Electric vehicles deal with the same driving conditions as non-electric vehicles, but roadgoing EVs (cars) don't use hub motors. The motors which they do use are well sealed and at least splash-proof, and likely "waterproof" for minimal immersion for a limited time.So far, we cannot find any wheel motors that have a decent IP rating. Why is this? Do electric vehicles not go through pools of water? Do they not get submerged up to the hubs?
Hub motors are popular in electric bicycles, and some types of equipment (such as some robotic devices), but rare otherwise. I realize that this thread is about a robot vehicle, but this should be understood to be a specialty application.That probably explains their overwhelming popularity. I thought it would be more to do with their more compact use of space, lack of requirement for reduction drives, transmissions and associated losses, reduced weight etc.
Hub motors do have the same requirement for reduction gearing as other motors. With any motor location there is always a tradeoff between the cost, bulk, and weight of a reduction drive, or the cost, bulk, and weight of a much larger motor that is required if the motor must operate at wheel speed due to the lack of reduction drive. The location of the motor in-wheel or inboard is not related to the need (or lack thereof) for multiple transmission ratios.
The only advantages of in-wheel motors are packaging, and the avoidance of an axle shaft (especially in some cases such as where ability to steer the wheel through the large angle is valuable).