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Detroit Electric
- Thread starter TEG
- Start date
Not necessary, transmission will always improve performance of any given motor, be it under sized, over sized or right sized.
Of course it has to be such a transmission that does not brake and changes gear in acceptable manner.
I welcome Detroit Electric to the stage but please excuse me for not being thrilled about it.
It is 10 years too late to be thrilled about a low-production-number roadster without any special engineering accomplishments.
What was astonishing 10 years ago, is old news today.
I'd be much more interested and thrilled about a company that buys say series 1 chassis' from BMW and convert them into pure BEVs with say +150mile EPA range, fast charging, nice performance for a nice price.
Even if it had say two or three gear transmission.
If the motor has enough torque to break the tires free at the range of RPMs in question, then I would tend to disagree.
A transmission can slow you down by power drop during shifting. For instance, I understand a P90D can be accelerating at the limits of the tires from say 5MPH to 60MPH+ with no shift lag in there, so I am not sure how adding a transmission in that case would help performance.
Sure, if the motor isn't super powerful like that, a Transmission can help with torque multiplication.
Performance is a broader term then 6-60 acceleration.
Transmission simply gives you ability to output max available power at much wider speed interval. Usually from some min speed up to max speed.
With single gear ratio, maximum power is not available above some speed.
Of course, if your battery is 3 times stronger than motor, than above does not apply. Little logic applies to such strangely imbalanced systems.
Transmission simply gives you ability to output max available power at much wider speed interval. Usually from some min speed up to max speed.
With single gear ratio, maximum power is not available above some speed.
Of course, if your battery is 3 times stronger than motor, than above does not apply. Little logic applies to such strangely imbalanced systems.
I prefer the Artega Scalo over this SP:01. Have a look: http://www.artega.de/en/vehicles/artega-scalo/
I'd still choose the Tesla Roadster over the SP:01 and the Scalo, if they were all still selling new today. Tesla did such a great job back in 2008, that it's still unbeaten by any competition anno 2015.
- € 170000 price tag.
- Limited to 12 cars built.
- DC fast charging (64kW) and 3-phase charging (22kW).
- Downsides are higher weight (3500 lbs) and limited battery capacity 37kWh.
I'd still choose the Tesla Roadster over the SP:01 and the Scalo, if they were all still selling new today. Tesla did such a great job back in 2008, that it's still unbeaten by any competition anno 2015.
I can't tell from that website if the Scalo is in production or not, but if the company has stated only 12 will be built, I am not impressed. By 2015, 7 years after the Roadster went into production, I expected that there would be other BEV sports cars available in significant production volumes. Unfortunately, there are none.
I think it is elegant and useful that eMotor can have a wide enough torque band to avoid the need for any multi-speed transmission. (Evidence: Tesla)
I look at EVs with multi-speed transmissions as ones where the motor wasn't so good, so they resorted to a transmission as a "band-aid" for their lack of torque at some RPMs.
This evidence proves my point ... a tesla with multigear transmission would have much better high speed (above 80mph) acceleration.
It certainly would. But I would prefer that Tesla not spend any resources towards developing multi-speed transmissions at this time because the increased sales that would result would be minimal. For the vast majority of prospective buyers a single-speed transmission is all they need. Obviously some additional sales might result if a multi-speed transmission was available, but since Tesla remains production constrained for the foreseeable future I see no compelling reason to invest engineering resources in an option that only a small number of buyers would choose to pay for.
To me that is not important. I value the reduced weight, cost, and lower complexity as worth it since I am almost never driving above 80MPH.
Perhaps that is because we don't have "autobahns" here, and people generally aren't racing their Teslas on a track. Perhaps the multi-speed transmission would make more sense in parts of Europe (with no speed limits) and in certain racing situations.
Olle
Active Member
I tend to disagree too, if a motor can give max power (i.e. has tall enough gearing) at top vehicle speed and can break tires free at any speed where max power is traction limited, a multi speed wouldn't add performance.
Every vehicle surely has its own cost/benefit equation in this regard, but the common sentiment seems to be that any such calculation would result in moving resources (weight, space, money) from multi speed transmission toward bigger inverter, battery and motor and end up with a better performing system as a whole. Another consideration is that inverter electronics are evolving, while transmission technology is more or less static. So even in a vehicle where a tramsmission gave a slight advantage at the outset, you might benefit from going single speed so as to not have to change vehicle architecture during its production life (e.g. Roadster) when a better inverter would later get the upper hand. Remember S85 top speed increase from 120 to 140 Mph anyone?, a clear example of modernized power electronics (I think, or was it a motor improvement, not 100% sure)
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Remember poor performance of model s at high speed anyone? And all that crying about promised improved performance?
A gearing calculated for max power at top speed will result in less efficiant low speed performance. A more efficient low speed performance will result in drop if power before top speed is reached. No way around it. Breaking traction is not the only low speed metrics. Anyway, all this is moot as 6 speed gearbox is overkill, two speed is optimal.
A gearing calculated for max power at top speed will result in less efficiant low speed performance. A more efficient low speed performance will result in drop if power before top speed is reached. No way around it. Breaking traction is not the only low speed metrics. Anyway, all this is moot as 6 speed gearbox is overkill, two speed is optimal.
If it is so optimal, why do you think we don't see it in the marketplace?
I guess Tesla though that was a way to go with the early Roadster, but it proved so unreliable that they abandoned it.
We got an answer why those gearboxes where problematic - no one took the problem seriously enough.
Why there ain't out there?
Tesla got burned badly while trying and won't look back until CEO and CTO change.
Neighborhood EVs have zero wish for good high speed performance.
No other serous EVs out there.
Why there ain't out there?
Tesla got burned badly while trying and won't look back until CEO and CTO change.
Neighborhood EVs have zero wish for good high speed performance.
No other serous EVs out there.
Olle
Active Member
Aren't the D models in essence two speed already, by having different torque curves for front and rear drive unit?
We don't know if that is the case or not. Don't assume it to be so.
I don't expect Tesla to move away from a single speed gearbox any time soon. There is no compelling reason for them to do so as it would only fractionally increase their addressable market and since Tesla is still production constrained it would not increase their sales.
Olle
Active Member
We are in agreement, no reason to introduce a 2 speed tranny. What I was saying even if both DU have 9.73:1, because the front motor is smaller f and r may have different torque curves, and voila!, it becomes a two speed car! Not from a mechanical standpoint but from torque as function of speed standpoint.
Gerasimental
Member
I'd thought about this too, and it seems like the obvious thing to do, but wouldn't it be very clear from the car's performance (much better at high speeds, much worse at low speeds) if this were the case? I think it's possible they didn't do this and sacrificed high speed performance for good 0-60 times.
Olle
Active Member
Perhaps they did it to some extent, but not by a huge amount? Range has obviously been a consideration along with performance. Clearly Model S D versions have better high speed acceleration than the RWD versions 140 to 155 mph :wink:
Seems there would be only a limited ability for any AWD EV to use different gear ratios front vs. back, due to bearing max-speed limitations on the low-geared unit.
Only way around that is to use a clutch to mechanically disengage the low-geared unit at high speeds, and now we're back into the realm of moving/wearing parts and added drivetrain complexity.
Only way around that is to use a clutch to mechanically disengage the low-geared unit at high speeds, and now we're back into the realm of moving/wearing parts and added drivetrain complexity.
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