Originally Posted by
pphaneuf
Would a slave motor with a set resistance could be used in place of a flywheel to do a spin up, to get most of the torque curve? It wouldn't go all the way to zero (it'd stop short of the free running RPM), but would it generally work for the rest of the RPM range?
I'd be a bit worried that the torque reading wouldn't be linear through the RPM range, but if you optimize for each given RPM (use the timing that gives you the best torque at each RPM), it could make sense, right?
It's not difficult nor terribly expensive to use an electronic current sink (controlled by a microprocessor, of course!) on the slave motor to vary the load on the motor under test. That's how the fancy dynos for brushed motors worked. But torque output needs to be measured with a separate sensor like a strain gauge to get good accuracy. Just measuring the current loading the slave motor isn't good enough.
Originally Posted by
pphaneuf
The
RC Benchmark dyno that recently came out is just shy of US$450! It looks like the current version is aimed at other applications than RC cars (like quadcopters, robots, etc), but they seem interested in developing something that would be good for car racing...
The slave motor could simply replace the propeller as the load on the RCBenchmark dyno, since it already has a strain gauge to measure torque.
The flywheel dyno still gives more complete data in a shorter time, but if one needs to run a motor under a continuous load for an extended period of time (perhaps for stress testing), then the absorption dyno the proper device.