You dyno test a PTO the same way you dyno test rear wheel horsepower, I would think. You hook the PTO to a torque converter and read the pressure it develops against a braking force at stall. Or something similar to that, anyway. I can think of several different ways to do, depending on how accurate you need to be. Heck, you could do it with the PTO hooked to a generator and apply successively higher loads to the generator until you determine the maximum it will generate then convert watts to horsepower. Okay, that one's a bit far-fetched but it would work.
It seems tome that it would be much easier to dyno test a PTO than rear-wheel horsepower on a tractor due to issues with ag tires on dyno rollers. :confused2: Perhaps that's why tractors are generally rated for PTO horsepower rather than brake horsepower? I do know from talking with Ronald that he uses the PTO dyno testing to tune up the tractors he sells/services. And having spoken with him a number of times on technical issues I definitely trust his information.
