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.