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Old 12-31-2012, 01:20 AM   #7 (permalink)
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Originally Posted by cRiPpLe_rOoStEr View Post
I also love Bimmers. But if I would ever consider to convert one to all-electric drive I'd consider to remove the gearbox and use one of those reversible motors, to take some weight away and eventually leave more room for a bigger set of batteries.
Unfortunately, direct driving a car requires a very large motor - 11" or 13" or larger - and the increased weight offsets the weight savings of ditching the transmission. One possibility is two 9" motors end to end and parallel/series switching them to achieve both the required start off torque and high speed.

The beauty of converting RWD cars is that the transmission is out of the way to begin with, leaving much more room under the hood for other goodies. Ridding the engine compartment of a motor (moved to the ex-transmission's spot) doesn't really gain a whole lot.

In all my research, it seems that the only proper solution is to keep the transmission. Even though electric motors have a flat torque "curve" (line?) down to almost zero RPM, they do not have a wider effective RPM band than gasoline engines. One gear is never enough, unless of course you spend big money on high end AC componentry. But even the Tesla roadster has two speeds.
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