I'm a big fan of the single-speed gearbox that Tesla and other vehicles have. But, costs will have to be cut. Manufacturing a motor to run at over 15,000RPM is expensive as the rotor requires improved balancing and cooling. A lower-cost design would have a two-speed manual gearbox with a less powerful, slower, cheaper motor. The first speed would cover almost all vehicle speeds up to 70mph improving 0-60 acceleration further. The second speed would cover speeds up to 155mph or beyond, as necessary.
For the vast majority of driving the vehicle would remain in the 1st speed. No more city shifting, eliminating one of the complaints around manual boxes. Another bonus will be the car can be locked in the 2nd gear all the way down to a stop as the motor RPM can drop completely to zero. The disadvantage of leaving the motor in the 2nd gear is that acceleration would be reduced from a standstill and efficiency would also likely be reduced.
I know the prototype Roadster had difficulties with a two-speed gearbox system but that was due to poor engineering from Borg-Werner. I don't think it's impossible to design a gearbox for an electric motor, but engineers need to think differently.
Manual cars use a friction clutch to buffer the connection between the gearbox and wheels. The clutch acts as a way to slip the engine power, which allows gears to be engaged easily. Electric motors don't require a clutch - at all. By simply open-circuiting the motor (turning off all power switches in the motor driver) the motor can be made to free wheel ("virtual" clutch down.) The gearbox can then switch gears, using dog teeth as in a standard manual gearbox to synchronise the now open circuit motor and connected wheel speed. Finally, the motor circuit is re-energised with the motor controller matching wheel RPM quickly. (The effect on the power consumption/meter would be to see a slight regen of power while the motor wants to lag, then power would increase to the original level, plus/minus efficiency changes. Improvements in motor firmware could reduce this change to no noticeable drop in power by matching the speed quicker.)
Shifting would probably be similar to a DSG gearbox. Automatic mode would almost certainly be available (D mode.) Budget EVs could even have a "clutch" pedal and manual shifter... the clutch being an electronic input only.
Thoughts? I doubt Tesla will do this for Model 3 as they'd like to keep complexity down. But perhaps we'll see this for even further cost reduced models.
For the vast majority of driving the vehicle would remain in the 1st speed. No more city shifting, eliminating one of the complaints around manual boxes. Another bonus will be the car can be locked in the 2nd gear all the way down to a stop as the motor RPM can drop completely to zero. The disadvantage of leaving the motor in the 2nd gear is that acceleration would be reduced from a standstill and efficiency would also likely be reduced.
I know the prototype Roadster had difficulties with a two-speed gearbox system but that was due to poor engineering from Borg-Werner. I don't think it's impossible to design a gearbox for an electric motor, but engineers need to think differently.
Manual cars use a friction clutch to buffer the connection between the gearbox and wheels. The clutch acts as a way to slip the engine power, which allows gears to be engaged easily. Electric motors don't require a clutch - at all. By simply open-circuiting the motor (turning off all power switches in the motor driver) the motor can be made to free wheel ("virtual" clutch down.) The gearbox can then switch gears, using dog teeth as in a standard manual gearbox to synchronise the now open circuit motor and connected wheel speed. Finally, the motor circuit is re-energised with the motor controller matching wheel RPM quickly. (The effect on the power consumption/meter would be to see a slight regen of power while the motor wants to lag, then power would increase to the original level, plus/minus efficiency changes. Improvements in motor firmware could reduce this change to no noticeable drop in power by matching the speed quicker.)
Shifting would probably be similar to a DSG gearbox. Automatic mode would almost certainly be available (D mode.) Budget EVs could even have a "clutch" pedal and manual shifter... the clutch being an electronic input only.
Thoughts? I doubt Tesla will do this for Model 3 as they'd like to keep complexity down. But perhaps we'll see this for even further cost reduced models.
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