Forums

I doubt they'd ever allow for all electronic braking. I think mechanical brakes would still be required by the NTSB. Mechanical brakes are designed so that there's no single point of failure, i.e. dual master cylinders, etc. You might be able to get away with smaller brakes, like the Prius does. Inductive motors require excitation power to generate electricity so if your main power supply (i.e. battery) dies or have an electrical fault you'd have no brakes.

@Protean; But,each of our motors is 800 N.m peak torque and more torque feels better

Tesla Model S standard 85kWh version gives peak motor torque of "only" 440Nm, but that then gets multiplied by reduction gear so that output torque is 9.73*440Nm = 4281.2Nm. 800*4 = 3200Nm, or 4281.2/4 = 1070.3Nm. That's with single motor. Doubled to AWD you get over 2000Nm measured from the wheels.

Performance version gets even more impressive numbers.

The fact is that hub-motors just are not powerful enough, not for passenger cars anyway. Hub-motors could be useful as brake replacements though, especially for very heavy vehicles with multiple wheels. Regen would be much better I imagine.

@ Iph .

100% regen braking under current NHTSA regulations would not be allowed. There MUST be a redundant mechanical system, Air or Hydraulic in place.

@Superliner, I imagine that is one regulation that could be removed if the regen as brake could be proven to be equally powerful and more reliable (magnetic brake essentially, with no moving parts it could be more reliable than ordinary brakes).

Complete stop at low speeds must still be managed mechanically. Unless you run the motor in reverse to apply decel.

To address some of the follow up comments....we can regen as much as we "gen" or about 80kW per motor. Our motors were used on both the Brabus EV and the Brabus Hybrid cars, based on a Mercedes E Class. Just from regen, we can develop about 0.3G of decell, which is enough for most normal stopping maneuvers. However, we also have conventional disc brakes (not breaks) because of regulation requirements. (belt and suspenders)

Finally,we use a conventional wheel and tire, not a special design, as long as it is at least 18". Thanks for listening.

Protean,

On this forum, it's "breaks", not "brakes". You will learn...

Protean, don't listen to him. Group-think misspellings are still boners. >:p

@Protean

Do you think it might be possible in the future to add aftermarket in-wheel motors to the front wheels of Tesla S to get 4wd?

I realize there are not all positive effects from using such motors regarding unsprung weight but for many users the benefits would far outweigh! the downside. And after all, Tesla S is first and foremost an every day car - not a track day car or a trailer queen. For me living in snow and ice 6-8 months a year I do prefer 4wd. Yet I would not like to wait for the Tesla X.

Will it be possible at all to mount your motors in the front wheels?

The Toyota i-Road has been revealed at the Geneva Motor Show. The two front wheels have in-wheel electric motors. I think Toyota should really start thinking about producing and selling these i-Road vehicles. They are ideal for the city, where there is lots of traffic. This could be a real success. It's better than the Renault Twizzy anyhow.

@torst1 - I don't think it is a good idea to retrofit hub motors, as I think you need to design the suspension around the extra unsprung weight and torques that will be created.

Retro fitting Hub motors wouldn't require a re-design of the Suspension geometry, a recalculation of the damping and rebound maybe and change the springs and shocks. If you were planning on converting your ICE car you would have to do that anyway.