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Next gen Roadster
- Thread starter dsm363
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- Future Tesla
I think the motor RPM limits may be due to mechanical things like bearings etc., so I'm not sure how different you could make the gear ratios without overspeeding your low gear drivetrain at top speed...
Tesla has dropped hints that they may be able to make motors with higher RPM redlines than the outgoing Roadster motor did.
If you are talking about different ratios front/rear, then yeah, I would be worried that top speed could overrev a gearbox on the other wheels configured for lower speed torque peak. If they did something like that perhaps they would need some sort of clutching mechanism to disengage the low speed gearbox once the high speed wheel set has taken over.
SByer
'08 #383
I don't want a transmission, period. If possible, I'd like to keep power steering out of things too, but I accept that I'm probably just weird on that front.
I'd want better 0-60 and range. I don't think the next gen Roadster will make it all the way to trackable (but I can see where that's a strong desire), and if it doesn't make it all the way, then there's not too much point in more top speed (certainly not at the compromise of putting a transmission in). But the stronger regen that could come with an AWD system would be awesome.
More comfy seats, a bit more storage (not for me), and still a convertible would be great.
I'd want better 0-60 and range. I don't think the next gen Roadster will make it all the way to trackable (but I can see where that's a strong desire), and if it doesn't make it all the way, then there's not too much point in more top speed (certainly not at the compromise of putting a transmission in). But the stronger regen that could come with an AWD system would be awesome.
More comfy seats, a bit more storage (not for me), and still a convertible would be great.
You could easily decouple the motor with a simple automatic clutch. But you would loose RWD at high speed (because you want RWD geared low to launch). It would definitely lend to some interesting vehicle dynamics. I don't think something that automatically cut on and off power to a drive wheel would be good during racing.
One nice thing about induction motors is that you don't loose that much (other than weight, and space) making them bigger. Efficiency still stays pretty good. I could see Tesla putting on a stupid huge motor (double torque) and taller gearing to get it to 155+ mph. With a large motor cooling it may actually be easier.
stopcrazypp
Well-Known Member
I suspect the next gen Roadster will have 4WD. It'll be geared directly to over 155mph, and the torque will be enough to give excellent acceleration even with that gearing. Remember the Eliica had a version that was geared for 230mph and it still had a 0-60 of under 4 seconds (with 8 motors making 480kW in total).
It is not just about really high acceleration, it is also about prolonged highpower and lowspeed driving like climbing up a hill on a curvy road doing lots of hard accelerations.
Low speed means low rpm. High power at low rpm means high amps, high amps mean high losses, high losses mean overheating,
Single speed gearbox is simple but it also means vehicle is almost never capable of outputting its max rated power.
ICE car accelerating to its max speed goes over max power six times (with six-speed gearbox), Roadster and Model S only once.
Constant torque is nice - much nicer then low/no torque at low RPM of ICE engines, but even nicer and much better would be constant power from 0 to max vehicle speed.
I'd really like to see someone mate a CVT and electric motor. And no clutch.
Low speed means low rpm. High power at low rpm means high amps, high amps mean high losses, high losses mean overheating,
Single speed gearbox is simple but it also means vehicle is almost never capable of outputting its max rated power.
ICE car accelerating to its max speed goes over max power six times (with six-speed gearbox), Roadster and Model S only once.
Constant torque is nice - much nicer then low/no torque at low RPM of ICE engines, but even nicer and much better would be constant power from 0 to max vehicle speed.
I'd really like to see someone mate a CVT and electric motor. And no clutch.
Just to clarify - single-speed EVs definitely do put down max rated power - the only issue is that you have to be moving fast enough to do so - the real issue is that you only have a very narrow window of max rated torque and power along with a maximum RPM at which you can maintain max rated power. Max rated power is often limited by what the battery and other components are capable of delivering as well as how well the motor is cooled.
Typical single speed EV motor puts down constant torque from a stop to 30-60 mph or so depending on gearing - above that speed torque starts falling with power staying approximately flat up until you start approaching top speed at which point torque starts dropping off more quickly along with horsepower. Maximum torque of a motor is typically limited by the amount of current that it can draw.
Remember that rate of acceleration is purely determined by torque - multiple gears allows you to change the amount of torque that gets to the wheels maximizing acceleration.
Let's look at a simple example (ignores drag and many other things)
You have a motor capable of a maximum 100 units of torque from 0-5000 RPM and 100 units of power from 5000-10000 RPM and your single speed EV is geared so that 10000 RPM = 100 mph.
In this scenario, rate of acceleration will remain constant from 0-50 mph and then start dropping off linearly until you get to 100 mph at which point you can't go any faster as torque falls to zero.
Now let's add a 2 gears - a low gear (1st gear) and a high gear (3rd gear) in addition to your existing gear (2nd gear). 1st gear is half the ratio of 2nd gear and 3rd gear is twice the ratio of 2nd gear.
Now from 0-25 mph you will be able to accelerate twice as fast as before. Somewhere above 25 mph torque to the wheels (along with acceleration) will fall to what 2nd gear is capable of delivering - at which point you shift into 2nd gear and acceleration remains constant up until 50 mph. Somewhere past 50 mph torque to the wheels will fall to what 3rd gear is capable of delivering at which point you shift into 3rd until you hit your new top speed of 200 mph.
Hope that makes sense. I'm sure a picture would help visualize this...
WhiteKnight
_____ P85 #549 _____ Sig Red / Sig White
I am betting that they make a standard Model R that is like $150,000, which is luxurious inside and has a 0-60 time of 3.3 seconds and they have a Model R / Racing / Ring Edition that sells for $250,000 and is AWD with 0-60 time of 2.5 seconds and a top speed necessary to make it the fastest lap at Nurburgring. This hyper-performance version would be all carbon fiber, have special batteries (probably fewer of them to save weight) et cetera. Basically they do everything necessary to shave the weight and increase the performance until they have a Ring beater.
The great thing about the Nurburgring is that it's only a 7 minute / 12.8 mile race and it carries tremendous credibility with car nuts.
Going 250 miles is stupid because you can only do it on an airstrip or special racetrack and besides there is no chance the Model R will ever break 200 mph. So if you want to be "the fastest car in the world" you better aim for a preposition of "around the Ring" rather than "in a straight line."
I totally disagree on the carbon fiber super car.
The Gen3 is likely to be aluminum or steel+aluminum. They are not going to build a carbon fiber low volume version of it.
I expect the Gen3 Roadster to be aluminum. It is even possible that the Gen1 Roadster chassis+body will be lighter.
I do hope they make a higher end "ring beater" version, but I bet it is not carbon fiber.
Hopefully my Gen1 Roadster plus a battery upgrade ( that lightens the car and lowers the CG with higher density cells filling only the bottom of the battery box ) won't be totally outclassed by the Gen3 version.
I'm with richkae on this one, Tesla will not be in the supercar business. They have positioned themselves as The Electric Luxury Car maker. They have a big factory with robots to make lots and lots of cars. They will make another Roadster but it will not be a supercar except that it will showcase electric car phenomenal numbers. I'd expect something that will beat a sporty 911 and be priced to move for $60k to $120K maxed out. Tesla will want to sell 5K to 10K a year and that is what will drive the design parameters.
You'll be able to order the Furtive-eGT at the Paris Autoshow in September.
With 0 to 100 km/h (~62mph) in 3.6 s and a 287 km/h (~180mph) top speed I think it will set a production EV benchmark for Tesla to beat :smile:
With 0 to 100 km/h (~62mph) in 3.6 s and a 287 km/h (~180mph) top speed I think it will set a production EV benchmark for Tesla to beat :smile:
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