A simulation of a track similar to the one shown in this video [login to view URL]
The model would be a bit different. The two long poles shown in the video would go along the edges(along the length) of a sleeping bed. The two poles would be connected by a thin horizontal cylindrical bar. Once installed on the bed, one should be able to slide the cylindrical bar from the foot of the person lying on the bed to his head. The movement of connecting cylindrical bar would be controlled by a circular wheel attached to one of the poles along the edges. The wheel has to be rotated in order to move the cylindrical bar in a linear fashion.
A running simulation of the cylindrical bar moving upon the rotation of the wheel is needed.