This thread grew out of another in the Guild Matters, from which the first two posts have been copied across.

1. Jim Snowdon, Aug 23, 2017

Transferred from Guild Matters, in which place the topic had emerged but didn't belong:-

Alistair Dowse said:

I believe that the 31.5 mm gauge came about as a result of some amongst us using modern finescale wheels which do not conform to Guild fine standards, causing drop in at the common crossing of a pair of points built to fine standards and also excessive lateral movement on plain track, I believe that increased back to front with a tightening of check rail clearances could have achieved the same result either way it shows how a manufacturer can influence the hobby to a degree that has in the past seen some vile postings on this site, to my mind it is the tail wagging the dog.

Alistair

I won't claim to have invented 31.5mm gauge, as the original BRMSB standards refer to it as the track gauge, widening to 32mm on the tightest curve, but I may have started its more recent revival with the article I wrote in MRJ99. In essence, the origins of the problem lie in several different places - the Guild standards of the time adopting 32mm as the gauge for straight track, with further widening on curves, followed by Peco adopting 32mm for their track, and a woolly definition by the Guild of the flange thickness, and (as I understand it) Slaters opting to reduce the flange thickness to the lower of the permitted values and reducing the tread width in order to improve the appearance. All this, against a background of people taking the back-to-back as the “magic” dimension that defined everything. The result - a set of inconsistent standards for the wheelset/track interface, with the problems we all know about.

As explained in the MRJ article, there are two ways out of the problem if, that is, you want better running. Either modify the wheelset dimensions to fit the track, or modify the track to fit the wheelsets. Many of us build track, few build wheelsets, and none of us want to lose the ability to take our stock to other layouts, ie club layouts, so there really is only one answer - modify the track (and sort out the standards, which the Guild has now done, bar the actual publication).

Jim

2. Jim Snowdon, Aug 23, 2017

Also copied across, on behalf of John H., who posted it:- Jim, your last paragraph sums up the situation very well and I think needs to be translated into action. The technical Committee has done a lot of work on standards and is about to publish. We have the majority of O gauge modellers using 32mm with Slaters or similar wheels so it is likely to take as long for the currently most popular standards to be replaced as it has done to move away from coarse scale. Simple techniques for making 32mm work (as your article on Peco curved points) are needed. Also this topic is too important to be hidden under 'operating deficit' so could it be re-started in Modelling?

John Hobden

3. John Castle, Aug 23, 2017

The Fenland group all have a mixture of Peco, Marcway and scratch built track at 32mm gauge and also a variety wheels, yes we get wheel drop on real finescale wheels. All I do is open up the back to back to 29.5 or unsolder 3 sleepers on the running rail opposite to the nose of the frog and ease it in 0.25mm. I also found out that the old Jackson coarse scale brass wagon and coach wheels ran through all our point work with no problems when opened up to 29mm B to B.

Cheers John Castle, co-ordinator Fenland group.

4. Simon Dobson, Aug 23, 2017

Pretty much sums up what Jim says, either fix the track to suit the wheels, or fix the wheels to suit the track. IMO, fixing the track is the better option, as RTR runs without wheel drop - that's RTR Ixion/Minerva locos, and RTR Peco/Slaters/Peartree/whoever's wheels, on my stock, and on that of anyone who visits. Best Simon

5. Jim Snowdon, Aug 23, 2017

Re: Post #4:-

Exactly. Try adjusting the gauge of the wheels on any RTR loco and not only are you getting into territory that is difficult for the amateur but ending up with a loco that is incompatible with other people's track. Then, you have to adjust all the check rails, as what you have ended up doing is making the wheelset check gauge larger than that of the track, so the check rails can no longer do their job properly. Taken to its logical conclusion, there is a large collection of 7mm scale LNWR rolling stock in the care of the NRM, built to 33mm gauge that is completely un-runnable as it fitted only the railway for which it was built. Importantly, and often ignored, the dimensions that govern wheels and track are an inter-related set. Dimensions cannot be tweaked without understanding what else is affected by that change, and anything else is simply bodging. It is why the Guild published a set of standards back in the beginning (even if they didn't get things quite right).

Jim

6. Stuart Davison, Aug 23, 2017

Re: Post #3:-

I have always understood that the cause of wheel-drop is because finescale wheels are narrower than the gap between the two wing rails immediately in front of the crossing nose. (this applies to any standard of course, not just 0 gauge fine) To avoid drop requires the wheel width (tread+flange width) to at least equal this gap, which is “2 x flangeway + width of blunt nose”.

So for fine standards that means 2 x 1.75mm + (typically) 0.5mm for the blunt nose width, i.e. 4mm in total. I think most finescale wheels are now more like 3.5mm in total width, hence the drop; and of course why reducing the flangeway to 1.5mm will sort the problem because the total gap then equals 3.5mm. Changing the b-to-b on the wheels can't alter the situation because it doesn't change the relationship between wheel width and crossing nose gap. So the layout that John refers to will have been improved because of the changes to the flangeways alone. I have just started building pointwork, and had decided to adopt 1.5mm flangeways at the crossing (the check rail flangeways stay at 1.75mm of course), where I managed to get the flangeway to 1.5mm exactly I get totally smooth running ( as good as Scaleseven!!), where in my ham-fisted way I ended up with a slightly wider flangeway (1.6mm) there is still some discernible drop.

Kind regards, Stuart

7. Jim Snowdon, Aug 23, 2017

The logic of “2 x flangeway + width of blunt nose” works if you assume that the wheel is in flange contact with the gauge face through crossing nose. Except that with 32mm track and 31mm gauge wheelsets, this isn't always true, with the result that the effective wheel tread width is reduced correspondingly and wheel drop will occur. Reducing the gauge moves every wheelset closer to the crossing nose, which gets more of the tread width working. Widening the wheelset does the same thing, but without correspondingly altering the check rail positions away from the crossing nose, there is the potential for the wheel to strike or go the wrong side of the crossing nose. Jim

8. Dave Round, Aug 23, 2017

… originally Peco points had adjustable check rails, which was a great idea. You could at least set them up, to remove the sideways slop, or at the other extreme, stiffness, on running through, with courser wheels . You got the best of all worlds. The only irritation with Peco points, I find, is the tendency for the switch rail, to be short, and the use of a use of a fish plate, to give continuity, is a recipe for disaster. I am in the process of soldering mine up and relieving the 1st couple of moulded chairs, to allow the blade to swing . The frog being of the switchable polarity type.

Dave

9. John Castle, Aug 23, 2017

The only problem is on diamonds and slips where the gap is shared equally between both roads. We have cured that so now OK. All the loco's we use must have a bit wider tread as none of them drop in the frog. It appears it's only skinny wheels that drop. That is our conclusion.

John.

10. Pat Buckley, Aug 23, 2017

I stopped using Slaters coach wheels on my stock many years ago when I discovered the Easybuild wheels. With the slaters wheels running on the two layouts that my then club had derailments were common but with Easybuild wheels even on the 30 year old test track that I run on they never happen. The one set of coaches that I have with Slaters on is my Kirk quintuplet set that is also fully compensated and for some reason it has never derailed on any track I have run it on so there must be a lesson there somewhere ! Pat.

11. Alistair Dowse, Aug 23, 2017

The description of wheels in the adverts of many traders leave a lot to be desired, take (finescale wheels with 29 mm back to back) is the advertiser trying to tell me the wheels are to Guild fine standards or (which is the more likely) that they are closer in fidelity to the prototype than wheels to the Guild standards, also 29mm back to back has no meaning unless I know at least the flange thickness the tread width would also be handy to know, unless we can get the wheel suppliers to state these measurements working to any standards will be very difficult, as an aside there are many people who refer to finescale standards when in the Guild manual they are known as “ fine standards ” ( Jim put me right on this a while back ) by referring to them as finescale standards can cause confusion especially to any new comer to the hobby.

Alistair

12. Bob Comerford, Aug 24, 2017

Re: Post #8:-

Dave you can just bond the point rails to the stock rails with a flexible wire. Absolute necessity outdoors and even indoors I recommend it. I use r/c servo extension lead ( comes in a three colour cable) . I buy it in metre lengths from an Asian r/c supplier but you might get in shorter lengths locally from a hobby shop but will be more expensive. Cut the plugs off, strip off one of the colours and go. :>) cheers

Bob

13. Phil Harding, Aug 24, 2017

A very interesting debate, and it is a bit like walking around Aldi on specials day, lots of valued solutions to problems I never had. I machine wheels to the lower end of fine scale tolerances, I have lots of slaters wheels in coaches and locos, my back to back is 29.20mm and I have Peco track plus C&L hand built track. My stock does not derail, wheels don't drop and my stock runs on other layouts. Should I be having a problem or anxiously awaiting a new guild standard?

Phil

14. Simon Dobson, Aug 24, 2017

Phil The same debate is r unning on RMWeb, Martin Wynne of Templot fame posted the image above, explaining how wheels drop, http://www.rmweb.co.uk/community/index.php?/topic/124869-315-vs-32mm-gauge/?p=2809317 I hope & trust he won't mind me re-posting it. If you have narrow treads, and wide flangeways, I would like to understand how you don't have wheel drop, as it seems inescapable to me - there is no support for the wheel from the blunt nose until the outer edge of the tyre climbs back up the wing rail - until the yellow overlaps the right hand blue rail in the picture. Best

Simon

15. Jim Snowdon, Aug 24, 2017

Phil,

In a word, no. If what you have works for you, and your stock runs on other fine standard layouts, as it will, then you don't need to do anything. Remembering that the wheelset standards remain the same, what O-MF (and O-SF) do is provide better running than O-F (ie “traditional 32mm gauge); it's not that O-F doesn't work, it just doesn't work as well as it could. The important point is that the track gauge is a minimum, and the wheelset gauge is a maximum. The glue that ties everything together is the check gauge. The wheelset back to back and check flangeway dimensions are incidental, being simply derived dimensions, not standards.

Jim

16. Phil Harding, Aug 24, 2017

Jim/Simon

Thanks for giving me an understanding of the 'issue'. When I modelled in 4mm scale I moved to EM for a while and then aspired to P4 for extra realism, two stages of widening the track work. A solution in 7mm is to go to Scale 7 standards I guess, that's 1mm wider than finescale (33mm v 32mm) but this new idea is to back off by 50% the difference between acceptable standards and the ultimate S7 (back to 31.5mm) in the coarse scale direction. It seems illogical to me.

I assume Peco get away with it by having a base through the nose which supports the wheel flange for a short distance. Some of my points (not all) also have a base but much shorter and less obvious so that is probably the reason why I don't suffer from wheel drop. It doesn't look unsightly if it is a short support and weathered. I suppose a solution could use 32mm plain trackwork reducing to 31.5mm through the point.

Phil

17. Malcolm Trevena, Aug 24, 2017

I am amazed, saddened and disappointed that in 2017 we are still having discussions/opinions/debates concerning track and wheel standards. It seems that we have to either narrow or widen the track gauge to accommodate varying wheel standards to produce consistent reliable running. I have no wish to start a 'gauge war' those arguments were exhausted a long time ago but the problems still linger. As reliable running is fundamental to model railway operation a compatible track gauge and wheel standard that is adhered to by all manufacturers would be a minimum starting point. This problem is not peculiar to 7mm but occurs across all model railway scales from N-gauge to G1. The 'scale' societies each have their own agreed standards but each come with their own sets of problems to overcome, which are not insurmountable, but which often produce a barrier to wider acceptance. The Guild, with its membership numbers is in a position to lobby manufacturers to produce track work and wheels that do not require modifications to produce reliable and consistent running, why do we continue to accept wheel drop, excessive side play and derailments as part of the modelling experience? It's just as well that I enjoy building track, back to the bench.

Malcolm

18. Jim Snowdon, Aug 24, 2017

Phil,

Reducing the gauge may seem illogical, but so long as we want to continue using fine standard wheels, they represent a fait accompli. I would challenge anyone to see the difference in the gauge, or even the difference between 31.5 and 33mm with the naked eye. What is apparent, in terms of appearance are the changes in the small dimensions, ie the flangeways, because the proportional changes are much greater. The same, in the reverse direction, is essentially the difference between fine and coarse standard - the gauges are visually the same, but the flangeways are even larger, with necessarily much wider treads on the wheels. Coarse vs Fine is ultimately a matter of appearance.

Getting back to practicalities, a solution based on 31.5mm through the pointwork and 32.0mm elsewhere is viable, and has doubtless already been used. The eye will not spot the change in gauge provided it is done gently.

Jim

19. Alistair Dowse, Aug 24, 2017

The ability to work to any standard depends on the availability of wheels from manufactures to comply with those standards otherwise newcomers to the hobby will mix and match and because of poor running possibly give up, my first priority is excellent running a few missing rivets on a locomotive , a slightly larger diameter wheel and incorrect non visible items don't bother me so much but poor running does

Alistair