BMW’s latest patent filings show a longitudinally mounted electric motor, which is quite different from traditional electric bike designs.
BMW Motorrad‘s latest patent filings reveal a new design in mounting the electric motor on its upcoming electric two-wheelers. While the typical layout for electric bikes includes the motor positioned transversely across the chassis, just ahead of the swingarm pivot, BMW’s latest patent images show the electric motor mounted longitudinally, in the same pattern as the German brand’s traditional shaft-drive boxer-twin engines. In such engines, the crankshaft is in line with the chassis rather than running across it. The design apparently has some advantages as well.
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The position of the motor would create a bike that is more compact, and it will use an intermediate shaft between the motor and the front of the shaft final drive. What this offers is flexibility to position the motor anywhere on the chassis, so it can be moved forward, or back, up, down, or side to side. The advantages of such a flexible positioning of the motor are many, ranging from freedom in styling, weight distribution to battery placement.
The patent filings also show the use of a reduction gearbox. The idea is to gear down the mechanical power of electric motors before transferring the power to the bike’s rear wheel, because electric motors tend to spin fast. On electric bikes with transversely-mounted motors, a secondary gear shaft is needed which runs parallel with the motor. In the new patent filings, BMW has introduced a planetary gearset (labelled 20 in the patent drawings) which is mounted directly behind the motor, which reduces the output shaft speed, while keeping it in line with the motor’s main shaft.
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The idea of the design is to keep the design simple, and this motor position will probably be used in one of the Vision DC electric models that BMW Motorrad is working on. BMW’s next electric model, the CE 04 electric scooter, will use the traditional transversely mounted motor design, but with several trademarks filed under the DC name, from DC 01 to DC 09, the longitudinally mounted electric motor will likely be used in the DC models.