Strain gages on the drive shaft for torque measurement

[Thor Johnson]

How does this strike you:

  Use a flexible coupling (or possibly a small shaft that can stand the 
torsion/power), and mount a disc (with a slit) at each end so that they 
are in-line with each other at rest.   Mount some optical sensors (that 
will detect the slit) on a stationary (relative to the shaft) beam.

Your torque should be related to the time difference of the signals from 
the slits.

Bear in mind these are the ramblings of an EE type with little/no 
mechanical expertise... FWIW.

                Thor Johnson
       johnsont at falcon.mercer.peachnet.edu
   http://falcon.mercer.peachnet.edu/~johnsont
                                                    
         Have you seen the WarpMap lately?                    
 http://falcon.mercer.peachnet.edu/~johnsont/warpmap