One big disadvantage of wheel motors is greater unsprung weight. This will make for poorer ride quality, or more expensive/complicated suspension systems. Because the wheel needs to move over bumps, if it has less mass, it can accelerate with less energy input.
LeTourneau (a personal hero of mine) powered his giant square-wire-wound electric motors with even more powerful diesel engine/generator sets. His machines were diesel powered with electric transmissions.
The article misses the "elephant in the room" point that the electric motors are the easy part. They always have been. It doesn't much matter if you cram the electric motor into the wheel or under the hood. Getting a power supply with enough power density and a short enough charge cycle that its actually feasible for daily use is the silver pearl.
> His machines were diesel powered with electric transmissions.
Large mining machinery (Haulpaks) are the same - electric with a diesel power plant.
I don't believe the wheel weight is a big issue in these cases - particularly for the AC systems, which are somewhat simpler and more robust (in terms of the wheel motor, the actual control system is much more complex).
The reason they use an electric system for Haulpaks is varied - but basically it's due to the fact that a mechanical drive system is almost infeasible at that size/load/torque. An electric transmission system is easier to control and more robust.
Also, electric lets you control the torque much better, particularly in the AC case where they can adjust phase/freq/etc to keep it controlled.
I worked at mines a few years back. These diesel electrics were stealthy. Don't make much noise at all, and the next thing you know they are charging at you at 60mph.
Actually, all the technical problems have already been solved. The silver pearl is already there for the taking. It's other factors that are the problem.
Your concerns over the ride quality for the wheel are addressed in the press release for the product from Michelin (I linked to it in another comment). The wheel will actually contain an active electrically driven suspension system. Michelin claims an extremely fast response time - just 3/1000ths of a second and all pitching and rolling motions are automatically corrected. I also believe that the idea that the wheel will not be able to accelerate as quickly to be unfounded. The same amount of weight it being rotated, as only the tire, which is roughly the same as any normal tire, is actually spinning.
These pictures give a far better idea of how the wheel is constructed:
I'm sure there are going to be plenty of complications with the design but it is really good to see large companies taking some initiative for innovation. They have already produced two concept cars with these wheels.
I was under the impression that modern electric motors weigh less per foot/pound of torque than ever before and that most of the weight of an electric vehicle is in the battery pack.
//me wants a all electric version of the dymaxion car
The unsprung weight is not that big a deal, really the inertia from the rotating tire is so great that the addition of some stationary components in the middle don't add that much.
While the angular momentum of wheels and tires does make a pretty large contribution to overall vehicle inertia, the fact that the wheel is rotating won't influence the specific issue of unsprung mass one way or another.
One big disadvantage of wheel motors is greater unsprung weight. This will make for poorer ride quality, or more expensive/complicated suspension systems. Because the wheel needs to move over bumps, if it has less mass, it can accelerate with less energy input.