Hi CK, thanks for the answer posted re: fitting the belt correctly. I was just as stumped as Shaun, it may seem obvious to appliance techies, mine is a Tricity Bendix TM220W really great tumble dryer I spent hours staring at it after buying a new belt, Im writing this to help others; even although I realised it needed tensioning I couldn't see how it worked, then I noticed that the motor moved and the spring brought it back? It wasn't until I read your answer that I saw how it worked I was running the belt around the wrong way, so that the idler pulley wasn't actually doing anything, it would have meant removing a side section and then the spring, what I did instead was move the motor clockwise and cut a biro to wedge the motor over, with a string tied to the panel side of the biro, then feeding the belt around the drum making sure it stayed in place on the motor and the idler pulley/Clamping roller, then once the drum was in it's original position, replacing only two of the top screws to start with then yanked on the string releasing the biro and problem solved. However I would advise buying an idler pulley if the belt simply slipped off.
Bertie, January 2010