Wheel back to back dimensions

[gordon]

We had a bit of a argument today at my Club's AGM (that'll teach the chairman to have AOB as a agenda item!).

The unexpected dispute was over what is the correct standard wheel back to back measurement.

In the GL5 standards it talks about wheelies that have 4 & 5/8 back to back and also 4 & 11/16ths.
The SMEE just points to GL5 as a reference.
So do we actually have two standards?

Help appreciated in sorting this one out else there may be fisticuffs at next meeting
Gordon

[Eddyg]

Gordon,

The GL5 Standard is 4-11/16".

Historically there were few ground level 5" gauge railways and on a raised track without turnouts the back to back was irrelevant and there was really no standard. Martin Evans did publish wheel set dimensions in more than one of his books and this provided a range for the back to back of 4 5/8" to 4 11/16". The GL5 standard merely advises that if the narrower dimension is used the theoretical clearance is only 2.5 thousanths of an inch where there are co-incident checkrails on turnouts built to GL5 standard . In the imperfect world in which we live this is likely to cause problems.

Hopefully you can come to a diplomatic resolution of your argument.

Eddie

[gordon]

Thank you Eddie.
I went through my stock and found that my tank engine, one raised track ride on truck and all my Aristocraft coaches are 4 5/8", my U and Merchant Navy along with my ground level ride on truck are 4 11/16".
Other club members are apparently doing similar checks as if the 4 11/16" back to back measurements are strictly enforced (as proposed) then we needed to find out what the impact would be on members running their own locos, etc.
The outcome could be a most unpleasant scenario.
Cheers
Gordon

[Eddyg]

Gordon,

Your club should build their railway to the 4 5/8" standard. This way both back to backs will run without difficulty. Ryedale, where the Main Line rallys are held, is one such railway (see the Track Section on their website) and all locos and stock perform perfectly well there. Do guard against the temptation to try to accommodate narrow gauge profiles as well. This will end up causing problems for everyone. If your members want to run narrow gauge locomotives then their wheel sets should be to the normal standard for 1 1/16" scale.

best of luck

Eddie

[gordon]

Thanks again Eddie.
The track has been down for years (decades?) and so changes to what's there is a huge problem especially as it is all welded steel!
We've been getting derailments at some points and forcing use of wider back to back seems to be the way that some folks think the problem will be fixed. There's going to be more to this I reckon.
Truly appreciate the guidance though.
Best regards
Gordon

[Eddyg]

Wheel sets have to be a long way out of tolerance to cause derailments. You should look to track alignment first.

Check the gauge, it should be 5" minus nothing to plus 1/16" on the straight and plus up to 3/32" on curved track dependent on the radius. Obviously the horizontal alignment should be good so check for abrupt changes.

Check that the rails are at the same height. Rapid change in relative level is a likely cause of derailment, in particular short dips in one rail. On straights the rails should be at the same level and on curves if super-elevated, the cant should be constant. Application of cant should be over a distance of not less than 6 to 8 feet.

If the rails have been in use for a long time they may be worn sharp on the running edge which helps the wheel to climb out particularly if also worn. A small radius on the running edge prevents this.

Look also at the vehicles. Bogies should be able to rotate relative to each other in the vertical plane to take up track irregularities and four wheelers should be fairly lightly sprung for the same reason. Look at the wheels to see if the flanges present a vertical face to the running edge of the rail. If so they should be re-profiled to 20 degrees with a radius in the root. Wheels that rotate independently on the axle are also prone to climbing the rail face.

Hope that gives you a few ideas

Eddie

[gordon]

Thanks Eddie.

Some good pointers in your posting and I will have discussions arond them. Just hope that the messenger doesn't get shot .

You highlighted some stuff that I already know ito be an issue so your remote analysis is actually very useful.
For my own track in the garden - about 250 yards long - I'm spot on with your thinking with gauge widening and superelevation.

I did find a mathematical formula in, of all places, a US Army Corps of Engineers document on "how to build a railroad" that got sent to me by a miniature railroad colleague in northern California in which one can calculate the amount of superelevation. The resut that I found was for 40ft radius curves it needs to be 1/4" to feel level at 8 mph. ... And it does.
Here's the link: http://www.hnd.usace.army.mil/techinfo/ti/850-02.pdf" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

Cheers
Gordon

[hudrail]

Hi
So much sense from Eddy . Brent house railway is built to 4 5/8 back to back as when I started building back in 1964 that was the standard ! I now use 4 11/16 and have no problems on any track . The real broblem now is the 7 1/4 people using a narrow gauge fiange profile on scale multi gauge track as the flanges will not go through the flange ways . The locos will ride over the flangeways of the switches and if you open the flangways out 5" and 3 1/2 will no longer be able to use the track ! There is NO standard for narrow gauge flanges in any gauge even 7 1/4 and no necessity for them as standard flange sizes will never wear out in the lifetime of the maker . Check all visiting locos for conformation when they arrive .
Brent

[Andy G]

Hi Brent,
Just to clarify your last post. Are you saying that a ground level 71/4 track that has narrow gauge engines (such as a Romulus etc) running on it, is not then suitable for a third rail to be added later to allow the use of 5" gauge engines as well ?
Thanks
Andy G.

[Ballan Baker]

Hi Andy, yes that is what Brent is saying. We at the Lindsey Model society have visited quite a few tracks that were ground level and where any of them were running a Romulus or Charles or other Narrow gauge loco s ( 7 1/4 ) then we could not run as our waggons and Loco s would not cross the crossing Knoses, or frogs to some. So don't try to mix them because it does not work. Regards Ballan.

[Andy G]

Thanks Ballan for making that clear, The narrow gauge being different from standard gauge had not registered with me prior to this comment from Brent.
It is of interest to me, as I along with other's at our club have been lobbying a move to install the third rail giving access to the 5" sector of the club, but a number of member's run the Romulus etc.
Cheers
Andy G.