Various Lifting Machnies:

Lifting machines are utilized to lift large loads. Their use becomes essential in handling of heavy machines, loading & unloading of ships, railway wagons, etc. There are several types of lifting machines; a few of them are being described in the following sections.

System of Pulleys or Pulley Blocks:

Pulley is a wheel that is made of metal or wood. It contains a groove around its circumference for accommodating rope or chain. Various pulleys may be arranged to make a pulley system. The following assumptions are made when deriving formulae for different pulley systems:

 (i) The weight of pulley is very small as compared to the weight lifted and thus, this is neglected.

 (ii) The friction between the pulley and rope is negligible. Thus, the tensions on the two sides of the rope passing out round the pulley are taken equal in magnitude.

The pulleys are utilized for lifting loads employing their appropriate combinations. These combinations are utilized to obtain higher mechanical advantage. There are four system of pulleys which are extensively utilized :

1. First system of pulleys

2. Second system of pulleys

3. Third system of pulleys

4. Weston's differential pulley block.