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topic: 265800-SF minimum radius and gauge widening questions
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posted: 26 Mar 2015 22:00

from:

madscientist
 
 

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Hi folks, some questions for some experienced builders

Two Questions

If , due to space constraints , I'm pushing the radius , especially on crossovers to reduce the length of the total setup.

1.
Do I consider gauge widening the flange way gap , or it's it only the stock rail that gets this treatment. Or it not the flange way do I consider reducing the check rail to wing rail dimension


2. What's the best combination of point design that gives me the most constrained crossover length, with the best radius.

Thanks

Dave
Last edited on 26 Mar 2015 22:01 by madscientist
posted: 26 Mar 2015 23:20

from:

Hayfield
 
United Kingdom

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Dave

The gauge widening is on the stock rail, the flange way gap remains 1 mm and the check rail also stays exactly the same as it is set with the check rail gauge

posted: 27 Mar 2015 00:24

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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madscientist wrote:
Do I consider gauge widening the flange way gap , or it's it only the stock rail that gets this treatment. Or it not the flange way do I consider reducing the check rail to wing rail dimension
Hi Dave,

This is why I sometimes think I'm wasting my time writing tutorials and docs. No-one ever reads them. I have posted the following dozens of times on RMweb and here, most recently only yesterday on RMweb. :)



The check gauge is constant. For 00-SF (and 00-BF) it is always 15.2mm. Check gauge tools for setting this are available from C&L.

Consequently if there is gauge-widening on sharp curves, the check rail gap increases by the same amount as the gauge-widening. This is true for all gauges and scales, always has been, and is also the case for the prototype -- special widened check rail chairs are made for use where there is gauge widening.

Here's a diagram:
2_010658_360000000.gif2_010658_360000000.gif
 
A is the check gauge. It is the most critical dimension in pointwork. If this dimension is too small, wheels running from left to right can hit the nose of the vee and very likely derail, or at least bump. If this dimension is too large, the wheel backs will bind or jam on the check rail. To make sure it's correct, the check rail is set using check gauge tools. For 00-SF and 00-BF this dimension should be 15.2mm. You can use the same check gauge tools for both these standards (they are both running the same wheels).

B is the crossing flangeway gap. It's also important. If this dimension is too small, the wheel backs will bind or jam on the wing rail. If this dimension is too large, the gap in front of the nose of the vee will be too wide, and the wheels may drop into it with a bump. This gap is set using a small piece of metal shim called a crossing flangeway gauge shim. For 00-SF it should be 1.0mm thick. For 00-BF it should be 1.3mm thick.

C is the track gauge. It shouldn't be less than the specified dimension, but it can be wider. It is often widened on sharply curved track to ease the running of long-wheelbase vehicles. The track gauge is normally set using roller gauge tools, or alternatively using a 3-point gauge tool, which automatically widens the track gauge on sharp curves. For 00-SF this dimension shouldn't be less than 16.2mm. For 00-BF it is normally 16.5mm.

D is the check rail gap. The width of this gap doesn't matter a damn, providing it is wider than the wheel flanges. It's whatever you end up with after setting A and C correctly.

But where the check rail is combined with a wing rail in complex formations (i.e. in parallel-wing V-crossings) D must be the same as B. Consequently in such complex formations gauge-widening is not possible.



I have written this stuff so many times now that I'm weary of it, and I think from now on I shall concentrate on software questions and leave trackbuilding topics to someone else.

regards,

Martin.


posted: 27 Mar 2015 03:36

from:

madscientist
 
 

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Thanks Martin. I appreciate your reply, I have seen that post several times , but wanted to make sure.

My second question. Was actually more interesting to me.

I read one of your posts where you suggested 9 ft points as opposed to ' A' and curvi-form crossings , yet I read another where you stated not to use curvi form on crossings

Dave

posted: 27 Mar 2015 08:09

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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madscientist wrote:
2. What's the best combination of turnout design that gives me the most constrained crossover length, with the best radius.
I read one of your posts where you suggested 9 ft points as opposed to ' A' and curvi-form crossings, yet I read another where you stated not to use curvi form on crossovers
Hi Dave,

This is one of those "lengths of string" questions where everything depends on what rolling stock you will be running, and any curving through the crossover.

For bogie passenger stock, minimizing the reverse curve in the centre of a crossover is important to avoid excessive end-throw at the corridor connections and possible buffer-locking. You can reduce end-throw by:

1. using a regular type V-crossing to increase the length of straight between the reverse curves.

2. placing the crossover on a significant curve, so that there is no reverse of curvature through the crossover road. You can then use any type of V-crossing.

3. using a flatter V-crossing angle.

Here is a screenshot showing how at significant curving, there is no reverse curve for stock traversing the crossover road. This is a B-8 crossover in 00-SF:

2_270246_040000000.png2_270246_040000000.png

You can see that in this case there is no reverse curve anywhere in this formation, all curving is in the same direction. The diverging turnout radius for the inner turnout is showing negative, i.e. it is curving in the same direction as the main road. To see that more clearly I have added a straight red line on this template print:

2_270251_030000000.png2_270251_030000000.png

With no reverse curve you can safely use any type of V-crossing for such a crossover. Here I used generic V-crossings. That lengthens the turnouts, making an easier radius in the outer turnout.

For a smaller shunting layout, or in goods yards etc. where bogie passenger vehicles won't be running, usually you want the crossover to be as short as possible, and reverse-curve effects may not matter so much. Generally it is then better not to use the REA switches, but change to older pattern loose-heel switches. For example using a 9ft straight switch instead of an "A" switch, or a 12ft straight switch instead of a "B". There is a bigger range of options in the GWR-pattern loose-heel switches. Or of course for a specific prototype you can create a custom switch of any design.

If you post your .box file here it will be easier to make suggestions based on your specific case.

More about types of V-crossing:

 http://templot.com/martweb/gs_realtrack.htm#xing_types

More about the effects of using curviform V-crossings (called "curved" on this very old page):

 http://templot.com/martweb/tut5e.htm

regards,

Martin.

posted: 27 Mar 2015 08:34

from:

Hayfield
 
United Kingdom

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Martin

Your answers are not in vain, which is shown by how quickly C&L have run out of 00sf track gauges. One problem is how different folk search for answers, put in the right words, most times you get what you are after, get one of the words wrong and you may not

Also sometimes (especially with us older folk) things stick others don't. Slide through peg I am always looking up for example. Then there are those who are new to what they are looking for, or just need a double check for reassurance.

We all are very grateful for your assistance. Perhaps an additional section or forum for frequently asked questions. Encourage the owner of the 00sf website to add a few more pages etc may help

posted: 27 Mar 2015 09:26

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hayfield wrote:
Encourage the owner of the 00sf website to add a few more pages etc may help
Hi John,

:)  I'm the owner of the 00-SF web site:  http://00-sf.org.uk

Rodney Hills owns the 00-SF Yahoo Group: http://groups.yahoo.com/neo/groups/00-SF/info

Yesterday I came across some old paperwork for my trade stand at the Gauge 0 Guild show at Telford 1998. That was the first time I started selling Templot. That's 17 years ago now, and it soon became clear that not only did I have to explain the software, but also the basics of building model track. Not something I ever expected or wanted to do. I have written the same stuff over and over again so many times now, that I'm weary of it.

I'm happy to go on developing the Templot software and explaining it, it still interests me and I'm coding at present. But not trackbuilding methods and techniques. I spent 10 years doing that commercially, but it was a long time ago now -- over 40 years since I started. Hundreds of other modellers are building track and competent to explain it, so over to someone else.

Derek Genzel's original 1970s articles are still a good read:
 
 http://scalefour.org/members/digests/dl.php?f=62-0v1-2.pdf

 http://scalefour.org/members/digests/dl.php?f=23-0.pdf

 http://scalefour.org/members/digests/dl.php?f=21-0.pdf

And from Tony Wilkins:

 http://scalefour.org/members/digests/dl.php?f=23-6-1v2.pdf

 http://scalefour.org/members/digests/dl.php?f=23-6-2v2.pdf

 http://scalefour.org/members/digests/dl.php?f=23-6-3.pdf

regards,

Martin.

posted: 27 Mar 2015 11:37

from:

madscientist
 
 

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Thanks Martin, keep the faith , there cant be too many more that you have to convert !.



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