Stripped Bafang 8FUN Planetary Gear

Bloody 'eck. This happened again about 30 minutes ago. I've managed to strip four adjacent teeth on one of the nylon gears. It happened after only 10 minutes of riding and it's an unusually hot 28C today, so I assume that it's purely down to the fact that the motor is overheating.

How would running one metal and two nylon planetary gears overcome this heat issue? Surely the nylon gears would still suffer the same fate.
 
I wonder if that red coating isn't trapping some heat? Yes, it seems that heat makes the nylon gears soft. Maybe you would benefit from a temperature sensor in the right place and then being aware of the critical temperature.
 
The red coating is just painted on. I wouldn't have thought it causes any problem. A temperature sensor is a good suggestion, but I'd rather avoid any additional wiring.

Has anyone tried those thermometer stickers? Obviously not as practical as an audible alarm, but I suppose it's better than nothing.
 
This is an interesting topic. I have a small foldable ebike with 12" wheels. It has a geared hub motor, you guessed it, nylon gears.
I have only a couple hundred km's on it and all looks good, however I am preparing myself for gear failure. One more thing that is bugging me - gear noise. Also I would like to increase the torque, which would be too high for nylon to handle.
So here goes my question: anyone considered swapping the whole gear to helical steel gear? These could be narrower and with lower modulus (smaller teeth). I did some research and could not find much info on the topic, so I might consider making some custom helical gears...

Any thoughts?
 
circuit said:
This is an interesting topic. I have a small foldable ebike with 12" wheels. It has a geared hub motor, you guessed it, nylon gears.
I have only a couple hundred km's on it and all looks good, however I am preparing myself for gear failure. One more thing that is bugging me - gear noise. Also I would like to increase the torque, which would be too high for nylon to handle.
So here goes my question: anyone considered swapping the whole gear to helical steel gear? These could be narrower and with lower modulus (smaller teeth). I did some research and could not find much info on the topic, so I might consider making some custom helical gears...

Any thoughts?
Click to expand...
I'm not sure this would be possible since geared hub motors feature a large ring gear that forms part of the motor casing. Helical gears would not mesh without some serious reworking.

FYI, I am running a bafang geared motor in a 26 inch wheel at around 50v @18 amps (battery current) and the motor runs pretty quiet. What kind of noises are you hearing?
 
I have not disassembled it fully, however it looks like the large ring is pressed into the case:
DSC_1882.jpg


So it should be possible to remove it and replace with other one. By "do a full gear swap" I mean to swap all the gear set, sun, ring and planets.

I am running it at 12A equivalent, which is hard to compare to your larger wheel due to kv difference. The noise is not very bad, however it is noticeable from up to 5 meter distance, which I don't like. My girlfriend has a similar ebike with completely different make and model of motor and noise level is very similar, so it is not a failure of some kind, just a design flaw. I prefer a completely silent motor.
 
I'm afraid I have to agree with the noise problem. I've had a bunch of gear motors, mostly Bafang's but also some steel geared brushed motors like in the Mongoose cx450, and tried many "fixes" to make them quieter. No go! I love the initial "take-off" and torque of the small gear motors but the noise is the deal breaker. We use DD simply for that reason, even though they weigh a ton and have less oomph off the line. That unsprung weight makes you have to tighten up your rear suspension and lose the soft ride. Silence is golden. I thought that the Keyde roller gears might be the answer, but the new ones (at least the ones Justin got) have gears, not rollers. Wah!
otherDoc
 
The noise from these motors comes more from the commutation than the gears if you're talking about the low speed growl.

It reduces s bit with a sine-wave controller.
 
circuit said:
Noise level is the same at all speeds and is torque dependent. With no load it is almost silent.
Click to expand...
.
The commutation pulses have much more impact at high current. Imagine any object: When you tap it gently, you get low noise, but when you tap it hard, it makes loud noise. The sine-wave controllers don't tap so fiercely - more like pressing.
 
I did have a crystalyte 5303 motor running at 100 amps, so I do know what you are saying. However please read again what I was saying: noise level is the same at all speeds. It is not the case of cogging, which is worst at near to zero speeds and at certain resonance speeds.
 
danielrlee said:
Bloody 'eck. This happened again about 30 minutes ago. I've managed to strip four adjacent teeth on one of the nylon gears. It happened after only 10 minutes of riding and it's an unusually hot 28C today, so I assume that it's purely down to the fact that the motor is overheating.

How would running one metal and two nylon planetary gears overcome this heat issue? Surely the nylon gears would still suffer the same fate.
Click to expand...

I stripped the Nylon gears in my old Bafang SWXH as well but it ran off a 35A controller for the last 1400km... ;)
Since Nylon gears will get soft above some 80°C I swapped them for three steel gears and filled the hub motor with 60ml ATF. Temperature isn't a problem anymore but the darn thing was quite loud for the first 1000km or so. Here is a little summary in my blog: http://etrike.wordpress.com/2013/07/06/bafang-swxh-with-steel-planetary-gears-a-short-summary
 
Marc S. said:
danielrlee said:
Bloody 'eck. This happened again about 30 minutes ago. I've managed to strip four adjacent teeth on one of the nylon gears. It happened after only 10 minutes of riding and it's an unusually hot 28C today, so I assume that it's purely down to the fact that the motor is overheating.

How would running one metal and two nylon planetary gears overcome this heat issue? Surely the nylon gears would still suffer the same fate.
Click to expand...

I stripped the Nylon gears in my old Bafang SWXH as well but it ran off a 35A controller for the last 1400km... ;)
Since Nylon gears will get soft above some 80°C I swapped them for three steel gears and filled the hub motor with 60ml ATF. Temperature isn't a problem anymore but the darn thing was quite loud for the first 1000km or so. Here is a little summary in my blog: http://etrike.wordpress.com/2013/07/06/bafang-swxh-with-steel-planetary-gears-a-short-summary
Click to expand...
Nice blog mark. I'd actually come across it a few weeks ago while trying to source replacement nylon gears.

This has now became a matter of urgency as I've just busted ANOTHER gear - the third in 6 weeks. Here is a photo of the latest:

5u9a4edy.jpg


I don't seem to be suffering the usual peanut butter gears, so I don't think my problem is due to excessive heat, but rather shock loading. I am only running 49V @17.5A, not so powerful compared to most other failures I hear of. Also, my controller has a nice soft start, which should help avoid this.

I think I just need to bite the bullet and switch to steel gears. Does anyone know of a source for the 36-tooth steel gears? A UK supplier is preferred, but not important.

EDIT: I just remembered that I did a few bunny hops at full throttle trying to clear potholes this morning on the way to work. Maybe this has caused the failure this time. It was only when I set off to come home that I noticed the clicking sound though.
 
NOTE TO ADMIN: Some of this post is copied from another thread of mine, but I feel the conversation is best continued here.


Although i haven't checked yet, I think I've busted another gear today having only replaced it yesterday. Assuming there is nothing wrong with my ring gear as d8veh has suggested on the aforementioned 'other thread', there are two possible solutions to resolve this satisfactorily:

1) Source some metal gears and run either 1 metal and 2 nylon, or 3 metal.

2) Replace the geared motor with a direct drive unit.

Having refined my first build over the past year (you might have read my ghEttoBIKE thread on pedelecs.co.uk), I have reached the point where I am totally happy with the performance of my bike. The reliability issue of my geared motor really is the last remaining problem.

I would really rather prefer the first solution to the second. So many on this forum rave about running metal gears, but not a single person has been able to advise on where to source them from. I have spent hours looking on the interweb, but I just cannot find them in the 36-tooth variety.

I'm getting desperate now as I'm about to use my last spare nylon gear, so I'd really would be appreciative if anyone knows of a source of metal ones.
 
I still say option 2.

Anybody also named Danny will be impossibly hard on everything he touches. Danger Dan is my real nickname. Yours too?
 
I don't have a geared motor and never worked on one so ignore if this sounds silly.
I'm guessing it's the planetary gears you are talking about, but what is the condition of the motor pinion, and the hub one? Any damage or wear on them would affect the planetary gears, especially under heavy loads.
 
Yes, it's the nylon planetaries that I'm referring to. I haven't had a chance to check the gear assembly yet and I won't until Sunday now because I'm currently travelling to Wiltshire for the weekend.
 
Daniel, did you check inside your hub motor for debries from your former busted gears?
I can't imagine your gears breaking that fast without some left over debries getting into the new gears... :shock:
 
shenzhen_ex said:
danielrlee said:
I'm getting desperate now as I'm about to use my last spare nylon gear, so I'd really would be appreciative if anyone knows of a source of metal ones.
Click to expand...
TAOBAO has metal gears

Sorry, I realize that link was probably of no help.
Click to expand...
No, quite the opposite. I may not understand the text, but it's the best lead I've got. Thanks.
 
Marc S. said:
Daniel, did you check inside your hub motor for debries from your former busted gears?
I can't imagine your gears breaking that fast without some left over debries getting into the new gears... :shock:
Click to expand...
I'm certain I've removed the bits of broken gear previously as I have accounted for every stripped tooth. It's looking increasingly likely that either the sun or ring gear is damaged. I cannot confirm his until Sunday however.
 
Having had a chance to open up my motor again last night, I have realised the source of the problem - I am an idiot.

Upon detailed inspection of the gear assembly, I found no broken teeth on the gears themselves, but a slither of compacted nylon stuck to the sun gear. Having now removed this, the motor is running as it should without any excess noise. I am hoping that this debris has been stuck in there since my original gear failure, causing all subsequent problems. The motor ran great today during my regular 12 mile commute.

This is a great example on how NOT to have dealt with gear problems. Even though I thought I was thorough, there was still some debris left in the gear assembly. The fragment was tiny, but certainly caused havoc. Do yourselves a favour and remember my plight the next time you have gear train issues. I really am kicking myself for this. CHECK AND CHECK AGAIN!!!

Thank you to everyone who's time I have wasted. Hopefully there'll be no need for further posting on the issue from me. I will still be attempting to order the metal gears from the source provided by shenhzen_ex (tried emailing ecrazywhateverhisnameis, but had no reply), so I'll let you all know the outcome if I manage to translate the site successfully.
 
After the feeling of embarrassment goes isn't the sense of relief great!
It's good news that you have the answer, not months of trials.
 
Yes, you're right. It is a great relief now its working and I've stopped beating myself up. As dogman pointed out earlier, I can concentrate my efforts on trying to break it again.
 
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