B2B wheel creep

Discussion of model and prototype wheel/rail interaction.
User avatar
steve howe
Posts: 600
Joined: Sun Feb 01, 2009 10:16 pm

B2B wheel creep

Postby steve howe » Sat Jul 15, 2017 11:27 am

I am not sure if this has been discussed elsewhere, but I am wondering if it is, theoretically, possible for plastic centered wheels to 'creep' over time, thus reducing the back to back dimension? I ask this because I have had some stock, mainly 4 wheel wagons, in store for a while and known to be reliable runners. On trying some out an our P4 inglenook recently I found some shorted out when passing through the three-way turnout. Examination showed the B2B to be tight on the gauge and easing the wheelsets slightly seemed to resolve the problem. (The track BTW has been checked for gauge and is spot on) I am wondering if temperature fluctuations between steel and plastic might be setting up some sort of contractile action causing the wheels to creep inwards. I would be interested to know if anyone else has experienced similar issues.

User avatar
Russ Elliott
Posts: 930
Joined: Thu Jun 02, 2011 6:38 pm

Re: B2B wheel creep

Postby Russ Elliott » Sat Jul 15, 2017 12:14 pm

I don't understand how a plastic-centred wheelset could short out over a 3-way, whatever its BB was.

Armchair Modeller

Re: B2B wheel creep

Postby Armchair Modeller » Sat Jul 15, 2017 12:18 pm

One tip I have seen is to put a drop of superglue or varnish around the wheel/axle interface after you first check the BTB is OK.

User avatar
grovenor-2685
Posts: 3330
Joined: Sun Jun 29, 2008 8:02 pm

Re: B2B wheel creep

Postby grovenor-2685 » Sat Jul 15, 2017 1:51 pm

Russ Elliott wrote:I don't understand how a plastic-centred wheelset could short out over a 3-way, whatever its BB was.

It can if the switch and stock rail are at opposite polarities, eg if the switch blades are bonded to the crossing (frog) instead of to the stock rails.
Probably just co-incidence that it shows up on 3-way, either that's the only one bonded that way, or it just has a smaller switch opening.
Regards
Regards
Keith
Grovenor Sidings

allanferguson
Posts: 362
Joined: Sun Jul 20, 2008 6:27 pm

Re: B2B wheel creep

Postby allanferguson » Sat Jul 15, 2017 2:03 pm

Russ Elliott wrote:I don't understand how a plastic-centred wheelset could short out over a 3-way, whatever its BB was.


Unless the switch blades were live to the crossing?

Allan F

User avatar
steve howe
Posts: 600
Joined: Sun Feb 01, 2009 10:16 pm

Re: B2B wheel creep

Postby steve howe » Sat Jul 15, 2017 3:21 pm

grovenor-2685 wrote:
Russ Elliott wrote:I don't understand how a plastic-centred wheelset could short out over a 3-way, whatever its BB was.

It can if the switch and stock rail are at opposite polarities, eg if the switch blades are bonded to the crossing (frog) instead of to the stock rails.
Probably just co-incidence that it shows up on 3-way, either that's the only one bonded that way, or it just has a smaller switch opening.
Regards



It was shorting between the switch and stock rail caused by back of wheel touching the switch rail. Can't remember where the bonding strips were but I'll check.

User avatar
Tim V
Posts: 2397
Joined: Tue Jul 29, 2008 4:40 pm

Re: B2B wheel creep

Postby Tim V » Sat Jul 15, 2017 4:29 pm

I find myself agreeing with Armchair on this. Drop of glue on the back of the wheel, though I use epoxy instead.

Can't see how you would get shorting, at no time should there be the possibility of rails in a gap that small be opposite polarities. I there are problems, your wheels will find them. So in the search for reliability, eliminate the possibility.
Tim V
Scalefour News Editor

User avatar
steamraiser
Posts: 444
Joined: Thu Dec 31, 2009 4:49 pm

Re: B2B wheel creep

Postby steamraiser » Sat Jul 15, 2017 7:47 pm

Once I am happy that the B to B is right and centred on the axle I put a drop of Loctite 601 / 603 on the back of the wheels / axle and allow to cure overnight before fitting.

Gordon A

Philip Hall
Posts: 1438
Joined: Mon Aug 10, 2009 7:49 pm

Re: B2B wheel creep

Postby Philip Hall » Sun Jul 16, 2017 1:30 pm

I have found rolling stock wheels moving on axles over time but never worried about it, just put it right.

I use 601 or 603 as does Gordon, but I take the wheel off the axle and lightly abrade where the wheel goes by rolling the axle under a file. This usually makes the wheel a stiffer fit, but do twist the wheel back onto the axle instead of a straight push, this helps to keep it wobble free. I twist it on a little, put a drop of 601/603 at the back of the wheel and twist it on fully, checking with a B-B gauge. The Loctite then goes around the axle into the abrasions and between the axle and the wheel.

The alternative fix is to abrade the axle and the back of the wheel and put on a dab of epoxy, like Tim. Which is probably quicker!

Philip


Return to “Vehicle dynamics and trackholding”

Who is online

Users browsing this forum: No registered users and 1 guest