Cross Belt Drive:
In cross belt drive pulleys rotate in
opposite direction.
The belt has to bend in two different
planes, as result of this belt wear is
more.
3. Compound Belt Drive:
The compound belt drive is used when
power is to be transmitted from one shaft
to another through number of pulleys.
It gives relatively high reduction ratio.
9/20/2018

72. Velocity ratio of belt drive
Speed ratio or velocity ratio of the belt drive is the ratio of speed of driving
pulley to the driven pulley.
The linear speed of belt, Or
The speed ratio or velocity ratio i,
If thickness of belt is considered, then velocity ratio i
9/20/2018

73. Power transmission capacity of belt drive
The power transmitted by belt drive is given by,
Equating the power transmitted by driving and driven belt, we get
9/20/2018

74. Types of Belts
There are three types of belts which are commonly used for power transmission,
Flat belt
V- belt
Rope
Rope or circular belt:
Used to transmit large amount of power from one pulley to another, when the
two pulleys are more then 5 meter apart.
In circular belt pulleys are provided with the grooves.
9/20/2018

75. Types of Belts Flat Belt:
The flat belt is rectangular in cross section. The pulley for this belt is slightly
crowned to prevent slip.
Flat belt transmit moderate amount of power from one pulley to other pulley
when shafts are considerable distance apart (but < 15 m).
Advantages:
Transmit power over large distance.
Relatively cheap and easy to maintain.
High efficiency.
Disadvantages:
Slip is more.
Occupy more space.
Can not transmit very large power.
Can not be used for short centre distances.
Applications: Floor mills, pumps, stone crushers, conveyors.
9/20/2018

76. Types of Belts
3. V Belt:
The V-belt is trapezoidal in section having included angle 400.
They are preferred when large power is to be transmitted over comparatively
shorter distance.
Several V belts can also be used together if more power is to be transmitted.
Advantages:
Transmit more power as compared to flat belt.
Compact construction.
Can be used for high velocity / speed ratio.
Operation is smooth and quite.
Disadvantages:
Efficiency is lower than flat belt.
Costlier as compared to flat belt.
Can not be used to transmit power over large distances.
Applications: Blowers, compressors, pumps, Lathes, Farm machineries etc.
9/20/2018

77. Comparison between Flat and V Belt
Sr. No.
Flat Belt
V Belt 1
Rectangular in cross section.
Trapezoidal in cross section. 2
Flat belts have joints.
V- Belts are endless. 3
Flat belt drive requires flat pulleys, which are simple in construction.
V-Belt drive requires V-pulleys, which are complicated in construction. 4
Used to transmit power over large distances.
Used to transmit power over short distances. 5
Used to transmit medium power.
Used to transmit large power. 6
Can not be used for high speed reduction ratio.
Can be used for high speed reduction ratio. 7
Flat belts are cheaper.
V-Belts are costlier.
9/20/2018

78. Material Used for Belts
The desirable properties of material used for belt are:
It should have high coefficient of friction.
It should be flexible.
It should have high durability.
It should have high strength.
The material used for belts are:
Leather
Fabric
Rubber
Polyester or Polyamide.
9/20/2018

79. Chain Drives
In case of belt and rope drives the slipping may accour, to avoid slipping, steel
chains are used.
The chains are made up of number of rigid links which are hinged together by pin
joints in order to provide the necessary flexibility for wrapping round the driving
and driven wheel.
These wheels have projecting teeth of special profile and fit into the corresponding
recesses in the links of the chain.
9/20/2018

80. Chain Drives
9/20/2018

81. Chain Drives Advantages Disadvantages
As no slip take place during chain drive, hence perfect velocity ratio is obtained.
Since chains are made up of metal, therefore it occupies less space and transmits more power than belt or rope drive.
It may be used for both long and short distances.
It gives high transmission efficiency.
It gives less load on shaft.
It can operate at high temperature.
The production cost of chain is relatively high.
The chain drive needs accurate mounting and more maintenance particularly lubrication and slack adjustment.
9/20/2018

82. Gears
Slipping of a belt or rope is a common phenomena, whereas the chain do not
transmits motion precisely and constantly.
In case of precision machine, belts, ropes, chains can not be used. There we require
positive drive, called as gears.
9/20/2018

83. Gears Friction wheels:-
Consider two plain circular wheels A and B mounted on shaft.
When wheel A is rotated by rotating shaft , it will rotate the wheel B in the
opposite direction.
9/20/2018

84. Classification of Gears
Spur Gear
Parallel Axis Gears
Helical Gear
Herringbone Gear
Gears
Intersecting Axis Gears
Bevel Gear
Non parallel Non intersecting axis gears
Worm Gear
Rack and Penion
9/20/2018

85. Types of Gears Spur Gears: To transfer rotating motion between two
parallel shafts.
Helical Gears:
To transfer rotating motion between two
parallel shafts.
Bevel Gears:
To connect two non parallel shafts whose
axis are intersecting.
9/20/2018

86. Types of Gears Worm and Worm Wheel:
To transfer rotating motion between two
shafts whose axis are non-intersecting
and non-parallel.
Rack Pinion:
To convert rotary motion into linear motion
and vice versa.
9/20/2018

87. Spur Gear
Spur gears are used to transmit the power between two parallel shafts.
The spur gears are having teeth cut parallel to axis of gear.
They are used for transmitting moderate amount of power.
Advantages:
Easy to manufacture.
Cheaper as compared to other types of gears.
Efficiency is high.
Disadvantages:
Operation is noisy.
Not suitable for high speed application.
Power transmitting capacity is low.
Can’t take heavy loads.
9/20/2018

88. Spur Gear Drive (Simple Gear Train)
Velocity ratio or Speed ratio is defined as ratio of speed of penion to
speed of gear.
Module =
9/20/2018

89. Power transmitting capacity of Gear Drive
The power transmitting capacity of gear is given by,
Power in the pinion = Power in the gear
9/20/2018

90. Thank you
9/20/2018