Originally Posted by Rivet gun
I was about to write a post about turbine stators, but barit 1 got in first with an excellent explanation. As barit's example shows, most of the torque in a turboprop is generated in the gearbox (and it is this that the torque gauge measures) but the turbine stator torque still contributes to the total...
Actually, it doesn't make any difference
where you measure the torque, so long as you know what the correct value should be be
at the point it's measured.
For example - GE T64 and CT7 and Allison T56 turboprops measure torque delivered from the PT to the gearbox, by sensing the torsion in the coupling shaft. It's rather clever if you ask me. The big recips had a hydraulic torquemeter in the mounting of the stationary ring gear of the planetary set. (Perhaps some engines still use this system today)