How to add rubber belt to a model

[Michael Heidemann]

I assume you are looking for LSynth (http://lsynth.sourceforge.net/)

You can do funny things with that, but I can not be of great help on this

That is for any bendable part. If you read how it works, you know what to do.

Please see also the really good tutorial from holly-wood (http://www.holly-wood.it/lsynth/tutorial-en.html).