What is a Pulley?
Before jumping into the details of the pulley let us start with its definition.
A pulley is a mechanical component that helps in the transfer of motion from a shaft to a belt or rope (and vice versa).
Now let’s understand above definition.
All we have driven bicycle in our childhood. We know we push pedal and that push used to rotate wheel.
And one of the most important part of this process (pressing pedal and moving forward) is chain and sprocket.
As you can see in above diagram chain and pedal drive each other with the help of positive engagement.
Similar is the case with rope (or belt) and pulley arrangement.
A pulley acts as an intermediate link between rotating shaft and belt while transferring power.
In earlier days the use of pulley was mostly seen in the wells. At that time pulleys were used to support rope while drawing water from the well.
However since pulleys work with the help of friction so there is a problem of slip. here is a solution for this problem.
In modern days now, we also have toothed pulleys which are used with timing belts (or toothed belts).
Lets us now see advantages, disadvantages and applications of pulleys.
Advantages of pulleys
- It provides mechanical advantage while lifting heavy loads
- Silent in operation
- At acts as a support for long distance moving ropes
- Easy and cheaper to manufacture than gears
- No lubrication required
Disadvantages of pulleys
- It works makes use of friction while transferring motion hence there are chances of slip. However, this problem can be solved using timing belt and timing pulley as discussed above.
- It is not a suitable solution for very high-power transfer at high rpm.
- While taking mechanical advantage lifting distance increases.
- In long time fatigue and creep happens to rope.
- Not as reliable when compared with gears.
Applications of pulleys
- I-pulley can be used as can idler: the same case which is used for fetching water from the well.
- For motion transfer between shaft and rope (or belt)
Types of pulleys
- Idler pulleys
- Intermediate pulleys
- Loose and fast pulleys
- Guide pulleys
Attribution: By Keithonearth – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7947402