Front Hub Motor Not Working

Electrically assisted bikes, trikes, etc.
Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Front Hub Motor Not Working

Postby Col18 » 22 Aug 2018, 12:54pm

Hi
I'm hoping someone might me able to offer advice/help.
My front hub motor is not working properly.
The bike is out of warranty now.

Battery, power and connections are ok.
As I can hear the motor spinning inside the hub.
But the wheel does not spin.

I will take this apart.
But just as seeing if would know possible issue/problem and how to fix, before taking apart.
Photos attached.
Thanks
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hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 22 Aug 2018, 9:54pm

It sounds possibly like the internal planetary gears are slipping and may be due to worn nylon teeth not engaging with the hubs outer driving gear ring.
The Bafangs with side plate are easy to remove and I have had my BPM & CST apart to regrease and replace worn bearings. Use a pair of levers opposite each other around the face plate if a bit tight. If I remember correctly there is no need to undo any thing from the axle on the opp side of face plate unless you need to remove axle for bearing for renewal.

Planetary gear complete assemblies are availble though you may have to search for the correct unit or seperate toothed gears can be had if replaceable, often a circlip fitting affair.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 28 Aug 2018, 4:35pm

Thank you for the advice and info.

I got it working again.
After I removed the screw, I could not remove the cover, I put flat head screw driver and tried to lever the cover, but was worried it would snap the fixing area.
I could rotate the cover, but it did not 'unscrew' off either. But rotating seem to have sorted it out....(I think temporary).
It does not feel the same as before, it does not have that 'strong' pull from the standing still.
I do suspect the teeth are worn as you say.
But I may have to take another stronger attempt to 'prise' the cover off.

hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 29 Aug 2018, 12:35am

It's been 18 months or more since I last open my front Bafang hub, the side plate has bearing in it so is usually quite easy to remove to replace it. Possibilty is some moisture has settled and rust between axle and bearing may be holding it on tightly so you could try gentle heat and gentle taps with a rubber mallet to remove also try a drop of penetrating oil down the axle.
The clutch assembly is under the face plate AFAICR so it might have become stuck and the rotating of the face plate has released said clutch mechanism. If you do get the side plate off a regrease is always a good idea, once any other work has been done.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 29 Aug 2018, 1:26pm

I see...so the motor on my bike is a Bafang?
I search on you tube SWXB and a few videos came up.
So I just need to be strong and knock the cover off (after unscrewing all the screws), either with a mallet or 'knocking the axle from the other side?' would this damage the motor?

https://www.youtube.com/watch?v=lBU8uIAjYgw
This video shows a 500W....it looks similar.

At the moment it is still working but something is not right or the same.
The motor still drives at the speed it should when I look at the speedo.
But when i spin the wheel...it spins a bit more free than before. Which suggest the teeth are worn?
Last edited by Col18 on 29 Aug 2018, 1:54pm, edited 1 time in total.

hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 29 Aug 2018, 1:45pm

Yes SWX series are Bafangs's.
Should be no need to hit or tap the axle as I say it's been a while since I have had the lids off they are initially firm but pry off if done evenly around the edges.

Apologies, yes on the brake side you have to remove the hub casing nut as you would with a std hub nut/cone set up then the plate and innerds should part company from the main hub shell, though may be a bit tight but should come apart quite easily.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 31 Aug 2018, 2:49pm

ok... finally opened up the motor.
As it did not spin/turn as normal.

I couldn't prise open the cover so bangs the axles from the non cable side and it popped open.

Moisture has got in
Nylon Gears are ok
Bearing spin but with crud all over not smoothly at some points
Motor side spins ok
Underneath the crud/rust/dirt the white grease is there and quite thick

Is it it a case of cleaning it out.
Degrease
Once clean, re-grease.

Disappointed as this has lasted less than 2 years. I bought the bike new, used as commute to work about 3 days a week, winter and summer.
Washed the bike when dirty.

Moral of the story, don't buy cheap and if you do, don't ride along canal path in the wet and don't wash the motor.
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Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 31 Aug 2018, 10:15pm

Ok....I cleaned the insides as best I can.
Could someone advise on what, where and how much grease to apply.

I 've got park tool hpg1 grease....is this ok to use?
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hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 31 Aug 2018, 11:46pm

As I thought rust was stopping the motor from parting (didn't expect the inside to look that bad), the clean up looks a lot better. A good liberal coating of grease and only needs applying to the nylon cogs and the drive gear in the hub body needs to be one that doesn't harm plastic/nylon a non petroleum based product. Whilst apart check and replace any bearings if they don't run 100%.


Next Q is how has the water got in, hosing down or pressure washing is a no no, as is riding through standing water to axle.
Water acces is most likely via the axle/cable side, when fitted the axle slot should face down so that cable exits downwards and the cable forms a drip loop, also the disc fixing holes can allow moisture through even when the bolts are in. Some disc fixing holes are blind others aren't.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 1 Sep 2018, 9:43am

No jet wash....use only garden hose in a low strength sprinkle/hose to rinse.

I'll be avoiding washing in this area....just like on rear sram hub gear now. And just clean with damp cloth.

I can only assume moisture got through the axle some how. The cover and the seal look tight.

Crud was doing something/ not letting the middle piece rotate correctly. The part where it rotates in one direction and locks in the opposite.

As the wheel on one occasion just span without resistance.

I need to buy a thin rubber seal that goes around the cover edge. I'll grease areas as you mentioned. And hopefully this should get it going and give me back the full 250w. Lol

Thank you for your help hemo.

Marc
Posts: 56
Joined: 18 Aug 2016, 6:03pm
Location: Hamburg, Germany
Contact:

Re: Front Hub Motor Not Working

Postby Marc » 1 Sep 2018, 10:48pm

Image
If you install a hub motor with the motor cable going up, water (rain, your washing) will go down the cable, find its way between cable and the hollow axle inside the motor.
To prevent this, you always install the motor with the cable coming out of the motor going down. Sorry to say, but thats a typical user/install error.

hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 1 Sep 2018, 11:18pm

Yes this I also mentioned in my post, the cable when it exits south (from under) then naturally will form a drip loop.
As in the pic water will track straight in to the hub easily filling it with water.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 2 Sep 2018, 9:38am

Ok....will make sure the cable drop down first.

Last bit....I'm struggling to assemble the hub back.
I've put the motor back in. But there is like another 6mm gap...I'm pushing hard but the cover won't go back on.

Is it just more force or am I doing something not right?
Thanks
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hemo
Posts: 437
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Front Hub Motor Not Working

Postby hemo » 2 Sep 2018, 9:52am

Could be two or three reasons nothing major.
The Clutch gears three nylon gears need to mesh in nicely with the hub body's fixed ring gear, so a bit of patience and manipulation by gently turning the axle shaft ACW & CW. Also on one end of the axle shaft there is a splined gear/cog this also needs to align so patience is needed. No force should be needed and all should fall in to place, sometimes you may have 2 or 3mm gap and this can be tight. Evenly turning opposite face plate screws will gently pull everything together.
Lay the wheel even and flat on some blocks and then try manipulating together.

If it feels like gears/cogs/splines are falling in place nicely the gap could be the magnetic force between hub motor and out body casing in which case the screw method should work though you initially might need to use longer threads.

When fitting to drop outs make sure the axle slot is also to the underside, then loop cable back up but not in a tight arc. Cable can be secured to fork with cable tie (not to tightly) or a double sided Velcro.
If you cable tie to tight you run the risk of the small wires pinching in side and cracking the sheathing and can cause a break or short.


When fitted and all connected back up before powering up rotate the wheel freehand, it should freewheel forwards and have some resistance backwards.

Col18
Posts: 21
Joined: 13 Jun 2018, 3:23pm

Re: Front Hub Motor Not Working

Postby Col18 » 8 Sep 2018, 10:37am

Ok...the gap was actually small enough for the screws to meet the thread (I didn't think to try at the time)....so screwed in each in opposite places...as you said...the cover popped into place......

Put the wheel back on the bike and it ran smoothly. It sounds quieter than before. Happy now.

I took the motor apart too check. Grease spread around outer gear and nylon gears evenly...I put some more grease. The thin rubber seal broke so used plumbers tape around the rim of the cover.

If I can, I try a post a link with a video.
It just sounds so much smoother than before.

The cable is not long enough to form a drip loop...so I have to be careful when it is wet (avoid puddles) and when washing the bike.

I guess this should be like an annual service

Thank you for your help hemo again.
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