what is a camshaft

A camshaft is a shaft that contains a row of pointed cams, which are used to convert rotational motion to reciprocating motion. Camshafts are used in piston engines to operate the intake and exhaust valves, mechanically controlled ignition systems, and early electric motor speed controllers. The camshaft consists of a cylindrical rod running the length of the cylinder bank with a number of cams (discs with protruding cam lobes) along its length, one for each valve. As the cam rotates, the lobe presses on the valve (or an intermediate mechanism), thus pushing it open. Accurate control of the position and speed of the camshaft is critically important in allowing the engine to operate correctly. The camshaft is usually driven either directly, via a toothed rubber "timing belt" or via a steel roller "timing chain". The shape of the cams greatly affects the engines characteristics, and the shape of the cams themselves is also carefully crafted to control the speed at which the valves open and close, which is better known as variable valve timing. The camshaft is connected to the crankshaft via a timing belt or chain, and in most modern engines, timing chains are usually used because they are maintenance-free and do not need to be replaced.