Earlier I showed off a torque transducer and the calibration fixture I used for it. I’ve now got enough assembled to make an entire dynamometer:

This has the torque transducer on one end, coupled to the “fixture” moteus controller through a bearing support. Then that is connected via a 3d printed coupler to the “device under test” moteus controller, which is hard mounted to the base plate. Any net torque between the two controllers will be coupled back to the transducer resulting in a measured torque.

I mounted it all to a nicely machined fixture plate I got from ebay. It’s flexible enough that I can build one for the qdd100 on it as well, although I might just get an entire second setup so that I can leave them both assembled all the time.