Pason, is the working prinicple of an engine dyno similar to a electric motor dyno? RC Electric motor's dyno usually works on calculation by spinning a fixed mass. For Gas engine, what does it use? What type of Load cells? I remember you posted somewhere before rite?
Nipple,
Basically the eddy current dyno is similar to our brush motor.
If you remember Tekin dyno introduced >10yrs ago or Competition electronics,
they make use of a secondary motor to measure the Test motor.
Base on the rpm and current/voltage induced, they are able to give you a quite accurate data.
If you need a fixed mass dyno for DC motor, I can lend you my Fantom motor dyno.
There is also a special rotating torque sensor which the sensor rotate together with your motor...but the price is around $5~10k per sensor....crazy price.