Next gen Roadster

[stopcrazypp]

I dispute the fundamental premise that the new Roadster needs 440kW to beat the benchmark ICE.
The benchmark of 2.7 sec 0-60 ( From the earlier post 2012 Porsche 911 Turbo S 530hp/395kW @ 3494 pounds ) was given although I can only find a 3.1 sec 0-60 for that car.

I got the number here (as well as the GT-R number); the number was obtained by Car and Driver Magazine:
http://en.wikipedia.org/wiki/List_of...y_acceleration

I think the original goal was a world record production car in terms of acceleration. Which means beating not only the 911 Turbo S, but also Veyron. That's why I erred on the side of caution when considering target numbers. And I'm not making any assumptions about how the power to weight ratio scales or how much less max power an EV can make do with. I just picked slightly better numbers than cars that have shown they are able to get sub 3 second 0-60.

As for a multi-speed transmission, I also find it unlikely Tesla will bother. 0-60 is something you can experience even on public roads; top speed isn't. Plus only a small percentage of sports cars/super car buyers actually drive on the track (some super cars are barely even driven in the first place!). Seems like a lot of engineering (and possible loss of efficiency) for something that will rarely be used.

It's actually possible to have both 0-60 and top speed given lots of power and with very high gearing (direct drive or close), examples:
http://inhabitat.com/new-lola-drayso...-seconds-flat/
http://en.wikipedia.org/wiki/Eliica

I just noticed the Eliica (which has both acceleration and top speed of 200+mph; its almost a electric Veyron) "only" has 480kW of power and weighs 2400kg/5300lbs. I think a Model R with 440kW and around 3500lbs should also have pretty amazing performance.

[ElSupreme]

It's actually possible to have both 0-60 and top speed given lots of power and with very high gearing (direct drive or close), examples:
http://inhabitat.com/new-lola-drayso...-seconds-flat/
http://en.wikipedia.org/wiki/Eliica

Except the Eliica has 2 modes (read two gearbox setups) it can only get to 120 during acceleration mode. You aren't going to get sub 3 sec 0-60 and over 120mph without a stupid huge motor.

[rabar10]

Except the Eliica has 2 modes (read two gearbox setups) it can only get to 120 during acceleration mode.

Yep - quoting from the earlier-linked Wikipedia article on the Eliica:

There are currently (as of 2005) two versions of the Eliica: a Speed model and an Acceleration model. The Speed model is made to challenge gasoline-based records and has a top speed of 370 km/h (230 mph) with a range of 200 km (120 mi). The Acceleration model is made for the street and has a top speed of 190 km/h (120 mph) with a range of 320 km (200 mi).

[Doug_G]

With electric motors there are probably some novel architectures that could be used. For example, you could perhaps have two motors each with different gearing driving the same output shaft. At first the low gearing motor is doing all the work, but as speed increases the higher gearing motor starts pulling. As the speed increases further the low gearing motor becomes a liability, so a clutch is released and the higher gearing motor continues the acceleration. When decelerating the low gearing motor would spool up to match RPMs and then clutch back in. Done properly the acceleration could be seamless.

[WhiteKnight]

Porsche sells 18 flavors of 911. I think that Tesla should produce 1 version that 99% of the people will buy and another version Model R 'Extreme' that sells for twice the price of the standard version and can not only accelerate from 0-60 in 2.4s, it can also achieve a top speed high enough to hustle around the Nurburgring in under 7 minutes! I don't know what the prices would be - maybe $80K and $160K. Which, by the way, match the prices for the 911 Carrera and the 911 Turbo S.

The Model R Extreme would be a sports car bred for a single purpose. Toss out the back seat, strip down the interior, add additional motors, etc, until you've got a car that can meet these extreme milestones. Then you've got a tremendous Halo car that will give you huge street cred with the car junkies that read Motor Trend, Car & Driver, etc.

[richkae]

With electric motors there are probably some novel architectures that could be used. For example, you could perhaps have two motors each with different gearing driving the same output shaft. At first the low gearing motor is doing all the work, but as speed increases the higher gearing motor starts pulling. As the speed increases further the low gearing motor becomes a liability, so a clutch is released and the higher gearing motor continues the acceleration. When decelerating the low gearing motor would spool up to match RPMs and then clutch back in. Done properly the acceleration could be seamless.

I wonder what the mass ( rotational inertia, blah blah fancy physics terms ) is of the rotor in the motor versus a couple of clutch plates.
I wonder what RPM a rotor can handle before it wants to fly apart.
Then I wonder if you could just let it spin.

[Doug_G]

I wonder what the mass ( rotational inertia, blah blah fancy physics terms ) is of the rotor in the motor versus a couple of clutch plates.
I wonder what RPM a rotor can handle before it wants to fly apart.
Then I wonder if you could just let it spin.

For the Roadster, the maximum motor speed is 14,000 RPM. I suspect that's approaching a practical limit, and is why I suggested the clutch.

[stopcrazypp]

Except the Eliica has 2 modes (read two gearbox setups) it can only get to 120 during acceleration mode. You aren't going to get sub 3 sec 0-60 and over 120mph without a stupid huge motor.

Yep - quoting from the earlier-linked Wikipedia article on the Eliica:

That quote is very misleading, as the "Speed" model is also capable of the same acceleration:

The Speed model's current top speed is 370km/h (230mph) and a 120 mile range per charge while the Acceleration model's specs are 190km/h (120mph) with a 200 mile range. Both cars are capable of 0-62mph in 4 seconds, which is close to the Tesla Roadster's speed.

http://www.futurecars.com/future-car...heel-at-a-time

If you look at the photo page, it shows both versions (they call it Eliica 1 and Eliica 2):

Right:Eliica1, recorded max speed 370km/h．Left:Eliica2,street-legal car.

http://www.eliica.com/English/project/eliica/photo.html

Eliica 1 is the one used to do demonstrations on the track (the one with the red "lipstick" in the front bumper, many more stickers, much smaller mirrors, etc). It doesn't have a full interior (it has racing seats instead), while Eliica 2 does.
It's Eliica 1 that did the acceleration race against the Porsche 911 Turbo in this popular video (notice the same red part on the front bumper, the racing interior, the smaller mirrors, plus all the stickers):

Here's the specs for the Eliica (edit:it may be a mix of specs, for example the 4 seats and the range doesn't match Eliica 1):
http://www.eliica.com/English/project/eliica/spec.html

[ElSupreme]

I wonder what the mass ( rotational inertia, blah blah fancy physics terms ) is of the rotor in the motor versus a couple of clutch plates.
I wonder what RPM a rotor can handle before it wants to fly apart.
Then I wonder if you could just let it spin.

Yeah having the rotor come apart can happen. But bearing heat generation is the real concern.

High speed flywheels use magneticly levitated shafts.

[WhiteKnight]

Yeah having the rotor come apart can happen. But bearing heat generation is the real concern.High speed flywheels use magneticly levitated shafts.

Well with $80,000 to spend (from $80k to $160k) to become Lord Of The 'Ring maybe Tesla could install motors with mag-lev driveshafts!

If 14,000 RPM gets you to 120mph then 28,000 RPM should get you to 240mph.

By the way, at what point does a car become so insanely powerful and fast that it is no longer safe to sell to the general public?