For the bell cranks (elements 7 and 13), the definition of these generalized forces is obtained using the virtual work formulation
The topology (figure 1) corresponds to a double wishbonetype front suspension with push-rods, which connects the lower rocker arms to the bell crank and is attached to the chassis with torsion bars instead of coil springs.
This system is simplified by replacing the fixed joint for a revolute joint between the bell crank and the chassis and a torque in opposition to its motion as a function of the torsion stiffness of the bar and the turn of the bell crank.
One of the mechs found a FIT rubbing against a bell crank, which eventually could have made a hole in the FIT and started a horrendous fuel spill.
We also noticed that the FIT we had replaced a week ago once again was rubbing the bell crank that sits on the inboard side of the FIT.