[artdutra04]

It's difficult for roller chain to stay on pitch over long distances of continuous tooth engagement, as slight tolerance variations can really add up. Generally using sprockets with more than 100-120 teeth should be avoided because of this.

One way to get around this tolerance limitation of large sprockets that do not have to rotate continuously is to use a toothless sprocket and physically lock the roller chain to some point on the sprocket; torque is transmitted through a combination of friction and the locked position.