Unsprung mass of an f150??
Just preordered my aptera and started looking at the specs, claim was a wheel motor that does not add hardly any unsprung weight. I thought i should fact check that. Turns out its complex, the motor/break/bearing hub is 33kg(72.6lbs).
This requires a 19" rim and tire. The claim is 17.6 kg (38.7lbs) of added weight is considered "almost nothing". This is true if you are using the motor on an SUV as intended. The issue is we have a light weight vehicle compounding the problem as well as modern EVs that have very low unsprung mass like the model 3. This is the benchmark we should at least try to reach.
Heres what i want, start with a light tire thats near its designed working load. I picked a geo metro tire. Then think like apple and make a tire wheel motor unit thats all combined.
Basically we create a geared wheel motor with 4 rc helicopter motors.
this motor is 1.45 lbs and 17hp peak, turns at 25,000 rpm and hits 96 % efficiency.
Next we combine the rim and hub motor into one, this allows for a far lighter design because the rim has to withstand offset loading. For brakes we attach the disc to the motor, at 25000 rpm theres almost zero torque and we have 4 so theres redundancy meaning we can reduce all unneeded weight.
As for gear life/noise/efficiency Herring bone gears are very long life, near silent and over 99% efficient. A proper designed oilless system should easily hit 10 million miles because the gears are rolling instead of sliding like normal hypoid gears. Making the ring gear from a non conductive material would be a really good move as teslas suffer from edm (electrical discharge machining). All motors with conductive bearings or gears have this issue, its just that digital motor drives cause more edm for a given frequency and use of new transistors like SiC or GaN allow 100x higher switching frequency. This means nonconductive gears and bearings are preferred.
I like gearless hub motors but we cant let them kill the performance of a good car. I don't want the ride of an old pickup truck!