An idler sprocket is a device used to maintain the tension in a chain or chain drive system. Often consisting of nothing more than a sprocket mounted on a spring tensioned arm, the idler sprocket pulls against the chain in a constant manner to keep the chain tight at all times.

What is a chain idler?

Chain Tensioners/Idler Sprockets are essential for chain drive. Excessive chain sag can cause vibration/noise and prevent the chain from properly engaging the sprocket, which prevents the chain from operating smoothly. ... FR idler sprockets provide stable rotation by using bearing units with hubs.

How many types of sprockets are there?

There are four main types of sprockets as established by the American National Standards Institute (ANSI): Type A sprockets, which are only the plate with no added thickness or hubs. Type B sprockets, which have a hub on one side. Type C sprockets, which have hubs of equal thickness on both sides of the plate.