Society Gauge Widening Tool

[Will L]

However that has completely nothing to do with gauge widening on curves or the triangular gauge.
Regards

Keith I think you said above that a B8 doesn't need any GW. What I was finding was that I needed at least 0.1, perhaps going up to 0.2, GW on the switch and the curving area where the blade flexes for reliable running of even a short wheelbase wagon that I knew to run reliably on the group layout.

Julian

A relatively well known problem is that it can be quite tricky to avoid a little gauge narrowing through the switch blades. Your description here is typical of what then happens. It is something we all have to watch and often proves to be a particular problem for people building their first points until they get used to looking for it. The tighter Clearance between wheel and track in P4 means we are more likely to meet this problem than our EM or OO collogues.

There are several experts about better qualified to explain the technicalities of track building than I, but issues range from the switch rail not accurately following the curvature of the stock rail, the switch rails not being filed thin enough along their length, or not enough room being allowed to accommodate the switch rail against the stock rail. One approach to the latter is to follow the GWR and joggle the stock rail outward a touch so there is room for the nose of the switch blades. The thing is nobody would have thought to describe this as Gauge Widening, because by the time the switches where in place the gauge would be back to normal.

[Martin Wynne]

A relatively well known problem is that it can be quite tricky to avoid a little gauge narrowing through the switch blades. Your description here is typical of what then happens. It is something we all have to watch and often proves to be a particular problem for people building their first points until they get used to looking for it.

Gauge problems through a switch are often caused by failing to put an adequate set in the diverging stock rail.

I have posted this stuff numerous times on RMweb, and also on Templot Club:

http://85a.co.uk/forum/view_topic.php?id=491&forum_id=1

so I may as well post it here too:
___________________

Isambard Kingdom Brunel wrote:
"I seem to be having problems with the "SET", does anyone have or can someone take a photo of the "SET" on an actual turnout."

The best pictures I can find so far are in Rod Cameron's post at: http://www.rmweb.co.uk/forum/viewtopic. ... 72#p190472

Here I have marked up an extract from Rod's picture:



The common REA bullhead A, B, etc. switches are "semi-curved" designs. For an ordinary straight turnout, that means there is a straight portion over the length of the tapered planing (machining) on the switch blade, and only beyond that the rails are curved. Here's a diagram to explain it:



Straight turnout:

To make a size B curved stock rail for a straight turnout in 4mm/ft scale, do this:

1. Make two marks on the rail with a fine felt-tip pen, 29.3mm apart.

2. At the first mark make the "set", a sharply-defined shallow bend. Sharply-defined means that it is very clearly in one particular place on the rail, a kink, not a curve. Shallow means it is a very slight angle (1:32 for a B switch). It's very easy to overdo the angle, but you can flatten it back by squeezing the rail in flat pliers.

For a simple way of making a precise bend in rails, see: http://85a.co.uk/forum/view_topic.php?id=492&forum_id=6


3. Make sure the section of rail between the set and the next mark is dead straight. Don't inadvertently curve it.

4. Beyond the second mark you can gently curve the rail between your fingers.

5. Lay the rail on the template. If it is a Templot template the two marks will be on the template. You can align the rail over the template and check that the set angle matches the template. Time spent at this stage checking and adjusting will be well repaid later. If you have stuck the timbers on the template, it is worth printing off another one to check the rail against more easily.

6. Fix the straight stock rail first, it is just plain rail.

7. Start fixing the curved stock rail at the switch front, gauging from the straight stock rail in the usual way. Don't go beyond the set yet.

8. Transfer your attention to the second mark, location X in the diagram above where the rails begin to diverge. Measure the "stock gauge", that's the distance between the two stock rails at this location, i.e. between X and Y in the diagram. It should be exactly one rail width greater than the track gauge. For 4mm scale that means:

00-SF stock gauge = 16.20 + 0.92 = 17.12mm

EM stock gauge = 18.20 + 0.92 = 19.12mm

P4 stock gauge = 18.83 + 0.92 = 19.75mm

If you don't have a suitable means of making this measurement, you can improvise by combining an oddment of rail with your track gauge tool.

A ready-made 19.75mm stock gauge would be a very handy thing for the Society to supply. The dimension is the same for all sizes of switch.

9. If the stock gauge is correct, you can fix the stock rail at X. If it isn't, you may be able to adjust the set bend slightly in situ. If it is a long way out, you should remove the stock rail and correct the set bend angle. Don't try to correct the stock gauge by curving the rail, the section between the marks must be dead straight as shown.

10. If all is well, you can now fix the rail between the marks, checking with a straight-edge that it is dead straight. Then work forward over the curved section, aligning to the template and gauging from the crossing vee.

For an A switch, the 29.3mm dimension between the marks is shortened to 22.0mm (i.e. the set angle is 1:24). The stock-gauge remains the same dimension as before.

A bit of practice helps of course. Don't expect to get it perfect on your very first turnout. You will soon discover the importance of checking the rail against the template before starting to fix it down.

11. If you get it right you will find adding the switch blades later is dead easy. They will seat properly along the full length of the planing and almost gauge themselves.

You may even want to delay making the switch blades until the stock rails are in place. You can then try clipping them against the stock rails and filing the planing until they seat all along and align correctly at the stock gauge position to give the correct track gauge.

Another point to remember is that switch blades also need a slight set (bend) at the end of the planing, so that the filed front running face lines up with the plain rail beyond. Do this before curving the curved switch blade. Here's a quick sketch of that:

bend_in_switch_rails.png

More diagrams and notes about all this at: http://www.templot.com/martweb/gs_realtrack.htm

Curved turnout:

For a curved turnout the procedure is essentially the same, and it's a good idea to prepare the stock rail first as if it was for a straight turnout. The difference is that the dead straight section should then be curved to match the outer radius for the turnout. In other words the orange-coloured sections on the diagram above are all either straight or all curved to the same radius. The smaller turnout radius (the inner radius) begins only where the rails diverge. The stock gauge and lengths remain unchanged.

To get this right, it's a good idea to print a rails-only copy of the template on tracing paper, and lay it on top of the rails during construction to check the alignments.

Another picture kindly supplied by Mick Nicholson, showing the "set" bend on an LNER switch:



regards,

Martin.

[Julian Roberts]

Apologies that I can't find time to acknowledge/reply till now.

Will and Martin
Thank you both for your replies, and for all that info Martin.
I was already a student of your writings Martin and have applied all the information I could find from you when making the B8's.
I doubt extending this thread to cover exact point making techniques would be very welcome. Maybe another thread would be called for if the following seems controversial or just too complicated to get into properly.
Yes I understand Will that there can often be narrowing through the switch. And beyond that, as I have seen at exhibitions people rather forlornly trying to increase the gauge where the blade flexes between the switch planing and where the rail is fixed, because they are getting derailments there. Not saying it was P4, I can't remember.
I am talking about soldered construction here with rivet and ply, a B8.
So I followed all your instructions Martin but with the difference that, because the gauging is so critical along this area, I made the diverging stock rail break at the prototypical rail joint around Sleeper 13, so that it can be adjusted more easily after the end of the set at the stock gauge, sleeper 6. So the stock rail is the datum from Sleeper 3 to 6, (the set), but after that, from 7 to 13, the switch rail becomes the datum*, as once that has been filed and fettled to fit correctly and to gauge within the set along the planing (3-6), and the slight bend made to make the running gauge face straight at the end of the planing, and fixed down as far as possible accurately according to the template, it is easier to then get the gauge correct* by having the flexibility to adjust the gauging of the stock rail from the switch rail 7 - 13, and easier to correct later if problems arise. If the stock rail is all just one long length as per normal it is slightly less flexible in that critical area.
Following my first experimental turnout where I found there was a LOT of filing to do to the switch blade gauge side to get even short wheelbase stock to run through reliably, and a need to have a gauge of the upper 18.9's, on the next turnout I adopted the CLAG dodge of applying GW from before where the set is, so the whole switch on both roads is 0.1mm wide. On the next turnout I did the same but tried 0.2mm. As I increased the GW here the filing became less absolutely critical (obviously the side of the blade that fits against the straight stock rail has to be accurate in all cases and doesn't change with GW CLAG style.)
For all this stuff it would have been impossible if I had not bought the C&L incremental gauges. From beyond sleeper 13 the stock rail is one piece of rail. I used the triangular tool to gauge it from the switch rail (once that was fixed down to follow the template) which carried through to the rail joint between 27 and 28 and beyond that from the crossing which was already fixed down. (I am looking at the Society B8 template picture here downloaded a few months ago, not the Templot picture which was the actual template used)
I know this is not the same as the use of the GW triangular tool and one might say I am extrapolating from this mistakenly - fair enough. However the "point" ( ) of this thread isn't my experiences, shortcomings, whatever, it is the actual theory of the numbers, which Russ, Martin, and Keith have so eloquently er amplified on Monday, and which leave many interesting issues. Tomorrow I spend on another long rail journey and will have time to work out Russ's question, which I have realised is, how much GW can you have before the knuckle and wing rail starts acting as a check rail - though while that might be serious on the real railway I would not have thought particularly so in the model. The flare on the end of the wing would have to be carefully angled for going in the trailing direction.
Going back a long way Martin, on your info re industrial turnouts and four wheel wagons and locos, was that supposed to show anything other than the fact that some really sharp bends can be done and with turnouts? There is a column called Check, with the number changing about half way down - what is that? Dreaded question - is GW used at all in such circumstances?!

(Edit) *With the switch clipped in the diverging position along the planing

[grovenor-2685]

There is a column called Check, with the number changing about half way down - what is that?

That is the length of the check rails.
Here is a 1:2 industrial turnout i built as an exersize some time ago, the straight switch had gone missing when I took the photo. You will note that I had to gauge widen quite a lot on the curved road, just so I could push a 9ft wheelbase wagon through.

Ind-no2-2.jpg

Regards

[Martin Wynne]

Going back a long way Martin, on your info re industrial turnouts and four wheel wagons and locos, was that supposed to show anything other than the fact that some really sharp bends can be done and with turnouts? There is a column called Check, with the number changing about half way down - what is that? Dreaded question - is GW used at all in such circumstances?!

Hi Julian,

I included that table simply to show that 528mm might seem sharp as a bottom limit, but the prototype can go a lot sharper. But not on the main line. Which seems to be the factor missing in all these discussions -- which bit of track are we talking about? Figures which make sense for a running line don't necessarily make sense for the gasworks sidings. That's why I regard the standards as purely for guidance, and someone else's idea in the first place. What does annoy me is when someone uses different figures but still claims to be modelling P4, as happened in the EM wheels topic. If you adopt your own standard, give it a new name.

The Check column shows the length of the check rail. The silly metric figures should be converted back to their original traditional sizes, i.e. 3.048 metres is in fact 10ft. Giving it 3 places of decimals is just plain daft.

As far as I know gauge-widening wasn't routinely applied to industrial sidings, if only because they would be laid using the materials to hand, which wouldn't include special check chairs. The idea being that you don't send 6-wheel horseboxes to the gasworks. If a particular location was causing problems, even with short 4-wheel wagons and an 0-4-0 shunter, no doubt the local gang would do something about it (without contacting HQ first).

Sorry I didn't follow your switch gauge problems. When I build a switch the stock rails are fixed in place first, the switch rails are done last. As explained in my previous post. If you are gauging the stock rails from the flexible switch rails you are asking for grief.

Most USA railroads use gauge widening by 1/8" through switches, but they use a different design of planing so not directly applicable.

You can find UK pre-group switch drawings with similar gauge-widening.

Years ago I wrote a web page about A and B switches, it is still online: http://templot.com/martweb/rea_a_or_b.htm

regards,

Martin.

[Russ Elliott]

on the next turnout I adopted the CLAG dodge of applying GW from before where the set is, so the whole switch on both roads is 0.1mm wide.

Strictly speaking, it is not a 'CLAG' dodge; my webpage was merely exploring what I (as opposed to a corporate, err, 'CLAG') thought was an interesting and legitimate issue, as raised by John Anderson in his article in Snooze 151. Besides which, I always had a sneaky suspicion that Tony Wilkins' track gauges (some venerable but excellent triangulars from Studiolith), and which built all of Green Street's trackwork, might just be a tad generous. I mention this latter point, because, as we have all seen throughout this thread, the bits of metal and fashions in those bits of metal that implement our desired dimensions have changed over the years. Some of them are good, some of them have been nonsense, and others have been rubbish. The last two TG gauges (of different manufacturers) I've bought from the Stores were unfit for purpose. All batches of metal things are different.

Tomorrow I spend on another long rail journey and will have time to work out Russ's question, which I have realised is, how much GW can you have before the knuckle and wing rail starts acting as a check rail - though while that might be serious on the real railway I would not have thought particularly so in the model. The flare on the end of the wing would have to be carefully angled for going in the trailing direction.

The prototype does not have a problem because GW is not applied and the wing is cleared. (If only by a whisker!)

Whilst check and wing rail flares should be gentle (I think 1:27 was a common value), the angle of a closure/wing rail at the vee end is unlikely to be anywhere near that gentle, and for outer roads of curved model turnouts, the wings could indeed act as checks. I say 'could', because the conundrum is also dependent on the direction of the prevailing longitudinal force: if vehicles are being pulled through in the facing direction, wheelsets are likely to be up against the inner rail (so it wouldn't even matter if GW was applied!), and the problem is unlikely to arise, but if they are being pushed through in the facing direction, those wheelsets are more likely to be up against the outer rail, and hence the rear face of the opposite tyre can bump into that knuckle area. All this depends on where one fancies one's BB setting of course. The traversing speed might also be a factor in where the wheelsets are situated. Any superelevation will lead to a different analysis. The standard is perhaps inarticulate and unqualified, but it has to attempt to address all situations.

My personal view is that is a good thing to do everything in one's power to prevent the rear faces of model wheels striking anything.

Have a good journey.

[Allan Goodwillie]

This is just for the pleasure, I mentioned a while ago that I was building one of Chris Gibbons' medium Barclays and have been looking for photographs of it's rear and low and behold there was the very engine at Dunaskin with only the rear visible. Now what is interesting is the point that the locomotive had to go through to get to where it was needing to go, so I will start with that. (Liked Keith's little experiment by the way.)

DSC06072.JPG

There are quite a number of check rails in this view of the point. The running rail on the right is hidden under coal dust / ballast. Before reaching the point there is a check rail on the right hand side. (This was definitely not part of another point by the way.) Then there is the extra check rail on the right following the curved road, opposite where this stops another check takes over on the inside of its opposite number - all the way past the crossing V. Then two checks one on each side as we go around the curve. Note that the check does not continue into the wing rail, which is interesting. Note the typical stubby blades of the industrial point. Beyond sits a small Barclay - but further round the curve behind the buildings on the left was number 8 - my 0-6-0T with Giesel Ejector. (See below)

DSC06113.JPG

The poor old engine is in a very rusty state, but the one question I needed to solve was whether the loco had the number on the rear buffer beam - which of course it does. Its last paint job was in the blue with yellow buffer beams. It will look very different from your loco Julian, quite brutalist really, but will contrast with the Wemyss Barclays I am building. I had thought in this picture that the loco did not have any flanges on the middle wheels, but when expanded up I could see that in fact they were there. There was a groove down the centre of the wheels however, creating a flange on both sides of the wheels! Now that's what I call wear.

Here is a photo of the loco in black and white days working at Methil /Michael

wprc21.JPG

And finally some trackwork we were looking at at Dunaskin - I am sure Martyn will enjoy this, quite a variation in chairs and sleepers, ballasting, rail type, joiners, etc.

DSC06105.JPG

DSC06106.JPG

DSC06107.JPG

[Julian Roberts]

That was a happy day Allan! No maths talked as far as I remember...

My personal view is that is a good thing to do everything in one's power to prevent the rear faces of model wheels striking anything.

Well Russ it took even me just from Arrochar to Ardlui to work out that as far as the leading wheels are concerned you can't have any GW on that curved turnount at all, and even with BB max 17.75 and CF max 0.68 you get the inside face touching the wing rails, 18.83 - 0.68 = 18.15 and 17.75 + 0.40 = 18.15. And that's with the wheelset tangential to the curve so for a big wheeled Pacific or 9F, or Pacer dmu, all the more the issue. Though whether this would amount to derailment might be to do with speed and whether cant can be applied...?

[As my journey as well as long is one back in time, I have had no internet for several days and have had second thoughts about the initial responses that follow.]

Surely that means that even the 31mm triangular gauge is out for any kind of pointwork - other than, let me have another go at nomenclature, let's say a 'straight turnout', is that a correct term? I.e. one that has one straight road and one diverging road, of whatever lead, radius, switch type etc. Nowadays, could not P4ers cope with an instruction to use a roller gauge for all other types of p&c work?

The nuances around the word 'should' never occurred to me. I think I am right in saying - correct me if I am wrong! - that Keith on his website cheerfully shows what "should not" as opposed to "must not" means regarding applying GW to pointwork, the photos show the triangular gauge being used on 'straight turnouts'!

In contrast, plenty of us follow the "should not" as an injunction, which means using a roller type 18.83 track gauge to make a 'straight turnout' and means (doesn't it?) it is normal to use the crossing flangeway gauge to set the checkrail (in soldered construction at least).

I'm not sure I see why the length of the triangular gauge compromise as you described earlier Russ is in part predicated on the problems of its use in a situation where plainly it shouldn't be at all...? Perhaps there are more layers of subtlety that I am not seeing.

[Now my second thoughts : is this behaviour (of the back of the wheel on the inside of the curve) not happening anyway even on 'straight' turnouts (my term)? The wheel back at 17.67 must be banging onto the check rail if its partner wheel flange is hard over on the outside of the curve. But with GW this does not worsen, as the check rail moves away from the adjacent stock rail. However, on a model railway, assuming realistic speeds for the curvature, does this matter? Obviously such a wheel/rail crash will cause severe jolting and wear on the real thing, but need either concern our small passengers and track engineers? And... if I am arguing against any GW on a curved crossing what has happened to my argument in favour of generally twice as much GW being (perhaps) desirable!? Its my blood on the carpet now...]

Apologies for describing your writing on GW at the switch as a CLAG 'dodge' - more carelessness with words from me.

[grovenor-2685]

The nuances around the word 'should' never occurred to me. I think I am right in saying - correct me if I am wrong! - that Keith on his website cheerfully shows what "should not" as opposed to "must not" means regarding applying GW to pointwork, the photos show the triangular gauge being used on 'straight turnouts'!

I have never used a roller gauge for P4, the triangular gauge can do it all for 'normal' turnouts. (ie. those that are not using small radii in need of gauge widening) Look at how the gauge is used at the crossing in my photos you will see that it keeps the gauge correctly. This does fall down when dealing with the outside road of a curved turnout as you can end up with unwanted gauge narrowing. In this case you set the checkrail with the checkrail gauge and then the stockrail off it with a crossing flangeway gauge. The normal triangular GW can be applied between the switch and the crossing and again after the crossing. This allows some latitude for 6 coupled locos as only one axle at time is in the non GW section at the crossing.
Regards

[Russ Elliott]

Well Russ it took even me just from Arrochar to Ardlui to work out that as far as the leading wheels are concerned you can't have any GW on that curved turnount at all, and even with BB max 17.75 and CF max 0.68 you get the inside face touching the wing rails, 18.83 - 0.68 = 18.15 and 17.75 + 0.40 = 18.15.

Yes, that is a 'passing' case, and the prototype dimensions give an equivalent passing case. It's worth noting that many BB gauges manufactured under Society auspices were made to be at the top end of the P4 BB range. But it is also why some of us prefer a BB slightly in excess of 17.75mm. As I have advocated before, a BB in the range of 17.7 to 17.8 would perhaps be a better way of stating the objective in the standard, and would avoid the somewhat unhelpful second decimal place.

Surely that means that even the 31mm triangular gauge is out for any kind of pointwork

I tend to view a turnout as 3 different sections: the crossing, the bit between the crossing and the switch, and the switch. On the prototype, the overall geometry of crossings and switches are usually not 'curved'. (Although doubtless Martin will have plenty of pictures to show exceptions.). The section between the crossing and the switch is usually or often curved, on one or both roads, and that is where a triangular gauge is perhaps most useful in a turnout, as explained by Keith.

[Martin Wynne]

On the prototype, the overall geometry of crossings and switches are usually not 'curved'. (Although doubtless Martin will have plenty of pictures to show exceptions.).

Hi Russ,

I would swap there your descriptions of "usual" and "exception". I think it would be an exception where a entire crossing is laid dead straight in a curved running line. David Smith has some comments about this on page 31 of his book on GWR track.

It's true that over the length between the knuckle and the end of the vee splice, say the two timber spaces between the X-A-B chairs, it is not physically possible to curve a crossing which has been manufactured straight. If that part is required curved it must be specified and ordered from the Crossing Shop as such. If a straight crossing is supplied to site, it can only be faired into the ruling curve over that short section. But beyond that short section, over the full length of the crossing (i.e. the length of the check rail) the rails can be curved to match the ruling curve and I would regard that as the usual practice, rather than an exception.

Here's a picture as requested -- this strikes me as normal practice, not an exception:



In the context of this topic, an interesting comment in David Smith's book is that great efforts were made to avoid laying crossings tight to gauge. To the extent of laying them up to 1/8" wide to gauge as standard practice (with ordinary 1.3/4" check chairs).

regards,

Martin.

[Russ Elliott]

Thanks, Martin. (Trust you to choose curved outside slips at Shrewsbury...)

In the context of this topic, an interesting comment in David Smith's book is that great efforts were made to avoid laying crossings tight to gauge. To the extent of laying them up to 1/8" wide to gauge as standard practice.

Interesting. Leaving aside the question of whether some of our model gauges are accurate to within 0.04mm, the dictum of ensuring nothing is tight to nominal gauge (whether for crossing work or plain track) is always sensible. One could perhaps argue that prototype 1/8" easement is a validation of using a triangular gauge in the very close vicinity of or even at a model crossing. (And Julian will feel vindicated!) In partial defence of our model standard though, I would say there is a significant difference between an 0.04mm easement at a check and a full-monty 0.22mm GW. The GW allowance is intended primarily to assist sideplay allowance on middle axles, so I would say if anyone needs to ease the curved road of a turnout over the switch area for that reason, then I can't argue with that. Again, it all comes down to the inexactitude of the standard's word 'should'.

Btw, in such circumstances, presumably the wing rail CF was kept tight at 1.75" (because of the standard chair castings), and the easement was allowed on the check rail gap, with special chairs?

[Martin Wynne]

Btw, in such circumstances, presumably the wing rail CF was kept tight at 1.75" (because of the standard chair castings), and the easement was allowed on the check rail gap, with special chairs?

Hi Russ,

It seems standard 1.3/4" check chairs were used. Thus increasing the check gauge by up to 1/8" and also the check span.

Here are David Smith's actual words:

"During the installation of a piece of fitting work particular attention was paid to the gauge at the common crossing(s) to ensure that there was no tightness, as the guard(s)* would otherwise have been rendered ineffective. Indeed, a little slackness was considered preferable, up to a maximum of 1/8". "

*GWR terminology for check rails.

regards,

Martin.

[Russ Elliott]

Ah, so BC was increased to 4'5 1/8".

Hmmm...

[Martin Wynne]

Ah, so BC was increased to 4'5 1/8". Hmmm...

For the check span, yes.

That still leaves 1/2" clearance on the 4ft-5.5/8in wheels back-to-back.

Martin.

[Julian Roberts]

Btw, in such circumstances, presumably the wing rail CF was kept tight at 1.75" (?

This thread has seen me question the GW, Russ questions the BB, Martin is now showing the flexibility in what I thought was non-negotiable, the CG. Is there anything left that is definite?! Above, Russ seems to open the possibility that even the CF might be negotiable!? I am beginning to think I like the idea of this thread as being where to think the un-thinkable, as opposed to blind certainties, is possible.

I think Richard Chown who I quoted much earlier won't mind if I also quote him saying - though he was specifically referring to GW figures in the first sentence here

Modellers see all those defined single values and take them as gospel. On the traditional railway probably the only dimension that had to be consistent was the 1 ¾” crossing flangeway.

I happened to come across Mike Sharman's "Sundry Snippets" in Snooze 147 and can't resist quoting some bits of it - not to contradict what has been said, but to put another perspective, in the interest of broad-mindedness

I have probably bodged and broken my way through most of the “rules” laid down by the experts.
So, just to cheer up the like-minded souls among you - and more importantly - new members, I offer “Mike’s Rules” on -
1 Wheel gauges
The standard back-to-back gauge, as issued by the Society, must be used accurately, with no concessions, to ensure
good running. The gauge should be a very light ‘interference’ fit, i.e. the wheelset should just slide out of the gauge
with light pressure. I repeat - there is no leeway on this setting.
2 Track gauges
Again the Society provides and sets the standard for the relationships between the crossing nose-to-wing rail and
checkrail. This is the only critical dimension in our pointwork. Be it simple or complicated point and crossing work, one
gauge will do for the lot.
Now, here we have the first of those tweaks which we can allow for tight curves. For example, you would find that
those seven-foot diameter wheels back in the 19th century had more flange in the flangeway than a three-foot wheel,
and a slight tweak of the check rail can ease their passage on our models. When you think about it, the only purpose
of a check rail is to stop a wheel going the wrong side of the nose of the crossing, so adjust it to taste!
Incidentally, another obvious track gauge is a pair of accurately set driving wheels of about five-foot diameter. This
will help you to judge gauge widening.

3 Plain and curved track
With straight plain track, lay it exactly to gauge; but with curved track, use one rail as a ‘master’. Then you can do
what you like with the other rail, as long as the trains don’t fall in between the two. I know this sounds awfully wicked,
but model track does not flex and give under the vehicles like the prototype does. So, unless you have free movement
to slide in the chairs (which rules out soldered/riveted track!), when the sun comes out and shines on the layout (as it
does upstairs at Scaleforum), an inner rail on a curved section will try to – and will – go under gauge.
4 Locomotives
Because locomotive frames won’t bend and because we must have sideplay, I never build a chassis wider than 15mm.
I know it makes mounting realistic brake gear difficult, but unless you want a showcase model, the concession must
be made.
So, there we are. It’s not nearly so complicated as you might be led to believe. Just cheat a little!

[martinm]

But to set against that view , we have Will's conclusions in 'Gauge widening conclusions' that

I don’t see anything to suggest that an excess amount of gauge widening will improve running. This goes along with the societies general experience that the proper use of the society gauge produces perfectly usable track work.

With sufficient End Float on the centre axle (0.5mm) gauge widening is only necessary in extreme conditions.

.
But this is then qualified by the 'need' for a practical test

Following these threads with interest,

martin

[Julian Roberts]

But it is also evident there must have been considerable ambivalence within the MRSG over the subject - with a BB on the conservative side (as we now generally regard it), and a CF larger than the prototype equivalent, would there need to be much stress put on the implementation of GW? There were commercial arguments as well: producing a triangular gauge 50-or-so mm long was always going to be a lot more expensive than a 30mm one. Joe Brook Smith was not obsessed with popular evangelism like Malcolm was. And the commercial reality of the nascent P4 era dictated that multiple or different types of constructional TG gauge would not be economic, and might be perceived as too confusing to the potential P4 punter.

The result was a compromise length. It was a compromise arrived at by fallible individuals with divergent visions of what P4 could and should be.

I wonder if there is any more to know about the compromise you described. The differences between the original Aug 66 MRSG article (which left the Gauge Widening Factor radius an open question) and even its September 66 conclusion I find striking, with the latter's emphasis on the practicality of model railway type curves in P4 and a minimum not less than EM's.* My totally uninformed guess is that the "pure" scale modellers were persuaded by more pragmatic and commercially savvy ones to adapt the GW standard in a more contemporary direction than a pure scale standard would have inferred. Nowadays we are well used to a comfortable minimum being around 3' 6" to 4' but in those days where trainset curves were more the norm, perhaps such a minimum could have been seen to be laughably impractical # by some people.

The eventual replacement of the Mk 1 triangular Track Gauge by the Mark 2 TG roller gauge with 0.2 washer to be added 'on all curves' was introduced with the words (referring to the 0.2 washer) "This is the Gauge Widening Factor" - one can imagine an emphasis on the word "the"- as if this was the end of a lot of debate - or maybe that's just my imagination. I notice that Joe Brook Smith (the inventor of the triangular gauge?) had ceased to be a member of the Management Commitee between July and Dec 1973 - at least according to the roll call on each issue of "Precision", and this track gauge was introduced in August '76 (interestingly enough the same time as the 40 years we are celebrating)

I wonder what happened to it and if this still counts as part of the generality of P4 modelling, and why the Mk 1 gauge has subsequently returned to be the norm. Evidently for everyone it gives a quite adequate amount and more is unnecessary, yet a P4 tool giving a much closer approximation to the prototype already exists, or did exist. The Mark 1 31mm tool doesn't give more widening than the Mark 2 with its 0.2mm washer added until the radius is down to less than 2 foot.

Perhaps it gave too much widening for crossing work

The compromise gauge length was a balance between, on one hand, giving some GW on curves, and on the other hand, constraining the amount of GW at crossing work

but as it is now understood that crossing work shouldn't have any widening at all, we are all, presumably, aware that 18.83 roller gauges (e.g. the Mark 2 tool without the GW washer added) should be used here...or as Keith has explained, the triangular tool, with the widening done between the switch and the crossing on the curving section.

Perhaps unnecessarily I append a picture of the graph which shows how the Mark 2 tool relates to the prototype and the Mark 1 (31mm) tool, as well as a putative 44mm tool and the too long 54mm tool

2016-09-12 07.12.15.jpg

* I.e. just as small a minimum radius as EM gauge.
# I.e. too large, thus using an impractical amount of space.

Matthew Final Correct Black Spreadsheet JPG.JPG

Gauge Widening Spreadsheet Correct Compact Colour Version.pdf

The above spreadsheets give all the information this thread was seeking. The colour version has the figures colour coded to match the graph.

In the column to the left of the box are the important radii in feet and inches: the 528mm minimum P4 curve where 0.22 widening is given with the P4 triangular tool, and the three radii of prototype gauge widening steps when reduced down to 4mm scale.

In the first proper column is a list of decimalized radii in 3 inch steps (i.e. 6 inches = 0.5 ft, 9 inches = 0.75 feet etc), that additionally include those four steps just referred to.

In the second column the same steps are translated into mm

In the third column is a list of the widening produced at each of those radii by the triangular/oblong tool that as per the Standards gives 0.22 at 528mm

In the fourth column is a list of the widening produced at each of those radii by a triangular/oblong 44mm tool

In the fifth column is a list of the widening produced at each of those radii by a triangular/oblong 54mm tool

In the sixth column is a list of the prototype gauge widening at each of those radii (in 4mm scale).

[Julian Roberts]

It's time I put this up. The following may sound to some like re-inventing the wheel. But I had gone into P4 expecting to have a minimum radius of 4 feet, and making a 2 ft radius curve was never on my to do list.

November 2016

The club layout "Calderside" is being extended to incorporate exchange sidings, and it transpired that the plans (drawn up on Templot by our design boffins) included a short 600mm curve towards one of the two eventual offstage destinations, a brickworks. (The route to the offstage colliery is less tortuous.)

I had already started making a colliery locomotive (Hi Level Barclay Tank) and had not known about this curve, but luckily, after doing the versine sums, found the sideplay built in to the kit's P4 chassis would be adequate for this curve.

Sceptically I thought I would make a test plank curve made as simply as possible using the triangular tool. This was going to be a good test of all the words that have flown back and forth over the topic of curves and gauge widening in this thread.

I used a 00 gauge 24" (so 600mm is an approximation) Tracksetta to lay the outside rail of the curves which are in a kind of ? shape to incorporate a reverse, though this is not a requirement of the layout.

To my surprise I found it works very well, and my vehicles can be propelled without any problem as well as pulled. So I conclude that the problems of derailments on curves in P4 (which I had hitherto perceived as being endemic), where it is not a vehicle fault, are caused when, for whatever reason, no gauge widening at all has been incorporated. Flexi track is frequently undergauge. I wouldn't trust track that is undergauge to widen automatically on a curve even if it is claimed it should do. The only flexitrack I would trust for a curve (except the most gentle ones) is Exactoscale Fast Track in its Gauge Widened version. This is 0.2mm wider.

However I found the triangular gauge gives more widening than it theoretically should. I am not sure if it may be a tad wide for straight track too. I don't particularly trust my cheapo digital Vernier for all out accuracy, nor my skill in putting it absolutely square between the rails. Initial measurements with the digital Vernier suggest that the curving track is between 19.06 and 19.12 wide – the amount of widening (between 0.23 and 0.29) that I expected to be necessary, and 18.91 on the straight. According to the spreadsheet, the 31mm tool gives 0.1914mm widening at 2 foot radius, while I am actually getting up to 0.29mm. A 44mm tool would give 0.3899mm.

In any case, I really don't think it matters much what the measurements are - it works, the trains run without derailing far faster than a realistic speed, so can be trusted to be 100% reliable in realistic exhibition operation....

It's a bit of a shame I didn't have to do this earlier on in this online conversation. However, I don't retract from the general idea that more widening is better than less, and it's better to err on the wide side. I can see that my idea of a longer tool might have more relevance to simplifying S4 track building, but I'm not going to go that route simply because I basically like to make trains for other people's layouts, which are P4.

Here is a note I wrote to myself describing all this in more detail, including how couplings and buffers still work even at this radius.

600 mm curve construction PDF.pdf

Here is the graph and spreadsheet that shows the theory, if not the actuality, of the figures that have been bandied about. Worth re-stating that the Exactoscale Fast Track in its Gauge Widened version is the same line on the graph as the P4 Mk2 Track Tool with Gauge Widening Washer.

snip gw graph.JPG

snip GW.JPG

Here is a video of a short train at full speed on the curve, including a long wheelbase van and 6 wheel guards van. The Barclay has a top speed around a scale 25mph.

[youtube] https://www.youtube.com/edit?o=U&video_id=rPiVz1vDYhQ
[/youtube]

And to finish off this thread here is how Andrew Jukes succinctly put the general requirement for gauge widening recently -
viewtopic.php?f=5&t=5386

I mentioned I use a back to back of 17.82mm. With this (and with the exact scale 17.87mm) gauge widening is more important than it would be when using the original P4 standard of 17.67mm. The Society recommended back to back of 17.75mm falls somewhere in between. Differences in back to back translate pretty directly into different requirements for gauge widening. If you are using curves a lot tighter than my 1200mm radius and still using large-wheeled 6-coupled locos, then you are likely to need more gauge widening (and some, even if using the 17.67mm back to back gauge). On the other hand, if it’s short wheelbase 4-coupled locos (or Bo-Bo diesels) and short wheelbase 4-wheeled wagons, you can probably forget gauge widening.

In the end, whether through gauge widening, choice of vehicle, provision of sideplay or choice of back to back, the aim is to have all wheelsets with that little bit of running clearance everywhere on your layout. You can usually tell whether you’ve got it just by gently feeling for wheelset freedom with the vehicle sat on the track.

As Martin Goodall likes to say - An ounce of practice is worth a ton of theory

[Martin Wynne]

Hi Julian,

Here is a working link to your video. http://youtu.be/rPiVz1vDYhQ



Martin.

[Julian Roberts]

Many thanks Martin. On my post it seems to be working now too. Don't know what I did wrong...

[Martin Wynne]

On my post it seems to be working now too. Don't know what I did wrong...

It's an editing link. It will work for you only.

Martin.

[grovenor-2685]

Many thanks Martin. On my post it seems to be working now too. Don't know what I did wrong...

Julian,
When using the BB code tags, in this case the youtube code, hover your mouse over the button and use the syntax as shown##.
There are two ways of linking to youtube.
1. just use the full url, with or without the URL BBcode tags (the system assumes its meant to be a url link when it sees the http//).
2. use the youtube tags with the correct syntax, ie just using the final part of the url, the system then embeds the video.

You used the full url but with the youtube tags so confused things
Martin did one of each so you see both the link and the embedded version.

regards

##. NB Youtube have changed the desing of their urls so that the v= referred to in the syntax is no longer included, you just need the part after the last /.

[Allan Goodwillie]

That's interesting and very useful to know Keith and Martin - maybe deserves a spot somewhere on its own as it would be useful for others to see and use as long threads like this take a bit of going through sometimes to find items such as this, it also takes remembering where you saw the info when reading through the thread or threads. I may start adding some material to Youtube as well.

Thanks, I have not had much contact with the forum over the last couple of months as I have been busy building stuff instead. Beginning to catch up this week I hope.

[Noel]

That's interesting and very useful to know Keith and Martin - maybe deserves a spot somewhere on its own as it would be useful for others to see and use as long threads like this take a bit of going through sometimes to find items such as this, it also takes remembering where you saw the info when reading through the thread or threads.

There is a search facility under "Quick links" above. Searching on 'youtube code' produced 9 hits, with Keith's at the top...