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Wheel hub motor


No, the wheel hub motor doesn't seem to want to prevail. The arguments probably come from simple physics. It is said that the combustion engine's performance seems rather to come from the depth of its displacement, optionally with supercharging.

This is becoming more and more true, as the nominal speed has tended to decrease in the interests of greater effectiveness. On the other hand, the electric motor probably needs the rotational speed to be sufficiently effective. In a car it practically works with double or triple rpm.

This is in some contrast to the required wheel speeds, which, for example, are only around 1,000 rpm at 100 km/h. This requires a certain ratio for the combustion engine but a larger ratio for the electric motor. And so it leaves its most economical range at lower speeds.

The most popular counterargument are the larger unsprung masses of the wheel hub motor, although in the future it may be possible not to see the brake as a competitor in terms of space requirements, but to at least partially integrate it, perhaps as a drum brake.

There is undoubtedly more savings due to the absence of half the drive shaft, which also makes a significant contribution to homokinetics. The unsprung masses alone are not the decisive factor, but their ratio to the sprung masses, which are naturally higher in the electric car.

The argument that you need an inverter for every motor is almost impossible to take seriously. The brushless motor is already available in model railways today and the inverter is not even noticeable in terms of percentage. The real problem is the greed for performance, which is actually quite unnecessary, especially when it comes to combating climate change.

Concept of a wheel hub motor from Schaeffler

The top speed has already been significantly reduced, the only thing missing is the acceleration, which is more than sufficient for most electric cars. If more sacrifices were made, the engines could become significantly smaller and, for example, do without liquid cooling.

The possible 48V technology would make the way to the wheel much less dangerous. It is true that the industry is currently looking for more mechanical production options for electric motors rather than further development, but that will change again at some point.

The methods can then also be applied to the production of wheel hub motors, especially since there are currently visible opportunities for improvement, e.g. the much shorter motor developed by Mercedes in conjunction with an English invention.

The video above explains, among other things, the greater effectiveness of the wheel hub motor, although one specializes in those without a transmission. However, if you look at the supplier ZF, you will discover a rigid rear axle with geared wheel hub motors for buses.

ZF has already presented something like this in connection with compact cars for the city. Their steering angle went up to almost 90°. Imagine this comfort when parking when the rear wheels are also involved. And then of course the larger usable space should not go unmentioned.

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