Society Gauge Widening Tool

[Martin Wynne]

I infer from this that if the standard is wrong, the triangular tool is the wrong length.

Hi Julian,

It's not the wrong length because there isn't a right length, and can't be. Prototype gauge-widening doesn't increase progressively with curvature, it goes up in steps. The prototypical approach is to discard the 3-point gauge and use fixed gauges for 18.83mm, 18.92mm, 19.00mm, 19.08mm, according to the radius:

Straight and over 10 chains radius (2640mm scale): 18.83mm

Between 10 chains and 7 chains radius (1848mm scale): 18.92mm

Between 7 chains and 5.1/2 chains radius (1452mm scale): 19.00mm

Under 5.1/2 chains radius: 19.08mm.

Such fixed gauges are or were available from Exactoscale. All this information is well-known and published many times, and now once again. So I can't see the need for 6 pages about it.

19mm gauge-widened P4 flexi-track is available from SMP Scaleway, see: viewtopic.php?p=16659#p16659

SMP Scaleway track is often over-gauge, because their rail used is under scale width -- typically 0.8mm wide instead of 0.92mm. If C&L rail is inserted in the SMP track base, the usual result is an accurate gauge.

regards,

Martin.

[Julian Roberts]

LesG
As this is very easy stuff for you
What we need is the right length tool to create 1.6666...mm . gauge widening at 1452mm.
Can you say what that length is?
It is just a bit under 45mm.
Can you tell us what gauge widening such a tool will create at 1848 and 2640mm, and at what radius such a tool will create 0.22mm widening?

[Julian Roberts]

LesG
Sorry!
Expletive deleted!!!!!
I MEANT
0.166666mm !!!!!!!!!
NOT 1.66666

[Martin Wynne]

Hi Julian,

Why do you want 0.22mm? The correct figure is 0.25mm maximum widening (3/4" at 5.1/2 chains radius) .

In which case if HL is half the gauge length, HL^2 = 1452^2 - 1451.75^2 (simple Pythagoras, no computers needed).

then HL = SQRT ( 1452^2 - 1451.75^2 ) = 26.943 mm

Length of gauge = 2 x HL = 53.89mm for 0.25mm widening at 1452mm radius.

However, you can't use a gauge that long because it will produce excessive widening below 1452mm radius.

There isn't a correct length for the gauge because the widening should increase in steps with increasing curvature to match the prototype, not progressively.

Once the widening has reached 3/4" at 5.1/2 chains radius it shouldn't get any wider for smaller radii.

regards,

Martin.

[Julian Roberts]

Martin
Difficult to write till at home later.
Will explain then.
Don't put Les off please!?!

Les its 0.1666 at 1452

[Philip Hall]

Since I was quoted just now with something I said at the beginning of all this, I think I ought to come back now. As Martin as so succinctly put it, gauge widening was done in steps on the prototype, therefore (in theory) so should it be on our models. The triangular gauge was probably envisaged as a way of providing a degree of gauge widening without having to measure anything. The fact that it doesn't accord with the prototype actually doesn't affect running quality. I say probably envisaged because none of the people who devised the standards are around now.

What does affect running quality is absolutely concentric and absolutely wobble free wheels, which is almost impossible. W E Ward - Platt's article in the October 1965 Railway Modeller referred to the impossibility of wobble free wheels. That article is still in many ways my bible of how to achieve reliable running; more common sense has rarely been written about the subject. So a little bit of gauge widening helps when a wheelset goes out of kilter, as it most certainly will. The Exactoscale widened track bases at 0.2mm widening do just fine.

If a wheel wobbles it will be tight to gauge on one side and loose on the other. So we should only need a little widening on a curve to stop the vehicle visibly hunting. Just to help a bit. My approach was to put a Society rectangular gauge in the four foot and waggle it a bit. I know this is dreadfully unscientific but it worked. You get to know the feel of such tolerances as you go on.

It would be very nice to pin down all these factors so that they can be readily reproduced, and I think Julian's efforts are laudable; to understand the reasoning 'why' in the pursuit of even better running. But I think that attempting to pursue perfection in this way is not going to help that much. The standards work, have been proved to work over so many years, and the thing that stops them working is, by and large, non adherence (accidentally) to these dimensions. Things like baseboards not being perfectly true and level, that sort of thing. The original standards were set out with manufacturing tolerances in mind, with the realisation that it would be very difficult to maintain such demanding standards without some tolerance.

If we are going to work to exact scale, proper Scalefour, then precisely pinning down widening will be important, but for our ever so slightly corrupted version of exact scale (don't say this to the 'outsiders') I don't think is
so. I have on many occasions witnessed heavy trains (uncompensated, unsprung, dead rigid) whizzing around the Epsom Club's 'Wadhurst' without a shimmer or a shake, and the track on that is very carefully made to the standards. I've built some of the engines (or rather, converted them) and the stock was built by people who are not renowned for making things with a lot of slop in them. So this approach works very well.

Philip

[dal-t]

If a wheel wobbles it will be tight to gauge on one side and loose on the other.

Err, isn't that the back-to-back will be tight on one side and loose on the other? It should only affect running if (a) it wobbles enough for the flange to bind/go the wrong side of a check rail, or (b) it wobbles more than the width of the wheel tread - or should that be half the width of the wheeltread? - so that it rides up/falls off the rail. In any case, that would have to be a pretty extreme wobble, wouldn't it - and isn't the width of the wheel tread only defined as 'no more than 2mm'? If I'm wrong with all that, fine - please tell me gently - but I must confess I'm struggling to believe that the differences being discussed here have any real effect on normal vehicles on normal track (where 'normal' means built to the kind of consistency most of us can achieve most of the time).

[Philip Hall]

David, you are quite right and that is the point I was trying to make. Even with the standard P4 there is not a lot of slop in the gauge. When a wheel wobbles, and if the back to back is at the upper end of the tolerance (17.75mm) then if the gauge is exactly 18.83mm there may be a tendency to hunt. It is the workmanship that we are able to achieve which is the most important factor. Unfortunately, a true wheelset, once assembled, can move about a bit later on (see Ward - Platt, as mentioned above) and then you might have trouble, if your track will not accommodate this. Yes, it could affect the passage through crossings and the like. I would say though that when a wheel wobbles the coning will cause the wheel to ride up and down a bit, such that it will be visible but not cause problems.

I have converted quite a few RTR engines and am now firmly convinced that the wheels MUST be perfectly concentric with a rigid chassis, perhaps a fraction less so with compensated or sprung. I see so many engines on layouts that merrily bounce up and down or waddle from side to side. I know that suspension is better but precision with wheelsets is a much better place to start than going to the Nth degree on the track.

Your last line sums up my feelings exactly, that this kind of precision with the track, so nobly intended, actually, maybe unfortunately, will make little difference.

Philip

[Julian Roberts]

Hi Julian,

Why do you want 0.22mm? The correct figure is 0.25mm maximum widening (3/4" at 5.1/2 chains radius) .

In which case if HL is half the gauge length, HL^2 = 1452^2 - 1451.75^2 (simple Pythagoras, no computers needed).

then HL = SQRT ( 1452^2 - 1451.75^2 ) = 26.943 mm

Length of gauge = 2 x HL = 53.89mm for 0.25mm widening at 1452mm radius.

However, you can't use a gauge that long because it will produce excessive widening below 1452mm radius.

There isn't a correct length for the gauge because the widening should increase in steps with increasing curvature to match the prototype, not progressively.

Once the widening has reached 3/4" at 5.1/2 chains radius it shouldn't get any wider for smaller radii.

regards,

Martin.

Martin just back from work. Long day rehearsing for prom concerts Saturday and Sunday at RAH. Belatedly, thank you for coming in on this since the early hours this morning.

This maths looks simple to you but what does ^ mean, and I just don't get any of it.

Can anyone do the sums?

Re: Society Gauge Widening Tool
Post by Julian Roberts » Wed Aug 17, 2016 4:13 pm

LesG
As this is very easy stuff for you
What we need is the right length tool to create 1.6666...mm . gauge widening at 1452mm.
Can you say what that length is?
It is just a bit under 45mm.
Can you tell us what gauge widening such a tool will create at 1848 and 2640mm, and at what radius such a tool will create 0.22mm widening?

LesG
Sorry!
Expletive deleted!!!!!
I MEANT
0.166666mm !!!!!!!!!
NOT 1.66666

Yes the radius at which 0.25mm is created would be useful to know too. NB 0.1666mm is the question

Once someone can come up with the figures I can explain.

[Allan Goodwillie]

Chaps I did say I would get back regarding the range of chairs that were available to engineers building full scale track. There has been much talk of the gauging of different companies tracks and why and the wherefore. Which, personally, I have found all very interesting. It is also interesting to see different peoples approaches and how they regard what they are doing. It all adds to our knowledge.

It is in this frame of mind I thought I would pass this on, as promised. It shows just what range of chairs were available to the North British Railway track engineers. NB chairs were mainly 4 bolt - but consider the chair variations held by all the other pre-group companies (although there would,I am sure, be many similar) and add the variations in track weight, sleeper spacing etc. Can you imagine the range and variety? What happened at grouping - were new standards laid down and new designs of chairs, including ones for flat bottomed track introduced (as Terry was quite right to point out) and what was the range there? Richard Chown has produced a book recently on BR track from '47-present day looking at the complexities of the period and range of fixings and approaches - "Fix and Forget" for example. There are just as many theories on the real thing as on the model, so in many ways this discussion follows the real thing - railways , like life are organic and constantly in a state of change.

So, just as a taster here is the page from the NBR's own volume (1906-I think) on track showing the variety of chairs -

Re083.jpg

Now, I was asked to be technical advisor to the East Group ( being the only person in the group who had built a large P4 layout similar in size to what we intended to build with Burntisland) when we built the first stage of Burntisland. There are many tales I could tell, but we have a policy of having only "official" views, so I will not go into the 6 weeks that the layout lived in my garage in the layout's embryo form, when it was my task to get what people had built to work. However, we did not manage to build the track to the detailed standard that true adherence to the prototype required. There was talk and thought given to the idea of moulding our own chairs on site using a number of patterns of chair moulds. In the end the track was made using rivet and ply with cosmetic C&L chairs. This allowed me to alter the track just by heating (which was just as well) and the cosmetic chairs made it look alright. We did have a sample drawing of a NB point as something to go on, but probably not correct for the era - a bit early, but, however, we did try to build to known practice, so it was as close as time and technical ability would allow.

Julian's locos run beautifully, partly because he has set himself high standards and perseveres until he gets it right. He also questions things that are just handed down as he is always looking for improvement - a quest that we all share I hope. He happens to be going through the same thing with track building at the moment and making we, who are longer in the tooth, reconsider - very useful to be looking all the time for ways to make things better. Philip's comments about wheel wobble are apposite and I spent some time myself trying to cure such things and now have a method, which I have published on the forum in the beginners section, as I thought it would be good for them to pick up on that and find a cure early, rather than struggle for years.

[Martin Wynne]

This maths looks simple to you but what does ^ mean, and I just don't get any of it.

Hi Julian,

^ means "raised to the power of"

In other words, ^2 means "squared" (multiplied by itself), ^3 means "cubed", etc. This notation is used for unformatted plain text.

Can anyone do the sums?

I'm sure many of us here can do any sums you are likely to want. But what I at least can't understand is what you want? Are you going to make yourself a new 3-point track gauge? And where does your 0.16...mm come from?

Once someone can come up with the figures I can explain.

That's back to front. No-one can come up with any figures until you have explained.

regards,

Martin.

[Martin Wynne]

What happened at grouping - were new standards laid down and new designs of chairs...?

Hi Allan,

Yes. The Railway Engineers Association (REA) set about creating a new range of "Standard Railway Equipment" (SRC) for bullhead track which was adopted for renewals by all the new companies, except the GWR, and later BR(W), who continued to use their own designs.

A reprint of the "Standard Railway Equipment" designs as at 1926 is available from NERA, sourced from the LNER:

https://sites.google.com/site/northeast ... blications

Scroll down to "STANDARD RAILWAY EQUIPMENT – PERMANENT WAY, 1926".

90 years later, those designs are still essentially the same for new bullhead track, while flat-bottom track has gone through numerous designs.

regards,

Martin.

[Julian Roberts]

Fair enough Martin.

Sorry I am likely to be interrupted.

You did not need to tell me about prototype gauge widening steps, thanks all the same, the topic is well rehearsed in all its nuances on these pages, but useful if anyone new is reading it.

Here is a graph that I have put up before that shows visually the prototype steps, and a curve given by a tool that gives the gauge widening required for 0.25mm at 1452mm. As you say it gives too much widening at lower radii

So the real question is what tool length gives the absolute requirement at 1452mm, which is 1/2", not 3/4".

This graph is nearly correct but not absolutely. You can't tell till you see the spreadsheet giving the numbers that a 45mm tool gives 0.1721 widening. But it is already apparent that the curve goes SOMEWHERE NEAR the middle of the next step, and NEAR TO meeting the first step. Replacing the 0.1721 with 0.1666 will change the yellow line nearer to the prototype requirement at 2640.

In other words, that gauge gives a near enough approximation of what we need. Corrected with the right figures will simply confirm the exact numbers. The minimum radius will be somewhere more than appropriate for P4 users, around 3 foot 3".

The blue line shows ALMOST what the Society gauge does. It is based on a length gauge of 29.75 which was how long mine is.

2016-08-08 09.29.03.jpg

2016-08-08 09.31.32.jpg

[Julian Roberts]

Martin
This is all me speculating, with a few facts.

The MRSG had among them the inventor of the triangular gauge, Brook Smith, if I understand correctly.

The triangular gauge was a brilliant concept as it meant gauge widening could be automatically created without the user having to know what radius he was at.

The guiding principle of the MRSG was bringing scale wheels and track, etc etc, but its other guiding principle was that it should all be accessible and practical for the average modeller.

So in that it emphasized gauge widening as an integral part of the prototype track function, it had to replicate prototype widening in this easy to use tool. It had to average out the prototype. So the question was then exactly as now, what is that average, and what length tool is appropriate?

Clearly the longer the tool the more gauge widening you get for a given radius. So the question was also at the same time, what is the smallest radius you can have before you go too wide.

The only thing the original MRSG document specified was a maximum gauge widening of 0.22. That is 0.25mm reduced down by the P4 12%. There was no mention of 528mm. Obviously it is just semantics and theory - who cares if you go to 0.25mm in practice - but the figure of the radius at which 0.22mm is reached is another way of expressing the length of the tool.

[Martin Wynne]

Hi Julian,

Well I'm baffled. If you have produced those curves, and a spreadsheet, why are you asking us to do sums for you? You can very clearly do sums yourself.

You might find the curves easier to draw if you use curvature rather than radius for one axis. (Curvature is 1/Radius, i.e. in mm^-1 units.)

I don't understand:

So the real question is what tool length gives the absolute requirement at 1452mm radius, which is 1/2", not 3/4"

But if it produces only 1/2" widening at 1452mm it will produce only a fraction more at 1451mm radius, which will be outside the standard.

If you have gone to all this trouble the obvious thing to do is to discard your 3-point gauges, and used fixed steps, as on the prototype.

p.s. posts crossed.

regards,

Martin.

[Julian Roberts]

If you look at the figures for 1452mm you can see that the Society gauge gives way too little widening if you take the prototype literally

0.0752mm compared with 0.25mm

That's why people used to say that "P4 can't work"

But you don't need all the widening at 1452mm - after all it's daft to say that as you get tighter and tighter radius below that you don't need any more widening.

They were wrong, there is enough widening, and it does work, but only just.

The 45mm line shows the averaged out prototype widening. As you can see, the blue line steadily gets further away from the yellow. In other words, there is steadily less and less widening compared with the averaged out prototype. Here are the figures for Running Clearance based on the spreadsheet figures. The range of figures is from the tolerances on both model and prototype - i.e. BB 17.67-75, and 17.87-89

2016-08-08 08.46.40.jpg

The third column gives the figures for the yellow line on the graph (45mm tool)

[Martin Wynne]

Hi Julian,

It seems the question you are asking, in a roundabout way, is what is the minimum radius for P4 (for non-industrial/light railways, etc.)?

When you know that you can calculate the 3-point gauge length to give 0.25mm widening at that radius.

I suggest 750mm, but that's just me.

regards,

Martin.

[Julian Roberts]

Well Martin I was going to say the other way of looking at it is simply to decide what your minimum radius is, and design the gauge to give the 0.25mm there.

The commonly accepted minimum is 4 feet I believe but others might have different ideas. I make my stock with that minimum in mind for working out the sideplay on inner fixed axles.

[Julian Roberts]

Hi Julian,

Well I'm baffled. If you have produced those curves, and a spreadsheet, why are you asking us to do sums for you? You can very clearly do sums yourself.

You might find the curves easier to draw if you use curvature rather than radius for one axis. (Curvature is 1/Radius, i.e. in mm^-1 units.)

I don't understand:

So the real question is what tool length gives the absolute requirement at 1452mm radius, which is 1/2", not 3/4"

But if it produces only 1/2" widening at 1452mm it will produce only a fraction more at 1451mm radius, which will be outside the standard.

If you have gone to all this trouble the obvious thing to do is to discard your 3-point gauges, and used fixed steps, as on the prototype.

p.s. posts crossed.

regards,

Martin.

Hi Martin - Believe it or not I've only just seen this post.

I didn't produce these graphs etc. My son in New Zealand did, such is the power of modern communications. He is a maths genius. (Genes from his mother not me). But the idea for the graph came up much earlier on this thread, about page 3, from Alan Turner, who suggested the 45mm tool as the minimum requirement. His maths and my son's are slightly different, presumably because of a different programme. That I assume is why his spreadsheet says 0.1721 rather than 0.1666 for 1452mm.

It doesn't matter if it is outside the standard at 1451mm. It will be until that widening is reached at around 3' 3"

What I have never been able to get over on this Forum is that I see the curves on the graph as an expression of what the prototype actually would do if it could, because what is happening, i.e. the flanges gradually taking up more space as the curve radius decreases, is not happening in steps, it is progressive. But the widening can only be done in steps, you can't have infinitely incremental widening on the real thing - at least if you could nowadays you couldn't have before. It is incredibly hard to talk about this. This is how Keith put it:

grovenor-2685 » Thu Apr 21, 2016 8:31 am

"The widening of gauge on the prototype is a step function - it is not continuous." (Alan Turner)

Indeed, so if you want to model that exactly you need a series of gauges, or the P4 Mk2 gauge with a series of washers.

However the prototype does not use steps because that is theoretically correct, more for the practicallity of building it.

With either ply and rivet or chairs and glue use of a triangular gauge gives us variable gauge widening with no practical difficulties.

If you can tell the difference when looking at a layout you must have exceptional eyesight.

[Martin Wynne]

What I have never been able to get over on this Forum is that I see the curves on the graph as an expression of what the prototype actually would do if it could

Hi Julian,

I'm not convinced about that. If it was progressive it would make maintenance far more complex. If a wagon derails you want to be able to say to someone "go and measure the gauge at location X and see if it's correct". You can't do that if it requires access to the original design specs for every individual sleeper.

We are not talking about high-speed transitioned junctions here. Track requiring gauge-widening is typically in depots, yards and sidings, so a step-function is near enough for most practical purposes.

Where it gets more problematic for us is that we are using those goods-yard radii for our main running lines.

regards,

Martin.

[jim s-w]

<sticks head up into firing line>

You do realise in the 6 months this discussion has been going on you could have just built something and see if it worked?

<ducks back into the safety of my trench>

[Julian Roberts]

<sticks head up into firing line>

You do realise in the 6 months this discussion has been going on you could have just built something and see if it worked?

<ducks back into the safety of my trench>

Jim
Well absolutely right, good point haha an ounce of practice is worth a ton of theory, as our revered iconoclast Martin Goodall often says.
Yes I have built something - not very much, but enough to show me the truth of what Mark Tatlow was saying on his problem finding checklist - that wide to gauge is OK but narrow to gauge is not.

A small degree of over gauge is acceptable; any under gauge is not.

And then later talking about turnouts:

Due to the unrestrained length of the switchblade, there is a tendency for it to flex slightly as the gauge is used and thus give a falsely wide reading. Callipers are thus best to check this – a good alternative are the Exactoscale miniature roller gauges which come with a +0.1mm, +0.2mm (etc) versions. As this is a curve, some gauge widening will be required (especially for tight turnouts) and a slight over-gauge is preferable to the risk of it being under-gauge.

I've made four B8 turnouts, one experimental and then three for the West of Scotland 4mm Group extension that Allan is talking about (by the way thanks for the plug, Allan!) and found that to get good running through the switch it was critical that the gauge was at least 0.1 wide, and that as Mark says, to have it wider (by maybe filing a bit more off the switch blade gauge corner) improved reliability. I have only been able to test them at home with just enough track in advance of the switch to place a loco, as the baseboards are only getting completed now, but it has been enough to convince me of the importance of having the gauge wide enough through the switch, as many people have said ad nauseam on other parts of the Forum - though maybe not as "ad nauseam" as my contributions to this thread saying the same things over and over again....

Mark's checklist did not get much comment, but of course it's vital. What I am after here is that the standard (0.22mm @ 528mm) locks us in to a widening that is not as generous as it should be, and why? - for no good reason, and Martin has shown that it is rubbish

It doesn't matter a damn who put those figures in the standard, because they are just plain wrong, and should be ignored.

[Julian Roberts]

Oh by the way Jim I found my three "production" turnouts, just to prove it here they are, far from perfect visually but they do work as far as I am able to tell at home. Oh and by the way I experimented on the first experimental one and two here with different ways of fixing the blades at the right distance apart, but haven't bothered with the last one. Includingo on one the heretical idea of stretcher bars that don't involve electrical isolation - after all, if they prototypically are wide enough that the inside face of the flange never touches the open blade, why not make stretcher bars much stronger by not having to use any glue anywhere? But I found that one of my locos has such desperately undergauge front wheels that it did short - but I never knew until then, it runs perfectly well through all the pointwork on our exhibition layout Calderside.

2016-05-21 23.14.59.jpg

Oh and here by the way is an experimental 45mm gauge. It doesn't change much because it is not accurate enough to gauge, but this is (approximately) what the future looks like. Here it is being used to get the gauge widening before the switch begins as per the CLAG "easing the traverse through the crossing" - but this gave 0.3 widening. I think that is the equivalent of the GWR joggle...?
http://www.clag.org.uk/switch-traverse.html

2016-05-14 21.48.12.jpg

[Julian Roberts]

What I have never been able to get over on this Forum is that I see the curves on the graph as an expression of what the prototype actually would do if it could

Hi Julian,

I'm not convinced about that. If it was progressive it would make maintenance far more complex. If a wagon derails you want to be able to say to someone "go and measure the gauge at location X and see if it's correct". You can't do that if it requires access to the original design specs for every individual sleeper.

We are not talking about high-speed transitioned junctions here. Track requiring gauge-widening is typically in depots, yards and sidings, so a step-function is near enough for most practical purposes.

Where it gets more problematic for us is that we are using those goods-yard radii for our main running lines.

regards,

Martin.

Hi Martin

Unfortunately I had to go to bed and have to go to work soon, this discussion is at exactly the nub of the issue as I see it.

I can't get over what I am driving at, as your reply shows, though thanks anyway!

The yellow line on the graph (45mm tool) shows the resulting widening at 1848mm is not adequate in literal terms - it only meets the requirement at 1452. But that means it is enough. So, similarly, the yellow line (after it is corrected, which I still await!! ) will meet the 0.25 (and/or the 0.22) at the right place - it is one continuum as is demonstrated by the fact that it meets the minimum at 2640mm

Of course the prototype couldn't do it except by incremental steps, though with modern technology and information storage it could now be possible maybe to individually design spec each sleeper and record it - though totally unnecessary.

I don't know if my idea is getting over!

Now you have got people into the idea that maybe the Standard is wrong, I can say that it seems to me the 528mm was the wrong answer to the wrong question (what is the tool length required to give 0.25mm widening at 1452mm), and the right answer to the right question is the one I'm asking for.

[Last sentence edited to correct minor error]

If you look at the correspondence for April 21 and 22 you may see what I mean. I hesitate to actually say, as I may be wrong, but you will see why I am being so opaque if you find it. Bear in mind that the 528mm is given by a tool 31mm long, and that the EM gauge tool is also 31mm.

2016-08-16 22.46.42.jpg

[Julian Roberts]

(what is the gauge widening required to give 0.25mm at 1452mm), 

This nonsense may be baffling. I meant

What is the TOOL LENGTH required to give 0.25mm widening at1452mm.

I will edit the post.