Filed under: EV/Plug-in, Tesla Motors
Breaking: Tesla has a solution for their transmission woes: get rid of it!
The primary issue that has been preventing Tesla Motors from getting their electric Roadster into full production for the last several months has been the unfortunate tendency for the transmission to self-destruct in only a fraction of a car's normal lifespan. In December, the company announced a plan that would see them launch production in the first quarter of 2008 at a slow rate with an interim single-speed transmission in place of the planned two-speed unit while they continued to develop a two-speed unit that could withstand the punishment of the electric motor. Once a newly-developed two-speed unit was validated, Tesla planned to retrofit the early cars with new units.
One of the many questions people raised was why use a transmission at all? Virtually all other EVs just use a reduction gear. Tesla has now come up with a plan to resolve the problem and guess what? The two-speed is history. The two-speed was originally used in order to meet the performance requirements for acceleration and top speed. The solution came from work that was being done for the WhiteStar sedan. In order meet their performance targets, Tesla has modified the power electronics module to be able to send significantly more current to the motor and hence produce sufficient peak power to get the four second 0-60 time. Read on after the jump learn more about what Tesla is calling DriveTrain 1.5.
[Source: Tesla]
As was discussed in the previous story about using the Roadster as a track car, the limiting factor there is the heat build-up in the motor. The air-cooled AC induction motor would simply get too hot causing power limiting logic to kick in and not be useful on the track. One of the changes being developed for WhiteStar, which will be a larger heavier vehicle than the Roadster requiring more power, is a liquid-cooled motor. The Roadster will now also get a liquid-cooled motor. This will allow to produce more sustained power than before.
Getting power to the ground will be accomplished with a newly-developed single-speed transmission. The new unit is essentially a reduction gear. The new transmission is not based on any existing design and will be manufactured to Tesla's specifications. Major powertrain engineering consultancy Ricardo is assisting Tesla with transmission design. They are used to working with transmissions for high-powered cars having developed the gearboxes for the Bugatti Veyron and Ford GT, among many others. Components are currently be tested and a vehicle with a development version of DriveTrain 1.5 should be ready for testing next week.
Tesla is giving no time-line for when validation of the new hardware will be finished, but sometime later this year would be a likely target. In the mean time, series production of Roadsters with the interim single-speed transmission will begin on March 17, 2008 in England. Tesla has now received all necessary regulatory approvals to start selling cars and the first production model that was completed recently at the Lotus factory in Hethel has been crated up and will be shipped to the U.S. shortly. Once the new power-train has been validated, production will ramp up quickly and early units will be brought in to be retrofitted with new motors, transmissions and PEMs.
January 23rd, 2008
SOURCE: Tesla Motors
Tesla Motors Completes all Regulatory Approvals and Sets Schedule to Begin Production
First production 2008 Tesla Roadster Imported – Series Production Begins in March
WHAT'S NEWS
• Tesla Motors has received all regulatory approvals to import the first production Tesla Roadster ("P1") for sale. This includes all necessary EPA and DOT approvals, including completion of all Federal Motor Vehicle Safety Standards (FMVSS.)
• P1 will arrive at Tesla Motors headquarters next week for delivery to customer Elon Musk, Chairman of Tesla Motors.
• Series production of the Tesla Roadster is scheduled to begin March 17th, 2008
ADDITIONAL BACKGROUND
• As communicated previously, early production units will be equipped with an interim transmission that meets durability requirements but limits acceleration to 5.7 seconds from 0 to 60 mph.
• Separately, Tesla Motors engineers have designed a permanent solution for mass production that supports the original specification of 0 to 60 mph in 4 seconds.
• The planned solution has some very positive benefits for our customers. Instead of a complex 2-speed transmission design, Tesla will achieve the original performance goals with a simpler one-speed unit mated to a higher rated Power Electronics Module (PEM.) The existing motor will be modified to have advanced cooling capabilities to handle the additional power. The permanent transmission unit will be engineered to handle the higher torque of the powertrain.
• The planned solution reduces program risk, provides better efficiency, lower weight, equal or better range, better thermal performance and quicker quarter mile acceleration due to the elimination of the need to shift gears.
• The planned solution incorporates the latest developments of our powertrain team which has been continually improving on Tesla's core technology.
• Early production will proceed at a limited rate and then ramp up to full production when the permanent powertrain solution is production ready later this year.
• The upgrade from the interim solution to the higher power, permanent solution will be provided to our customers free of charge when available later this year.
Reader Comments (Page 1 of 2)
Kardax 9:32PM (1/23/2008)
Interesting. I wonder if the top speed has changed.
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Dave B 9:49PM (1/23/2008)
Does this mean the Whitestar is right around the corner?
Second, what's this do to the cost of production? It's got to simplify it doesn't it? Will that be passed on to the consumer?
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Sam Abuelsamid 9:54PM (1/23/2008)
Top speed will dip slightly to about 125mph from 130mph. As for cost the difference will likely be negligible, considering the added cost of liquid cooling the motor. Although the trans is simpler it is now custom made rather than off the shelf which will likely negate cost savings there too
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Noz 10:05PM (1/23/2008)
That's the problem...they've got the British involved. How the Brits have made such a reputation in the automotive business is beyond me. Their cars are pure junk...and to think they are crawling around in F1 like cockroaches.
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rob 10:08PM (1/23/2008)
So... Martin was correct all along, this car doesn't need a multi-speed transmission?
I'm guessing he's having a lot of mixed emotions on that at the moment...
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Yanquetino 10:20PM (1/23/2008)
I've gotta give Martin a big "high-five" here! What goes around, comes around. Literally, it seems! Too bad so much time, money, blood, sweat, tears --and careers-- were wasted instead of simply going with his original vision. Over at headquarters, do you think they'd like a little ketchup to go with that crow?
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Kardax 10:24PM (1/23/2008)
rob: I don't think Martin's original design called for a liquid-cooled motor, though (at least, not for the first model year).
Elon's plan is clearly to make the first car amazing... they can't go back now and cut down the performance specs. This ordeal is incredibly wasteful, but history will forgive him if Tesla delivers.
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Joseph 11:10PM (1/23/2008)
Martin said as a comment in his blog (his and other's comments have been removed unfortunately)
that he always wanted there to be a ONE speed transmission and (I'm almost absolutely certain about this one) that he wanted the power electronics to go through an upgrade before the Roadster reached production. (Someone correct me if I'm incorrect.)
Elon objected both, and now, as we can see, he's going right back to them. Poor Elon! :(
This will be a funny story to tell people. The plans went from one-speed to two speed, of which (appaerently) four different transmission suppliers failed in some way, and then back to the one-speed, which was the original plan from the founder who got fired!
Some interesting links:
http://teslafounders.com/ There's a new post!
http://www.motortrend.com/roadtests/alternative/112_0803_2008_tesla_roadster A Tesla Roadster Review!
By the way...
Sam said,
"Top speed will dip slightly to about 125mph from 130mph"
I don't think the lower top speed has anything to do with this because the top speed was lowered months ago.
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Mort 11:13PM (1/23/2008)
I said something like that and was ridiculed on this board. Duh, use a capacitor. They probably don't have a clue, judging by how long it took them to come up with a fix. White Zombie!
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Sam Abuelsamid 11:25PM (1/23/2008)
The information on the liquid cooled motor was direct from Tesla.
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max andrews 1:05AM (1/24/2008)
Haven't they heard of a CVT?
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jake 1:07AM (1/24/2008)
@Sam Abuelsamid
This is certainly exciting information, esp if the liquid cooling (track days possible now?) is true. The single speed should mean much less complication. Wow, didn't expect this positive turn of events. I was hoping for some better cooling for the engine since this was a complain earlier on. I'm also interested for the source too, if possible.
@Joseph
I though the top speed dropped from 135 to 130 awhile ago. The 125 drop should be new.
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Phil L. 6:50AM (1/24/2008)
max andrews -
Electric motors have far different torque characteristics that ICE engines. Current CVT designs would likely be shredded in short order, just like the two speed design.
That said, the ability to select different gear ratios still has significant advantages. I believe we'll see a Tesla transmission update at some point in the future.
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Dave 9:24AM (1/24/2008)
Get this baby on the market so it will drive other potential manufactures of EV's to get their butts in gear and get their products to market ( GM Volt ).
Time to market is key here and will benifit consumers, increase breadth of choice as soon as this is in volume and available.
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Don A 9:50AM (1/24/2008)
Sam Abuelsamid said:
"Top speed will dip slightly to about 125mph from 130mph."
jake said:
"I though the top speed dropped from 135 to 130 awhile ago. The 125 drop should be new."
The drop to 125mph is not new. This excerpt is from the Tesla Motor blog "Where the Rubber Meets the Road" dated 9/24/2007.
"We have therefore decided to electronically limit the production Roadster’s top speed to 125 mph in order to maintain long-term reliability in the powertrain."
http://www.teslamotors.com/blog4/
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GoodCheer 9:53AM (1/24/2008)
I'm kinda surprised that they didn't drop in a totally conventional manual tranmission (you know, with a clutch you operate with your left foot and all that). It would certainly be heavier than a single speed, but I would think it would be lighter than any kind of automatic or dual-clutch transmission. For the number of times you're going to shoot straight from a standstill to 125mph I would not call it an inconvenience, it's not like you'll have to feather your clutch in stop and go traffic. For the few times a week that a Tesla driver would have to change gears I would think backing off the throttle (or having it happen automatically when the clutch is depressed, sort of a main-motor synchro-mesh) would be worth getting the full performance range.
Does anybody know it this option was looked at?
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Tony Belding 10:33AM (1/24/2008)
GoodCheer, I'm not aware that using a fully manual transmission (i.e. with a clutch pedal) would have helped the situation any. Seems to me it wouldn't matter whether the mechanism is activated by your foot or by an electro-hydraulic actuator, either way the internal stresses are going to be the same.
The interesting possibility that I'm imagining now is a "virtual gear shift". I mean, we already have a shifter knob in the car, right? It was only an electrical switch anyhow, so. . . It could be used to switch between different software parameters. In position 1 you could have maximum power available to the motor and aggressive regen, and in position 2 you could have limited power and more relaxed regen, for those times when you don't want to smoke the tires.
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Dr. Kenneth Noisewater 12:50PM (1/24/2008)
Liquid cooling?
Any chance of a Stirling engine in the radiator plumbing to reclaim that much more juice, or would that add more weight than it's worth?
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Karkus 2:35PM (1/24/2008)
Adding a manual transmission to a Tesla would be like adding a vacuum tube or punch card reader to a supercomputer.
The problem was too much torque. I don't think a manual transmission would help...it would just add unnecessary weight and complexity, and decrease efficiency and acceleration. Electric motor behave WAY different than ICEs (electric motors have lots of torque at 0 RPM), so the need for transmissions is reduced or eliminated.
I used to love manual transmissions, but they are a thing of the past. CVTs and DSG type transmissions are taking over, since they get rid of the inefficiencies and jerkyness of standard transmission. Some hybrids (Toyota, Ford) have mechanically simpler (but computer controlled) ECVTs, which are even smoother and more efficient. http://www.cleangreencar.co.nz/page/prius-transmission
After driving the Toyota ECVT, I won't go back to anything more primitive. And EVs shouldn't really need transmissions at all. Bye Bye transmission.
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bradkkaye 2:47PM (1/24/2008)
Dashboard
Really? Was that the best font & sweeper gauge needle they could develop for the instrumentation of a $100k car? Looks like the dash out of a '93 Saturn.
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