boostjuice wrote:Hi Ricky,
As for more voltage, I say go for it. Your set-up to test these better than anyone.
I've also thought about filling mine with light oil for cooling purposes. My thoughts are you'd want to fill the channels in the lamination stacks with epoxy and turn it down to a smooth cylinder to reduce unwanted drag. However, that brings up balancing issues as well as the epoxy detaching under centrifugal force long before the magnets break through their captive lamination cutouts.
It's a real shame there is no solid thermal path between the windings and casing on these motors. If the coils were vacuum filled with thermal epoxy like an Astro, ill bet they would handle considerably more power.
Epoxy like the astros does sound good but I imagine the process control to get that right could be quite difficult.
I'll probably take it slow. I'm not sure about my ability to epoxy things right and don't have a lathe to turn the rotor so i might try it now as it is (maybe see how balanced the rotor really is first).
If balance isn't too bad I think the key is to keep the motor current down near stock so the resistive losses don't get out of hand to control temperature. The wire used in the motor is pretty thin. The extra RPM through the crank and bike gears is great even at 57V ( Don't even think about pedalling in the low gears, you will never keep up
). 44t front and 30t rear does nearly 30Kph on 57V (26" wheels).
I have already added an NTC to my motor to measure the end wind temperature already but I need to measure the resistance and convert it to degrees but thats not hard.
I did wonder if holes in the case and a blower would help cool it but that would end up being bigger than the little motor
I wonder if its possible to liquid cool the windings without causing the motor to rust... If we could somehow seal off the inside of the stator to liquid and flow liquid through the stator between the windings it would be good but might bee to difficult to achive.
I did wonder about a total loss cooling solution of dripping water over the outside of the motor but I guess the windings inside would still get too hot unless we can do somthing like the astros.
I have been running 57V and never got round to putting a heat-sink on the motor.
I think in a really hot climate you would need to be careful but here it seems to cope without cooking the windings.
I hope I don't go too far and end up having to order a new motor next year but if I do then this ones had a good life anyway
I wonder if we could rewind these suckers for better copper fill.
I guess keeping mindful of the torque limitations of the gearbox is a good idea.
Mine seems to be lasting well as I've kept the phase current down but the voltage high so more RPM rather than more torque.
I think at higher RPMs oil in the gearbox is probably a good idea. Mine although not sealed well has had a splash of lawn mower oil thrown in with grease and it has stayed quieter for longer than the original grease but messey because I didn't silicon it up.
Just a thought if the rotor isn't well balanced I guess because the magnets are captive so magnets coming lose won't be a problem but the bearings would take a hammering.
I wonder how bad the wind loses actually are?