2. PULLEY S
Pulleys are used to transmit
power from one shaft to another
with the help of belt orrope
running over them . Pulley are
made from cast iron , cast steel ,
wrought iron or aluminium. They
are also some time made from
non metal like wood , nylon,
plastics , fibres etc .
3. HUB
Is a central hollow cylinder portion of
pulley . The size of bore on hub is
corresponds to the diameter of the shift . It
is mounted on shaft . A keyway is provided
to fasten the pulley to the shaft with the
help of key .
4. ARMS
It is joining member of the hub and the
rim of pulley. It may be straight or
curved . Its cross section may be
circular of elliptical. Pulleys with
smaller diameter are provided with a
rib which is like a circular disc joining
hun and rim.
5. RIM
It is the periphery of the pulley on
which the belt runs . The outer face of
the rim is made slightly convex which
is called crowning . This kept belts at
center when pulley is misaligned.
6. TYPES OF PULLEYS :
1. SOLID PULLEYS
2. SPLIT PULLEYS
3. STEPPED OR CONE
PULLEYS
4. FAST AND LOOSE
PULLEYS
5. JOCKEY PULLEYS
6. GUIDE PULLEYS
7. GROOVED PULLEYS
14. CHAIN DRIVE :
In belt or rope drive , the velocity ratio
does not remain constant , but varies
due to slip . A chain drive that is
positive drive there is no slip , hence
the velocity ratio remains constant . A
chain drive is suitable for small centre
distance and it can be used upto 3
metre .
16. ADVANTAGE S OF CHAIN DRIVE
1. It is non slip ( positive ) drive.
2. Efficiency of very high (upto 99%)
3. It can be used for shafts which are at small and
midium centre distance .
4. It can transmit higher power than belt drives.
5. Chain drive can operate under adverse
temperature and atmospheric conditions.
6. It occupy less space and more compact than belt
drives.
17. DISADVANTAGES OF CHAIN DRIVES
1. The driving and driven shaft should be
accurately akigned . So shaft axes are
required exactly parallel .
2. Chain drive require more lubrication .
3. There are more fluctuations in velocity .
4. Initial cost is high .
5. The operation is noisy.
18. FRICTION DRIVE
friction drive is used for light load
transmission between parrallel shafts
or intersecting .
If there is no slip , the surface speed of
both wheels will be equal .
πd1N1=πd2N2
