We often want the a dyno to maintain a given speed and do torque control with or motor under test. These roles can be reversed too. When working on water pumps

We often want the a dyno to maintain a given speed and do torque control with or motor under test. These roles can be reversed too. When working on water pumps I didn't need a dyno, as the fluid provided sufficient load. It was a bit tricky to make before/after comparisons though be cause getting the exact same operating conditions (torque and speed) was not simple.