Moment about Instantaneous Center of Rotation???

[brmech]

I have a mechanism that can be modeled as a crank-slider mechanism. An external force acts on the rigid body, that is the modeled as the slider, causes the body to rotate and translate while it is translating along the slider path. The rotation is equivalent to the rotation of the connecting rod rotation.

Is it correct to evaluate the instantaneous torque that causes this rigid body rotation as the moment from the external force about the instantaneous center of rotation?

Assume no friction or inertia.

 

[Biggadike]

I can imagine no other way of solving your problem. If you know the instantanious centre of rotation and the forces then they must equate to static calculations albeit instantaniously.
You could then plot the total range of torque seen by any particular part.
I've been confused by systems with 'instantanious elements' in the past but the solution has always been as you are suggesting

 

[brmech]

The other way to solve the situation is to sum the moments about the point of mechanical roatation. The external force and the reaction forces in the linkage (connecting rod in this case) caused by that force create a couple acting about the mechanical point of rotation.