Bafang Motor Modifications, removing internal gears?

[LI-ghtcycle]

I happened upon something Spinning Magnets had posted off-hand in the "wanted" section, and wanted to hear what everyone had to say about the possibility of taking my Ft Wheel Bafang motor, removing the internal gears to make it into a DD, and since this is a front motor, I would want to find a dead rear motor case to get one that has threads for a freewheel as I am hoping this might be able to give me a smaller compact motor to put behind my seat instead of hanging it down below.

I'm sure this is all do-able, just wondering how practical and easy this might be?

Thanks!

P.S. I forgot to mention that I will be running at 45V LiPo, and I will see if I can identify exactly which Bafang motor I have.

 

[dogman dan]

Not possible I think. Can't run without the gears. Possible to make it similar to direct drive by locking the clutch though. That would allow regen to work.

 

[neptronix]

It may work actually, but it will take a lot of machining.
The gears actually connect the outer sun ring ( the outer case which is connected to the spokes ) to the axle that the stator is connected to.

You'd need to figure out a way to permanently attatch the axle to the sun ring.

 

[spinningmagnets]

I haven't gotten my hands on a geared hub to play with, very busy right now. My leading candidate is a cell_man geared kit (I like the size). We might be able to add the metal gears and then lock them somehow. This would make the output the same RPM as the motor, usually 5 times the usual wheel RPM. A reduction can then be achieved by an external belt-drive.

This may sound like a lot of hassle to end up right where we started, but such a drive would have the same power as the original, plus it would be much quieter (406's not available new anymore). The shell can be skeletonized to allow it to run much cooler than they are known for, and the plastic gears would no longer be a weak link (though I concede they are useful as an inexpensive mechanical fuse).

Thats the theory at least, and until I have one in my hands, I can't really describe the many ways in which I am likely wrong. Think of them as an inexpensive narrow 8-inch diameter outrunner with factory-installed hall-sensors for a non-hub mid-drive. Here's one example of a mid-drive I like many of its features.
http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=25685&start=30#p434365

 

[dogman dan]

Remove the gearing, and the tiny little motor inside would be stalled at all times. Bye bye. It needs the reduction gearing to let the motor spin faster, as it must given the winding used.

But they can behave a lot like a dd motor, if you lock the clutch.

 

[Rassy]

I'd also be concerned that there wouldn't be enough room to allow for a track cog or freewheel because the front axle is so much shorter than a rear axle.

I think a rear Bafang would make a great mid-drive motor right out of the box. The internal freewheel would mean just the hub, but not the motor, would turn when pedaling only. With the NuVinci gearing, I don't think the noise of the Bafang would be too bad since it would never be working very hard.

The only problem area would be affixing a track cog so that it wouldn't just unscrew when the motor was running. I think a couple of set screws drilled and threaded into the track cog flange would do the trick, but have never tried it, yet.

You could also machine (or hack) off the spoke flange to make a hub motor even smaller around. I almost did that to my 9C, but of course it could never be laced into a wheel again.

That front Bafang was for a 26" wheel, meaning it is the slower winding or geared version, however they did it. So even though it was in a 20" wheel, that was done to make it a better hill climber at the expense of top speed.

 

[Rafabaca]

If you weld the gears to the motor casing then it will run at one one, but im sure that will kill your motor in no time, unless you say at speeds of maybe 4 miles per hour. its not worth your investment. you can probably get a small DD for 60, 70 bucks, motor alone.

 

[LI-ghtcycle]

Yeah, I have moved to a small DD at this point, this is just too much trouble to go to just to use something I already have. :wink:

Thanks all for the input! Looking into small diameter DD Xlyte 406/4011 atm. 8)

 

[John in CR]

I got rid of the gears for a Fusin geared hubbie and made a hollow axle with a bearing support at the end that fits on the ring gear. I haven't decided whether to retain the outside housing which will now be stationary, or make a new smaller one for the quite small motor inside. The planetary gears are a 4.6:1 reduction, so on most installs it will require a reduction before taking it to the wheel. I did this with the idea to ventilate the motor with some centrifugal blowers and take the little motor to several Kw.

Sorry I have no results to report as I haven't run it yet other than to spin the motor up and make sure it was still well balanced after my mods. I got distracted by riding more than building, and targeting high power motors first.

I wouldn't try it locking the housing to the rotor unless you pull off some ventilation magic, because the air would be quite static at the magnet bell. In original form there's lots of turbulence with the housing spinning one direction and the motor spinning much faster the other direction.

 

[dbaker]

Use a front disc brake version and mount a cog to the disc brake flange. Likely cheaper if you do some shopping:

http://tomicog.blogspot.com/

 

[dogman dan]

Yes, as John points out, the motor would run fine with the gears removed, if it was then geared down on a chain drive set up.

Once going chain drive though, lots of small motors could be used. Perhaps a cordless skillsaw? Cordless chainsaw? wheelchair or tread mill motor?