Steel planetary gears for the Bafang SWXH

Finally shiny new planetrary gears arrived to fix my broken Bafang SWXH. That took quite a while.
SWXH steel planetary gears
As I had to find out the hard way up to 2011 the planetary gears in the Bafang SWXH had 28 teeth and a modul of 1.25mm while from 2012 Bafang changed the gears of the SWXH and SWXK geared hub motors to a finer pitched modul of 1mm and 36 teeth planetary gears.
Since the teeth of my old Nylon planetary gears where mostly shredded I didn’t bother to count teeth but ordered spares for the SWXH relying on various web shop descriptions. Not smart.

You can imagine my frustration when the wrong gears arrived at first. Luckily Ebike-Solutions offers the older 28 teeth gears for Bafang 250W hubs and as it turns out had three 28 teeth gear wheels left made from steel while the newer 36 teeth version is everywhere available only in Nylon (probably PA 6 or PA 6.6).

Since PA 6 and PA 6.6 have a ‘glass temperature‘ of 50-60°C in hindsight it’s no wonder the planetary gears shredded in my overvolted hub. Thats about the temperature the hub motor had after a prolonged full speed ride or a short uphill. The oil cooling works pretty well but these small hub motors really aren’t made for shedding 200-500W of waste heat on a regular basis…
With the new gears made from mild steel my ATF cooled hub motor should be pretty temperature resistant well over 80-90°C now. I’m courious about the noise, though. I can imagine the whisper quite days of my SWXH are over…

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