Stripped Bafang 8FUN Planetary Gear

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danielrlee   10 kW

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Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 2:55pm

Hi all. During my morning commute today, my rear wheel hub motor developed a clicking noise. Upon inspection, it appears that I have stripped a couple of teeth from one of the planetary gears.
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Two questions:

1) Does anyone know where I can get a set of replacement planetary gears? A UK supplier is preferred, but isn't important.

2) How do I remove the existing gears from the motor? I cannot see any obvious means to further dismantle the stator:
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There is a C-clip at the other end of the axle (not shown), but I don't have any replacements for if I were to remove it, so I haven't attempted it yet.

Also, there are six screws around the circumference of the red part (not sure what it's called) in the image below, but again, I don't want to blindly take this thing apart:
uploadfromtaptalk1375991649729.jpg
uploadfromtaptalk1375991649729.jpg (61.26 KiB) Viewed 2751 times
So, any ideas? Thanks in advance for any assistance you are able to provide.

Dan.
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Kepler   1 GW

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Re: Stripped Bafang 8FUN Planetary Gear

Post by Kepler » Aug 08 2013 4:25pm

The Planetary gear assembly just slides off over the shaft. Give it a bit of tug and it should come off.

You can get the parts from here. http://www.greenbikekit.com/
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 5:06pm

Thank you. A quick tug and it came apart. I do love this forum :-)

Is there any particular technique to removing the clips securing the planetary gears to the clutch assembly? I cannot seem to get 'em off and just nearly skewered myself with a screwdriver.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by kriskros » Aug 08 2013 5:59pm

ebikesf use to have steel replacement gears for the bafang....use one steel with 2 nylons and it will go forever... i had the same problem and that is what i did... put over 1800 miles on it before i sold it... cell man might have some replacements, but i think he might only have gears for a mac :mrgreen:

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Re: Stripped Bafang 8FUN Planetary Gear

Post by Kepler » Aug 08 2013 6:15pm

danielrlee wrote:Thank you. A quick tug and it came apart. I do love this forum :-)

Is there any particular technique to removing the clips securing the planetary gears to the clutch assembly? I cannot seem to get 'em off and just nearly skewered myself with a screwdriver.
No problems. with regards to removing the circlips, you really should use proper circlip pliers. I have seen people grind down the tips of a pair of pointy nose pliers but there is no substitute for the correct tool for the job.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 7:01pm

Okay, I've just ordered a pair of circlip pliers.

Looking at the replacement gears on greenbikekit, there are a few choices of motor from which to specify. I am not sure of the exact model since I bought it as damaged for peanuts on eBay last year and repaired it myself. Looking at the photo (link below) I would say my broken gears look like those listed as SWXK/SWXK5 (is there any difference between those two anyway?). Mine have 36 teeth, as do the ones in the photo. Are these likely to be the correct ones?

http://www.greenbikekit.com/index.php/e ... ement.html
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 7:08pm

kriskros wrote:ebikesf use to have steel replacement gears for the bafang....use one steel with 2 nylons and it will go forever... i had the same problem and that is what i did... put over 1800 miles on it before i sold it... cell man might have some replacements, but i think he might only have gears for a mac :mrgreen:
I had a look on ebikesf, but they appear to no longer list the bafang gears. I'd read previously about the one steel / two nylon combination, but always thought that the nylon gears were spec'd as an intended point of failure. Isn't there additional stress put on other components when running with this combination?
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Re: Stripped Bafang 8FUN Planetary Gear

Post by spinningmagnets » Aug 08 2013 7:18pm

Circlips can be used many times if care is taken to remove and reinstall them gently.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 8:05pm

spinningmagnets wrote:Circlips can be used many times if care is taken to remove and reinstall them gently.
Ta. That has answered my next question.
Last edited by danielrlee on Aug 08 2013 8:14pm, edited 3 times in total.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 08 2013 8:12pm

I've gone ahead and ordered two sets of what I think are the correct gears on 4-6 day shipping, so not too long to suffer public transport. I still haven't replaced my car that got written off at the beginning of the year, since it turns out that 'by bike' is much more fun :-)
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Re: Stripped Bafang 8FUN Planetary Gear

Post by d8veh » Aug 09 2013 3:12am

In the first photo, it looks like the bearing in the gear collapsed and caused the gears to mesh incorrectly. Could yoy confirm if this is so?

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Re: Stripped Bafang 8FUN Planetary Gear

Post by kriskros » Aug 09 2013 6:11pm

DEFINITELY look for a steel gear... i have had white nylons in both bafang and puma...they stripped VERY quickly...bafang running 36v,12amp and mac running 36v,20amp... with both motors i went to one steel two nylons,no further problems... the syeel is a bit noisy for the first 200 or so miles. email ebikesf, he might still have one or two or at least know where to one :mrgreen:

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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 10 2013 6:50am

d8veh wrote:In the first photo, it looks like the bearing in the gear collapsed and caused the gears to mesh incorrectly. Could yoy confirm if this is so?
I'm not sure how these gears should be, but the bearings look the same on all three, so I don't think this was the issue. Could powering over speed humps on a 5% incline at 15-20mph have caused this? I remember that the evening before this happened, I let the motor pull me up a quarter mile hill, complete with humps, without pedaling to see how well it would cope, which I wouldn't normally do.

EDIT: I run 12s4p lipo @ 15amps and we have been experiencing hotter than average weather for the last month.....
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 10 2013 6:57am

My circlip pliers have arrived and although they are too large for the tiny clips, they did do the job with the aid of a screwdriver to initially spread them part-way.

With the circlips now removed, I am only able to remove one of the gears from the assembly. I'm not sure why the others won't come off as easily, but I plan put the assembly in a vise and lever them off with a couple of screwdrivers after some lunch. Hopefully this won't screw anything up or damage the posts.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 10 2013 8:08am

All it took was a little mechanical advantage and the remaining two gears popped right off :-)

Am I okay to clean the clutch with degreaser, or will this damage it?

Also, what should I relube the assembly with? I already have the choice of a multipurpose lithium based automotive grease, a lith-moly MoS2 automotive grease and a silicone dielectric compound. Are any of those suitable?
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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 13 2013 1:58pm

danielrlee wrote:All it took was a little mechanical advantage and the remaining two gears popped right off :-)

Am I okay to clean the clutch with degreaser, or will this damage it?

Also, what should I relube the assembly with? I already have the choice of a multipurpose lithium based automotive grease, a lith-moly MoS2 automotive grease and a silicone dielectric compound. Are any of those suitable?
:BUMP

I've done lots of further reading on my lube question above and am getting conflicting information from the four corners of the internet. I have read that lith-moly grease is the preferred lube to use on the nylon gears in hub motors, but elsewhere I am being told that it will attack nylon and to use silicone grease instead.

So, which should I use?
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Re: Stripped Bafang 8FUN Planetary Gear

Post by d8veh » Aug 13 2013 3:27pm

Nylon does swell a bit with some greases. There was a guy on Pedelecs forum who's gears had swollen so much that they touched each other making a noise as they went round. He had to file them down to reduce their OD. Silicone grease is pretty safe.

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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 14 2013 2:50pm

Yeah, I think I'll go with the silicone lube.

I've order two sets of nylon gears, so I'll have spares after replacing the old set. If I manage to strip them again, I'll look into running a single steel in combination with two nylons.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by teklektik » Aug 14 2013 3:12pm

FWIW: BMC reccomends Mobile 28 grease for their geared hubs.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by jlpmedia » Aug 14 2013 7:44pm

anyone know of a link to find a bpm2 planetary gear? greenbikekit.com has never worked for me and aliexpress doesnt have the 42T gear that im looking for.
I've modded my motor quite a bit so far (liquid cooling, thicker gauge wires, removed the clutch-for battery charging, changed the gear ratio, etc) so if its a steel gear, id gladly take that. i just dont have the time or access to a hobber to make one myself.

But now I'm thinking since nylon is a thermoplastic, i can just make a mold of an existing gear and vacuum form a new one?

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Re: Stripped Bafang 8FUN Planetary Gear

Post by d8veh » Aug 15 2013 8:57am

jlpmedia wrote:anyone know of a link to find a bpm2 planetary gear? greenbikekit.com has never worked for me and aliexpress doesnt have the 42T gear that im looking for.
I've modded my motor quite a bit so far (liquid cooling, thicker gauge wires, removed the clutch-for battery charging, changed the gear ratio, etc) so if its a steel gear, id gladly take that. i just dont have the time or access to a hobber to make one myself.

But now I'm thinking since nylon is a thermoplastic, i can just make a mold of an existing gear and vacuum form a new one?
Greenbike kit ordering system requires cookies to be enabled in your computer security settings. Try a different computer and it should work, or change your settings. The gear is a precise component, you can't make one yourself.Even if you could, what grade of material would you use? There'es loads of types of Nylon with different properties for strength, stabilty, durability etc.

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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 16 2013 4:53am

Okay, the old gears have been replaced with new ones and the motor is running quieter than ever. I don't remember it being this smooth even when new. In fact, I'd have described the motor previously as a little 'notchy'. Makes me think that the previous gears weren't quite right to begin with.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by jlpmedia » Aug 16 2013 9:28am

d8veh wrote:
jlpmedia wrote:anyone know of a link to find a bpm2 planetary gear? greenbikekit.com has never worked for me and aliexpress doesnt have the 42T gear that im looking for.
I've modded my motor quite a bit so far (liquid cooling, thicker gauge wires, removed the clutch-for battery charging, changed the gear ratio, etc) so if its a steel gear, id gladly take that. i just dont have the time or access to a hobber to make one myself.

But now I'm thinking since nylon is a thermoplastic, i can just make a mold of an existing gear and vacuum form a new one?
Greenbike kit ordering system requires cookies to be enabled in your computer security settings. Try a different computer and it should work, or change your settings. The gear is a precise component, you can't make one yourself.Even if you could, what grade of material would you use? There'es loads of types of Nylon with different properties for strength, stabilty, durability etc.
I'm a machinist by trade, so Id like to think that i could make a simple spur gear. although with only a bridgeport, cnc and chucker at my disposal, it might take a couple days with my busy schedule. I've never melted a thermoplastic before to reuse in a mold so the outcome would be interesting. I imagine it would lose some of it's chemical properties after I reheat it, either way, i ordered some alumilite casting resin and I have a 3d printer available at my disposal to print just about everything imaginable, but with my experience in 3d printing, the integrity isnt all to great. we'll see I guess. this is all one giant experiment for me. :)

But thanks for the help with regards to the website. it turned out to be a coding error on their end. I emailed them and they fixed it within 12 hours.

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Re: Stripped Bafang 8FUN Planetary Gear

Post by danielrlee » Aug 16 2013 2:44pm

Having done a few more miles on the new gears, I can confirm everything is running well. Thanks everyone for your help.
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Re: Stripped Bafang 8FUN Planetary Gear

Post by nechaus » Aug 16 2013 8:26pm

You could give some printed nylon or polycarbonate gears ago haha

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