I must have been sleeping under a rock, but I totally missed an incredible new series of tests that QuadMcFly is doing over at his site Mini Quad Test Bench: Dyno tests!
Here is a sample screenshot of one of his results from the Dynometer:
As labeled, this chart plots the efficiency of the brushless motor undergoing test at converting electrical energy to motive force as a function of RPM and torque. That was a bit of a mouthful, but put simply it allows you to see how efficiently a motor performs over a wide range of conditions. Great motors will have large regions of high-efficiency, meaning that they are capable of running efficiently with a wide range of different props and flight conditions.
These charts also allow you to derive some really useful information about the motors under test. For example, it allows you to visually see whether a motor likes to be over-propped, like so:
Notice that the efficiency curves point upwards, indicating the motor does best when higher loads are applied against it. This also works for finding motors that like a more under-propped set-up, like so:
Note the curves are pointed downwards, indicating that the motor prefers to run at low torque and high RPM. It’s cool to see that these results are reflected in low-kV and high-kV motors, respectively. That’s exactly what I expected from experience, and the data supports it! Along those lines – this will be a really cool tool to see the effects of different windings (e.g. different kV values) on what are otherwise identical motors. For example, the EFAW 2407R 2200kV vs the 2500kV version.
These charts also helpfully plos the torque requirements of various popular propellers as an overlay, allowing you to see where the props lay in the efficiency curve of the motor (in a static test situation). Remember that in flight the propeller will unload, moving all lines downward and to the right. This is especially valuable in being able to see motors that are clearly not tuned for miniquad operations — such as the BR1103B 8000kV pictured above.
As of this writing, miniquadtestbench has posted results for microquad-sized motors (e.g. “1xxx” sized motors). I am really excited to see him further develop this new testing feature for the larger motors more conventionally seen in 5″ miniquads. Kudos to him and the community for putting together this awesome data!