Compute Torques  
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Diagram shows a gear B, with 100 millimeter diameter, is placed above the gear C with 200 millimeter diameter. A shaft passes through gear C. A torque T in counter clockwise direction is applied on the shaft at D, a torque T subscript B in counter clockwise direction is applied on the shaft at B . The x-axis passes through the shaft. A force F is applied in the rightward direction on gear B. Distance of F from the center of the gear is 50 millimeter.

The external torque T=685 N-m applied to shaft (2) creates the following torques in the system:

Likewise, gear C exerts a force F on gear B that is equal in magnitude but opposite in direction.
Gear B's teeth exert a force F on gear C. For gear C to be in equilibrium, the force F exerted by gear B must satisfy:

∑Mc=TC-F×DC/2=0       ∴ F=685 N-m100 mm