Most ebike motors are air cooled - ie. Outdoor air goes into the motor and flows around the magnets and coils to cool them.
Such a design is fundamentally incompatible with being fully water sealed.
Such a design is fundamentally incompatible with being fully water sealed.
BLDC motor design also has a conundrum - most of the heat is made in the motor coils, and they can be designed to get up to about 250C, which makes them easy to cool.
However, they are wrapped round thermally conductive steel touching thermally sensitive neodymium magnets which have to stay below ~60C for full performance.
So it isn't simply a matter of getting rid of heat - it's a game of preventing heat transfer.
The engineering challenges make sense. Hopefully it is something that is being actively R&D'd.
A kettle sits on top of a flame... which is combustion.
Axles should not be getting hot. You want to get your car checked.
Brakes are intentionally designed to cause as much friction as possible, the opposite of an electric rotor.