Many thanks to Mr. Phaneuf for creating this thread while I was out racing!

Welcome to RCTech, Jebarus! And thank you for offering your dynamometer to the public.

All of my comments below apply to RC car motors:

Of utmost importance is determining the peak power output for a motor. It is also very useful to get a complete (or as nearly complete as possible) curve of output power vs RPM, over the full range of RPM. Efficiency is of lesser interest, but is still useful information.

The dyno results would be used for comparing different motors, and also to determine the commutation timing setting that gives maximum output. In many racing classes, rules require that the timing remain fixed while the motor is in use. In other classes, the timing may be electronically varied (this is called "dynamic timing", "ramping", "boost", etc.), so the dyno can be used to find the timing that gives maximum power output at any given RPM, with the final goal being to create the optimum timing advance curve to program into the ESC.

A flywheel dyno is best for our application because it can give all of the information (at least for one motor timing setting) in a few seconds.

There aren't many cost-effective dynos available, and those that are available tend to use flywheels that are far too light since the flywheel is mounted directly to the 1/8" motor shaft, with no other support. Heavier flywheels are needed to get a sufficient number of data points for the necessary accuracy. (I also have a concern that these affordable dynos don't compensate for aerodynamic and frictional losses, which can be measured during the spool-down time.)

Our motors have built-in Hall sensors, so the dyno doesn't need any additional hardware to measure speed.