[DonRotolo]

There are commercial tensioners as well.

One is an idler sprocket on a bearing, you slide it along perpendicular to the chain somewhere to add tension to the chain

Another is an arrangement just like on the big CIM motor - an idler with bearing, mounted to an arm with a spring (often adjustable tension).

Third are various plastic slides and such, as mentioned already.

McMaster sells all of these.

Don