What makes a MAC freewheel fail?

izeman

1 GW
Joined
Jun 21, 2011
Messages
5,131
Location
Vienna, Austria
Question relates to all other geared motors as well of course.
My MAC takes 2.5kW peak and 150A phase. It's clear that it won't last forever. The bike is used for rough mountain biking.

When I felt the freewheel slip the first time and heard that awful noise, I took it apart, cleaned it thoroughly, checked all claws and springs, regreased it and put it back together. Worked for 10min and then it slipped again.

So my question is : what parts are worn? What parts need replacement? Springs? Claws? The whole assembly?

Any ideas welcome!
 
The whole clutch assembly. You can re-use the gears but they're such a PITA to get off with the tiny bearings and no way to grab them without leveraging against the races that I just buy new gears, too.

Any high load situation (power getaways on an incline, impacts/ruts when running with lots of throttle) cause the face of the clutch to get a small deformity. This prevents the clutch from holding in that region in the future, so more you bash it, the worse things get until finally it has a hard time grabbing anywhere. It's sort of like losing traction when you are braking or accelerating on a bumpy road. Paul recommends lighter power for a while to make the clutch last longer and I believe this works. I think the face gets work-hardened which makes it take hits better later in life.

If you are pounding the amps through it (which is huge fun), then you need to ramp your power on getaway (CA3 or controller throttle ramp). This won't help with the impact breakaways, but it will make the clutch last hugely longer.
 
If you avoid "drops", you most likely have to deal w/ things like broken racks, broken wheels, flats and other things before you will have a motor failure.
Search the posts of kfong for his insightful posts of using a MAC for hard off-road usage.
 
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