We're looking for people who want to participate in one of the biggest recent breakthroughs in the thermal management and hence power handling capability of direct drive hub motors. If you've got an ebike setup with motor temperature monitoring and routinely see core temperatures in the 100+ oC range, then please read on because this post is for you!
See, earlier this year we built a wind tunnel in our lab for doing full testing of hub motors in conditions that mimic riding in the road. Our motivation was to better understand and model how hot motors get in heavy use at different vehicle speeds, both for predictive reasons and see what techniques can push that working envelope further.
Well, in addition to the usual suspects of ventilation holes, vanes, and oil cooling, we also experimented with magnetically active ferrofluids. The theory was that the magnetic fluid would stay put in the air-gap and not leak out everywhere as is common with conventional oil cooling. What we didn't anticipate was just how TINY an amount was required to achieve remarkable effects. With just 4-5 mL, you could have almost as much cooling benefit as a full cup of messy ATF, with almost no perceptible increase in the rolling drag of the wheel.
The net effect is that you can run a given motor at about 40% higher continuous torque and power outputs without overheating. Or correspondingly, a motor that used to run at like ~110-120 degrees in a given situation would now be sitting at a much more comfortable 70-80 degrees. Have a look here at our own GRIN designed prototype hub motor when dissipating just under 100 watts of power. The steady state core temperature drops from 68 °C down to 43 °C.
You get this without exposing the motor core to the outside environment like air cooling, and without the impossible sealing complications and additional rolling drag from oil fills.
What we are still looking to understand are the long term stability and maintenance concerns; whether it lasts for years and years or will need frequent or occasional replenishment, and also what if any compatibility issues might exist with magnet bonding adhesives in the motors. If you want to be part of this endeavor, then we've got 10mL syringes of Statorade packaged and bundled and ready for you.