3rd transmission supplier?!

[AGR]

donauker, from my readings the majority of the drives are done in high gear without shifting, the cars are locked in high gear. One car shifts the other car does not shift, the car that actually goes into 1st gear would be used for 0 to 60 times to come close to the 4 second time, the other car is used for all the other timed runs. A 50-70 run can be done in high gear, the quarter mile car be done in high gear.

VP9 has a shiftable transmission and is used for the 0 to 60 runs, VP10 has a locked transmission and is used for the driving. It can get confusing.

 

[Cobos]

I also come down on the side of 2 speed transmission necissary for the Roadster. For the Whitestar on the other hand a 2-speed transmission would be silly. The Roadster is a Halo-car as has been said here for Tesla and then you need serious acceleration, and the reason it's gotten so much PR is simply because of the good specs. You also need a topspeed which is above illegal and insane even though it's a lot lower than other supercars.
And as I've mentioned a few times before compared to other cars with similar performance the Roadster would cost only about 33% of cost of similar dinocars like the Dodge Viper in Norway. It's only about twice the price of a new Miata, so the price is fine considering the performance you get.

Cobos

 

[donauker]

AGR: There are a number of owner drive reviews starting from Oct. 22 that have driven the 2 speed trans. They are currently only in the owners forum section on the Tesla Motors site. All drivers seemed to be very impressed with the shifting. A quote “Not having driven the old 2nd-gear-only, I can't compare, but the transmission was smooth, shifting was completely seamless.”

Also there is no way that they are going to publish quarter mile times for second gear only, it would be quite unimpressive. Also VP9 is being used for all the timed runs not just the 0 – 60 run. There are fairly detailed nightly reports in the owner forum.

 

[TEG]

It would be an interesting poll of owners--who is looking for performance and who is looking for "green" driving?

I would bet that most want both.

That is one of the major "features" of this car - you can "have your cake and eat it too" because the eMotor is very efficient even when used for performance driving.

--------------------------------------------

Technology for race cars isn't always appropriate for street cars.
A 12000+ RPM redline is typically only ever seen on race cars.
Race car transmissions have different durability requirements from street cars.
A racer may well chose a lighter transmission that breaks after 5 races because it is worth the reliability hit for the slight advantage that could make the difference between 1st or 2nd place. It is common in many races to have some cars fail to finish (DNF) because something broke during the race.

 

[AGR]

donauker, Thank You for clarifying. Then what is really delaying this car if the transmission seems to shift well. They mention durability where and when did they do the durability tests.

TEG, 5 races would be comparable to how many miles in a street application? Do you know who supplies the transmission, how its mated to the eMotor, how does it shift?

 

[tonybelding]

It would be an interesting poll of owners--who is looking for performance and who is looking for "green" driving?

It probably shouldn't surprise anybody here to learn that I'm focused on the performance side of things. I'm looking for a new and improved driving experience -- something that I believe will be more fun to drive than my Esprit.

The whole "green" aspect is . . . intellectually interesting. We have a national problem with oil, we have a global problem with oil, and I'm all in favor of moving the nation and the world away from burning the stuff as fuel. But. . . Honestly, I don't see that as being my personal problem.

I don't drive that much. I don't commute to work, I don't take long trips regularly, and I have put. . . hmm. . . about 40,000 miles on my Pontiac in the 12 years that I've had it. Even my huge, gas-guzzling, 4WD "hillbilly truck", the Ford F-250. . . I've been driving it for 22 years now, and it has 45,500 original miles. It's barely broken in. I've never felt "guilty" about driving, because I don't drive that much anyhow, and nothing I do to change my personal driving habits is going to Save The World.

I do think that the "green" aspect of the Roadster will add to the "fun" aspect, though, in the sense that it will drive interest and conversation. Because you know, part of the fun of owning an exotic car is showing it off and talking with people about it. Because the Roadster is so new and so novel, there'll be plenty of explaining to do -- and I think I'll enjoy that.

 

[TEG]

TEG, 5 races would be comparable to how many miles in a street application?

Hard to say. "5 races" was just a made up number I threw out as an example. Sometimes the durability limitation is just in "hours of use", and a street app doesn't actually fair much better than race use. On the other hand, race proven technology is a good starting point towards long term durability.

Do you know who supplies the transmission, how its mated to the eMotor, how does it shift?

No, I don't know any details about transmission #3.

I think it was reported that #1 was "Xtrac", and #2 was "Magna"

I am fuzzy on the details now, but I think they may have tried to do something ambitious with #1, like having it be clutchless and having eMotor controls match revs exactly during shifts. Apparently #2 was "electro-hydraulic" with a computer controlled clutch of some sort... But again, I am not sure of what really has been going on.

I stopped asking them questions about this sort of stuff because it is no longer "fun" for me. When I thought everything was under control and going great it was fun to learn of their successes... Now that they have been struggling I am content to let them sort through it as best they can. Perhaps sometime in future they can give a "postmortem" ("retrospective") report of what they tried and did.

I bet Tesla insiders read this kind of stuff and just grit their teeth and bite their tongues. We bloggers know enough to ask annoying questions, but not enough to offer helpful suggestions.

 

[tonybelding]

No, I don't know any details about transmission #3.

I think it was reported that #1 was "Xtrac", and #2 was "Magna"

Elon's comment about three transmissions was very vague. I can't help thinking maybe Xtrac was second and Magna was third, and the other one would be something way back in early development that we never heard about.

If anyone from Tesla would elaborate on that, I'd appreciate it very much.

Because from where I sit. . . If they are going to a third transmission now, it would lead me to suspect that:

1. It will be very hard to ship Roadsters earlier than 2009.

2. Tesla Motors will not survive such a delay in the program, which effectively means that no Roadsters will ship ever.

3. Tesla didn't belong in the car business anyhow.

 

[DDB]

It probably shouldn't surprise anybody here to learn that I'm focused on the performance side of things. I'm looking for a new and improved driving experience -- something that I believe will be more fun to drive than my Esprit.

I'm glad you're keeping all the greens and libs in check. Seriously, if electrics aren't made sexy to the masses, it isn't going to sell. personally, I'll take anything that doesn't burn mid-east oil.

 

[TEG]

Elon's comment about three transmissions was very vague. I can't help thinking maybe Xtrac was second and Magna was third, and the other one would be something way back in early development that we never heard about.

Because from where I sit. . . If they are going to a third transmission now, it would lead me to suspect that:

1. It will be very hard to ship Roadsters earlier than 2009.

2. Tesla Motors will not survive such a delay in the program, which effectively means that no Roadsters will ship ever.

3. Tesla didn't belong in the car business anyhow.

Lets hope you are completely wrong about those 3 points.

But, VP10 being locked in second gear right now leaves me nervous about the situation.

 

[Brent]

I am fuzzy on the details now, but I think they may have tried to do something ambitious with #1, like having it be clutchless and having eMotor controls match revs exactly during shifts. Apparently #2 was "electro-hydraulic" with a computer controlled clutch of some sort... But again, I am not sure of what really has been going on.

I'm not great with this kind of tech either, but when I asked for a real basic explanation of the problem at the L.A. Auto show, I heard something about getting the transmission to reduce its RPM from 13,000 to 6,500, to engage with the next set of cogs, and to do all this in an acceptable timeframe. The shifts were too slow with the earlier suppliers. I guess few, if any, production car transmissions have ever had to deal with these kinds of RPMs.

 

[WarpedOne]

I heard something about getting the transmission to reduce its RPM from 13,000 to 6,500, to engage with the next set of cogs, and to do all this in an acceptable timeframe.

This is what I was thinking about. The eMotor doesn't have a flywhell but it by itself is a quite heavy flywheel. I'd guess the rotor weighs in around 30kg and has around 8inches of diameter. At 13.000rpm that is over 200 spins per second. Trying to reduce that to only 100 spins per second in one second means you are taking a lot of energy out of it very very fast.

Maybe the PEM and batteries just aren't capable of absorbing all that energy so fast - not powerful enough. I do not have my phisics formulae at hand to try to calculate the power numbers, but I am not confident that 185kW would be enough. So some other energy absorbers might be needed to slow it down (cluches).

Where is Anatoly when one needs him

 

[AGR]

Imagine trying to slow down an F1 engine from 19,000 to 12,000 these guys run a 7 speed transmission and it shifts.

After all this time Tesla has not arrived at a workable solution? The "monkey" is passed along to transmission suppliers.

 

[malcolm]

I heard something about getting the transmission to reduce its RPM from 13,000 to 6,500, to engage with the next set of cogs, and to do all this in an acceptable timeframe.

Wow! So any and all shifts have to occur at a fixed RPM. That's an interesting approach. Can't help thinking it would generate a lot of heat to make sudden adjustments like that.

Why 6,500? Was this figure chosen since it is the optimum shift point from first to second on a 0-60 run (52 mph?) or just half way up the rev band?

 

[TEG]

I don't think he was saying that is the only possible shift point.
He was giving an example where you rev close to redline then shift.
With only 2 discrete gears, the difference in ratio between the two is rather dramatic. It would be like running an ICE car to redline in 1st, then shifting to 5th every time. You have to let the engine revs drop a lot to get to the next gear. That makes shifts (potentially) take longer since the motor/engine has to slow way down to be ready to match the other ratio.

 

[malcolm]

And presumably a dramatic / badly mis-timed down shift could dump a lot of power to the battery by way of regen. Although that issue will always remain, irrespective of the gearbox/clutch solution

 

[AGR]

Does anyone have the gear ratios of the transmission? Does anyone know how fast the car will actually go in top gear? Does anyone know the differential ratio? I would be useful information before engaging in any discussion of RPM's and shift. The size of the tires we know.

 

[TEG]

Ballpark recollections (but I could be wrong).
Top speed in 1st: ~55MPH
Top speed in 2nd: ~125MPH

I assume that both of these are near redline.

* 1st gear: 4.20:1
* 2nd gear: 2.17:1
* Final drive: 3.41:1

Redline now: 13,000 RPMs. Original planned redline 13,500 RPMs

Those ratios are far apart...

The original redline may have gotten one to 60MPH all in first, so keeping 0-60 under 4s while reducing the redline (for durability reasons) would be a hard to reach goal since a shift would now be required.

I would think they would be better off if they could change the ratio on 1st so that you could do 0-60 all in the 1 gear again.

 

[Kardax]

Gear ratios can be found here: http://www.teslamotors.com/performance/tech_specs.php

With the old redline, top speed in 1st was about 65MPH (now it's probably about 60-61). Second was 130, now it's 125.

Reverse uses first gear and spins the motor backwards. You could theoretically do 60MPH in reverse in the Tesla Roadster. I think it's electronically limited for production-intent cars, but this feature could be useful if disabled for an Action Movie appearance

-Ryan

 

[AGR]

With the gear ratios on the spec sheet and 225/45R17 Yokohama Neova tires in the back (835 revolutions/mile) in 1st gear the car would do 60mph at 11,900 RPM, shifting into second the eMotor revolutions would drop to 6,200.

If you look at the power and torque curves of the eMotor the torque curve is flat from 0 to approx 6,000 RPM the horsepower curve starts dropping off past 8,000 RPM.

I'm sure the folks at Tesla have done various tests, it seems that the eMotor would perform better between 4,000 to 10,000 than 6,000 to 12,000.