Tesla Roadster's 98% efficient transmission nominated for innovation award
 

Found this interesting tidbit:

http://www.blogcdn.com/green.autoblo...rdrive-630.jpg

(Image source: Borg Warner announces new single-speed eGearDrive transmission for Coda electric sedan — Autoblog Green)

BorgWarner, the designer of the gearbox for Tesla's roadster has been nominated for the "prestigious 2010 Automotive News PACE Awards, recognized around the world as the industry symbol of innovation."

(Here's a link to past PACE Award winners & finalists.)

98%!

Something to be said for a single speed transmission, for sure.

(Makes me want to open up the ForkenSwift's gearbox and get rid of all those extra wasteful gears that are uselessly meshed together all the time.)

Source: BorgWarner's eGearDrive(TM) Transmission Named 2010 Automotive News PACE Award Finalist | Reuters

I'd call it a gearbox rather than a transmission, since tranmissions in automotive use generally imply multiple speeds. For a single set of helical cut gears, 98% is good, but not tremendously higher than average.

The gearboxes we use in my industry tend to be about 80% efficient and that is good. But those are worm gears.

See? I've been advocating for fewer gears instead of more for a long time now...

That's good context. Any idea what average would be?

The Solectria Force Geo cars also all used custom single speed gearboxen.

I couldn't really get away with it in the low power ForkenSwift... well maybe I could (the Citicars were all single speed 48 volts). But I like to have the ability to downshift to keep amps low when cruising (or climbing very steep stuff at low speed), and upshifting when I want more power.

I actually do use all 5 gears - but mostly 2 & 3 with a bit of 4 once in a while. I could probably get away with just 2, 3 & reverse. Wonder what kind of difference it would make...

You'd like the Golf twin-drive hybrid then. One forward gear. Electric up to about 30 mph, then diesel power (and/or blended ... I forget) from there up to top speed.

I guess ForkenSwift and E-Sandra are like apples and oranges: big motor and 48v vs. itty-bitty motor and 72v, but I find myself using gears MORE than I do with an ICE! I go from 1st to 4th to get to about 25 mph. I could certainly stay in one gear, but it would be much slower to get there. I attribute that mostly to my throttle only going to 1970 Ohms, but just the throttle limit (I would guess anyway) wouldn't change the need to shift, would it?

Oh, I think it definitely would. You need amps to accelerate, and need to be able to open up the pot to get the amps.

The fastest way for me to accelerate from a stop to 30 mph is to put it in 3rd gear and floor it, then switch to 4th when it starts to run out of steam around 25 mph. More or less. Pulls very battery-unfriendly amps when I do that though (200-300).

Well I didn't get my amp gauge from China yet, so it's all conjecture for me:p, but my guess is I am attempting to overcome lack of amps by upshifting to draw more amps. Accessing more throttle would then make it so I would need to shift much less. Makes sense:)
Also, when I get to 4th is when the voltage drops the most (down to about 58 volts) which I'm guessing equates to more amps drawn? I really should know more about this stuff before I converted the car:p

I think your conjecture is probably right.

Don't worry - I didn't know anything either (lots I still don't know). It was an "immersion" learning experience.

I'd agree. For the gearboxes we make (helical gearing), we use a 1.5% loss per gear mesh. That is our average.