I've build a 3D printed Axial Flux Motor (okay the rotor is already made out of aluminum). The Motor has 24 stator coils (3x8) and 32 poles. (since the arrangement is a little different to radial flux it is really 32 poles (vs 16 pole paires). One stator drives two rotors (each has 32 poles). The diameter is about 160 mm. The windings are 3x0.8mm copper with 9 windings per coil.
I powered it first with a regular hobby king ESC (3S; 30A) pretty much without problem; it just needs a firm manual input to speed up initally. Roughly it draws 4.5A with a 3S LiPo, no load (the bearing are quite big due to the hollow shaft and cause a lot of initial friction). I checked the phases with an oscilloscope and all three are there (120° apart).
Recently (yesterday) I received a VESC6plus. I updated the firmware and performed the motor detection. As expected, L is very low with 4mH. During calibration, the VESC accelerates the motor first slowly, than it seems like that the electric field rushes away and the motor stops. In the next step, where the motor is only turned very slow left/right it follows the the field again.
However, when I want to control it with the VESC Tool, the motor is either "very bumpy" (independent of the settings, no reaction when ERPM is <1000rpm or when the duty cycle is very little), and it only "jumps" from one position to the next one (the direction is correct) without that you really can call it "spinning". If the ERPM is set too high (>5000rpm) or the duty cylce is set high (0.5 and up), it appears again that the electric field rushes away.
I assume that the mass (+friction) is too high to follow the field when the acceleration is too high, or the inductivity is too low? But then (second case) it would never turn, but it does at the very beginning at the test and when the slow position turn commands are given during calibration. Is there a possibility to slow ramp up to a speed? Would a position sensor help? Or do you see any other reason? (I assume that all three phases of the windings are correct out of the oscilloscope measurements)