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Comment by ak217 | Hacker News Reader

> The simplicity advantage of electric will soon take a quantum leap when driveshaft-free 4 motor all wheel drive vehicles hit the market

You can't just eliminate the driveshaft because the wheel must be on a suspension. Remove the driveshaft and you have to put the motor on the wheel, increasing unsprung weight, exposing the motor and making high voltage parts subject to damage.

4 motors is more complex than 2 and doesn't buy you much except in niche packaging applications (like buses). As far as torque vectoring, you can achieve the same effect with differential braking (the duty cycle of torque vectoring is very short, so you don't lose any efficiency). A 2-motor Tesla is probably already the optimal passenger car configuration.

Agreed on everything else though.

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4 electric motors on wheels is extremely simpler than 2 motors, mechanical differentials and couplings.

I actually helped a mechanical engineer to create a simulator for car dynamics in software.

Today's cars are over engineered mechanically in order to support and resist the forces and torques from the motor to the wheels.

When you put the motors in wheel you basically reduce the required rigidity and the weight of the car substantially.

You point out some disadvantage of the approach. The biggest disadvantage of all is that is not a proven technology, like 100 years old driveshaft. That means the company that commercializes it will eat all the risk, like what happens when people exposes the motor-wheels to wet surfaces and some part of it is damaged. The lawsuits could bankrupt even the biggest company.

I agree with you. I should have clarified - 4 motors in the arrangement envisioned by Honda (see the link above) is more complex than 2. It doesn't eliminate any of the driveshafts.

I don't think we'll see in-wheel motors any time soon for the reasons you and I mentioned. (Also, in high performance applications (anything but econoboxes) won't you need to strengthen the suspension/chassis in some places even as you get to lighten it in others, since the motor is now torquing the rest of your suspension?)

" 4 electric motors on wheels is extremely simpler than 2 motors, mechanical differentials and couplings."

Why not 2 on one axle? Do you really need all wheel drive?

Is anyone making hub motors for cars? The technology is probably workable now.

Also, while it's simpler, it's not really much cheaper (which is the big driver of a lot of automotive decisions). Motors and power electronics are far more expensive than the mechanical components which you are removing (and this is not easy to change, though there is more headroom for economies of scale on the EV motors ATM).

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