What are cams and followers?

• a cam is a rotating part attached to a crankshaft that moves a follower up and down
• eccentric cams use an off-centre pivot to move the follower up and down
• pear cams stay still for half a turn, then rise and fall gently
• heart cams make the follower rise and fall steadily with uniform speed
• snail cams keep the follower still for half a turn, then rise gently and fall suddenly
• flat followers have a flat bottom, handle loads well, but are not very accurate and have high friction
• roller followers have a roller at the bottom, are accurate, low friction, and can handle loads, but are expensive to make

A cam and follower mechanism has two main parts:

• a cam - attached to a crankshaft, which rotates
• a follower - touches the cam and follows the shape, moving up and down/reciprocating

Cams can be produced in any shape, but the most common shapes are:

1. Eccentric/off-centre
   Eccentric cams use an off-centre pivot to cause the follower to move up and down. The follower will rise and fall by a reasonably large amount. These can be seen in pistons, for example on steam engines.

2. Pear cam
   Pear cams are called this as they have the shape of a pear. It remains stationary for half a turn, then gently rises and falls. These are used to make carousel horses rise and fall.

3. Heart
   Heart-shaped cams have a shape similar to a heart. The follower rises and falls steadily with uniform velocity. There is no stationary period.

1. Flat
   Flat followers have a flat bottom that sits on the cam. These cope well under load but aren’t very accurate and have a lot of friction.

2. Knife
   Knife followers have a narrow point that sits on the cam. These are very accurate and low friction but are quick to wear away the pointed edge.

3. Roller
   Roller followers have a roller such as a ball bearing attached to the bottom of the following. These are accurate, low on friction and can withstand load, but are more costly to produce.