This document discusses various methods of power transmission, including belt drives, gear drives, chain drives, and rope drives. It provides definitions and classifications for each method. Belt drives can be classified by distance between pulleys, material, and power/speed. Gear drives can be classified by position of axes, peripheral velocity, and type of gearing. Chain drives are classified by usage. Rope drives use fiber or wire ropes. Each method has advantages like efficiency and flexibility, as well as disadvantages like noise and required maintenance. The document concludes that power transmission allows motion from one location to drive other mechanisms and alter characteristics like torque and speed.

1. Power transmission
Submitted To:
Ms. Zulfa Ferdous
Senior Lecturer
Submitted By:
Name: Atiqul Islam
ID No: 2016000400081
Batch: 31st
Section: B
Course Code: ME-2033
Course Title : Elements of theory of machine & machine design

2. Articles of discussions
 What is power?
 What is power transmission ?
 Methods of power transmission
 Definition of Belt drive
 Classification of belt
 Classification of flat belt drive
 Advantages and disadvantages of belt drive
 Gear drive
 Classification of gears
 Definition of gear train and its classification
 Advantages and disadvantages of gear train
 Chain drive
 Classification of chain drive
 Advantages and disadvantages of chain drive
 Rope drive
 Alignment of rope drive
 Advantages and disadvantages of rope drive
 Conclusion

3. What is power?
Power is the ability to cause or prevent any action. It is the rate of
doing work the amount of energy transferred per unit time.
Mathematically,
power=
What is power transmission?
Power transmission is a mechanism the transmission of mechanical
power, usually with a transformation of the forces, torques, speeds
and some cases , the nature of the motion.
Power can be transmitted by means of several types of methods. There
are four mean of power transmission process. They are given bellow:
 Belt drive
 Gear drive
 Chain drive
 Rope drive

4. Definition of Belt drive:
A belt is a loop of flexible material used to link two or more
rotating shafts mechanically, most often parallel. Belts may
be used as a source of motion, to transmit power efficiently,
or to track relative movement. Here power is transmitted
from one shaft to another by means of pulleys using belts.
Classification of belt:
(a) According to the distance from one pulley to another pulley, belt is three types.
They are:
01. Flat belt:
 It is used to transmit moderate amount of power.
 Incase of flat belt the shafts distance remains about 5-10
meters.
02. V-belt:
• Incase of v-belt, shafts distance is less than 2 meters.
• Used for transmitting high power at the moderate speed.
• V-belts are far superior to flat belts at small center
distances and high reduction ratios.

5. 03. Circular or rope :
 This type of belt is round in shape.
 They are smaller in length and contains smaller
Initial tension.
 Higher power can be transmitted with no vibration
and noise.
(b) According to the material used for belts, belts are
four types. They are:
01. Cotton or fabric belt:
 They are made by folding canvas or cotton.
 Cotton belts are cheaper.
 Suitable for using in warm and damp atmosphere.
02. Rubber belt:
 It is made by thin layer of rubber and flexible.
 They easily destroy because of excessive heat or oil.

6. 03. Leather belt:
 The composition material is leather which may
be oak tanned or mineral salt tanned.
 They are so soft and flexible in nature.
04. Balata belts:
 Balata gum is used instead of rubber.
 They are acid and water proof.
 Their strength is 25% higher than rubber belt.
(c) According to the amount of power and speed
Belts are 3 types. They are:
1. Light drives: Working speed up to 10 m/s and transmit small power.
2. Medium drive: Belt speed range is from 10 to 22 m/s and transmit
medium power.
3. Heavy drive: Used for compressor and generator and belt speed is
above of 22 m/s.

7. Timing belt:
 It is known as toothed, notch or cog belt.
 They are often used to replace chains and gears.
 Because of reducing noise and avoiding the usage
of lubrication bath this type of belt is used widely.
Classifications of flat belt drive:
1. Open belt drive:
 Here shafts are composed in parallel
condition.
 The direction of revolving shafts are similar.
2. Crossed belt drive:
 The shafts contain parallel arrangement.
 Angle of contact is higher than open belt
drive.
 It has high power transmission capacity.

8. 03. Quarter turn belt drive:
 It is also known as right angle belt drive.
 Shafts are arranged in right angle.
 Used with guide pulley.
 Required to obtain reversible motion.
04. Belt drive with idler pulley:
 Used for increasing belt contact area with pulley.
 Used for making driving process more compact.
 Gives high velocity ratio and required amount of
tension.
05. Compound belt drive:
 It is the large combination of simple belt drive.
 It is used for transmitting power from one
Shaft to another shaft through a number of pulley.

9. 06. Stepped or cone pulley drive:
 It has high mechanical efficiency .
 It is used for absorbing shock and helps
to run smoothly.
 Driven shaft moves or rotates at
constant speed.
07. Fast and loose pulley drive:
 It is used for starting or stopping the
driven shaft.
 Loose pulley unable to transmit power.
 The speed of fast pulley is equivalent to
the machine shaft.
 The fast pulley is keyed to the machine
shaft.

10. Advantages of belt drive:
1. Belt drive are ordinary and profitable.
2. They need to parallel shaft.
3. They are highly efficient(90-98%, usually 95%)
4. It can protect from the over load and jam.
5. They are lubricant free.
6. Notice and vibration are damped out.
7. Machinery life is prolonged.
Disadvantages of belt drive:
 Operating temperature are usually restricted to -31 to 185⁰F.
 The angular velocity ratio is not necessarily constant or equal to the
ratio of pulley diameters, because of belt slip and stretch.
 Some adjustment of center distance or use of an idler pulley is
necessary for wearing and stretching of belt drive compensation.

11. What is gear drive?
Incase of gear drive, power is transmitted by
gear. A gear is a form of disc, or wheel, that
has teeth around its periphery for the purpose
of providing a positive device by meshing the
teeth with similar teeth or another gear or rack.
Classification of gear:
(a) According to the position of axes of the shafts , gear are three types.
They are:
01.Parallel :
The gears teeth are parallel to the axis of the wheel. Example: spur gear,
Helical gear.
Spur gear:
A gear with teeth radically arrayed on the rim
parallel to its axis.

12. Helical gear:
A gear, whose teeth cut an angle to the face side
of the gear and teeth are inclined to the axis, then
They are called helical gear.
02. Intersecting:
The axes of two shafts intersect each other. Example: bevel gear.
Bevel gear:
Bevel gears are gears where the axes of the two shafts intersect and the
tooth-bearing faces of the gears themselves are conically shaped.
03.Non parallel:
The gears teeth are not parallel to axis of the wheel. Example: Skew
gear , Worm gear.
Skew gear:
Skew gear is such type of gear which are resembling to bevel gearing, for
connecting two shafts that are neither parallel nor intersecting.

13. Worm gear:
It is a such type of gear where two gears are used
for power Transmission. A worm which is a gear in
the form of a screw mesh with a spur gear.
(b) According to the peripheral velocity gears are 3 Types:
 Low velocity(velocity less then 3 m/s)
 Medium velocity(velocity between 3 to 15 m/s)
 High velocity(velocity is more than 15 m/s)
(c) According to the types of gearing , the gears are 3 types.
01. Internal gearing:
An internal gear is one with the teeth formed on the
inner surface of a cylinder or cone .The large one is
called annual gear and the smaller one is called
pinion gear. Both of them are moved same direction.

14. 02. External gearing:
It is such type of gearing system where, two types of
gears are allowed to mesh with each other externally .
The larger gear is known as spur gear and the smaller
one is known as pinion gear.
03.Rack and Pinion:
The gears which helps to turn the rotation motion
into linear motion and linear motion into rotating
motion, then the gear is called rack and pinion
gear.
Depending of the material gears are two types.
Metallic gear:
Those gears are made from metallic substance like: steel, cast iron, bronze,
aluminum.
Non- metallic gear:
Those gears are manufactured by non metallic substances like wood, raw hide,
Compressed paper etc.

15. Gear train:
Gear train is the combination of gears, used for transmitting power from one
shaft to another one. It also help to achieve large and different velocity ratio
in a small area or space.
Classifications of gear train:
Depending on the arrangement of gears wheel gear train are classified into 4
types. They are described below:
1. Simple gear train:
 Here only a pair of gear s are engaged with
each other.
 Their distance is very small
 They are situated in parallel position.
2. Compound gear train:
 It is the large combination of a number of simple gear trains.
 For large reduction ratios, compound gear trains are preferred over simple
gear trains.

16. 03. Reverted gear train:
 This is also a kind of compound gear train
 Here input and output shafts are collinear
to each other.
04. Epicyclic gear train:
An epicyclic gear train consists of two gears
mounted so that the center of one gear
revolves around the center of the other.
An arm is used to keep contact with two gears.
 Advantages of gear train:
 By using gear train large velocity ratio can be obtained with minimum
space.
 Gears are mechanically strong and so higher load can be lifted.
 Gears are used for transmission of large H.F.
 They are used for transmitting motion over small center distance of shafts.
 They are used for large reduction in speed and for transmission of torque.
 It has high efficiency, reliable service and compact layout.

17.  Disadvantages of gear train:
 They have no flexibility.
 Gear operations creates so noise.
 They are not suitable for large velocities.
 The error in cutting teeth may cause vibrations.
Chain drive:
Chain is the mechanical belt running over sprockets that can be used to
transmit
power or convey materials.
Classifications of chain drive:
On the basis of the chain’s usage, chains are classified into mainly 3 types.
They
are:
01. Hoisting and hauling chains
a. Chain with oval links:
 Linked portion of the chain is oval shaped.
 Used for low speed.
 Joint portion is welded.

18. b. Chains with square links:
 Chains are linked by square shape portion.
 Manufacturing cost is very low.
 Because of overlapping it may kink.
02. Conveyor chains:
 It can be used for transporting materials, as rollers can support
weight.
 It can be used just to support weight of chain if transmitting power
over long distance.
a. Detachable or hook joint type chains:
This types of chains are linked together by hook.
b. Closed joint type chain:
All the portion of these chain are closely joint
with each other.

19. 03. Power transmitting chains:
 Chains to transmit rotary power between shafts.
 It is used for more power capacity
 It is used for multi-strand transmission.
Power transmitting chains are 3 types. They are described below:
a. Block chains:
 It is also known as bush chain.
 It creates noise at the time of passing sprocket.
 Applicable for small speed.
b. Bush roller chains:
 It cause a little noise
 It can transmitted power more effectively.
 It consists of ordinary constructions.

20. c. Inverted tooth or silent chain:
• Over all effect is to reduce noise
• Profile of links are like involuted gear teeth.
 Advantages of chains :
 Have controlled flexibility in only one plane.
 Have a positive action over sprockets, no slippage takes place
 Carry very heavy loads with little stretch.
 They are more compact than belt drive.
 Disadvantages of chains:
 It may cause noise and vibrations.
 Typically for smooth movement it requires, frequent lubrication.
 Require more precise alignment than belt drive.
 Do not have the load capacity or service life of gear drives.
 Can not be used in applications where the drive must slip.

21. Rope drive:
The rope drive is widely used where a large amount of power is to be
transmitted, over a considerable distance instead of flat belt, rope .
Classifications of rope drive:
1. Fiber rope:
 The fiber ropes are suitable for hand operated
hoisting machinery.
 The ropes which are used to transmit power is
made from fibrous material like hemp, cotton,
manila.
2. Wire ropes:
 They are made from cold drawn wires.
 It is applicable for elevators, hoists cranes.
 It can increase in length and has durability.

22.  Advantages of rope drive:
 They are little affected by outdoor conditions.
 The shafts may be out of strict alignment.
 Used widely for larger mechanical efficiency.
 Gives very smooth, steady power transmission service.
 Disadvantages of rope drive:
 Do not work effectively in wet conditions.
 May torn out because of excessive tension.
 It may easily damage because of moisture.
 They are not so flexible like belt drive.

23. Conclusion:
Power transmission is the movement of energy from its place of
generation to a location where it is applied to perform useful
work. Power transmission allows several mechanisms to be
driven from one motor, reverses the direction of motion, alters
torque and rotational speeds while maintaining a constant
torque and speed for the motor and converts rotational motion
into reciprocating, helical or any other type of motion.

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