That was a biassed statement from a manufacturer of hub motor bikes Martin, and it was untrue, just sour grapes. Panasonic don't make things for such a narrow market, and some of the most expensive e-bikes in the world use this unit because it is so reliable and good a performer.
The unit is tremendously strong, stronger in construction than any hub motor, and will stand the strength of any rider. It's crankcase is motorcycle style cast alloy, the gears are helical cut precision steel components more commonly seen in motor vehicles, and the bearings are precision ball races of the kind only occasionally seen on a bike.
The motor power contribution is proportional to the rider input, up to the motor's limit of around 420 watts, but the rider input can be as much above that as is possible.
To have a look at the construction and operation, see my website
here.
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