freewheel mechanism in hub electric motor

[chantelauze]

many among the members of that forum complain that their motor has too much drag in case they are coasting or if they simply power off their motor and wish to use their e-bike as a plain bicycle

I here have attached some inside views from a Chinese hub motor – supposedly geared and brushless type of technology – so probably similar in technology to the Bafang motor that has been discussed extensively on that forum

I unfortunately find it very difficult to identify the freewheel mechanism and to understand how it’s operating

Can somebody help me ?

 

[flecc]

I have a full explanation on my Torq website, chantelauze, describing with a drawn diagram the full action, plus an animation of a Hall Effect functions:

Suzhoo Bafang Motor operation
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[chantelauze]

thanks Flecc for the accuracy of your description from the attached link

but i believe the freewheel mechanism comes into action in that chinese hub motor in a different way than with the Bafang you described, so since i have not tried that motor and the photos are being sent to me by a chinese trading agent , i am trying to guess how that mechanism can come into action to understand how efficient it can be , or if i will have an important resistance ...

 

[flecc]

There are different models and freewheel variations, but that one would have to be stripped out and properly cleaned to see any freewheel action.

Yours doesn't look as if it has a freewheel, but it's just possible that there's one incorporated within it's central output gear, between spindle and gearwheel. Not possible to see from the photos though.

My guess is that it has no freewheel so would have considerable drag.
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[chantelauze]

the sales man informs me that the freewheel mechanism is 100% efficient because intead of being made of ballbearing clutch like on Bafang ( ? ) it's made of an overrunclutch that makes the driveshaft of the motor to be totally disengaged from the bicycle wheel's shaft if the motor is not ON or if one wants to go coasting , and he's sending me this drawing to illustrate his demonstration , but it's not demonstrating anything to me

 

[flecc]

Thanks chantelauze, it seems it's on the spindle as I remarked it could be in my previous post. These very small diameter freewheels are usually made up with needle rollers inside a ring of tiny ramps. When the motor external shaft turns around the spindle, the rollers ride against the ramps and lock the two parts together.

If you have a look at the image below from one of my websites, inside the gear wheel in a red ring cage you can just see needle rollers. These run on the shaft at the left and lock on tiny ramps formed in the gearwheel to fix shaft and gear together in one direction only. It's the same clamping action as in a Shimano roller brake. This assembly is the freewheel mechanism inside the Panasonic bike motor unit:

As for the efficiency, it's effectively no different from a ball and ramp clutch, both highly efficient if lubricated, though there's a theoretical minute gain in having the minimal friction element nearer to the axis of rotation.
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