Rear Axle Slippage

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Mick F
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Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 10:29am

It's happened a few times with the Moulton now it has a SA 3sp hub.
I can tighten the wheel nuts until I'm blue in the face, but in low bottom gear - 16" - and climbing a steep hill, it can slip a tiny bit and the rear brake rubs a tiny bit.

The non-turn washers are serrated, but the RH one slips forwards in the horizontal dropout.

What can I do?
Is there a fitting that I can buy to hold the axle to stop it slipping forwards?
Mick F. Cornwall

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NATURAL ANKLING
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Re: Rear Axle Slippage

Postby NATURAL ANKLING » 25 Apr 2017, 11:38am

Hi,
This problem has always worried me, mechanically the whole set up is not good as it relies on all that power twisting the rear axel against what :?
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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 12:06pm

It's not twisting in the slightest.
The very stout non-turn washers combined with the thick axle with flats won't allow it at all.

It's slipping forwards, sometimes as much as an eighth of an inch, and the wheel rubs on the brakes and sometimes the mudguard stays.
Mick F. Cornwall

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[XAP]Bob
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Re: Rear Axle Slippage

Postby [XAP]Bob » 25 Apr 2017, 2:14pm

Get yourself some drum brakes ;) :p

Chain tugs and/or vertical dropouts... I assume you don't want to weld the axle into place ...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
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Re: Rear Axle Slippage

Postby scottg » 25 Apr 2017, 2:48pm

+++++++++++++++++++++++++++++++++++++
Why not the best, buy Cyclo-Benelux.

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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 3:14pm

Thanks guys. :D

Looking at the Monkey Nuts pages, they are designed to go behind the axle to take the place of adjusting screws.
Mine is in the dropouts as far as it will go. The dropouts aren't long - not like standard horizontal dropouts at circa 40mm.

Moulton ones are about 25mm long and there's only about 10mm spare in front of the axle and non-turn washers.

I'm thinking that I may have to make some sort of tab washer that hooks to the rear of the dropout. I'd only have to make one for the drive side. I suppose I was thinking something like that would be available somewhere.
Mick F. Cornwall

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Re: Rear Axle Slippage

Postby Brucey » 25 Apr 2017, 3:18pm

I would not so easily dismiss the idea that the axle is twisting, unless the movement occurs when you are in gear 2 in the hub. In high torque applications like yours, the NTWs need to be an exact fit in the dropouts and they very rarely are.

SA do various serrated washers and styles of NTW. Not all of them are proof against cracking. If you can do so, the best arrangement is probably to use two of the thick pressed steel single-dog NTWs (one each side of the dropout, four in total).

I can't overemphasise the point; if there is the slightest potential for the axle to move in the dropouts (check with the nuts loose) eg because the tabs on the NTWs are not a snug fit, then the wheel will probably move.

Thick powder coating on the frame won't help either. Chain tugs will help but if the axle is rotating (it'll go one way in the low gear, t'other in the high) then the whole arrangement is still going to be unsatisfactory.

cheers
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Re: Rear Axle Slippage

Postby Threevok » 25 Apr 2017, 3:50pm

Mick F wrote:I'm thinking that I may have to make some sort of tab washer that hooks to the rear of the dropout. I'd only have to make one for the drive side. I suppose I was thinking something like that would be available somewhere.


Reminds me of the "safety" washers (or whatever they are called) that you see on the front wheels of a BMX bikes.

Not sure of the length on the tabs on those would they suit ?

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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 4:36pm

Hi again.

Threevok ........... good idea I think. I must investigate.

Brucey ........... I agree with all you say, but these NTWs are substantial things with teeth with thick tabs and are a good fit in the dropouts. The axles will not turn, I'm am positive about this.

Originally, the tabs wouldn't allow the nuts to fully tighten as they were too long. A few seconds with the grinder sorted it, and I'm confident that they tighten properly.

Took one off to show.
IMG_0063.JPG
Mick F. Cornwall

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Re: Rear Axle Slippage

Postby rjb » 25 Apr 2017, 4:50pm

I recall riders using copper washers when they had problems with wheels slipping with chrome dropouts. I dont know if yours has chrome or even where the washer goes, inside or outside or both :wink: perhaps someone knows. :?
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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 4:58pm

Funny you should mention copper washers ................
I was thinking about that when I was looking at my photograph.

Just an idea ........ what about grinding off the teeth?
Perhaps the slippage is caused by insufficient friction?
The teeth can't bite because the dropouts are enamel coated hardened steel. They can't bed in to the paint or the metal. Increasing the surface area is a good idea.

The washer goes on the outside.
Here's the parts list and the instructions. Note that they are vertical dropouts, not horizontal ones.
http://www.sturmey-archer.com/files/cat ... CS-RK3.pdf
http://www.sturmey-archer.com/files/cat ... EEHUBS.pdf
Mick F. Cornwall

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Re: Rear Axle Slippage

Postby [XAP]Bob » 25 Apr 2017, 6:30pm

A single sheet of inner tube ;)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 25 Apr 2017, 7:04pm

Seriously?
Sounds like an off the wall suggestion, but it could work I guess.

I'll be off on a good ride tomorrow, and on Thursday as well as Friday perhaps. If it slips during any one of the rides, I'll try the "Inner Tube Technique".
Mick F. Cornwall

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Re: Rear Axle Slippage

Postby Brucey » 25 Apr 2017, 8:08pm

Mick F wrote:
Just an idea ........ what about grinding off the teeth?
Perhaps the slippage is caused by insufficient friction?
The teeth can't bite because the dropouts are enamel coated hardened steel. They can't bed in to the paint or the metal. Increasing the surface area is a good idea.


your dropouts won't be 'hardened steel' (if they were you would have flattened the teeth on your NTW already...), and any flat washer (unlike one with teeth) won't grip through a layer of paint. Removing the teeth is likely to be entirely counterproductive.

Re axle movement; the axle twists in one direction in the low gear and the other direction in the high gear. The result of this is that even if there is only microscopic movement possible, the axle will tend to gradually

a) be pulled in the direction of chain tension on the RHS (as you report) and
b) 'settle' (under simple gravity forces) on the LHS

as you ride.

NB the axle does not have to be able to 'rotate' wholesale in order for either thing to happen. If you find that the axle doesn't stay put in gear 2 on the hub, then axle twisting isn't really implicated, but otherwise it can be, even if the amount of movement is tiny.

If you have VDOs and the axle is able to 'move forwards' as you describe then the NTW and axle CANNOT be a properly snug fit in dropout, can they? There must be a gap; I cannot see how it could be otherwise. Your photograph shows an NTW (HMW534 I think) with a tang about the same width as the flat part of the axle, which would presumably make both parts about 8mm wide. Your dropout slot would normally be ~10.2mm wide if it is intended to accommodate a normal QR axle, which would make the axle and the NTW tang a pretty slack fit in the dropout.

If it is as I describe then I would suggest trying this; take two steel strips ~1mm thickness x ~5mm wide (just narrower than the dropout thickness) x ~30mm long and form an inverted 'U' shape with each. These would then be fitted (one each side) over the axle and the NTW tang such that the 'width' in the dropout is made up to be ~10mm rather than ~8mm. These would then prevent the axle from moving forwards appreciably or twisting in the dropouts.

If this arrangement works OK then maybe a more elegant permanent solution can be found.

cheers
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Mick F
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Re: Rear Axle Slippage

Postby Mick F » 26 Apr 2017, 8:00am

Hi Brucey, and good morning.
Thanks for your excellent info.

The tang on the non-turn washers are 9.6mm wide ............ and so are the dropout gaps.
Axle flats 8mm ........... as are the internal flats of the NTWs.
Measurements with my vernier callipers.
Everything fits very snuggly indeed.

The dropout measurement is less than normal. When I was using the QR standard hub, it was a tight fit, and was an absolute pig to slide the wheel in and out.

Off out on planned 40mile ride this morning, and I'll monitor the slippage issue, and also think about some sort of design of "holder".
Mick F. Cornwall