Quad Motor Teslas

[Haxster]

Current dual motor Teslas use two motors and two differentials. Four big metal cylinders.

Although Tesla motors are (probably) more expensive than differentials, for improved performance and efficiency, it would seem to make a lot of sense to offer a motor-per-wheel version. Still four big metal cylinders, but no differentials! (This is not a new concept. Porsche produced a motor/wheel electric car in 1900.) Lohner-Porsche - Wikipedia, the free encyclopedia

By my thinking, this would be an intrinsically cleaner and more flexible way to distribute and manage power to the wheels. And it would make it easier for the controller to better manage traction, stability, and skid control.

Why is it taking them so long?

 

[Johan]

Current dual motor Teslas use two motors and two differentials. Four big metal cylinders.

Although Tesla motors are (probably) more expensive than differentials, for improved performance and efficiency, it would seem to make a lot of sense to offer a motor-per-wheel version. Still four big metal cylinders, but no differentials! (This is not a new concept. Porsche produced a motor/wheel electric car in 1900.) Lohner-Porsche - Wikipedia, the free encyclopedia

By my thinking, this would be an intrinsically cleaner and more flexible way to distribute and manage power to the wheels. And it would make it easier for the controller to better manage traction, stability, and skid control.

Why is it taking them so long?

They've been busy getting the Model S and X to market and ramping up production to 100.000 cars per year.

Tesla's goal is to accelerate the advent of electric transport, not make the coolest supercar ever. They are actually going the oppsite way: from more expensive cars to less expensive cars.

With 4 motors, cost is an issue.

Technically unsprung weight is a problem.

All this said I would love to see a quad motor Tesla

As you probably know the SLS AMG electric has this, and is in production, and the Rimac_One will have it.

 

[TEG]

As you probably know the SLS AMG electric has this...

 

[Johan]

Thanks @TEG. So maybe the best of both worlds then? I.e. one motor på wheel but the weight is on the right side of the shock absorbder so as not to increase unsprung weight. The downside being the axle that one could do away with completely with a true quad in-wheel-motor car.

 

[Haxster]

No, not an in-wheel motor! Un-sprung weight would be a disaster.

My expectation was that there would be four chassis-mounted motors/gear-boxes with direct shafts to the wheels. Just no differentials. An elegant, symmetrical design.

If you look at the motor and differential sizes and positions in the chassis, it looks like Tesla could (essentially) replace each differential with a motor in its place (and shorten the drive shafts, et al). Better performance and probably a slight bump in efficiency.

Yes, the manufacturing cost might be higher by the added cost of four smaller motors minus two big motors and two differentials. I'm not sure that it would be that much. Tesla could certainly enjoy high margins on this option.

I would have thought that a quad motor version would have been on their road map a year or so after the dual motor was released.

 

[James Anders]

It takes time to refine and get something right. The Model S went through some growing pains but now Tesla has a capable and flexible platform for future growth. Any deviation from this platform would be a distraction to achieving their goals. Perhaps once the Model 3, Model Y, Roadster II have all been successfully brought to market then Tesla can think about Next Gen platforms and drivetrains.

 

[pr0teu5]

As people mentioned before, it is not the use of four motors that causes additional unsprung weight, but the use of in hub motors. So we will almost certainly never see in hub motors, but four motors mounted in more or less the same position that they are now could happen.

If it does happen it is not something I would just expect to be on all models. I would expect something like this to certainly be available on the next generation Roadster/Model R and I think it would probably be limited to such a car - at least initially.

Having four motors offers a suit of advantages and disadvantages. Quad motors would obviously have better traction that two motors, and they would allow for torque vectoring. Torque vectoring could allow for an even more nimble car.

The main drawbacks are of course weight and expense. The weight problem can be partially mitigated by the increased efficiency of newer power electronics. If employed on the new roadster - which is likely to be quite pricy - the increased cost wouldn't make much of a difference.

If quad motors are involved, the next generation Tesla supercar would be one of the most interesting supercars to ever come out.

 

[Haxster]

@pr0teu5

Well said!

I still think that the current S/X (or even a future version of the 3 platform) could also benefit from a four motor version for high-end performance.

And yes, the torque vectoring would be a key aspect of the performance (and safety) enhancement.

 

[Saghost]

Current dual motor Teslas use two motors and two differentials. Four big metal cylinders.

Although Tesla motors are (probably) more expensive than differentials, for improved performance and efficiency, it would seem to make a lot of sense to offer a motor-per-wheel version. Still four big metal cylinders, but no differentials! (This is not a new concept. Porsche produced a motor/wheel electric car in 1900.) Lohner-Porsche - Wikipedia, the free encyclopedia

By my thinking, this would be an intrinsically cleaner and more flexible way to distribute and manage power to the wheels. And it would make it easier for the controller to better manage traction, stability, and skid control.

Why is it taking them so long?

It's expensive, and they have other things on their minds like the secret master plan. Once the 3 is in production, I expect Tesla to do something like this - most likely for the next generation roadster, possibly for a PXXXQ performance sedan at the same time.

All of the electric supercars and concepts went this way, for good reasons (C-X75, Rimac, SLS, etc.) As others have noted, motors on the wheels is actually rather unlikely - instead, they'll be frame mounted along the centerline, driving conventional CV jointed half-shafts for reasons of unsprung weight.

There are a lot of interesting things you can do with handling characteristics when you have individual control of the wheels - look at what Honda's been doing with the Acura RLX sport Hybrid (which has a pair of small motors separately driving the rear wheels.)

See the video in this review for an example:
http://www.autoblog.com/2013/12/18/2014-acura-rlx-sport-hybrid-review-first-drive-video/

 

[SabrToothSqrl]

Why stop at 4? I demand 6 wheel drive!

 

[wallet.dat]

Having four motors offers a suit of advantages and disadvantages. Quad motors would obviously have better traction that two motors, and they would allow for torque vectoring. Torque vectoring could allow for an even more nimble car.

Quad motors also means the motors can be much smaller. Smaller diameter motors mounted on the floor means lower CG. Might be just the ticket for an all-out performance platform.

 

[pr0teu5]

Quad motors also means the motors can be much smaller. Smaller diameter motors mounted on the floor means lower CG. Might be just the ticket for an all-out performance platform.

I'm not convinced that the motors will be all that much smaller. They might be a bit smaller if you assume that you would have the overall power in the 4 motor setup vs the 2 motor setup, but all in all it shouldn't be that big a deal.

 

[Haxster]

And then there's the 4,000 motor Tesla. Just as in the battery pack, where they take thousands of small batteries and series/parallel connect them, they could take thousands of tiny motors from, say, mini-drones or cell phone vibrators and do the same. Oh wait...I forgot to take my meds. Never mind.

 

[Dithermaster]

The Roborace cars are going to have 4 motors, so the software can do torque vectoring. Awesome!