Well dave b on EV Geek Forum NZ DID IT and reported his results here:...also I wish someone would seal the side covers and fill one of these hubs 1/8 to 1/6 full of Dow Corning Heat transfer fluid, SYLTHERM XLT or SYLTHERM HF. Then we can add convective fins to the HubOD between the spokes to convect the heat out. Again, not a lot of oil, but a moving mist inside the housing.
Whooppee I say! Hat's off to the NZ men. Now let's get this cooling method going on ES... it's about time! It should have been an innovation out of our board, but I digress.With gaskets already fitted to the motor side covers to prevent water ingress, I was already in a good position to add 170 mls of INOX MX3 lubricant http://www.inox-mx3.com/inox.htm. This is in order to provide a heat transfer medium to dissipate heat from the windings to the outside of the motor. INOX MX3 has a viscosity of 10.04 centistokes @ 40oC and 2.54 centistokes @ 100oC. In comparison, water has a viscosity of 1 centistoke @ 20oC. The additon of this oil has added no detectable drag when pedalling alone (no load current @ full hub motor speed has increased by 200 to 300 milliamps), but it has significantly solved my heating problem. I can now get all the way up my hill and the windings only reach 65oC. The outside of the motor now gets hot which is good because airflow over it can now absorb the heat generated by the windings. I found this to be so when cruising along the flat into a head wind. Normally the motor windings would reach 70oC when doing 35kph into a 15kph headwind (55 to 60oC at 35kph with no head wind). But with the oil, more wind is of course resulting in more load, but it now reduces the temperature due to the increased air flow. For example, cruising on the flat around 35kph with the oil added now results in a temp of 38 to 42oC (instead of 55 to 60oC). When I went into a 15kph headwind, this temp actually dropped 2oC rather than increased. The pic below shows my setup. The small tube is a tiny breather to allow volatiles to escape keeping the motor from pressurising. The gaskets have been more than adequate for preventing oil leakage. The oil also seems to be fairly stable regarding drying out and going gooey. Time will tell as to how well INOX continues to perform.
Note that he added a 0.5 mm gasket to each side cover is all. (Edit from below: and a breather tube) This is foundational! It will also end the rusting problems within the motor. It will take AJ's Frocks to a higher level! MarkCycle should consider these results also.