Gear shift speculation

malcolm · Nov 2, 2007

Am i correct in assuming that there are three options:

1 Tesla gets the all-electronic(?) gear change working as intended

2 has to install some mechanical doo-dad such as the zeroshift which carries a slight weight and efficiency penalty.

3 has to install a clutch system ( A Clutch on top of Creep - Ugh!)

WarpedOne · Nov 2, 2007

I do not understand this fear from clutches.
There is no need for it to be foot operated, it can be completely automatic and transparent.

tonybelding · Nov 2, 2007

It's an electro-hydraulic dual-clutch transmission. There is no manual clutch pedal, it's all controlled electronically. I believe that is similar in principle to the paddle shifters that are appearing on some cars these days.

TEG · Nov 2, 2007

I wonder how much weight the dual clutches and electro-hydraulic actuators added to the transmission.

WarpedOne · Nov 3, 2007

Added?

You think it was supposed to be clucthless? Sorry, but think again

TEG · Nov 3, 2007

Well, what of all the talk of trying to do it without any clutches?

http://www.teslamotors.com/blog3/?p=68

Andrew Kelsey wrote on October 31st, 2007 at 11:42 am
I always thought the delay was mainly due to transmission, especially after Tesla changed suppliers. I’m no engineer but I imagine it must be pretty difficult to make a smooth, reliable change with no clutch and 13,000 revs on the clock in first gear.

Loren Carpenter wrote on October 31st, 2007 at 1:54 pm
I was fortunate to get a brief tour of the San Carlos plant a month or so ago. Toward the end of the tour Zak showed me one of the new transmissions on a workstand. It was smaller than I expected, especially as it includes the transaxle/differential. The very intricate castings told me that someone really good spent a lot of effort to design it for minimum weight. That was the transmission they recently installed in VP10 which some early customers have driven.
As I understand it, they got the clutchless transmission to work; but it’s response time was, in the end, not acceptable.

Michael V wrote on October 31st, 2007 at 2:13 pm
From what I’ve heard (please correct me if I’m wrong) the problem is that Tesla wants a completely electronically controlled gear change. That is; the gears separate, the electric motor changes to its proper speed with the new gear selection, re-engages. Literally no clutch is used.

WarpedOne · Nov 3, 2007

I'd still prefer definitive statement from Tesla.

Primarily because I do not know of a single case where clucthless transmission with fixed gear ratios was used in a car.

donauker · Nov 3, 2007

I'm not sure if you will get a definitive statement from Tesla at this point but based on my conversation with the Tesla people that were in New York City back in June of this year, this was indeed the initial design. While in theory this would work it did prove to be a huge challenge and they could not get the shift time down to an acceptable value. Also it would appear that it was rather easy to break the transmission when the shifting wasn't just right.

I think it would be rather easy to do clutchless shifting with a permanent magnet DC motor but it proved to be too much of a challenge with an AC motor.

malcolm · Nov 4, 2007

donauker said:
I think it would be rather easy to do clutchless shifting with a permanent magnet DC motor but it proved to be too much of a challenge with an AC motor.

I'm guessing that although it's easy to monitor the motor shaft rotation in both types, it's the electronic monitoring/prediction/control of the AC motor's torque immediately before and during the few hundredths of a second(?) change-over which is the tricky bit. Especially since a gear change can be initiated at any moment within quite a wide torque "window", including while the motor is decelerating the car/providing regen.

Any delay between gear change initiation and actual change-over (while the electronics try to catch up with what's going on) would be very frustrating; e.g trying to minimize 0 to 60 times with TC off by trying to hit the optimum 52 mph change-over point.

TEG · Nov 10, 2007

FYI, over here someone had said the original transmission was from Xtrac, then later switched to Magna.

Here they said it was changed to get quicker shift times.
Here they said the xtrac was "balky".
Here Tony said the Xtrac was 'unreliable'.

Kardax · Nov 11, 2007

TEG said:
FYI, over here someone had said the original transmission was from Xtrac, then later switched to Magna.

Here they said it was changed to get quicker shift times.
Here they said the xtrac was "balky".
Here Tony said the Xtrac was 'unreliable'.

The truth could be all of the above

-Ryan

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Gear shift speculation

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