[Al Skierkiewicz]

When I hear the phrase "chain tensioner" I think of two things. One is a threaded device used with two sprockets, one of which is moveable. The tensioner is inserted between the two sprockets and adjusted until the chain is tight, then the hardware on the moveable sprocket is tightened to hold it in place. The tensioner is then removed. The second is an additional sprocket that is moveable but is not used to couple power out of the chain. This sprocket is commonly called an idler and is used to take up any slack in the chain. The sprocket is positioned so that the reguired tension is placed on the chain and then the mounting hardware is tightened to hold it in place. Frequently idlers are placed in the long path of a chain where the sprockets are far apart. By pushing in on the chain, the sprocket(s) help hold the chain in place on the drive and driven sprockets and prevent movement in the chain that would allow it to come off one of the sprockets. Please remember that the chain tension is directly translated to the bearings supporting the shafts of the sprockets. If you tighten the chain too much, bearing failure will occur.