Quick question: is F the frictional force exerted by the carpet? or is it the wheels exerting force on the carpet? It looks like the force exerted by the carpet due to the direction, but I just want to clarify
Yes, I’ve done a force diagram of the wheel/gear system; all of the forces are acting upon the wheel and/or wheel gear.
D acts normally to the pressure face of the wheel gear. It is actually composed of elements at several teeth, the ones above further right, the ones below further left.
B essentially acts along the axis connecting the drive axle and the wheel axle. The main part of B is the reactive force of the chassis to the drive. As it is acting through the drive bearings, it must act through that axle. The pendulum return of the module and the by-product of the forces on the floating wheel are argued to be insignificant.