Tesla clarifies report of "temporary transmissions"
Tesla held a town hall meeting last week to give its customers the skinny on how development of the all-electric Tesla Roadster is progressing. As we reported, an attendee revealed that since development of the transmission was holding up the works, Tesla was considering delivering cars to its customers with a temporary transmission that to be replaced with the proper gearbox after it had been developed to spec. It turns out that there were a few important details omitted from this report that Tesla wanted to clear up, so they called Sam at AutoblogGreen and set the record straight.
For one, Tesla has no plans to deliver cars with transmissions that it knows will fail. Instead, the plan is to deliver some cars with a simpler, single-speed transmission rather than the two-speed gearbox being developed. Tesla assured ABG that this single-speed tranny will meet all durability requirements and not leave owners stranded on the side of the road. So these transmission are temporary in the sense that they'll eventually be replaced, not that they'll fail.
The single-speed trannies, however, won't allow the cars to go as fast as promised. The two-speed gearbox allows the Tesla Roadster to meet its goals of a 4-second run to 60 mph and a top speed of around 125 mph at the same time. The single-speed gearbox, however, will be trading off some low-end acceleration so that the car's can be delivered on time.
[Source: AutoblogGreen]
Reader Comments (Page 1 of 1)
ckm 5:14PM (12/19/2007)
Cheez, you think they'd know about using GM Powerglide transmissions. Those things can be built to take upto 2000 ft. lbs. of torque, more than 10x what a Tesla puts out.... And they're reliable too, some race drivers have been using the same transmission, no rebuilds, for 3 seasons.
With some relatively smart electronics and a little tuning, they could probably even make the shifts fairly smooth...
Chris.
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fawgcutter 5:29PM (12/19/2007)
Seeing one on a 350cid Boss Hoss reminded me of how bulletproof and huge a Powerglide is.
However, we're talking electric car here and weight does matter (gotta save GVW for them batteries).
ckm 6:05PM (12/19/2007)
True, they are large, but I think that th size is mostly the casing, not the internals. AFAIK, the internals are around 6 inches in diameter, should be possible to engineering a modern casing that's smaller. There are plenty of other transmissions out there that would work within spec, from Porsche to Audi and GM.
I think they are trying to develop one from scratch, which is non-trivial. Probably because they have X by Y afterthought space to fit it into and nothing out there quite fits. Normally, on a mid-engined chassis like the Tesla, you hang the transmission off the rear of the engine. However, if you need a trunk or large amounts of battery space, on a typical mid-engined car, you might get away with what is essentially a FWD transmission (I think that's what the NSX essentially did). Problem is, most FWD transmissions can't take much power or torque because of a 'folded' design. This is what happens when a bunch of design engineers try to put together a car rather than a bunch of old school car guys.... ;-)
And, since the chassis they are using was built around a different 'power package', they are having to build a bunch of new components to make it all fit.
tbyron 12:40AM (12/20/2007)
Weight, size and layout. Even if Tesla could tolerate the extra weight of such a tranny and could physically fit it into the required space, it simply wouldn't work in what is essentially a mid-engined layout.
why not the LS2/LS7? 2:07AM (12/20/2007)
A powerglide dumps about 10% of the energy right into the torque converter. This would hurt performance and range a lot.
It's a great tranny, but it's not really a good match for this car.
porschedevotee 5:21PM (12/19/2007)
Any word on when the two-speed will be available? Also, just how "slow" is acceleration with the single-speed?
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tbyron 12:37AM (12/20/2007)
I doubt it will substantially slower off the line. The second gear will mostly be enabling higher top speeds and somewhat higher cruising efficiency.
why not the LS2/LS7? 2:09AM (12/20/2007)
Other way around. The single speed loses the low gear. Top speed in the low gear is less than 60mph is my understanding so going with just it would be bad news.
Tsunami Racer 6:30PM (12/19/2007)
why don't these Tesla buyers just get an Exige S for $66,000, get their 29MPG and donate the remaining $40,000 to an environmental cause? dollar for dollar, that might make more sense from a carbon footprint standpoint. $40K buys alot of trees.
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GTX141 7:56PM (12/19/2007)
I want to say that I like how Tesla is addressing concerns, and trying to get their cars to customers ASAP. But, this is a very convoluted way of doing so.
What owner of a 6-figure car is going to want to get its tranny replaced after they buy it.
Just get it right and deliver a proper car.
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Xcountryflyer 8:26PM (12/19/2007)
At this rate, one has to wonder if this car will ever come to fruition.
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V1650 9:29PM (12/19/2007)
Keep in mind that the Tesla is a product of SiliValley minds. Consequently, the owners are going to be "beta testing" the finished product. And why not? After all, it worked for Lotus, and Ginetta, and Marcos, and TVR, and Rochdale, and...
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j_diesel 1:16AM (12/20/2007)
someone actually trying to do something different and getting it done. my hat is off to Tesla. how much longer do we need to hear about what can't be done from all the major auto companies? if/when this car performs well and shows viability for day to day operation i hope it shows the major corporations that a different way of powering vehicles can be done today not five years from now.
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Jay 4:17PM (12/20/2007)
Agreed, although if i were the buyer of one of these cars, I would want some kind of proof that the money is set asside for my transmission. It sounds to me like a few cars will get delivered, then they will file bankrupsy and skip town. Perhaps providing the customers with a rebate valued at $2,000 or such until they receive the transmission.
j_diesel 4:37PM (12/20/2007)
hopefully enough of them get sold so tesla doesn't need bankrupcy protection. i do understand what you are getting at. it would be nice to see some underdogs show up the big boys from time to time.
David Thompson 1:53PM (12/20/2007)
I wonder why they're bothering with a transmission at all when they could just pole-switch the motor windings?
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j_diesel 4:41PM (12/20/2007)
to get the speeds advertised they need full field excitation and mechanical gearing. DC trolleys use the field theory when they get to a certain speed the field is cut out and this allows further acceleration with a corresponding drop in torque. i think tesla wants the torque.
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j_diesel 4:42PM (12/20/2007)
assuming it is powered with a DC motor. it might be an AC induction motor.
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