Motionanalysis belt failure

Hello everybody,

I am currently working on a motionanalysis of four beltdriven wheels in SolidWorks 2012. Now I ran into a problem. One of the wheels has a free dimension (generate "belttension") and is "falling" out of my assembly when i add gravity to the analysis. The free dimension of the wheel is necessary because I want to use a fixed beltlenght. Has anyone a idea how i could solve the problem of the missing link between the belt and the wheel? Hope anybody can help me. The assembly is attached. Thanks

SolidworksMotion Studies