true four wheel drive, i.e., one motor per wheel

true four wheel drive, i.e., one motor per wheel

What will it be called when Tesla introduces a true four wheel drive, i.e., one motor per wheel? It'd be awesome on the track, but more importantly, it'll come in handy when it comes time to continue to justify the feature and price gap between the S/X and the 3/Y.

Quad Motor All Wheel Drive
1 to 1 Four Wheel Drive
Dual Dual All Wheel Drive
Theoretically Best All Wheel Drive
Zombie Apocalypse Redundant Dual Motor All Wheel Drive, P90Z
F1 All Wheel Drive

Dramsey | 11 novembre 2015

Probably never. The cost increase would be substantial and the benefits increase would be minuscule.

Timo | 11 novembre 2015

You would eliminate differential and that's quite big so mass increase would be less than just adding motors. It would also allow a bit smaller motors / tire and better torque vectoring.

There are benefits. Cost would increase, but not that much. Currently adding a motor is $5000, so eliminating two differentials and adding two slightly smaller motors and reducing size of the other two that remain... maybe $8000 more?

rlwrw | 12 novembre 2015

Unsprung weight per wheel would soar to the point where handling would be very adversely affected.
Now, a half shaft running to a dedicated inboard motor for each wheel would be more practical.
I like the idea of the wheel also being the motor, but the weight is the problem. Design a wheel motor with very little weight, and it will become win-win.

DTsea | 12 novembre 2015

It will be called 'not gonna happen'

Grinnin'.VA | 12 novembre 2015

@ bryandbaker | November 11, 2015

[[ What will it be called when Tesla introduces a true four wheel drive, i.e., one motor per wheel? ]]

^^ Count me in the group of MS owners who think Tesla has at least 25 higher priority things to do.

EcLectric | 12 novembre 2015

Good ideas come from solving problems, not from trying to find an application for something you think is 'cool'. It's great to "think outside the box", but when you're done thinking, if the idea doesn't solve your problem then put it on the shelf.

If you really want to contribute, think outside the box about improving range. That's not a huge problem for Tesla, but imagine if a battery had the energy density of gasoline with the efficiency of electricity. A car with such a battery would be able to go ... lets take a wild guess... 1000 miles on a charge. At 60 mph, that is about 16 hours of driving. Unless you and your driving partner are wearing diapers and willing to drive 8 hours each - there is no long distance trip that would reasonably require your car to be recharged before you stop.

THAT would be worth doing (sorry for shouting).

Brian H | 12 novembre 2015

Onboard potties.

Earl and Nagin ... | 12 novembre 2015

Not at totally crazy idea as many here seem to think. Hub motors don't make much sense but if the motors are in the suspension to avoid adding unsprung mass (as rlwrw points out), 4 motors could enable torque vectoring and active yaw control, thus making the cars somewhat safer.
I don't know if the benefits outweigh the costs however, and agree with Grinnin' that this should be a very low priority for Tesla today. Maybe in 20 years, after they have about 15 different models in different vehicle types and huge sales revenue coming in . . .

Bob.Calvo | 12 novembre 2015

What would it be called?

How about PDQ125L

bryandbaker | 12 novembre 2015

I don't think Tesla would ever put up with hub motors in the S/X due to the compromised handling performance of unsprung weight.

But two motors on each axle? Smaller and more motors = cheaper per motor.

While I agree the performance benefit would be small...

(torque vectoring, even more active safety, more individualized gear ratios? Wouldn't getting rid of the differential also reduce a source of energy loss, i.e. simplify drivetrain?)

...people will be attracted to it as a vanity piece. Look how much people are willing to pay for the slightest increases in performance in ICE tech.

Elon would definitely find the increased performance and differentiation between S/X and 3/Y desirable. But most of all I think he'd be attracted to the physics of it: the fact that it's the theoretically best possible.

Are there higher priorities? Sure. But this is so easily attainable/designable that it puts it higher up the list.

Elon might want to call it the "DD," i.e., "double D."

DTsea | 13 novembre 2015

More complexity is bad.

Timo | 13 novembre 2015

Not if it simplifies something else, in this case torque vectoring. Model S does that already somehow, but it is done at the differential or brake controls. With motors controlling that you would have way faster and more importantly way more precise car reactions to changes in conditions.

Motor is also pretty simple and quite reliable piece of hardware.

rlwrw | 13 novembre 2015

Actually, there are military vehicles that use hub motors on each wheel. If one fails or more likely gets shot out, the others keep truckin' on.
With these vehicles, unsprung weight is hardly a problem.

bryandbaker | 13 novembre 2015

EcLectic, I think the main utility of a 500mi obscenely large battery will be to charge to 40-60% or about 250mi (max range without needing a potty break) in less time.

Mark K | 14 novembre 2015

Independent thrust per wheel is the inevitable endgame.

There are problems to solve, but no fundamental physics barriers.

The dynamic properties cannot be equaled by the one or two motor architectures.

In CPU's, multi-core overtook Von Neumann think, and It's rational to expect the same here.

The D is already a better car than its predecessor, and the benefits continue to scale.

Quad drive will be an exciting change when it arrives.

DTsea | 14 novembre 2015

Why bother.

Timo | 14 novembre 2015

Why not bother? If you win in performance, efficiency and handling it is worth a bit more complexity. It would eliminate differential so even that added complexity is quite small.

DTsea | 14 novembre 2015

I dont see a gain in performance or efficiency. Double qty of motors, controllers, gear boxes, and power feeders, in exchange for eliminating the (very mature and simple) differential.

Why bother?

rlwrw | 14 novembre 2015

The thinking should be, "Ok, we have a great product. Now, how can we make it better/simplify it while still retaining all of the existing gains?"

Timo | 15 novembre 2015

DTsea: Torque vectoring. Currently you don't really have that only pale imitation of the real thing. It improves performance considerably.

Differential is rather heavy part of the drivetrain. "Gearbox" is just single fixed reduction gear.

DTsea | 15 novembre 2015

What aspect of oerformance will it improve? Are there any cars with individually driven wheela today?

DTsea | 15 novembre 2015

What aspect of performance will it improve? Are there any cars with individually driven wheela today?

rlwrw | 15 novembre 2015

Tesla probably has a test article that they are using to develop independent motor control for each wheel.
All of the "P" series have two motors in the rear. Although they are connected together via the torque controller.
My guess is that Tesla is working on electronic torque control which would allow each wheel to be powered by its own dedicated motor, thereby eliminating the existing electro/mechanical torque controller.

rlwrw | 15 novembre 2015

It is possible that the current torque controller can throw the power from both motors to one wheel.
Scenario: One wheel is on ice while the other wheel is on dry asphalt.
If this is the case, then isolated motor/wheel systems would be unable to accomplish this action, rendering one wheel/motor combo unusable until conditions improve.

Timo | 15 novembre 2015

In slippery conditions torque vectoring would improve handling a lot.

DTsea | 15 novembre 2015

No tesla cars have two motors in back AFAIK.

DTsea | 15 novembre 2015

No tesla cars have two motors in back AFAIK.

Timo | 15 novembre 2015

I don't know do they or don't, but the picture they give about "high performance rear motor" would either indicate two motors or one very wide motor.

Does anybody have any confirmed data which is it?

Timo | 15 novembre 2015

Nevermind, single motor model has same picture about the rear motor as high performance rear motor. So I guess that normal dual motor configuration has a slightly smaller rear motor.

Not that those pictures necessarily are same as reality.

DTsea | 15 novembre 2015

Looking at thr sleds in the store hard to see amy place to put an extra motor in the rear.

Timo | 15 novembre 2015

Basic 85D has a lot smaller motor at the back. Two of those could fit in there. Front looks like more tight of the two.

Ross1 | 16 novembre 2015

Tesla Founder Wright has the thing you are looking for.

Looks like a system to power any luxury car brand.

Ross1 | 16 novembre 2015

Sorry, Co-Founder Ian Wright

Remnant | 16 novembre 2015

Here is a list of benefits of in-wheel motors, as listed by:

Protean’s system can increase fuel economy by over 30 percent depending on the battery size and driving cycle. It is also powerful enough to be the only source for traction on a variety of vehicles. Its ease of integration can simplify the adoption of hybrid and electrified powertrains across a broad range of vehicles.

Protean’s in-wheel motors have the highest torque and power density of any of today’s leading electric propulsion systems. Each Protean Drive™ in-wheel motor can deliver 81 kW (110 hp) and 800 Nm (590 lb-ft), yet weighs only 31 kg (68 lbs.) and is sized to fit within the space of a conventional 18- to 24-inch road wheel.

Protean Drive™ also has superior regenerative braking capabilities, which allow up to 85 percent of the available kinetic energy to be recovered during braking. This can increase driving range up to 30 percent and contribute to the reduction of battery size and cost.

Grinnin'.VA | 16 novembre 2015

@ Remnant | November 16, 2015


[[ Protean’s system can increase fuel economy by over 30 percent depending on the battery size and driving cycle. ... ]]

^^ Why should we believe this claim?

jordanrichard | 16 novembre 2015

Where do you put the invertor/invertors?

DTsea | 16 novembre 2015

Grinnin +1

Timo | 16 novembre 2015

Can increase that much compared to something really bad. That's marketing-speak: "New toothpaste is 100 times better" ..than what? Cow dung?

Hub motors increase unsprung weight. In protean case 35kg / tire. You really don't want that in a car.

Remnant | 16 novembre 2015

@ jordanrichard (November 16, 2015)

<< Where do you put the invertor/invertors? >>

You miniaturize it and put it anywhere.

Then you can use the room left on the axle for the second motor on that axle, unless you have already opted for in-hubs.

Keep in mind that friction losses in the differentials and in the ABS (by using it for torque vectoring) become range and/or performance gains in a quad-motor system (where torque vectoring can be purely electric, like in the Daimler electric SLS AMG car).

EcLectric | 17 novembre 2015


Thanks for reading. The usefulness of the extended range is not that obvious unless you are planning a trip. A longer range gives you more freedom to fit charging in where you want. Sometimes you are pressed for time and you have to (for example) make a decision: drive fast and get there with no range left, or drive slow and not have to charge. If you have a long range, you don't have to make such a decision: drive fast all day, and then charge at night.

With respect to taking long trips, longer range also affects the SuperChargers. If everyone has a short range, people are using the SuperChargers more often and there is more waiting for one to open up and more plugging an unplugging. Even if charging is correspondingly longer, you waste less time on the practical matter of starting and stopping the process. This has an effect on the adoption of electric cars: the number of Teslas (for example) will increase until the load on the SuperChargers reaches a certain point, and then the inconvenience of waiting for a SuperCharger will limit the number where it is. This is similar to the idea that building more roads never improves traffic. Building more roads makes cars that much more convenient, so more people buy cars until the increased traffic from these cars again fills up the larger roads, at which point the number of cars stabilizes at its new (higher) value.

I would like to see the number of electric cars stabilize at a new (much larger) value, and longer range helps with that, given that people have the need to know they can take their car on a long trip (conveniently).

PhillyGal | 17 novembre 2015

I thought I read that the Jaguar e-type concept might have four motors but now I can't find it.

bryandbaker | 17 novembre 2015

Model S dual motor cars definitely have only one motor for each axle. For the P90D/P85D, it's a very large rear motor, and what you might see as a second motor on the rear axle is the inverter/controller, which is correspondingly large.

Rematch the launch of the D, and Elon specifically says it allows for "shifting power front to back at the millisecond level." He does not mention shifting power left to right, because it can't be done. They can break independently left to right, which is still great for slalom, but not nearly as good as true torque vectoring left to right and front to back.

Dramsey | 18 novembre 2015

Hm. registered on February 23, 2009.

Number of vehicles using Protean in-wheel motors today: 0.

I did like some of the claims on the web site, like "...and is sized to fit within the space of a conventional 18- to 24-inch road wheel."

Cough. A how big a wheel now? Even 22s look stupid on any civilian vehicle. And I imagine the larger wheels are necessary to fit the most powerful motors.

I see the motor weighs 68 pounds by itself. A 19" Tesla wheel and tire come in at just under 60 now you're looking at almost 130 pounds of unsprung weight per corner.

In short: No.

RedShift | 18 novembre 2015

Yep, it's the unsprung mass, plus it's rotating .

Hells no!

Larry@SoCal | 18 novembre 2015

Again all the above objections are valid.
However, Dramsey for "... a 30% improvement ..." I bet people would accept the sight of a 24" wheel.

Dramsey | 18 novembre 2015

I wouldn't accept a 24" wheel, period. I don't care if the car never needed to be plugged in.

A man's gotta have standards.

bryandbaker | 18 novembre 2015

Hub motors will never go into a model s or x. Very, very remote for even model 3/y. But if they were to make a model 4, a true el cheapo people's car in the design style/philosophy of a VW bug or Toyota me.we... sure. That tall wheel requirement will appeal to some buyers, be in line with a quirkier design of a people's car, and has the advantage of increasing the surface area presented by the tire onto the road (and therefore increasing traction/handling) without increasing the friction of the tire on the road.

bryandbaker | 18 novembre 2015

Dramsey, +1 for the Real Genius reference.

Remnant | 19 novembre 2015

@ PhillyGal (November 17, 2015)

<< I thought I read that the Jaguar e-type concept might have four motors but now I can't find it. >>

Here is an excerpt of a news piece in this regard:

[It's] likely that the Jaguar will be an all-electric version of the F-Pace. Included in the sparse details Jaguar has released on its upcoming gasoline F-Pace is that it will be a 5-seat a crossover scheduled to arrive next year. Jaguar describes it as a “family sports car” that combines luxury, performance and all-weather capabilities.

It won’t be surprising if Range Rover also piggybacks off Jaguar’s BEV platform at the same time. Last fall, Director Group Engineering Jaguar Land Rover Dr. Wolfgang Ziebert hinted at plans for a battery electric vehicle that was targeted as a “second or third car for a wealthy family.”


Remnant | 19 novembre 2015

@ bryandbaker | November 17, 2015

<< [P90D] can [brake] independently left to right, which is still great for slalom, but not nearly as good as true torque vectoring left to right and front to back. >>

Indeed! True electric torque vectoring in an on-axle (rather than in-hub) Quad Motor system can be seen in the Mercedes-Daimler all-electric iteration of SLS AMG.