Triangular gauge use in building pointwork.

Discuss the prototype and how to model it.
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Paul Townsend
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Triangular gauge use in building pointwork.

Postby Paul Townsend » Sun Jul 08, 2012 3:52 pm

In the "Lounge" topic re FAQs Jim S-W said:

(don't ever use a triangular guage when building point work either)

This is an interesting emphatic recommendation; lest it deflect from the FAQs I have opened this topic in this more appropriate place.

I have built over 70 turnouts mostly with the original Studiolith triangle and don't have all my trains falling off!

Justify please, Jim.

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 4:05 pm

Hi Paul

Several people involved with designing and building the real thing have advised me that gauge widening must not be used in pointwork

Not much help I know

Jim

Armchair Modeller

Re: Triangular gauge use in building pointwork.

Postby Armchair Modeller » Sun Jul 08, 2012 4:29 pm

Out of sheer curiosity, did their comments apply to modern pointwork, or pointwork in general, Jim?

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grovenor-2685
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Re: Triangular gauge use in building pointwork.

Postby grovenor-2685 » Sun Jul 08, 2012 5:11 pm

It is not usual to use gauge widening in pointwork, the main reasons being that check rail chairs and their flat bottom equivalents are manufactured to give the correct check gauge without gauge widening and having lots of special parts would create more problems. Also it is rare for pointwork to be on tight enough curves to need gauge widening. And where they are the stock using it is probably restricted to vehicles that can cope. But none of this is directly relevant to our models where I can confirm that use of the triangular gauge for building pointwork has not had any detrimental effect for me.
See http://www.norgrove.me.uk/points.html
Regards
Keith
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Keith
Grovenor Sidings

JFS
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Re: Triangular gauge use in building pointwork.

Postby JFS » Sun Jul 08, 2012 5:18 pm

Armchair Modeller wrote:Out of sheer curiosity, did their comments apply to modern pointwork, or pointwork in general, Jim?


And did they say why not to widen the gauge?


The issue with prototype track is that the check rails are spaced from the stock rails using spacer blocks - these ensure that the FLANGE WAY remains constant, fixed and immovable. Therefore, if gauge widening is introduced, then the CHECK GAUGE becomes incorrect. Since the most important dimension is the CHECK GAUGE then gauge widening is clearly a no-no.
The same would apply to model point work when using the Exactoscale check chairs. However, for people using soldered construction, it is fine to use gauge widening (given that we are trying to get pacifics through b6 turnouts!), PROVIDED the CHECK GAUGE remains accurate. (sorry for the caps, I am not shouting just making a distinction.
I think that the importance of the accuracy of the check gauge is too often underestimated - it is actually far more important than track gauge. With a mate of mine, we built his P4 layout more than forty years ago and the ONLY guage we used was the old Studiolith Check Gauge - and it did not go too badly considering it was built by two spotty teenagers!

The same strictures of course apply to switches - again, I feel that too many P4 derailments in this area are because the switch opening has been measured from the adjacent stock rail - fine unless the gauge is slightly wide - better to measure it from the opposite switch blade.

Hope that makes sense and is helpful.

Best Wishes,

Howard.

Armchair Modeller

Re: Triangular gauge use in building pointwork.

Postby Armchair Modeller » Sun Jul 08, 2012 5:39 pm

Thanks for that. I was really thinking about straight-cut point blades and the sharp bend in the diverging rail at the toe end of the turnout - characteristic of older pointwork. I seem to remember reading somewhere on here that you should widen the gauge slightly, as this bend effectively narrows the gauge. Apologies if I got the terminology wrong :shock:

allanferguson
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Re: Triangular gauge use in building pointwork.

Postby allanferguson » Sun Jul 08, 2012 5:43 pm

I would reinforce Keith's comments re prototype pointwork. But since we modellers usually set the check rail from the crossing rather than from the adjacent stock rail, a little bit of gauge widening in this area may be helpful, and is unlikely to be harmful, depending on the curve through the crossing.
However, at the switch end I have found gauge narrowing to be endemic; this is because we rarely get switch blades filed to the correct profile, we rarely get them to sit tightly against the stock rail, and we often don't put sufficient set in the curved stock rail to accommodate the width of the blades. To demonstrate this, since a triangular gauge is not very usable here anyway, take a pair of callipers and measure the actual gauge through the switch area. Then allow for the fact that, with straight cut switches (and how many of us accurately file curved switches?) you have a deflection at the switch equalling quite a sharp curve, which certainly would have gauge widening -- which is where I came in, I think!
One of the problems, I think, is that of all the jigs and gauges available to us, none is really suitable for measuring in the area of the switches; I have now taken to using callipers exclusively in this area.

Allan F

Armchair Modeller

Re: Triangular gauge use in building pointwork.

Postby Armchair Modeller » Sun Jul 08, 2012 5:54 pm

Thanks for describing things far more eloquently than I could ;) That is really helpful.

JFS
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Re: Triangular gauge use in building pointwork.

Postby JFS » Sun Jul 08, 2012 6:06 pm

Armchair Modeller wrote:I was really thinking about straight-cut point blades and the sharp bend in the diverging rail at the toe end of the turnout


Well, Richard, I suppose it depends at what level you are looking. At a micro level, if you think (for example) about GW switches, there is a significant (3/8" if I remember correctly) joggle on the diverging stock rail thus, if there were no gauge widening before the joggle then there must be 3/8" after it!!! Even where there is no joggle, there is - as you say a significant "set".
But at the more macro level, the stock rails would be held very accurately to gauge at the approach to the switch tips. At the heel end of the switches, the switch rails are again located off the stock rails by means of blocks or chairs, so again the opportunity for fiddling with gauge on the real thing is limited - you would be widening the gauge on both the straight and the curved roads. In model track, to me, there is no reason not to widen the gauge at the heel end of the switches, provided it is help accurately at the entry to the switches.

I have to be honest though, I have never owned a triangular gauge and I have never worried about gauge widening - there is already plenty of "slop" in P4 standards due to the under scale back to back. And my 28xx will - as you have seen - go round a highly illegal 1:6 slip on a curve!!!!

Best Wishes,

Howard

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Russ Elliott
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Re: Triangular gauge use in building pointwork.

Postby Russ Elliott » Sun Jul 08, 2012 6:08 pm

allanferguson wrote:One of the problems, I think, is that of all the jigs and gauges available to us, none is really suitable for measuring in the area of the switches; I have now taken to using callipers exclusively in this area.

Image

JFS
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Re: Triangular gauge use in building pointwork.

Postby JFS » Sun Jul 08, 2012 6:13 pm

Sorry, my post crossed Alan's and I would endorse everything he says. In fact, I would go further. the "classic" approach to building track involved fixing both stock rails then addining the switch rails. For the reasons Alan describes, this must result in a tight gauge. For that reason, I build the stock rail and the switch rail as a unit and gauge each off the other (as the prototype does).

I would add that the Exactoscale type gauge - which does not attempt to "grip" the rails - is the only one to use in this situation.

Howard.

Armchair Modeller

Re: Triangular gauge use in building pointwork.

Postby Armchair Modeller » Sun Jul 08, 2012 6:14 pm

Thanks Howard - and apologies to the OP for seemingly taking over the topic :? It just seemed very relevant as I am building a couple of turnouts at the moment. I now have answers to several issues that were beginning to worry me. I do not own a triangular gauge either, but there are alternative ways of widening the gauge, deliberate or otherwise!

JFS
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Re: Triangular gauge use in building pointwork.

Postby JFS » Sun Jul 08, 2012 6:15 pm

JFS wrote:Sorry, my post crossed Alan's and I would endorse everything he says. In fact, I would go further. the "classic" approach to building track involved fixing both stock rails then addining the switch rails. For the reasons Alan describes, this must result in a tight gauge. For that reason, I build the stock rail and the switch rail as a unit and gauge each off the other (as the prototype does).

I would add that the Exactoscale type gauge - which does not attempt to "grip" the rails - is the only one to use in this situation.

Howard.


...as Russ demonstrates!

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Martin Wynne
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Re: Triangular gauge use in building pointwork.

Postby Martin Wynne » Sun Jul 08, 2012 7:50 pm

JFS wrote:The issue with prototype track is that the check rails are spaced from the stock rails using spacer blocks - these ensure that the FLANGE WAY remains constant, fixed and immovable. Therefore, if gauge widening is introduced, then the CHECK GAUGE becomes incorrect. Since the most important dimension is the CHECK GAUGE then gauge widening is clearly a no-no.

Hi Howard,

The prototype used special check chairs when gauge-widening was required within pointwork.

p.56 of BRT3 says:

".. chairs are also made in a special form to hold check rails, and for these a letter C is added to the description of the chair. In addition check chairs of each type are made of different dimensions to give varying check flangeway clearances, and the width of the flangeway is also added to give the complete description of the check chair. Thus for track of 4'-8.1/2" gauge, the check chairs normally required would be known as CC-1.3/4" chairs, the 1.3/4" being the check flangeway clearance."

and on p.68:

"The normal flangeway of 1.3/4" must be increased by the same amount as the gauge is widened in order to maintain the dimension of 4'-6.3/4" between the bearing edge of the check rail and the running face of the high rail, and special check chairs or baseplates are used for this purpose."

So those using 3-point gauges for gauge-widening within pointwork can happily go on doing so, and ignore the gainsayers. Just remember to use the proper check gauge tool to set the check rails.

regards,

Martin.
40+ years developing Templot. And counting ...

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 8:07 pm

Hi Martin

Do either of those quotes relate to point work? They dont say

Cheers

Jim

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 8:10 pm

Armchair Modeller wrote:Out of sheer curiosity, did their comments apply to modern pointwork, or pointwork in general, Jim?


Depends on your term modern. I am usually interested in '80s practice but even then my layout is set a quarter of a century ago. Very modern point work looks a fair bit different to even then

Cheers

Jim

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Martin Wynne
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Re: Triangular gauge use in building pointwork.

Postby Martin Wynne » Sun Jul 08, 2012 8:16 pm

Hi Jim,

Prototype pointwork was rarely curved sharply enough to need gauge widening, and where it was so curved it was usually in yard areas used only by 4-wheel wagons and short-wheelbase shunting locomotives, which don't generally need gauge-widening.

Nevertheless, where gauge-widening was needed within pointwork, the necessary chairs and fittings were available to provide it.

The huge difference in ruling radius between the prototype and many models does mean that what was very uncommon on the prototype becomes the norm on a model.

The differences between present-day p.w. engineering and the traditional steam railway are so great that few remain to tell the tale. See this video for example:

http://85a.co.uk/forum/view_postx.php?post_id=13098

regards,

Martin.
40+ years developing Templot. And counting ...

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 8:41 pm

Would make sense that the check rails on curves (those about 8ft radius or less when scaled down) would be gauge widened and have a wider check gauge to suit.

Cheers

Jim

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Martin Wynne
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Re: Triangular gauge use in building pointwork.

Postby Martin Wynne » Sun Jul 08, 2012 8:47 pm

jim s-w wrote:have a wider check gauge to suit.


Hi Jim,

Nothing ever has a wider check gauge. A fixed check gauge is the fundamental requirement:
Image

check gauge A is critical

crossing flangeway B is important

track gauge C shouldn't be less than quoted

check rail flangeway D is don't care

regards,

Martin.
Last edited by Martin Wynne on Sun Jul 08, 2012 9:22 pm, edited 2 times in total.
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allanferguson
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Re: Triangular gauge use in building pointwork.

Postby allanferguson » Sun Jul 08, 2012 8:48 pm

I seem to remember that there was a previous discussion on this topic, during which I also forgot about the Exactoscale gauge; well, as somebody maybe said (I forget) "at my age I like to forget at least three things before breakfast"

My apologies. But I still feel happier using a calliper in that situation, which tells me exactly what gauge I've got, including whatever gauge widening I've chosen.

Allan F

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 9:23 pm

Are you sure Martin?

Think about it, on a tight check railed curve if the check gauge is the same as on a straight piece of track there would be no effective gauge widening at all and things would jam.

Cheers

Jim

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Martin Wynne
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Re: Triangular gauge use in building pointwork.

Postby Martin Wynne » Sun Jul 08, 2012 9:29 pm

jim s-w wrote:Are you sure Martin?

Yes I am sure Jim. I have edited my previous post to include a diagram. A is fixed. D is don't care (C minus A). Special check rail chairs are used on gauge-widened curves to allow D to be wider than normal (by the same amount as the gauge-widening).

regards,

Martin.
Last edited by Martin Wynne on Sun Jul 08, 2012 9:33 pm, edited 1 time in total.
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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 9:32 pm

I just can't see how a curve will work Martin. I'll ask a few of my contacts

Cheers

Jim

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Martin Wynne
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Re: Triangular gauge use in building pointwork.

Postby Martin Wynne » Sun Jul 08, 2012 9:42 pm

jim s-w wrote:I'll ask a few of my contacts

Hi Jim,

Ask away, but you will get the same answer -- see my previous quote from BRT:

"The normal flangeway of 1.3/4" must be increased by the same amount as the gauge is widened in order to maintain the dimension of 4'-6.3/4" between the bearing edge of the check rail and the running face of the high rail, and special check chairs or baseplates are used for this purpose."

That dimension is the check gauge, and it doesn't ever change.

I think we must be at cross purposes somewhere, otherwise I don't understand how you could have built New Street to work. :?

regards,

Martin.
40+ years developing Templot. And counting ...

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jim s-w
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Re: Triangular gauge use in building pointwork.

Postby jim s-w » Sun Jul 08, 2012 9:48 pm

I don't have any check railed curves (will just a little one) but as stated earlier I havent used gauge widening.

Cheers

Jim


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