I have found this equation that applies to torque as applied thru an angle.

T * cos A = TA; where TA is the applied torque (to a bolt), T is the torque applied from the wrench, and A is the angle between the plane of the wrench and bolt.

For example, at 40 degrees (the angle between the two extension bars joined by the joint, stright up and down is 0), only 75% of the wrench torque is applied to the bolt. (This equation may be wrong.)

But to the main question about the swivel that is used to implement this angle. This "U" joint is a common flexible coupling you find in many tool socket sets.

Does this common joint apply torque evenly throughout its rotation? My feeling is that it doesn't. And if it doesn't, is there a "constant force" joint that will? (constant velocity joint?)

Thank you.

Torque is being applied slowly and constantly.