According to Energica website, the motor in the Experia is a hybrid one, a
permanent magnet assisted synchronuous reluctance motor. It is my understanding that this is a marriage ot two different types of electric motors, namely one with and the other without permanent magnets. Maybe it is worthwile to note that there are no rare earth magnets but simple ferritic ones.
Thanks @Smithy for the additional pic! I am convinced that Energica built in the gear primarily as a noisemaker.
From the technical point it makes not so much sense to reduce the rpm of a motor which is frequency controlled and could run at lower rpm anyway, does it?
Straight toothed gear was cheaper in the past when CNC machinery was expensive, today helical toothed gears are cheaper because you can transfer the same power with smaller teeth, i.e. your gear gets smaller. The reason behind this is that while two straight toothed pinions have contact in one tooth at a time, two helical geared pinions have always contact in 1.5 teeth.
That is also the reason why helical gear is less noisy, the transfer of forces is smoother.
Of course, helical gears produce side forces that have to be considered when designing the bearings and casing, but that is not rocket science.
In the EU it is, since July 2021, mandatory for electric cars and trucks to produce sound (sound pressure of 56-75 dB(A) in 2 m distance) at speeds below 20 km/h, it is called AVAS - Acoustic Vehicle Alerting System.
Motorcycles and other vehicle types are not included, but maybe should. The other day I met a guy riding a RGNT electric motorcycle which is running with a rear wheel hub motor, practically noiseless at low speeds.
