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 2 of 2)
Snoopchan@hotmail.com 7:36PM (12/13/2007)
They're using Mass Production techniques that are inefficient. Why don't they use Lean? It's faster if they would let both suppliers work together and not fight each other for the tranmission prob. That's why American automakers and Tesla alike have unnecessary supplier problems and on-going shaky relationships with them. WHAT A PITY. They can't learn until they come to a crisis or waste billions of dollars.
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T2 7:50PM (12/13/2007)
@ Mau
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.
"Yeah but" it takes only four seconds to do it !
T2
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RogerRed 8:43PM (12/13/2007)
Darryl is a tool. His insincerity is so painfully obvious. He has no experience in this industry and really should go back to selling insurance. Tesla needs strategic PR now, and not some idiot who seems to self-promote through getting people fired. What is Tesla thinking with keeping this guy on board?
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Yanquetino 11:36PM (12/13/2007)
Kardax:
Well, yes, I know that the HP was lower in the EV1, the RAV4-EV, and the tzero. But that wasn't my question. What I wondered about was their transmissions.
AC Propulsion claims that, with its 200 HP, the tzero will go 0-60 in 3.6 seconds. Yow! I don't know what its top speed is, but whatever it uses for a transmission doesn't seem to dampen its acceleration. And I believe that the EV1 (well, an Impact) set a high speed record for an EV. So... what do/did they use for a transmission?
Plus... AC Propulsions claims that the tzero's li-ion battery pack can go 300 miles on a charge. That's quite the combination of power and range, despite the lower HP than the Roadster. True, only two are in private hands on the streets, so durability remains unproven, but... whatever it's got sounds like it might be worth emulating.
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Sam Abuelsamid 6:01AM (12/14/2007)
The thing you need to remember about the Tzero is that it is not, and never was intended to be a production vehicle. It does not not meet safety requirements and has not been durability tested.
In fact the reason that Martin Eberhard started Tesla is because AC Propulsion declined to produce the Tzero. Building a one-off is pretty easy, as Tesla and others have learned building series production vehicles is much much more difficult.
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Yanquetino 11:09AM (12/14/2007)
Sam: I do remember everything you stated about the TZero. Again, it obviously hasn't undergone safety and durability testing. And AC Propulsion has made it quite clear that they do not plan to put it into production --although they must have toyed with the idea when developing it. It was, apparently, the prime model that inspired Martin Eberhard to develop the Roadster.
But it still begs the question: what kind of transmission does it use? My guess (?) is that it was probably a larger and stronger version of what the EV1 had (which was a tested design), i.e., a direct motor-to-wheel layout.
Whatever it has, I suspect that Martin had originally intented to use a similar drivetrain. It was reportedly Musk who insisted on the change. It is really too bad, because otherwise those Roadsters might already be on the streets --albeit with more limited capacity (100 mph top speed perhaps?) And the weight would likely be lower too, thus increasing its range even further. So sad.
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kert 11:55AM (12/14/2007)
The problem can be viewed differently. You know your motor maximum RPM, you know the top speed you want to achieve and your wheel diameter.
That tells you what fixed gearing you need for your high speed driving.
The question now becomes, why did Tesla need a FIRST gear ?
Because, the torque that they got from the motor and inverter at start and low speeds was not enough to meet their acceleration goals.
They could have redesigned the motor to a larger diameter, or maybe gotten better torques with better control algorithms ( im sure theirs is state of the art anyway ) but they chose mechanical solution.
Obviously, it has bitten them in the behind. Thats not to say that the other solutions would have been easy.
Note that the torque characteristics for induction motor setups and synchronous motors are a bit different. So what applies to RAV4 ( IIRC it was using synchronous motor ) doesnt apply here necessarily.
And control algorithms can only get so good, with the latest generation vector control in DSPs you are approaching theorethical limits.
There is no obvious way out without a mechanical solution. You cant increase motor RPMs to insane speeds, they'll fly apart or become very expensive to manufacture. You also cant increase the diameters for better torque endlessly, its going to impact the top RPMm and other design variables.
So for something that accelerates well, and has high top speed, you have to make a tradeoff somewhere.
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BlackbirdHighway 12:47PM (12/14/2007)
The T-Zero only had one gear, but it was also much lighter, (700 Kg), not having to withstand crash testing. So it had quick acceleration, but a lower top speed than the Tesla, 105 mph is the max ever tested.
As I understand it, auto rules say that if the production run crosses Jan. 1st, then that is the year of the model. By producing a car now, in Dec. 2007, and continuing production into next year, they can call it a 2008 model. If the first car were not produced until after Jan. 1, 2008, and production continued through Jan. 1, 2009, then they would have to call it a 2009 model.
I think that is the significance of producing the first car now, even it will require a "service pack" upgrade.
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OhmExcited 11:32PM (12/14/2007)
The EV1 could reach 184 mph but was limited to 80 mph and didn't have a transmission per se.
For something so radical as a new electric car out of Silicon Valley, they probably should have taken baby steps first, i.e. a single gear transmission, but hindsight is wonderful.
It's clear that the only problem with production is the transmission, and that as Yanquetino suggested, it was likely not Martin's idea in the first place to have a dual mode tranny. I still can't figure out for the life of me why they tossed him off the train. At the very least he could be blogger in chief.
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Yanquetino 11:52PM (12/14/2007)
OhmExcited: I think we're on the same wavelength here. For the life of me I can't imagine why they didn't just go ahead and produce the Roadster according to Martin's original vision, i.e., a single-gear drivetrain, Lotus's higher doorsills, off-the-shelf headlights, etc. Not that Musk's pet peeves wouldn't be "nice" to have, but... couldn't he have been patient enough to incorporate such changes into the NEXT model of the Roadster, say, in 2013? Just doesn't make sense when you think of it. Buyers would be driving them right now! So sad. And the biggest irony of all is that Martin ends up being shown the exit. Sheesh.
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OhmExcited 12:17AM (12/15/2007)
Do you have any idea who is on the board of directors at Tesla besides Elon? Are they major shareholders or basically Elon's yes men?
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BlackbirdHighway 3:42AM (12/15/2007)
It was a modified EV1, with a different gear ratio, that went 183 MPH, not a stock version. The modified version would accelerate too slowly to be useful anywhere except in Bonneville. The reason the stock version had to be limited to 80 MPH is because it only had one gear. And 80 is fast enough for most people, but not fast enough to charge $100,000 for.
I feel it is unfortunate that Martin was let go, but I wasn't there so I don't know the whole story.
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Ed R. 6:01AM (12/17/2007)
Actually, I believe the reason it should have a transmission is for efficiency. Electric motors are most efficient when they are spinning quickly; situations that require lots of torque at low speeds, like starting from a stop, normally uses a lot of electricity and significantly shortens range. Sure, you *can* get good torque by throwing lots of power at the motor, but it'll be very wasteful. Gears allow the motor to do that while using less power, greatly helping range.
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Johnny English 6:11PM (1/10/2008)
As Tesla uses 3 phase ac induction motor why not use star-delta windings to give high torque low speed then lower torque high speed. this is used in industry and is well proven.(no need for gearbox).
would like tesla to carry ultracapacitors and use new
carbon nanotube anode lithium ion batteries.
can't wait till I can afford one.
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