Templot Club Archive 2007-2020                             

topic: 95Straight crossings on GWR
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posted: 23 Jun 2007 04:46

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Templot User
 
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I am planning a new layout in P4 and am trying to do so using Templot. My period is GWR in 1910 and I am using curved loose-heel switches and straight crossings. I can see that Templot produces straight crossings when the main closure rails are straight, but can find no way to keep the crossings straight when the closure rails curve. The GWR supplied standard crossings as a unit and as far as I can see only produced curved crossings as 'specials'.


posted: 23 Jun 2007 05:43

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Templot User wrote:
I am planning a new layout in P4 and am trying to do so using Templot. My period is GWR in 1910 and I am using curved loose-heel switches and straight crossings.
If you are modelling GWR track David Smith's book is essential reading:

GWR_Track_200px.jpgGWR_Track_200px.jpg

Available from Great Western Study Group.
I can see that Templot produces straight crossings when the main closure rails are straight, but can find no way to keep the crossings straight when the closure rails curve. The GWR supplied standard crossings as a unit and as far as I can see only produced curved crossings as 'specials'.
This is a common misunderstanding which keeps cropping up. Where a V-crossing is laid in a curved running line it is normally either supplied ready curved, or curved on site to match the ruling radius in the main road (as far as this is practical within the physical limits of the components).

There is a long discussion about this on page 31 of the above book, but the essential conclusion is "In a curved turnout of similar or contrary flexure the two legs of the vee were curved during manufacture as required and specified by the designer."

In a curved turnout, Templot by default runs the ruling curve through the V-crossing (and likewise through the switch). If you want to change this behaviour you have two options:

1. Place the turnout in a transition curve template -- set a zero-length easement to straight at the position of the wing-front rail joints (geometry > transition curve > menu items).

2. Create the turnout as two partial templates:
Start with a straight turnout. Blank it up to the wing-front rail joints (CTRL-F3 mouse action or do > blank up to V-crossing menu item) and store it on the background. Now cancel the blanking, and shorten the turnout (F4 mouse action) to just clear the stored one, put the peg on CTRL-9, and curve it (F6 mouse action) as required. Store and background again.
Method 1 is simple and quick. Method 2 is better if you want to create a crossover, or if the template already has a transition curve in it somewhere else.

However you should have a good reason for doing either of the above. You will obtain much neater looking track (and smoother running for the passengers!) if you flow curves through the crossings in the prototype fashion. In the case of contraflexure (negative curving), change to a curviform type of V-crossing unless the turnout is part of a crossover.

regards,

Martin.



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