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3rd transmission supplier?!

Discussion in 'Roadster: Technical' started by TEG, Dec 5, 2007.

  1. TEG

    TEG TMC Moderator

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    From http://blogs.business2.com/greenwombat/2007/12/tesla-motors-fo.html
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    Telsa put plans to sell electric car batteries to other manufacturers on hold while it focuses on the two-seater's transmission, which hasn't met the company's durability standards. "It’s our biggest issue," says Musk. "Unfortunately the company picked the wrong supplier, not once but twice, and now we’re on to our third."
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  2. AGR

    AGR Member

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    Is the transmission issue the tip of the iceberg? At this stage it would be simpler and more expedient to have no transmission(single speed), humbly admit that it will not do 0 to 60 faster than a super car, and start delivering car to customers.

    There are always qualifiers prior to a Tesla going down the road.
     
  3. TEG

    TEG TMC Moderator

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    I always thought one speed made sense because 90+ is illegal and potentially unsafe on public highways in the USA. The "low RPM torque, moderate max HP" (for a supercar) of the eMotor limits max top speed anyways, so even gearing to get to 125MPH still doesn't get a lot of street cred for top end. Might as well leave other supercars to attempt the 200MPH+of the gas guzzling autobahn supercars designed for Europe or the race track.

    Since 2nd gear is geared to get to ~125MPH, it limits 0-60 to around 6.
    I bet if they had one speed, and it was geared to reach 90MPH max then they could get 0-60 well under 5s with no shifting required.

    Another thing to consider is that the battery pack stores much less energy than a fuel tank in a gasoline auto. Higher speeds reduce efficiency, so BEVs really should consider limited top end to preserve range capability.
     
  4. malcolm

    malcolm Active Member

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    Will it have to go to a fourth transmission supplier?

    The perfect seems to be getting in the way of the good here.
     
  5. AGR

    AGR Member

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    You get the feeling that at some point it was an excercise to outdo AC Propulsion, and Wrightspeed for whatever reason. Bringing up similarities between an unproven and untested electric car and proven and tested super cars was an ambitious undertaking from the outset.

    The best part is that many people bought into the idea of an electric supercar.

    Extrac is an English company that makes all sorts of transmissions for a myriad of racing applications, if their transmissions can endure racing applications.....

    Single speed reasonable acceleration with a top speed slightly north of 100 MPH is more than enough for such a car. Its a Lotus Elise with an electric motor replacing the Toyota motor.
     
  6. DDB

    DDB Member

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    Correct me if I'm wrong, but wouldn't they save money on a single transmission?
     
  7. tonybelding

    tonybelding Active Member

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    I guess I'll have to be the dissenting voice here. . .

    I think the two-speed transmission is one of the more appealing features of the Roadster, and to me it's clearly the Right Way to go in a sports car. It appears to be the main reason why the Roadster can outperform a Venturi Fetish, for example.

    Would it have been quicker and easier to use a single speed? Sure. . . However, there was no reason to expect the transmission would lead to the extent of problems that it has. Transmissions are not new technology, they aren't rocket science. And honestly, if Tesla can't get a two-speed transmission to work, then they have no business making cars.
     
  8. TEG

    TEG TMC Moderator

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    I think a very high performance electric drivetrain could possibly stress a transmission unlike a conventional arrangement. The eMotor has no flywheel and can make very sudden torque transitions if asked to do so. I would guess they are trying to work out transmission reliability not just with mechanical transmission parts, but also with software changes to control how the eMotor treats the transmission. (Reduced redline could have been one result we saw). [ Or maybe I really don't know what I am talking about ]

    One beauty of an eMotor arrangement is that you can go in reverse electrically, so you don't really need any transmission at all (whereas an ICE vehicle at least needs a way to go in and out of reverse gear). Also the eMotor has high torque a 0 RPMs so you can go clutchless, but once you introduce a transmission of any sort a clutch could be needed.
     
  9. malcolm

    malcolm Active Member

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    Thanks TEG. Starts to make sense of that weird "transient spike" comment made by the Volt executives.
     
  10. SByer

    SByer '08 #383

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    I have to agree with Tony. I think the transmission was necessary. A top speed of under 90 just wouldn't cut it, nor would a 0-60 time of around 6 seconds. At six figures, you either have to have the luxury or the performance, or some reasonable balance of the two. With the spartan cockpit, the Roaster needs the performance. With the transmission, it has it.

    I suspect that getting a clutch to handle the torque was/is a trick, but I'll also note that with careful software management and an actuated clutch, you also wouldn't have to worry about take up rate as much - you never have to feather the clutch for launch, and the clutch could have a much sharper uptake than something your left leg has to manage.

    I do wonder if the actuators add as much weight as a variant of Audi's DSG would have, though...
     
  11. WarpedOne

    WarpedOne Mainecoon Butler

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    #11 WarpedOne, Dec 6, 2007
    Last edited: Dec 6, 2007
    Well, 2. gear as it is now suffices for under 6 seconds 0-60 and 125mph top.

    Does shaving a third of time that time warrant a year of delay and XYZ amount of additional cost?

    Yeah, the best is the enemy of the good.
     
  12. vfx

    vfx Well-Known Member

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    I'll weigh in on the side of a 2nd gear mandatory.

    That 0- to 60 at 4 (3.86?) seconds is critical to the sales of an exotic sports car.

    I would hazard to look into the 3rd gear we talked about long ago. I believe Warpedone calulated it at a 160 mph top end. Maybe it's not 250mph Supercar speed so its not worth the trouble, but from a builders standpoint in regards to marketing clout, why not? Like the Ferraris and Lambos of the world, you would not use it much anyway.
     
  13. TEG

    TEG TMC Moderator

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    If they put in a 3rd gear, and tried to gear it for 160mph they might have overheat problems on the air-cooled eMotor. Also the range at that speed would be very short.
     
  14. BlackbirdHighway

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    If it was up to me, I would also have chosen a multi-speed transmission over a single speed.

    The big auto companies have a bunch of very experienced transmission experts, well equipped transmission testing labs, and long established transmission suppliers, yet they still run into trouble from time to time. I've heard of transmission problems with a lot of mainstream cars.

    I think that Tesla, without all those things, just took it on faith when the first transmission supplier said they could do it. It probably didn't help that these were more Silicon Valley guys than Detroit car guys, and probably throught transmissions were old technology, so it shouldn't be a big deal.

    Transmissions are tricky and tough to get right. I would have gone with a more conventional manual transmission with a normal clutch. Software could control the motor torque and make it emulate the behavior of having a flywheel to make the shifting work in a more conventional manner. Plus, go with a well established transmission vendor.

    Well, hindsight is 20-20. In reality, if I was in charge, it'd probably still be on the drawing board.

    Sounds like they are finally getting past this issue, hope it's the last (major) one!
     
  15. Michael

    Michael Member

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    I wonder if it's time to reconsider whether having a CVT is the proper choice!
     
  16. AGR

    AGR Member

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    The 2 speed transmission is there for the 0 to 60 times, and the single speed is there for the actual road tests...has anyone driven that car and shifted the transmission back and forth as you would in a supercar?

    The eMotor as TEG refers to it is air cooled and in a real super car application it would have to be water cooled to correctly endure sustained high performance operation. In one of the early customer road tests from the blog when pushed it was getting hot.

    At this stage it would be much simpler and efficient to have a single speed, with the air cooled eMotor, which is what everyone has been road testing and driving, and talking and raving about. At a later stage come out with the T version, 6 speed sequential shift, liquid cooled motor, carbon brakes, bigger tires, and a high performance battery pack to hang on to a Murcielago for at least a few miles.

    No one has ever shifted the 2 speed transmission on a regular basis on any of the road tests, and if the car gets driven aggressively the eMotor will get hot beyond the capacities of the cooling ducts to circulate additional air.
     
  17. DDB

    DDB Member

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

    Not that Tesla has enough resources to offer two versions [yet], but I'm curious about the owner perspective about those who have placed $30-$100,000 deposits. I would be willing to bet most owners would be willing to take a car that goes 90 mph in 6 seconds if it can be delivered in 2008...but of course that's a WAG.
     
  18. BlackbirdHighway

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    You might be right, but there is one owner, whose initials are E.M. who wants a two-speed, and his vote counts more than the rest

    Hardly matters now, if this 3rd transmission is finally the one, and production really starts next year. (Please, please, please, let it be so!)
     
  19. donauker

    donauker Member

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    I also agree that the 2 speed transmission is necessary. My main interest is in all electric “green” driving or more importantly zero oil consumption driving. But on the other side there is no way that I am going to pay $100K for a car that I need to make excuses for. I would wait a bit longer to see what other options may become available and continue to drive my Vectrix as much as possible.

    AGR: Owners have been driving the shiftable car since about the third week of October from the reviews I read. Also VP9 is obviously doing some serious shifting since it is being used for the time trials by all the magazines this week. The 50-70 and quarter mile times require max performance shifting.
     
  20. Kardax

    Kardax Member

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    0-60 in 6 seconds is Miata speed. You can't charge $100,000 for $25,000 performance.

    The Tesla Roadster might not be delayed as much with a one speed, and they'd probably sell a bunch to wealthy greenies, but if you want performance enthusiasts on board you need that quick acceleration.

    In the end, any 6-digit car costs 6-digits because it's not easy to make. Tesla's struggles with the transmission is earning them that price tag.

    -Ryan
     

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