Cam

Figure 1. A rotating cam. As the wheel rotates, it pushes the rod up and down creating linear motion.

A cam is a mechanical link that converts rotational motion into linear motion, or linear motion into rotational motion (see Figure 1). Long rods with a number of protuberances called camshafts are very useful for internal combustion engines. These cams take the cycles of an engine and turn them into rotational energy, driving the car axle to spin.

Different shaped cams give different types of motion; see Figure 2 for examples of possible shapes. Perturbations and indents along the wheel allow for the wheel and shaft to interact with different patterns, giving the motion created from the cam different rhythms and speeds.

Figure 2. Different shaped cams provide different types of motion.

Figure 3 below shows how cams were used in the Wright Brother's engine to provide timing for their internal combustion engine. The blue cams are pushing on the grey rocker arms to open and close the valves. This precise timing is part of what makes engines effective at turning heat into work.

Figure 3 The timing system for the Wright Brothers' 1903 engine.

For Further Reading

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• Internal combustion engine
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