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_fastest_production_cars_by_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-drayson-electric-racecar-goes-from-0-to-60-in-3-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-drayson-electric-racecar-goes-from-0-to-60-in-3-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-ca...heel-electric-tears-it-up-one-wheel-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?

 

[vfx]

Interesting.. So that would go back to the idea that Model R will be built on the Gen 3 platform, but the actual Gen 3 vehicle (bluestar) will come much later (and give the higher-priced entrants time to recoup some R&D on the platform)

But what about perception? Releasing a next gen roadster on the smaller platform might make some sense using the original Roadster plan of low volume high dollar car but won't critics bash them for being a rich man's car maker*? If they release the Bluestar low budget car the are not only pleasing more of the car buying public but staying closer to original plan and making fanboys happier as well.


* I am aware that the bashing will continue, regardless. Tesla has Gov loans to think about, that's all.

 

[stopcrazypp]

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?

When it can cause this to happen:
http://en.wikipedia.org/wiki/G-LOC

I find that unlikely in a car though, because it causes mostly horizontal G:
http://en.wikipedia.org/wiki/G-force#Horizontal_axis_g-force

The rest is governed by speed limits and laws against speed contests and reckless driving.

 

[TEG]

Things start to become questionable when people refer to the acceleration as "brutal" instead of "awesome"...

 

[cinergi]

WRT acceleration & power: Give me full torque at 0 MPH (it's tame at the low-end in the 2.5) and give me enough power to really wow me even at 80 MPH (e.g. don't let power start dropping off until after 65+ MPH). 3s 0-60 is sorta one of those "you get to 60 before you know it and the fun is over too quick" things. Just give me at least a TRULY flat torque curve from 0-65 MPH.
Then: Improve aerodynamics so that I can go 75 without burning 350+ whpm, and fix the wind & insulation issues.
Not that I'll be getting a next-gen Roadster :smile:

 

[TEG]

Even with full torque motor torque from 0 RPM, acceleration is going to be slightly muted at first due to the tall single speed gearbox.

 

[vfx]

...

I think the original goal was a world record production car in terms of acceleration....

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.....

A transmission help the bottom end to. 0-30 and 0-60 times would also be improved. In the launch metric, the Roadster's old 1st gear was even more amazing than the one we are driving now.

 

[stopcrazypp]

A transmission help the bottom end to. 0-30 and 0-60 times would also be improved. In the launch metric, the Roadster's old 1st gear was even more amazing than the one we are driving now.

True, but I'm assuming the transmission is already geared to optimize acceleration and the power is already enough for 0-60 records (where traction may be a bigger issue than gearing). A multi-speed transmission isn't really necessary to accomplish that, but it might be if you want both recording beating acceleration AND top speed.

 

[Norbert]

But what about perception? Releasing a next gen roadster on the smaller platform might make some sense using the original Roadster plan of low volume high dollar car but won't critics bash them for being a rich man's car maker*? If they release the Bluestar low budget car the are not only pleasing more of the car buying public but staying closer to original plan and making fanboys happier as well.

* I am aware that the bashing will continue, regardless. Tesla has Gov loans to think about, that's all.

It has the advantage that it revives their image as "cool sportscar" manufacturer. Then they can advertise the Bluestar as: "Built on the same platform as the Roadster". They may have a not quite as expensive RWD base model, and a much more expensive AWD carbon-fiber etc version. By the time the next gen Roadster is about to be delivered, the Bluestar may be ready for announcement, as now the Model X is announced before Model S is delivered.

 

[richkae]

Wouldn't it be funny for a car to be sold with a transmission as an option?

If you don't want the best acceleration or the highest top speed, you stick with the single gear.

 

[zachster]

It has the advantage that it revives their image as "cool sportscar" manufacturer. Then they can advertise the Bluestar as: "Built on the same platform as the Roadster". They may have a not quite as expensive RWD base model, and a much more expensive AWD carbon-fiber etc version. By the time the next gen Roadster is about to be delivered, the Bluestar may be ready for announcement, as now the Model X is announced before Model S is delivered.

Sounds great, but this brings up somewhat of a puzzling thought for me. Am I the only one who has a bit of a hard time picturing Tesla launching an aluminum intensive car line and then 3 years later ramping up a completely different model R composites manufacturing line (that can also work with the assumed bluestar aluminum)? This sounds VERY capital intensive (i do feel a sudden need for a more elaborate point besides "expensive/potentially inefficient" here).

I suppose it would be inconceivable at the same time to not use composites on the model R. I wonder if we could see tesla trying to eventually bleed the benefits of composite into their other lines (more in line with BMW i series or Aptera main tech advantages). But again, to built a state of the art aluminum line and then a state of the art composite line for a fledgeling car company just strikes me as crazy.

.... ....so here's the the crazy one's then?!?!

"Here’s to the crazy ones. The rebels. The troublemakers. The ones who see things differently. While some may see them as the crazy ones, we see genius. Because the people who are crazy enough to think they can change the world, are the ones who do." - Apple Inc. errrr and Tesla too.