Woosh DWG22C Rear Hub Motor 'Ticking' noise.

[Jodel]

Folks,

Here’s a little puzzle for you to consider if you would please - its got me stumped!

I have a Woosh DWG22C rear hub motor fitted to my tandem. It has covered about 600 miles since fitting in August this year. It is normally used with level 1 or 2 assist and the throttle (plus us pedalling of course) is always used to help when moving off from rest.

About a week ago I noticed a slight ‘ticking’ or light ‘knocking’ sound from the rear hub when freewheeling downhill. I’m sure it is the hub making the noise and not the brake disk or anything else rubbing on the rear wheel. The rim is completely true and the spokes are all in good condition and properly tensioned. The noise is intermittent, but has been getting more frequent and seems to be at the rate of about 1 click per wheel rotation. I initially thought it might be the sprag clutch, but either pedalling or using the throttle to engage the motor, makes no difference to the noise. There is no graunching noise or slippage of the sprag, so I think that can be discounted. The cassette freehub engages instantly and there is no slippage from it either. I can’t replicate the noise when the bike is on the workstand, it only happens when riding on the road. Could a faulty wheel bearing be the cause? I would have expected wheel bearing noise to be constant rather than intermittent if that was the case though.

The motor works perfectly well and aside from the ticking noise, operates as quietly as ever. To the best of my knowledge, we don’t subject the motor to any abuse. To try and avoid any overheating issues, we tend not to grind away at low speed / high power settings. Usually on the steepest climbs we’re on power level 2 (sometimes we use level 3) and maintain at least 8 mph on the (short) steepest sections - normally we’re a bit faster than this.

I fully understand that trying to remotely diagnose a noise is pretty much impossible, so my ‘stoker’ was able to take some video clips of the hub when it was making the noise. I’ve uploaded this to Dropbox, so you should be able to get an indication of what is going on. There’s a fair bit of wind noise unfortunately, but I think you should still be able to hear the ticking noise to which I refer.

Dropbox links:
https://www.dropbox.com/s/a0lz58obshl0ago/Rear Hub clicking.mp4?dl=0
https://www.dropbox.com/s/68tieat47p2naua/Rear Hub clicking 2.mp4?dl=0
https://www.dropbox.com/s/irtwcpuz9vg07s6/Rear Hub on workstand.mp4?dl=0

Any comments or insight would be appreciated. In my experience, mechanical noises don't just vanish of their own accord and I would rather address this issue now before I'm left at the side of the road with an unpowered tandem

 

[Woosh]

check for loose spokes?

 

[Sturmey]

In the last few years, I have had similar instances for three different reasons.
The first was a deep 'clunking' noise and this was caused by a loose freewheel bearing. You could remove or tie up the chain if you really want to eliminate this from your inquiry.
The second instance (with an newish wheel) was a musical clicking noise caused by slightly slack spokes . In this case, the clicking disappeared when the wheel was off the ground.
The third instance was a slightly duller click in a high mileage front wheel (mxus xf07) and was caused by a rough wheel bearing. In this case, the clicking was still present when the wheel was off the ground, on a stand.
From your description, it sounds like slack spokes as clicking stops when there is no weight on wheel. Its amazing how musical a spoked wheel is. (Think of a harp!) Even the slightest movement at the spoke crossing can generates a note. If you look carefully where the spokes cross, you can sometimes see a small amount of wear or flattening of the spokes as they rub off each other. This can cause a clicking action if the wheel flexes excessively during rotation when there is weight on the wheel.

 

[Jodel]

Thanks for the responses folks.

Loose spokes were high on my list of potential causes - especially on a tandem rear wheel. I have experience of 'tinkling' spokes on the tandem in the past. However, the spokes on this wheel are all fine - they are well tensioned and all have pretty much the same 'tone' when tapped with a screwdriver. As you would expect, the drive side spokes are at a slightly higher pitch than the non-drive side.

I had already applied a very light coating of oil at the spoke crossing points to eliminate at source any possibility of noise or wear being generated there. The rim is true to within 1mm of axial runout and a similar amount of radial runout.

It may be that I have to wait for things to get a bit worse before it is possible to accurately diagnose the problem. If it were not for the intermittent nature of the ticking noise, my gut feel is that there is a dodgy wheel bearing. Assuming the Shengyi motor internals are pretty much the same as the Bafang types, it should not really be a very big deal to swap out a bearing, but I'd rather have greater clarity before dismantling things.

I have experienced a rear wheel bearing collapse on a motorcycle wheel and it let go with little or no warning - the wheel was then wobbling about more than a dart player's belly!

 

[Woosh]

does it click when you stop pedalling? if it does not, tighten the crank bolts.

 

[Jodel]

does it click when you stop pedalling? if it does not, tighten the crank bolts.

The clicking noise is independent from any pedalling action. The BB's are tight in the frame and the cranks & pedals are torqued up to spec with no play or creaking. The only creaking noises come from my knees these days

I didn't think a loose or slack magnet within the hub motor would produce a 'once per rev' click, hence my reason for suspecting a wheel bearing.

 

[Woosh]

Do you have another bike that you can fit the wheel to just to see if the click is still there?

 

[garysnooker]

i had a ticking’noise on my Bafang BPM it turns out to be the allen nuts that holds the motor together were loose

 

[Jodel]

Do you have another bike that you can fit the wheel to just to see if the click is still there?

Yes - I have exactly the same hub motor on one of my solo bikes, so could swap the wheels over to compare. I'll check for any loose nuts when I remove the wheel from the tandem.

 

[Woosh]

when you have the wheel out, check that he lock nuts on the motor axle have not drifted and put pressure on the ball bearings. Use a 10mm spanner to turn the motor axle slowly to find any notchiness in the ballbearings.

 

[Jodel]

when you have the wheel out, check that he lock nuts on the motor axle have not drifted and put pressure on the ball bearings. Use a 10mm spanner to turn the motor axle slowly to find any notchiness in the ballbearings.

Ta - Will do!

 

[vidtek]

I recently had a rear wheel axle very slightly bent, trying to diagnose it I sent my motor back to Whoosh to check it. Once the wheel was off, spinning the wheel while holding the axle it was obvious the axle was slightly bent. It gave a very similar clicking noise as you describe.