Statorade

"Statorade is a line of low viscosity magnetically suspended motor cooling fluid that was jointly developed by Grin Tech, a pioneer in ebike R&D, and Ferrotec, the inventor and undisputed leader of Ferrofluid science since the 1960’s.
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**How it Works**

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The idea behind Statorade is brilliant and simple. A direct drive hub motor generates heat internally at the stator, but this heat has no easy path to escape since it is surrounded by trapped air. It is possible to cool the motor with vent holes and active airflow from outside, but this exposes the motor to the elements. Alternately, filling the motor with oil will cool the stator windings quite well, but with significant increase in motor resistance from fluid drag and an enormous sealing challenge to keep the oil from leaking.

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With Statorade, only a tiny amount of fluid is needed to achieve the same effect. Nanomagnetic particles suspended in a low-viscosity oil concentrate this liquid in the magnetic air gap of the motor. That is exactly where it needs to be to transfer heat through fluid convection between the motor stator to the motor shell, where the heat can then be easily shed to the environment via passing airflow.

The magnets on the rotor trap the fluid in the gap so that it can’t splash around and leak out through the ball bearings or cable wiring as happens with normal attempts at oil cooling. And it turns out that only a tiny amount of Statorade fluid is needed to achieve heat transfer, resulting in negligible effect on the rolling drag of the motor."