Different drive efficiency

Helical gears, well lubricated basicly bathed in very low viscosity oil, are the most effiecient way to get usable speed on our kinda high running motors (the BLDC should be most efficient at the 8k-9k RPM range) like an actual gearbox.

There are other systems that can also achieve similar (maybe even higher efficiency levels) like thin flatbelts or special chaindrives but these also need to run kinda loosly (kinda low tension) to be max efficient. But these are not usable in our application as we need a rigid non slipping system.

Direct drives are not very efficient because they need to run directly on the RPM needed for the application. This problem is that they can only work with a low kV this way, they also have a kinda strict size limit as they basicly need to be smaller than the wheels.

Yep, at low currents they should be the efficiency killer, since most loss are ohmic anyway

But start to push them and the inefficiencies start to show unless they are well designed

They have no gear ratio, how often do you see mtb with direct drive?

Based on my experience with Hubs(Meepo and Raptor 2.1), DD (Torqueboards 90kv) and the results I see based on our Prague rides with belts (DIY) and Gear drives (Bioboard) folks around me, I can say that the DD have the best efficiency of the bunch, based on regular usage (mostly flats, usually around 35/50km/h).

The hubs are coming really close, but can’t manage this high speed without drawing a lot of energy, and burning like hell after few Km.

The Bioboard (12s6p) could only manage to do 2/3 of the way my TB DD (12s5p) did. Sure, the rider was heavier (15Kg) but we were driving aggressively together (he was at 22Kw/h, I was at 11.5Kw/h).

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