If you drive a manual transmission car, you may be surprised to find out that your car has more than one clutch in it. And it turns out that folks with automatic transmission cars have clutches, too. In fact, there are clutches in many things you probably see or use everyday: Many cordless drills have a clutch, chainsaws have a centrifugal clutch and even some yo-yos have a clutch!
Diagram of car showing clutch location
In this edition of HowStuffWorks, we will learn why you need a clutch, understand how the clutch in your car works, and talk about some interesting and perhaps surprising places where clutches can be found!
Why Do We Need Clutches?
Clutches are useful in devices with two rotating shafts. In these devices, one of the shafts is typically driven by a motor or pulley, and the other shaft is driving another device. In a drill, for instance, one shaft is driven by a motor and the other is driving a drill chuck.
The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds.
In a car, you need a clutch because the engine spins all the time and the car wheels don't. In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission by controlling the slippage between them. To understand how a clutch works, it helps to know a little bit about friction.
In the figure below, you can see that the flywheel is connected to the engine, and the clutch plate is connected to the transmission.