Mechanical Systems - continued :)

Belt Drives transfer movements from one rotating shaft to another.

They are used in pillar drills to turn the drill shaft.

The belt links are flexible and can be moved into different positions on the shaft to make the drill move faster or slower.

Chain and Sporocket systems are used in bicycles and are very similar to belt drives.

In a bike the system contains two sprockets connected with a chain that contains links.

The advantage of the linked chain and teeth mean it won't slip off - this is better than the belt drive.

Pulleys are used to make lifting a load easier.

• However, if you only use one pulley then there is no mechanical advantage - you need to use two pulleys.
• One of the simplest pulleys is the block and tackle pulley which has one fixed and one moveable pulley. This pulley reduces the effort needed to lift the load by half.

CAMS change rotary motion to reiprocating motion. There are 4 main types.

• Circular cams - produces a uniform reciprocating motion.
• Snail cams - only works in one direction, the follower gently rises then suddenly drops.
• Pear cams - gently rises and gently falls.
• Four-lobed cam - consists of 4 'lobes', which cause the follower to rise and suddenly drop 4 times in a turn. They only work in one direction.
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