Trucks and trains are often not sprung, and can benefit from lighter, smaller,more efficient hub motors. Cooling is easier when the whole motor is moving through the air.
More than the body needs to weigh enough, you need a proper center of gravity via weight distribution or you're simply going to tilt the thing over and wreck everything when you lift an object (source: have multiple sit/stand/clamp lift certifications.)
"Size matters, in forklifts, which need to maneuver in tight spaces."
That's why we made the reach forklift, which is operated while standing up. Half the footprint of a traditional forklift with the ability to reach out across a shelf to pick up a pallet.
Where this will make even more sense is for driving conveyor belts on assembly lines. You'll save more power there in a manufacturing warehouse environment than you typically will switching your entire forklift fleet over to these new motors.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.678...
https://en.wikipedia.org/wiki/MagneRide
https://www.youtube.com/watch?v=hiaMpG4Y640
Further, on newer vehicles with the trend of 20inch+ rims, that is already 60-90+lbs (27-40+kg) of unsprung weight per wheel with tire. There is certainly room there for improvement to offset at least some of the motor weight.
Would have to know how much their in-wheel models would actually weigh though to determine beyond speculation if it could be reasonably compensated for in a highway vehicle.
The idea with motors at the wheel seems to be that the moving parts are all concentrated there. No mechanical distribution. Compartmentalization. But that is not incompatible with active suspension systems.
An active suspension requires power, too. And a heavier wheel would presumably require a more power-hungry active suspension than a lighter wheel, so you're not getting something for nothing in terms of efficiency.
I guess it is a matter of numbers, though. A CV axle also gives a wheel inertia, as it has mass and moves when the wheel does (partially). If you can make an insanely light motor, maybe you could make it so light that it's actually contributes less inertia than a CV axle would, in which case go ahead.
>Electric cars, being still relatively new, cannot afford to get a reputation for danger.
I'm really sick of this "anything that measurably effects handling in a negative way is a non-starter because safety" attitude that's become increasingly pervasive. The fact of the matter is that there is a range of handling that is "acceptable" and anything in it is fair game. Nobody is expecting a Dodge Journey or a Spark EV to handle like a Porsche. At 15kwh/kg these motors will be fine for vehicles with average power to weight ratios that do not place a massive emphasis on performance (i.e all the "appliance" vehicles that purists hate). For low power levels these motors may weigh on the same order as the parts you need to transmit power to the wheels in a conventional applications so there might not even be any net gain in some applications.
If there was a design tradeoff that allowed to somehow massively sacrifice efficiency for very low low specific mass and extreme heat tolerance, we might see the discs replaced with in-wheel "harvesting brakes" in addition to inboard high efficiency cruise motors.
But #1 I doubt that kind of tradeoff exists, at least not in sufficient magnitude, and #2 it would probably be quite uneconomic to exploit, lots of lower hanging fruits to pick first.
Also, a larger rotor weighs more than a smaller one.
Combined, a large wheel and tire will require more energy to move and to stop, and will add as 75 pounds or more to the weight of the vehicle. This has negative impact on handling and fuel economy.
The only reason why the manufacturers add a large wheel option is because people want them.
Larger wheel vs larger rim is not the same thing. A larger wheel has a larger weight but smaller rolling resistance. A larger rim on the same sized wheel has better handling characteristics and more room for larger discs, whether it is on a performance vehicle or a regular one doesn't really matter, plenty of mid-sized sedans of today are yesterdays performance vehicles.
There are outside exceptions (any SUV, ridiculously sized wheels on many American cars and people driving trucks when a normal passenger vehicle would be more appropriate). Those do have worse handling and fuel economy, but they're the exception, not the rule.
[edit]
Disc brakes add about 9.5kg on the front[2] (maybe half that on the rear?), so a single disc brake rotor weighs more than the entire weight of all 4 motors.
Obviously this is using Magnax's numbers for very large motors and assuming they scale down, which is silly, but clearly there is some weight at which it would make sense, particularly for a non-high-performance vehicle (1 motor per wheel has lots of advantages for handling, but AFAICT this is not unique to in-wheel motors).
1: https://www.tirerack.com/wheels/tech/techpage.jsp?techid=108
In a light vehicle, it's very important to minimize unsprung weight for the reasons you've listed. Not so much with a heavy vehicle.
Watching the video that was linked in another thread, it made me think that maybe the hub could be stationary, and the tire just spins around the outside. That could cut down a lot on wind resistance.
The Lohner-Porsche was a hit at the World's Fair in 1900 and was in development before that. I mean I guess a concept 120 years old is still new enough to get a bad reputation...
But I do hope they do not proceed with the in wheel concept. In wheel motors make the ride not only bumpier but more dangerous. This is because the wheel with more un-sprung weight bounces more and tends to lose contact with the road more, which in turn makes the car more likely to spin out of control, miss a turn, etc.
Electric cars, being still relatively new, cannot afford to get a reputation for danger.