Justin of grin tech once again proves that he does more to advanced EV tech than just about anyone in the western world!
He spends a lot of time talking about the trouble with water damage to hubs and hall sensors. Around 80% of the problems their customers have with hub motors is from water damage; which does a lot to re-enforce stereotypes of Vancouver as a very rainy town. His testing proves the theory that the temperature changes from a hub in use causes a negative pressure inside the hubs that ingresses water through the wires themselves as well as the various seals in the hubs.
Surprisingly, the option grin tech has settled on for preventing water damage and corrosion is ventilating the hubs!
Near the end he talks about he managed to redesign a typical 9c hub down from 6kg to 4kg while retaining the same performance! His design looks similar to the new, oft admonished Crystalyte G series.
Probably the coolest thing was the working prototype he built of a dd/geared motor hybrid hub. It's built so that on the flats it turns as a high speed DD motor, but for low speed hill climbing it turns to a slow speed geared motor. Very exciting, and very cool!