Ahh ... thanks for the correction. That is a lot better.
take a look at the graph I posted in #30
That's the approach which I was suggesting.
I don't care much about marketing. Never have believed a car salesman.
They can get more torque at the wheels below the current threshold speed - which they don't need - but not necessarily for less electrical power per unit of mechanical power.
I agree that a dual-clutch design is the obvious solution for automated shifting of a two-speed gearbox, and especially for multiple gearboxes (due to multiple motors). The Rimac Concept_One (more of a technology demonstrator than a production car, but a more-than-million-dollar extreme performance exotic) has this type of transmission for each rear drive motor (one per wheel).
It could be that the cooling system is running, but that wouldn't take anything close to 40 kW and my guess - since the chart shows substantial torque output at zero speed - is that the motors are being driven and the car is being held by the mechanical brakes. This is the electric version of the classic run-up before launching, and should be expected of a current automated launch system (which would not be expected in a Leaf). Unlike other current production EVs and hybrids, Teslas have induction motors, so the stator field is rotating (at the slip speed) with the motors stalled - it seems to me that could take substantial power.
sure, just take a bulletproof existing design and throw in a couple clutches and gears that can handle the 1000 odd foot pounds and 16,000 rpm, for an imperceptible change in performance and efficiency, what could go wrong?
The Tesla gearbox is the most common layout for production EVs, which is a two-stage helical spur gear train. The final gear is the ring gear around the differential, just like a typical transverse front-wheel-drive transaxle, so yes... that quoted reduction ratio is the motor to wheel speed ratio.
I haven't had a ride in a Tesla, so I have no idea what it sounds like, but I don't know why anyone would assume "at 21,000 RPM you are smoking a lot of things". Lots of machines run much faster than that, including gear trains and electric motors.
The gears are no problem, but yeah... with the clutches, the two-speed only seems easy. The design is actually straightforward, but dual-clutch transmissions in conventional cars have had varying success with durability of the clutches... although most work fine, even while shifting much more frequently than a 2-speed would require and slipping to get started (which the electric drive would not). It can certainly work, but most manufacturers think the risk or cost or weight or bulk or something is not worth the improvement in efficiency or available power.
The standard rear tires for a smart are 185/60R15, which have a rolling circumference of 1.83 m. 1.1 m would be ridiculously small - 350 mm or 13.8" diameter, which is much smaller than the tires on 10" wheels of an original Austin Mini. It doesn't matter to the Telsa battery, but if you're working out examples, they won't produce realistic speeds with the wrong tire size.
Hi Sol,
I reread the above statement and can't make any sense out of it. But I think it is academic anyway because nobody would operate a motor at such a condition.
Well sure, but that limit is set to prevent exceeding or closely approaching breakdown torque in the case of the induction motor. Beyond BDT, more motor current doesn't produce more torque, less in fact.
