Engineering is all about compromise, costs vs comfort etc. I just think for some classes of light vehicles it might end up being the optimal solution, but we will see. The new motor design would dramatically reduce the sprung mass of such a system and would do the majority of its braking too with regeneration, so hub brake components might be made lighter.
Also rear driven hub motors might be less prone to damage than front wheels so perhaps it would be a friendlier environment for more sensitive motors.
Not just comfort, if your tire does not have good contact with the road you can end up off it. Regeneration can only do half the job of stopping the car. And then the heat given off by the motor, will it be used to heat the car interior or just wasted? Then heat needs to come from the battery (thinking winter here). Might be better to have the motor inboard and coupled by shafts. This may be heavier but lighter in unsprung weight. The devil will be in the details. Not a lot of cars with hub motors going down the road currently, might be a reason for it. We will see.
I think the motor technology will not advance to a greater extent, the braking will have to be balanced front to back otherwise a nasty spin might occur.
It certainly isn’t a setup for a GT.
Guess one man's game changer is another's marketing.
One wonders how much a 20 to 40 HP axial flux motor would weigh, since the 800 HP one is such a feather weight. I figure these would be most useful in small EVs with low HP requirements, perhaps rear wheel drive to reduce the mechanical stresses on the motors. The spung weight issue could probably be addressed with aluminum wheels, lighter low side wall tires and lighter brakes with the motor doing most of the braking. Hub motors would save a lot of space in a small car and axial flux seems to be a good space and weight saving idea for larger EVs, though with a more conventional drive train.
You do not get most of the braking from the motor. A 30hp, 7kg,
emrax.com
If you use wheel hub motors in a rear-wheel-drive configuration it shouldn't weigh much more than an old-style rear end single axle with a differential as far as sprung weight goes. The British design (now BMW) axial flux motor seems less massive and chunky than some on the market. However automotive engineers will do what works and is cost effective so wheel hub motors might be common or rare depending on the class of vehicle. Axial flux motors in general however do seem to be the lightest and most power dense motors and a good choice for EVs and aviation.You do not get most of the braking from the motor. A 30hp, 7kg,
188 (60kW | 100Nm) - EMRAX
Axial flux motor / generator; up to 52 kW, up to 90 Nm; size 188 x 77 mm; weight 7 kg; air (IP21) / combined (IP21) / liquid (IP65) cooled.
Elaphe™ M700 motor
101 horsepower or 67 hp on a continual basis
51 pounds
Slovenian company makes in-wheel plug-and-play electric motors
Electric powertrains continue to redefine automotive engineering, but we haven't quite seen anything like Slovenian startup Elaphe has created. The company has spent 15 years working on in-wheel electric motors, and the result is the Elaphe M700, a plug-and-play, off-the-shelf solution for...www.motorauthority.com
Nobody builds a solid-axle road car any longer. (Except maybe Morgan.) That’s setting an unrealistic comparison.
I'm just comparing it to what has been done in the past and to illustrate how much unspun weight the suspension system could handle. Even though single axle rear suspension does not provide the handling capabilities of independent rear suspension, it still is safe to use and provides a good ride, it also used to weigh a lot too with the axle housing, differential and brake assemblies. If the motor is more sensitive to mechanical stress and damage, then the rear wheels would be the logical place for it. In an EV the motor is not the biggest center of mass, the battery is, so placing the drive wheels at the front under the engine has fewer advantages and adds complexity and expense in an EV.
But we’re not talking about obsolete suspension tech. You’re trying to distract from the intrinsic unfairness of the premise.
I'm having a conversation about ideas and pointing out that the sprung mass in the rear can be very heavy and still not adversely affect handling to any serious degree. I'm not trying to distract from anything, I don't think wheel hub axal flux motors in the power range I'm talking about weigh much anyway, if the right design is chosen. Aluminum wheels, low sidewall tires and other methods are used to reduce sprung mass. I'm talking about small compact EVs where I spend most of my focus, I tend to ignore the kilowatt guzzlers that don't really help solve the problem but just add more difficulties and require hundreds of KW motors to push tons of SUV or half ton around.
I think we disagree on the bolded. There’s a reason “sports pickups” are for drag strips and not mountain roads. Going from a modern suspension to a solid rear cannot be made benign if roadholding is a criterion.
These are regular vehicles for everyday use, not sports cars where fully independent suspension has been around for a while and transversely mounted FWD cars with rear independent suspension are a recent innovation and save space. A car with independent suspension will perform better, but the point was about sprung weight, and a traditional rear axle has a lot. In many EVs there are transversely mounted rear motor(s), though with CV shafts driving the wheels.
