Fun thread to read guys, ES at it's very best. On this topic, the comparison with BionX (another proprietary controller-in-motor system) came up a few times:
FalcoeMotors said:
It is a comparison with a 3-phase BionX motor. With BionX, you still have significant difficulty in pedaling. With Falco, the cogging torque frequency is much higher and the cogging torque drops 75%. That is pretty close to ZERO for all government purposes.
I just had chance a couple weeks ago to take apart a older BionX PL350 motor to wire it up with an external controller and test it out on the dyno setup. The net drag torque of the motor as a function of RPM looks like this:
So from a stall it takes 0.42 N-m to turn the wheel, and this increases at 0.034 Nm for every 100 RPM as the wheel speeds up (which is quite a bit less than say the Crystalyte motors, that rise at ~0.15 Nm/100rpm).
If anyone here has a Falco motor and an ammeter of any kind hooked up to the battery pack, then it is fairly straightforward to get the same data and compare, no need for a fancy dyno setup, and much more quantitative than a spin-down test. Just run the motor at full throttle with the wheel off the ground, and record the voltage, current, and wheel RPM. Then release throttle a bit, and now record the new voltage, current, and RPM, and repeat that until the throttle is basically off.
For each data point, you have the electrical power going into the motor (V*A), and the motor speed. Since the current is pretty low, there is almost no I^2R losses in the copper winding, so it's fair to assume all the battery energy is going into overcomming the cogging/hysteresis drag of the hub*. For instance, say at full throttle the motor was drawing 1.1A at 38V and spinning the wheel at 340 RPM.
Input power = 38 * 1.1 = 41.8 watts
Power = Torque * RPM * 2Pi/60 => Torque = Power / (RPM * 2Pi/60)
So the drag torque of the wheel is 41.8 W / (340rpm * 0.105) = 1.17 Nm
We just need that for a couple different RPM points, as the data usually fits on a straight line and is fair to interpolate/extrapolate linearly. Anyone have a Falco setup and an ammeter** or CA connected to the battery and able to provide us some no-load power vs. RPM results? That's all it would take to get at least this piece of the data puzzle.
-Justin
*This test will show numbers that are a tiny bit high since it also includes the air drag of the spokes and tire, but the difference is pretty minute whether the motor is laced or not.
**At partial throttles when the wheel is spinning slowly, the currents will be fairly small so you want a current measuring device that resolves accurately to the nearest 0.01A