Why does a wheelsets back to back move?

Model and prototype rolling stock, locos, multiple units etc.
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jim s-w
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Why does a wheelsets back to back move?

Postby jim s-w » Wed Mar 09, 2011 6:22 pm

Hi all

We have all been there. Find a wagon or item of stock starts falling off only to find the back to back has gone out when it was fine before. I am not on about the obvious occurances where a wheel is loose but those times when it all seems solid. Anyone know why this happens?

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Jim
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grovenor-2685
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Re: Why does a wheelsets back to back move?

Postby grovenor-2685 » Wed Mar 09, 2011 6:33 pm

but those times when it all seems solid.

Its not as solid as it seems ;)
Whenever running on curved track or through turnouts there are sideways forces applied to the wheels, little and often wins out in the end.
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Keith
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Tim V
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Re: Why does a wheelsets back to back move?

Postby Tim V » Wed Mar 09, 2011 7:25 pm

Try blobbing super glue onto the axle after setting the BtoB.
Tim V
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martin goodall
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Re: Why does a wheelsets back to back move?

Postby martin goodall » Thu Mar 10, 2011 12:58 pm

Tim V wrote:Try blobbing super glue onto the axle after setting the BtoB.


I rather doubt whether the super-glue would be able to get in between the axle and the wheel centre, even by capillary action.

I suspect that Keith's suggestion is the only practical answer - check the back-to-back on your wheels regularly.

Some makes of wheel seem to be more susceptible to slipping on the axle than others. I get the impression that Kean-Maygib wheels are pretty tight on their axles, whereas Ultrascale wheels do seem to be more prone to move.

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jim s-w
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Re: Why does a wheelsets back to back move?

Postby jim s-w » Thu Mar 10, 2011 2:42 pm

Indeed

My experience is superglue makes no difference at all.

Cheers

Jim
Jim Smith-Wright

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grovenor-2685
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Re: Why does a wheelsets back to back move?

Postby grovenor-2685 » Thu Mar 10, 2011 6:40 pm

I suspect that Keith's suggestion is the only practical answer

I didn't make any suggestion, I was answering Jim's question, ie "why does it happen?" not "how can I prevent it?"
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Keith
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Tim V
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Re: Why does a wheelsets back to back move?

Postby Tim V » Thu Mar 10, 2011 9:27 pm

My experience is that super glue does make a difference, notice I said a blob of glue, I don't expect it to work in by capillary action. I aim for a fillet of glue between axle and wheel, the gel types work better.
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Paul Willis
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Re: Why does a wheelsets back to back move?

Postby Paul Willis » Mon Mar 14, 2011 7:01 am

Tim V wrote:My experience is that super glue does make a difference, notice I said a blob of glue, I don't expect it to work in by capillary action. I aim for a fillet of glue between axle and wheel, the gel types work better.


I'm in the same camp as Tim. A *small* fillet in there seems to work well for me.

I can't see any reason why it *shouldn't* work as it's a physical "obstruction" to the b-to-b moving inwards.

Flymo
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Will L
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Re: Why does a wheelsets back to back move?

Postby Will L » Mon Mar 14, 2011 10:57 pm

Flymo748 wrote:I can't see any reason why it *shouldn't* work as it's a physical "obstruction" to the b-to-b moving inwards.


Because they can also move outwards?

Will

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jim s-w
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Re: Why does a wheelsets back to back move?

Postby jim s-w » Tue Mar 15, 2011 8:28 am

That's true and thinking about it they tend to go to wide over too narrow.

Cheers

Jim
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Paul Willis
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Re: Why does a wheelsets back to back move?

Postby Paul Willis » Tue Mar 15, 2011 8:56 pm

Will L wrote:
Flymo748 wrote:I can't see any reason why it *shouldn't* work as it's a physical "obstruction" to the b-to-b moving inwards.


Because they can also move outwards?


True... But I've stopped 50% of the range of possible movement :-)

And that extra little bit of "stiction" might just stop them from wandering outwards. I nothing else, it makes me feel (in a very English way, as I'm currently reading Jeremy Paxman's History of the English) that "Something Has Been Done" ;-)

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Russ Elliott
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Re: Why does a wheelsets back to back move?

Postby Russ Elliott » Tue Mar 15, 2011 9:39 pm

Flymo748 wrote:"Something Has Been Done" ;-)

What a wonderful antidote to "Getting it all right"!

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David B
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Re: Why does a wheelsets back to back move?

Postby David B » Sat Mar 19, 2011 10:52 am

Just been reading John Hayes' book, 'The 4mm Coal Wagon' in which (p55) he says he fits Ultrascale wheels. He goes on:

'I always dismantle the wheelsets and reassemble them with Loctite 290, checking the back-to-back dimension with a gauge. This ensures that the wheelsets stay correctly set permanently.'

David

David Knight
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Re: Why does a wheelsets back to back move?

Postby David Knight » Sat Mar 19, 2011 1:34 pm

I've found with Gibsons that a touch of PlasticWeld seems to have a positive effect once the back to back has been set. The wheels aren't actually glued to the axles but they are a good deal more snug.

Cheers,

David

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Guy Rixon
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Re: Why does a wheelsets back to back move?

Postby Guy Rixon » Fri Jan 11, 2013 9:58 am

Is there any pressing reason why P4 wheel-sets couldn't be one-piece mouldings, say in nylon? Maybe cost of tooling? It seems rather over-complicated to turn tyres, press them on to moulded centres and then press the wheels onto axles.

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Horsetan
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Re: Why does a wheelsets back to back move?

Postby Horsetan » Fri Jan 11, 2013 11:07 am

guyrixon wrote:Is there any pressing reason why P4 wheel-sets couldn't be one-piece mouldings, say in nylon? Maybe cost of tooling? It seems rather over-complicated to turn tyres, press them on to moulded centres and then press the wheels onto axles.


How would you propose to fit hornblock bearings to a finished moulding :?:
That would be an ecumenical matter.

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grovenor-2685
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Re: Why does a wheelsets back to back move?

Postby grovenor-2685 » Fri Jan 11, 2013 1:08 pm

Is there any pressing reason why P4 wheel-sets couldn't be one-piece mouldings, say in nylon?

This has been tried, in various materials in 00 over the years, experience shows that plastic axles are not particularly good and plastic wheel treads are even worse, hence even Hornby and Bachmann provide metal wheels these days,
for disc wheels a small plastic bush in the centre of a metal disc seems to give the best results, Maygib have done some as have Branchlines, and the original P4 wheels also used this method. But its not practical for spoked wheels of decent appearance.
Keith
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Keith
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Philip Hall
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Re: Why does a wheelsets back to back move?

Postby Philip Hall » Fri Jan 11, 2013 1:30 pm

A way to help Loctite stay put was described by Chris Pendlenton in his recent article in MRJ. A turned groove on the axle where the wheel sits retained the Loctite; I suspect that a scribed groove or two along the axle (or inside the axle hole) might do. Having said that, I've always used the blob of superglue approach so far.

Philip

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Guy Rixon
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Re: Why does a wheelsets back to back move?

Postby Guy Rixon » Sat Jan 12, 2013 6:46 pm

Horsetan wrote:
guyrixon wrote:Is there any pressing reason why P4 wheel-sets couldn't be one-piece mouldings, say in nylon? Maybe cost of tooling? It seems rather over-complicated to turn tyres, press them on to moulded centres and then press the wheels onto axles.


How would you propose to fit hornblock bearings to a finished moulding :?:


For coach and wagon wheels, I was presuming normal, pin-point, outside bearings. I would assume that these would also be nylon. Clearly, a one-piece moulding prevents inside bearings and so isn't applicable for most carrying wheels on locomotives.


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