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topic: 1256Two A7 turnouts, both straight, but different minimum radii
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posted: 29 Sep 2010 20:12

from:

Richard Spratt
 
Stockton-upon-Tees - United Kingdom

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the two turnouts in the box file are part of a fiddleyard.  Both are A7s, both are straight, one LH, one RH, but the RH has a minimum radius of 1919mm and the LH is 1770mm.  What's different?  Am I mad?  But they ought to be the same?
Attachment: attach_892_1256_different_radii_10_09_29_2008_05.box 329

posted: 29 Sep 2010 20:42

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Martin Wynne
 
West Of The Severn - United Kingdom

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Richard Spratt wrote:
the two turnouts in the box file are part of a fiddleyard.  Both are A7s, both are straight, one LH, one RH, but the RH has a minimum radius of 1919mm and the LH is 1770mm.  What's different?  Am I mad?  But they ought to be the same?
Hi Richard,

One has a generic type of V-crossing and the other has a regular type of V-crossing:


gen_xing.gifgen_xing.gif


reg_xing.gifreg_xing.gif


Full details at:

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

regards,

Martin.

posted: 10 Oct 2010 22:15

from:

Richard Spratt
 
Stockton-upon-Tees - United Kingdom

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I'd guessed it was something to do with the crossing.  But what I don't understand is that I made both templates one after the other by inserting them into previously drawn straight templates and they got different crossing types?

posted: 9 Feb 2011 07:46

from:

Gordon S
 
 

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Whilst searching for the answer, I came across this and am unsure if this is the same process.

If I take a 1000mm radius circle and insert a turnout, the radius comes out at 1000mm as you would expect.  The turnout is an A5.

However, if I now draw a straight line which is tangental to the 1000mm circle and then insert a turnout in the straight line, once it is aligned perfectly with the 1000mm curve, it shows the same A5 turnout but now it shows the radius as 597mm and not the 1000mm it should be.

Not a big issue, but my curiousity got the better of me....:)


Edit:  Just printed out the data and both have a 1 in 5.00 RAM regular crossing.  (1 in 5.05 CLM)

The only real difference I can see is the one inserted in the circle says the total angular swing on this template is 0 degrees, whilst the one inserted in the straight says the the total angular swing on this template = [-13.22] degrees ([-1 in 4.26] RAM) (in main road)
Last edited on 9 Feb 2011 07:59 by Gordon S
posted: 9 Feb 2011 08:44

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Gordon,

The radius showing as "minimum radius now" is the smallest radius anywhere in the template.

For a straight A-5 turnout in 00-SF with a regular V-crossing, the smallest radius is 597mm (to the track centre-line) -- as you would expect, it's in the diverging turnout radius between the heel of the switch and the V-crossing.

When inserted in a 1000mm ruling curve, diverging to the outside of the curve, the resultant diverging turnout radius in such a situation is actually greater than that at 1484mm. The smaller radius of the two is in the main road at 1000mm, so Templot shows that as the "minimum radius now".

That's actually a very ugly turnout. :(

If it is not part of a crossover it can be much improved by changing to a curviform V-crossing instead of regular, which increases the turnout radius to 2510mm.

Changing to a 9ft switch instead of an A switch is a further improvement, and the turnout radius is then 3635mm -- more than double the original 1484mm. :)

regards,

Martin.

posted: 9 Feb 2011 08:55

from:

Gordon S
 
 

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Martin Wynne wrote:
That's actually a very ugly turnout. :(
It's OK Martin, I was just experimenting with the idea of having a 2m diameter circle and using it as a 'double reverse loop' with tracks joining on a tangent either side of the circle.  Thanks for the suggestion of a different turnout shape.  I just used what the software threw at me.  I'll have to do some more investigation into turnout types....

Thanks as always..:)

PS.  I never thought for one minute there was a flaw in the software.  You're far too good for that...:cool:



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