My Bafang is up for a little overhaul

My Bafang SWXH hub motor is acting up. Since the beginning the one way clutch locked up sometimes on 70km+ rides, resulting in more drag while coasting but always broke free again after a longer pause or over night. The gear noise got louder in the last few weeks and now the clutch is stuck. It probably didn’t help that I was experimenting with some LiPo packs from the local RC store since I got a sturdier rear frame lately. Pressing about 750W output out of a 250W rated geared hub motor at 60V for 45km/h top speed stresses things a bit I guess… but boy that was fun! Currently I’m running it at a more sensible 48V. Anyway, it got about 6000km on the clock and is due for some service.

Yesterday I found a real E-Bike workshop where I could ask for some spare planetary gears. After some chitchat the owner went to the back office and brought a broken Bafang motor with perfectly working clutch and gears. For ten Euros it was mine.
Great! Lucky me!
Funny thing was when I left the shop my ‘broken’ Bafang freewheel suddenly worked flawless on the way home after being stuck for days. But that won’t last.

There are some threads in the Endless Sphere E-Bike forums about filling geared hub motors with transmission oil for better cooling and lubricating the planetary gears instead of the usual grease. Comparisons showed in the end that filling a direct drive hub with oil didn’t result in better cooling than drilling holes in the side covers for air cooling at power levels over 3kW. On the other hand the guy who finished third in the e-bike class at this years Pikes Peak Hill Climb race behind the two dominating FRR trikes but in front of several €10.000 Optibikes used a modified 9Continent 2810 hub motor with oil cooling in his garage-built budget e-bike.

It still sounds like a sensible idea for a little geared hub motor whose magnets have no direct contact with the housing for heat transfer at ‘slightly’ raised power levels since I can’t open it for forced air cooling without inviting dust, sand and other road debris into the planetary gears. For me it makes even more sense to try using transmission oil instead of grease if I swap the stock Nylon planetary gears with stronger and heat-resistant steel gears. I might even try a 72V battery for a change to flog the little bugger down the road or up a hill without fear for some cheap plastic gears to melt. I think I’ll endure the louder noise from steel gears. Hot rodding a Bafang… oh boy!

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