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

[MetroMPG]

1.5% loss per mesh. I really should think about ditching 1st and 5th then: 3% improved trans efficiency... And if I go ahead with the taller 5th for the Flea... guess what... I'll have an extra shaft I can remove gears from (though in terms of wear, it'll have unmatched gears on it).

[Daox]

I believe the gears must be engaged to actually be loosing that much. Obviously, if they are just churning oil you have additional losses.

[ALS]

When I had my 65 GTO I mostly only used first and fourth gear. I'd take first up to 3500 rpms and shift into fourth. It would drop down to 1,600-1,700 rpms. Got to love a close ratio four speed and a big V8 with lots of torque.

First gear at 5,500 rpms would take me to 55 mph. Fourth at 55 mph I would be running 2,750 rpms. Accelerating up to speed on an interstate on ramp there was no need for second or third gear. I would just hit 3,500 in first and skip to fourth and continue up to 55 mph.

That is the advantage to an electric motor also instant torque at lower rpms.
There is no need for a multi gear transmission or at least go back to a three or even two speed transmission. With a two or three speed transmission you can optimize the power to speed ratio so your not running the electric motor too slowly forcing it to pull more power than is really needed.

[jkp1187]

Wasn't Tesla trying to get a transmission with 2 forward gears to work? Did they completely give up on that?

[almightybmw]

telsa had a 2 speed to begin with, but had issues with it breaking the gear box. Thus the one speed design came second; although they wanted a one speed, implementing it by production time wasn't happening, so the "simpler" 2 speed was used as an interim.

[Allch Chcar]

Multi geared boxes usually make up for the loss in efficiency by having better acceleration. 1 gear boxes are rare. With electric and reversible drive 1 speed is all you need for 55mph or less so long as the motor isn't too small. But even electric motors have their peaks. The 2 speed Tesla box was supposed to give them a better top speed. Electric motors produce a lot of torque for their horsepower. Torque is the force that blows gears through transmissions and snaps axles.

Run-of-the-mill 5 Speed manual trannies with OD are 85%-88% efficient. Borg-Warner is probably the largest manufacturer of transmissions. My personal favorite is their T-56 . One speed transmissions are there just to give a better ratio than the final drive can provide.

[Frank Lee]

Originally Posted by MetroMPG

1.5% loss per mesh. I really should think about ditching 1st and 5th then: 3% improved trans efficiency... And if I go ahead with the taller 5th for the Flea... guess what... I'll have an extra shaft I can remove gears from (though in terms of wear, it'll have unmatched gears on it).

I noticed the default on the EM performance calculator is 95%.

I've been under the impression it's more like 85%, what with all those meshes and all.

Haven't found a really solid number though because this sort of thing is harder to pin down than it would seem.

[thatguitarguy]

If I'm understanding what I'm reading, with an EV, it's not about the transmission, but about the controller. The EV1 had a 1 speed transmission, and maintained full torque through the power band because of the controller. Do any of the DIY conversions have this kind of controller technology available, or is that the magic bullet that they don't want to let out of the box?

[Christ]

Originally Posted by MetroMPG

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...

I don't think I posted in this thread, I think I missed it altogether, but when I was into dirt track racing, one of the first things we'd do with the Borg/Warner T5's was remove all but 2/3. Didn't need the rest, only needed 2 to start, and 3 after the first corner.

[Allch Chcar]

Originally Posted by Frank Lee

I noticed the default on the EM performance calculator is 95%.

I've been under the impression it's more like 85%, what with all those meshes and all.

Haven't found a really solid number though because this sort of thing is harder to pin down than it would seem.

I know 85% is what most RWD guys use on the dynamometer numbers and it should be proven many times over by now. With 1.5% per gear it does sound about right too, 7.5% loss at the transmission for a 5 spd and 5% at the differential. That leaves 2.5% to other things like axles, wheels, etc. I've heard comments that suggest FWD only lose 12.5% but I haven't seen anything proving or even discussing it. A driveshaft for a RWD car can weigh 20lbs for Steel and 11lbs for Aluminum, which is roughly the weight of a forged wheel with no tire. I also know with AWD you get two more differentials and the loss is roughly 25% to all wheels.