[jacquesm]

The belts are industrial surplus.

If you look closely at the belt you can see the traces of many failed experiments before I found a shape that worked without accidentally getting stuck on a part.

It is attached with super glue to the belt. I use the narrowest parts because that way it doesn't end up fighting with the curvature of the belt when it goes over the roller.

The belt rotation is done with a 3 phase AC motor hooked up to an inverter for the vertical belt, the camera belt is driven by a DC motor hooked up to a variable power supply.

So no steppers, that would have made life a bit easier because then I'd know (modulo some slippage) where the belt is positioned. So now I have to reconstruct that optically, hence the wavy line on the belt.