Tesla: Roadster production unit #1 completed; future models may use range extender
On Wednesday December 12, Tesla Motors held a open town hall meeting for all of its customers. The meeting was hosted from San Carlos and made available via conference call to everyone who has put down a deposit. I spoke with Darryl Siry after the meeting, and he said a full transcript will be posted on the company web site shortly. In the meantime, frequent commenter here on ABG and elsewhere Tony Belding took notes and posted them on the Tesla Motors Club discussion board. Chairman Elon Musk and new CEO Ze'ev Drori provided an update on the status of the company and Roadster.
The weak link in the Roadster remains the transmission. The problem of surviving the process of shifting gears while the motor remains at full torque is a tough one to overcome. Both of the first two suppliers proved to not be up to the task. There are now two other transmission suppliers working feverishly in parallel to develop a robust transmission. In spite of these issues, production unit number one has been built at the Lotus factory in Hethel, England. That's Musk's car and it does not have a finalized transmission. Musk fully expects to have to replace the transmission in a few thousand miles. Continue reading after the jump.
[Source: Tesla Motors Club, Tony Belding]
In fact, in order to get production going, Tesla is considering shipping early cars with transmissions that they expect to fail and a slightly reduced performance calibration. Once the final transmissions are available, these early vehicles would be retrofitted with new gearboxes and software. Speaking of software that is still being tweaked, the previous test that yielded a 245 mile range was erroneous. Latest testing now puts the range in the 220-230 mile region.
In response to a customer query about increasing top speed, the response was that higher speed stability would require more downforce. The problem is that downforce is a trade off with drag, and that would cut the range too much.
From a business perspective, the plan remains the same, with management intent on staying independent. While another funding round is in progress, Elon Musk remains committed to the venture. Even if every other investor decides to pull out their money, Musk said he would personally back the company. Until things settle out with the Roadster, plans for future cars like the WhiteStar will not be finalized. Any future products will be electrically driven but may contain a range extender in addition to a battery. Check out all of Tony's notes and the responses at the discussion board.
Reader Comments (Page 1 of 2)
Aubrey 5:00PM (7/07/2008)
I have a question about the Tesla motor how many kw will it consume running at 1500 rpm.
Reply
Phil L. 9:43AM (12/13/2007)
Good news.
With all the management turmoil at Tesla in recent days, this is a critical step.
It's notable that we're talking about a transmission crisis at this point - not a battery problem, motor/control issue or something else related to the EV-specific components. For all its complexity, tranny technology is well understood. This problem is solvable.
If the rest of the design proves itself to be solid, early transmission problems will be forgiven in the long haul. Go Tesla!
Reply
Darryl 10:08AM (12/13/2007)
Sam - the error on the EPA range result was entirely that of the independent dyno testing lab. They notified us several months afterward and have taken responsibility for the error. We should have new data soon and will update our website etc. The important thing to note is that since the EPA cycle is largely modeled using many factors combined with a dyno run, this news does not actually change anything regarding the actual real world range of the Roadster, which we have seen as high as 267 miles around the city and as low as 170 miles in aggressive highway driving. Typically we see 210-220 is real world mixed driving.
Reply
Travis Rassat 10:57AM (12/13/2007)
This will probably go down as the dumbest question ever asked on AutoblogGreen, but why does an electric car even need a transmission? Couldn't it be more or less direct drive? Can't you just reverse the polarity to get reverse? Wouldn't a transmission have a negative effect on the overall efficiency of the car?
Reply
dwf 11:12AM (12/13/2007)
Does the "delivery" of a defective "production" car to the Chairman of the company really count as a milestone, or is it just a publicity stunt to be able to say they started "delivery" in 2008 like they had promised?
After the way they kicked Martin Eberhard out of his own company, they luster has worn off of Tesla.
(Note to Matin: In the future, NEVER EVER INCORPORATE if you want to keep any your business.)
Reply
Mike 11:57AM (12/13/2007)
Wasn't Martin the one who advocated a pure EV only model for Tesla? Reading between the lines, Did Martin got pushed out because he did not or would not support a range extender (like the Volt)? It sounds like the Whitestar will be a series hybrid like the Volt. Tesla has decided that GM is right and the series hybrid is the way to go, at least until battery technology improves.
Reply
Dave 12:25PM (12/13/2007)
I'd love some light shed on the necessity of the transmission question.
And how powerful is this electric motor? You'd think there would be an answer in the world of racing somewhere. Isn't that what racing is for?
Reply
Kardax 12:33PM (12/13/2007)
Travis Rassat: EVs don't _need_ a transmission, but having one enables you to have a high top speed _and_ good acceleration. For a $100,000 Tesla Roadster, those performance characteristics are important to earn the price tag.
The Tesla transmission doesn't have a reverse gear; it spins the motor backwards.
Although non-sports-car Teslas don't necessarily need a transmission, it's logical that future models will include it as a competitive advantage.
Reply
Kardax 12:34PM (12/13/2007)
Dave: Please refer to my response to Travis Rassat.
Race transmissions won't work because they're not designed to last 100,000+ miles.
Reply
Darryl 12:35PM (12/13/2007)
re: the transmission - even if you go with one speed you need a transmission with a reduction gear and a differential.
Reply
SuperQ 12:37PM (12/13/2007)
So if my memory serves, the transmission is 2 forward speeds, no reverse (no need, just reverse the motor).
The reason they have 2 speeds is for 0-60 time. With the low gear, the car can do 0-60 in 4 seconds, but tops out at 70-75mph I think. With the high gear, it can't do 4 seconds, but has a top speed of 120mph. According to the people at Tesla I talked to a while ago, the car drives great in high gear all the time.. but doesn't do the insane 4 second off the line time.
It's hard for car companies to give up those critical benchmark times.
Reply
fnc 12:51PM (12/13/2007)
I find it funny that a car to come out of Silicon Valley will get patched after release, so to speak.
But at least they are being forthright about issues they face and what customers are actually getting, a refreshing change of pace for a car company. While I'll never be able to afford one of these particular battery powered rockets, I hope the company can find its footing and go on to continue this kind of innovation. Every time I've had to turn a wrench on the Rube Goldberg device called an internal combustion engine in my driveway, I've longed for the day I could rely on a much simpler electrically powrered vehicle instead. Here's to hoping we can see that future.
Reply
why not the LS2/LS7? 1:17PM (12/13/2007)
They delivered a car they know doesn't even work right and I'm supposed to be excited? They say it'll be months before they get a working transmission. This is a huge problem.
And range dropped back toward 200 miles again.
I don't get how shifting under power is the issue. Do like modern computer-controlled gas cars do and reduce the engine output for a moment as the transmission shifts. This may not be cool, but if this was all that stood in the way of Tesla being done with their car, I'd expect they'd do it. So I have to wonder what the actual story is.
Reply
why not the LS2/LS7? 1:18PM (12/13/2007)
Dave:
185kW (248HP)
http://en.wikipedia.org/wiki/Tesla_roadster
Reply
Mau 1:25PM (12/13/2007)
The car's motor is rated at 248HP, according to the Tesla website, and I think that the trasmission issue here is a matter of efficiency.
As far as I know, 3-phase motors are most efficient at around 75% of their rated efficiency. Check out their torque & power curve:
http://www.teslamotors.com/performance/acceleration_and_torque.php
As the motor speeds up over around 6000rpm its torque begins to lower and at about 8000rpm its power peaks. The motor's top speed is 13000rpm. So I guess, ideally, to get the most power out of the motor, it would need to stay around that 8000rpm mark.
Now onto the transmission: The roadster has 225/45 R17 rear tires, their circumference being 78.45". That means that for every full revolution of the wheel, the car travels 1.993m.
The first gear has an overall ratio of 14.3:1, so at 8000rpm (peak power) the car would be travelling at 66.9km/h and at the motor's top speed (13000rpm) it would only do 108.7km/h. Surely, that would never be enough to please people looking for an exhilarating experience.
The second gear has an overall ratio of 7.4:1. This is when things start getting exciting. At 8000rpm, the car will be going at 97.0km/h and reach a full speed of 210km/h if it manages to revv up to 13000rpm.
Of course, this could all be done without a 2-speed transmission, but if it were a direct-drive system, the gear ratio would have to be like in the second gear and they'd have to sacrifice a lot of torque in the lower speeds if they hoped for the car to travel faster than 108.7km/h.
Reply
Travis Rassat 1:44PM (12/13/2007)
Thanks for the replies about my transmission questions. I can understand the need for the differential/gear reduction, but wasn't so sure about the need for multiple gears. Makes sense now! Thanks!
Reply
Yanquetino 3:21PM (12/13/2007)
What kind of transmission was in...
* the EV1?
* the Toyota RAV4-EV?
* the TZero?
I thought that the latter could do 0-60 in under 4 seconds.
Reply
Rojo 3:31PM (12/13/2007)
I'm going to trump your question, Travis. I'm sure this has been reasoned away somewhere, but I haven't seen anything concrete on the subject, so here goes:
Still on the subject of the transmission, why not use a CVT?
Maybe the torque and RPMs are at levels that would shred any belt? But surely if these work in anything from a massive combine to a Sentra, it could work in an EV...
Reply
Kardax 5:02PM (12/13/2007)
Yanquetino: The Tesla Roadster's motor (248HP) is much more powerful than the one found in the EV1 (137HP), the RAV4 EV (67 HP), and the tzero (200HP). I wouldn't even count the tzero, as it never faced the durability challenges of a production vehicle.
Rojo: I've never heard of a CVT that can withstand 13000 RPM...
Reply
Joseph 7:05PM (12/13/2007)
"They delivered a car they know doesn't even work right and I'm supposed to be excited?"
Honestly, do you think a Ferrari F430 is built for real durability. Do you think it is designed to built everyday. Tesla had indicated that the car is and from customer test drives, the car's suspension is rather smooth for a sports car so it's clear that it is an everyday vehicle. The trunk is large enough for a golfbag. Besides maybe a Z06, I don't know of any super cars (0-60 under 4 seconds) that can carry a golf bag in the trunk.
So, do you think any of the ultra-exotic cars acutally are very durable? Driven hard, a sports car's clutch wears down under 50k miles.
The car does work right. It's called a durability problem. Very, very different.
Reply