Quote:
Originally Posted by dieqast
Thanks for the links, I don't know the figures, but my hypothesis is that the efficiency of 4 seperate motors is better than mechanical efficiency of the drivetrain. My guess is that mechanical efficiency gets up to 80%-85% and the loss in efficiency between 1 and 4 seperate elektric motors is say low 90%'s. This is just guessing though, I haven't done any research on this. And my opinion is that the unsprung weight won't effect handling proportionately. Other than that, Tesla should stick to their current design for future models.
|
Before I start, it makes some difference here which Tesla drivetrain we're talking about. For simplicity I'm going to stick with 1.5, which just has a single reduction gear.
First note that these hub motors are not likely to run at wheel speed either, so they also need reduction gears. So it's not right to act like you skip all drivetrain losses by using hub motors. It seems to me that the only part you are getting around is the differential. These vary to a certain degree, but I would expect this part to be at least 95% efficient. And I would anticipate the four little motors would be less than 95% as efficient as the one big motor, but I can't find much in the way of specs around. In any case, whichever way you go it's going to be very close...you won't save more than a percent or so.
Of course, the whole question (while interesting) is basically moot...efficiency wasn't even the big reason Tesla cited for going with the one motor. You offer no explanation why you don't think unsprung weight matters. It does. In addition to the links TEG gave,
this Tesla blog on driving dynamics explains it well (and is good read for lots of other reasons). That plus the cost, weight, and complexity make great reasons to go with the single motor, and even if the hub motors
were a couple percent more efficient it wouldn't be enough to override these concerns.
Linear Mode
