Model S on the Track - A Review

[Zextraterrestrial]

The motor is liquid cooled. Inflow and outflow are on the same end of the rotor, liquid goes up center then around the copper core. The outer windings have fluid through the spaces you can see in the pic above.

...I pick up my set of autos wheels and tires tonight

Staggered 245 & 275 potenza re11, we'll see if that makes her stick a little tighter next weekend.

 

[WarpedOne]

The motor is liquid cooled. Inflow and outflow are on the same end of the rotor, liquid goes up center then around the copper core. The outer windings have fluid through the spaces you can see in the pic above.

What is your source?

 

[Zextraterrestrial]

What is your source?

patent? I think I was told by an engineer at the first factory tour or somewhere a few years ago. It makes sense from an engineering perspective to me. It would push the fluid a little due to the spin too, I think?

 

[Doug_G]

I don't own a Roadster, but in many threads I have read, the PEM overheating seems to come first and more often than the motor overheating. Maybe this is flipped on the track.

I have tracked the Roadster a few times, and I can absolutely assure you it's the motor that causes the limit, not the PEM. (That said, my car has the 2.5 PEM... this result could be different for 1.5 or most 2.0 Roadsters.)

Here's the evidence:

The PEM never got excessively hot, but whenever the motor reached a certain temperature, the power backed off to keep it from exceeding that temperature - namely 80 degrees C.

 

[WarpedOne]

patent? I think I was told by an engineer at the first factory tour or somewhere a few years ago. It makes sense from an engineering perspective to me. It would push the fluid a little due to the spin too, I think?

Damn, I wish your source had more substance
Patent doesn't mean much, "told by engineer few years ago" leaves too much opportunity for communication noise. It sure makes sense but it is not an easy thing to do and demands compromises on other 'more mundanely important' fronts.
Their motor is already top sh*t even without liquid cooled rotor. 600 Nm constant torque, +15k operation, 16k limit, 380kW, melon-size, 90 pounds of weight ... it is an engineering gem.

It is not a problem to bore a hole through shaft and circulate some liquid through it. Problems arise when such a rotor starts turning very fast under huge and changing loads. Rocket science.

 

[Miggs]

So I guess there is no point taking a Model S to the Nurburgring to see what sort of time it gets.

I just read this and wondered how well it would do.
http://www.engadget.com/2013/06/07/mercedes-benz-sls-amg-electric-drive-breaks-nurburgring-record/

 

[JRP3]

What is your source?

How about the three sources already provided, one of them being the picture that you linked of the Tesla motor with the hollow shaft going into the rotor, the other two being the patent and the article that I linked. I'd say at this point liquid cooled rotor is leading 3 to 0.

 

[stopcrazypp]

Getting a strong sense of deja vu with this rotor cooling discussion. doug had talked to JB and JB said they were not liquid cooling the rotor in the Model S.
http://www.teslamotorsclub.com/showthread.php/6685-Model-S-motor/page3?p=90303&viewfull=1#post90303

 

[JRP3]

Can't imagine why they'd bother using a hollow shaft if they weren't liquid cooling it, and Doug said that conversation was back in 2009. They may have changed their plans since then.

 

[WarpedOne]

I'd say at this point liquid cooled rotor is leading 3 to 0.

Voting is a poor way of determining reality.
Hollow shaft (with 'internal' teeht) is rather standard way of coupling the motor and gears. See here

 

[JRP3]

Those are not hollow shafts, they are solid shafts with a female spline on the drive end. Compare to the Nat Geo picture of the Tesla rotor you posted and you'll see that's a true hollow shaft with a solid male spline on the drive end. Completely different animal. A hollow shaft is not at all standard, and I'm not sure why you'd use one if you weren't running cooling into it.

 

[Doug_G]

Well, couldn't you build a hollow shaft with more stiffness and less inertia than a solid shaft? Modest increase in diameter, remove all the material from the middle...

 

[jerry33]

Well, couldn't you build a hollow shaft with more stiffness and less inertia than a solid shaft? Modest increase in diameter, remove all the material from the middle...

Not to mention more surface to dissipate heat (even if not liquid cooled).

 

[JRP3]

Good points but I don't know if there would be enough benefit for the added time and expense of making the part. Since it's a sealed liquid cooled motor I'm not sure how much cooling you'd get from a trapped pocket of air in the middle of the shaft. The weight reduction angle may have some merit, just not sure how much since the drive end has to be solid.

 

[Johan]

Good points but I don't know if there would be enough benefit for the added time and expense of making the part. Since it's a sealed liquid cooled motor I'm not sure how much cooling you'd get from a trapped pocket of air in the middle of the shaft. The weight reduction angle may have some merit, just not sure how much since the drive end has to be solid.

I agree on the cooling part of your statement. Also, removing weight right in the center of a rotating part would be of the least benefit right? I mean, it would somewhat reduce the gross weight of the motor (but negligable I would think since it's pretty heavy) but since the weight removed is very close to the axis of rotation it would probably not give much benefit when it comes to force required to turn the shaft around?

 

[WarpedOne]

Those are not hollow shafts, they are solid shafts with a female spline on the drive end. Compare to the Nat Geo picture of the Tesla rotor you posted and you'll see that's a true hollow shaft with a solid male spline on the drive end. Completely different animal. A hollow shaft is not at all standard, and I'm not sure why you'd use one if you weren't running cooling into it.

Do you have any other pictures?
That picture above doesn't necessary look like a hollow shat at all, it only shows one open end - liquid must go in and out through a separate path/tube.

To me the evidence that suggest rotor passive cooling are:
- JB saying so in 2009
- no explicit mention of such a cooling anywhere eventhough such thing would look *very* sexy in specs
- temperature limiting at high load i.e. at track use
- relatively straightforward way of increasing cooling power of everything already liquid cooled (bigger tank, stronger pump, bigger radiator, stronger vent)

It really does not matter what one agrees with or thinks, we have no confirmation that rotor is liquid cooled..
When there is no confirmation of existence, I default on nonexistence i.e. same as before.

 

[JRP3]

We also have no confirmation that the rotor isn't liquid cooled, neither proves anything. I'm not sure how "sexy" that would be, look at the picture above, that's pretty much what I'd expect it to look like. I don't know if it's liquid cooled or not but there are three pieces of evidence pointing towards that, the picture of a large hollow opening on one end, which makes no real sense for any other purpose, the patent, and the article saying that Tesla is liquid cooling the rotor in the Model S. On the other side of the argument we have a statement from JB back in 2009 to the contrary. It's quite possible that since 2009 they saw issues with the Roadster motor heating and decided that with the much heavier S they needed a cooled rotor, and maybe they figured a way to do it more easily. I don't think we know for sure that the Model S temp limiting at the track was due to the motor and not the inverter. They are bolted together and share coolant after all.

 

[bellwilliam]

this is pretty depressing, I was looking forward to take it to track......
not able to even do 1 hot lap is just not acceptable....

 

[Dave EV]

This whole topic seems to contradict a recent Facebook post by Tesla:

#WattsUp: With the most advanced cooling system, Model S drive unit & battery stay at an optimal temperature for performance and durability.

 

[Adm]

This whole topic seems to contradict a recent Facebook post by Tesla:

I don't recall Tesla claiming Model S to be a track car. The real test imho is how it behaves at Autobahn speeds. What happens when you drive 100+mph for an hour or more