A wheel cylinder is a component of a hydraulic drum brake system. It is located in each wheel and is usually positioned at the top of the wheel, above the shoes. Its function is to exert force onto the shoes so as to bring them into contact with the drum and stop the vehicle with friction.
This is a clutch plate for the Isuzu FTR model truck which connects two or more rotating shafts. In a manual transmission the clutch controls the connection between the shaft coming from the engine and the shafts which turn the wheels. It is a vital part of the working machinery as the engine generates power all the time, and has parts which are constantly rotating, but the wheels are not constantly spinning.