If you want to invite a fish to dinner, you have to entice it onto your hook. Anglers do this by using fishing lures that fool fish into thinking they’re seeing a tasty meal floating in the water.

The problem is that the best lures don’t simply look like a meal, they move like a meal too, moving and darting in the water.

Perth-based inventor Andrew Maeder realised that he could save himself a lot of work by developing a spool that does the moving and darting “automatically” as he winds in the fishing line.

Normal fishing spools wind smoothly. Andrew’s Pulse Fishing Reel sets the spool so that it rotates off-centre – just like an eccentric cam – causing the line’s length to become longer and shorter as the spool turns.

This way, the line, and the lure tied to the end of it, moves and darts in the water, making it appear much more appetising to a hungry fish.

And while the fish may be hungry, getting it on the end of your line means you won’t have to be!

How do cams make life easier?

Cams turn rotary motion into up-and-down motions.

Cams allow machines to apply pressure at particular moments in the cam’s cycle. They are used in sewing machines to push the needle and thread through material in regular patterns.

When many cams are threaded together on a camshaft, they allow you to control the up and down movements of followers in particular sequences. Camshafts are used in car engines to open and close valves in sequence and control the flow of air, fuel and exhaust running through the engine. You can see how this works by watching the cut-away engine in the Factory’s Crank the Engine.

Everyday uses of cams

Cams come in lots of amazing shapes! When you visit the Factory, check out the cams in the Toying with Cams exhibit. Their varied shapes are what cause the toy dog to ‘jump’ and the toy caterpillar to ‘wriggle’. Some of the more common shapes include:

Circular cams, also known as eccentric cams, are circle-shaped and fitted off-centre onto the driving shaft. These cams move very smoothly and are used to generate a wave-like motion in the follower. They are often used in mechanical toys to produce a smooth, recurring motion.

Pear-shaped cams are actually egg shaped. The follower is level for most of the cam’s rotation, then is suddenly pushed up at regular intervals. These are used in car engines to control the flow of air/fuel and exhaust in the engine.

Heart-shaped cams allow the follower to move at a constant velocity and therefore provide a very steady motion. They are used in sewing machines to wind thread onto the bobbin.

Drop-cams are shaped like a snail shell. These cams lift the follower gradually, then drop it suddenly.

The crank and slider is a special type of cam that you can find on the wheels of steam engines. It consists of a piston (the slider) that is attached to a circular cam (the crank) by a rod. The rod is offset from the cam’s axle. As the piston moves back and forth, it pushes and pulls on the rod, which turns the cam around. In a steam engine, the wheel is the cam!

Learn more

Want to learn more about cams? You can download background notes from our page of Educational Materials.