Clutching of two gears is very important when modeling a dynamic or kinematic mechanism. As one of my future targets is to model a whole engine cycle starting from combustion and ending with wheel rotation, lots of gear mechanisms are the mediators to transfer the energy. That's why, modeling of gear mechanism is significant to understand. Especially, if to think about friction coefficients as a driving force between teeth instead of tolerances (used in current case), then the problem obtains even sophisticated for calculation nature to model.