A torque wrench, dial indicator, and a little creativity will get you torque/deflection.
Polar moment of inertia (not sure if this is correct term?) is a little tougher but also obtainable with a stopwatch and some more creativity.
Combine the two and you should be able to calculate first order natural frequency of the crank, damper, flywheel assembly. Don't ask me to do it though, my math is rusty.
