Torque Roll Axis of an Engine

[mert1]

If I have the inertia, inertia axis and mass properties of an engine, how can I calculate the roll axis when a torque in some direcion (which I have the data for) is applied ?

 

[mert1]

I am trying to find the direction or coordinates of TRA. Lets say you have an engine and have all the properties including mass, com, inertias and directions. How can I find the coordinates or direction cosines for TRA?

 

[alexit]

If I picture this correct, you have (for simple) single piston engine, with load applied on output shaft. You know all mass and can compute force balance on output shaft, but you want TRA with respect to mounting for engine?

This should go through dynamic center of mass for whole engine, and you know value (applied torque = resultant) so make torque balance equal resultant, now vector this through dynamic CoM and you have axis.