Belt drive
Drive mechanism is used to transmit the power from one shaft to another shaft.
If the distance between shafts is long belt drive is used.
Belt drive is a friction drive. Friction between pulley and belt causes the transmission.
In most of the belt drives, 3 to 5% of power is lost due to slip and creep. Hence, velocity ratio is not constant.
Elements of belt drive
Belt drive consist of three parts.
1) Driving pulley mounted on input shaft ( or ) driving shaft.
2) Driven pulley mounted on output shaft ( or ) driven shaft.
3) Endless belt
Types of belt drives
Belt drives is classified as follows
1) Based on duty
a) Light duty drive
It transmits low power ( upto 5 kw )
Application
1) Fans
2) Blowers
3) Pumps
b) Medium duty drive
It transmits medium power ( 5 to 20 kw)
Application
1) Generators
2) machine tools
c) Heavy drive
It transmits high power ( above 20 kw )
Application
1) crusher
2) elevator
3) ship engine
2) Based on centre distance
a) Belt drive transmits power through a small distance ( below 5m )
b) Belt drive transmits power through a long distance ( 5 to 20 )
3) Based on structure
a) Flat belt drive
b) V belt drive
c) Toothed belt drive
d) Round belt ( Rope ) drive
Selection of belt drive
While selecting the belt drive, the following factors are to be considered
1) Amount of power to be transmitted
2) Space available
3) Speed of driver and driven shafts
4) Speed reduction ratio
5) Centre distance
6) Position of shaft
7) Working environment
8) Positive drive requirements
Advantages of belt drive
1) When the distance between shafts is long, belt drive is suitable to transmit power.
2) Cheaper than gear and chain drives
3) simple design
4) simple maintenance
5 ) Works under dusty environment
6) Withstand shock and vibration
7) Under overload belt slips and protects the machine parts from damage.
Disadvantage of belt drive
1) Loss of power due to friction
2) Requires more space than chain and gear drives
3) positive speed ratio is not possible due to slip
5) Short life.
Belt materials
Required properties of belt material are
1) High co efficient of friction
2) Strong
3) Durable
4) Flexible
Belt materials
1) Leather
2) Rubber
3) Balata
4) Cotton
5) Rayon
6) Woollen
Types of belt
1) Flat belt
2) V belt
1) Flat belt
It is rectangular in cross section. It is made leather, rubber, fabric. When the distance between shafts is less than 10 metre, flat belt is used to transmit power.
Application
1) Flour mill
2) Rice mill
3) Workshop
4) Factory
2) V belt
It is cross section is in V shape. It is made of rubber, fabric. When the distance between shafts is less than 3 metre, V belt is used to transmit the power.
Application
1) Wet grinder
2) Dynamo
3) Fan
4) Compressor
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