Wheel Hub Motors: Are they viable yet?

There are endless announcements of hub motor designs, and they all share the same problems:

Unspung weight is important to ride and handling. An electric motor of sufficient power (even for one wheel worth of propulsion) is heavy. The motor's weight can be minimized by operating it at high speed, but that means lots of gear reduction, which means a heavy, bulky, and expensive pile of mechanical hardware riding with the hub... increasing weight and packaging problems.

High power density leads to the need for cooling, which means hoses carrying liquid coolant between the motor and radiator. While many (probably most) DIY EV conversions make do with no more cooling than a fan on the motor shaft, continuous-duty motors in commercially produced electric vehicles are typically liquid-cooled. With a wheel motor, that means hoses running along the suspension links, flexing with suspension travel, and flexing through even greater angles with steering.

One reason to use a hub motor is to avoid the need for a jointed shaft to connect the hub to a motor or transmission... but those shafts are very effective and reliable, while a hub motor setup requires that the electric power cables flex with suspension and steering movement.

Although most braking effort for an electrically-driven wheel should be regenerative action by the motor, a mechanical brake is still needed to supplement regenerative braking, as a backup, or for parking. That's difficult to package in the hub assembly with a motor (and likely gearing as well). I noticed that a recent design actually used a drum brake, because it was easier to package than a disk brake, even though drums have long been obsolete for automotive use other than for parking.

Thanks for the input, i was thinking this was the case still, just wanted to ask to see if something new and amazing had come out that changed the situation...

Another idea that has been bouncing around my head is placing the electric motors in the nose area of the vehicle in front of the passenger area which is typically filled with nothing or just the brake system. I could mount a pair of narrow motors so the shafts face outwards and possibly either gear drive or chain drive them to a centered area on the side of the passenger compartment which allows the ability to run a short axle from the output gear/sprocket to the wheel hub like how FWD cars are connected from the transmission to the front wheel hubs. Even if it was chain, probably be best to enclose it inside of something to prevent road trash on the chain and possibility of filling partially with oil/grease for lubrication.

I still have a lot to learn, but curious if most motors could be wired up to spin opposite at the same rate of increased speed via the motor controller? so the 2 motors in the front would be somewhat equal in acceleration...

USAVeteranRealtor said:

Another idea that has been bouncing around my head is placing the electric motors in the nose area of the vehicle in front of the passenger area which is typically filled with nothing or just the brake system. I could mount a pair of narrow motors so the shafts face outwards and possibly either gear drive or chain drive them to a centered area on the side of the passenger compartment which allows the ability to run a short axle from the output gear/sprocket to the wheel hub like how FWD cars are connected from the transmission to the front wheel hubs. Even if it was chain, probably be best to enclose it inside of something to prevent road trash on the chain and possibility of filling partially with oil/grease for lubrication.

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After wading through the 39 pages of the other thread, I went for a walk and thought exactly the same thing: presumably the space directly between the front wheels is foot room, and so the interest in wheel motors, but you can still have individual motors without mounting them out at the wheels.

A more fundamental question might be why use this vehicle design, if radically changing the way it works? Three-wheelers have substantial challenges in dynamic behaviour, and the change from driving the rear wheels to driving the fronts has consequences. As Karter2 suggests, a more suitable design makes more sense.

USAVeteranRealtor said:

I still have a lot to learn, but curious if most motors could be wired up to spin opposite at the same rate of increased speed via the motor controller? so the 2 motors in the front would be somewhat equal in acceleration...

Click to expand...

I believe the answer is 'yes' regarding reversing motor rotation direction. Although some in this forum will tell you that individual motors are crazy and unworkable - and I agree that controlling them appropriately would be a challenge for DIY project - they are now done in a few production vehicles, so it is certainly a viable approach. Of course, every wheel motor design requires the same control of independent motors, but none of them have made it to production.