Templot Club Archive 2007-2020                             

topic: 3812Transition links
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posted: 10 Nov 2020 08:06

from:

Graham Long
 
 

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Hi
I have grappling with transition links. I have sucessfully produced an easement. I how want to link a transition between to plain track templates. I.e. I want to produced a link between a 1400mm radius plain track and a 2500 plain track. I have tried to follow Martin's video but it is linking two turnout templates. Do I have to make both templates turnouts to link them and then make them plain track again after having done so? So far I have made one of the templates a turnout and split off the approach road, but I am not clear on how to make this a dummy template as described. Then you are required to make a branch line from the other template. However, I think I would have to make this a turnout template as well. Could anybody clarify this for me.

Thanks

posted: 10 Nov 2020 11:15

from:

Godfrey Earnshaw
 
Crawley - United Kingdom

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Hi, Graham
I believe it is impossible to resolve your problem, we don't know the relative positions.

As martin keeps repeating submit a box file.

posted: 10 Nov 2020 13:40

from:

Martin Wynne
 
West Of The Severn - United Kingdom

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Hi Graham,

Info about transition curves is here:

 http://templot.com/companion/transition_curves.php

Transition curves can be used with any templates, plain track or turnouts. In the case of a turnout the transition applies along the main-road.

The make transition link function can create a transition curve between any two templates, but only provided several conditions are met. These conditions are not arbitrary limitations imposed by Templot, they result from the mathematics of a clothoid curve (Euler's Spiral): 

1. the templates must not be concentric (parallel). So for example it is not possible to create a transition between the inner and outer tracks in curved double track. Use a slew for that instead, or a simple link.

2. in a C-curve transition there must be a significant difference in radius between the two templates. Significant means more than a few mm. Otherwise you will get at best a wiggly transition curve, or at worst the infamous "matchsticks and broken glass" effect across the entire screen. :shock:

(For S-curve transitions the radii can be equal.)

This also means that it is not possible to create a transition curve between two straight templates. Only one of them can be straight. Insert a third curved template between them, and make two transition links to/from it.

3. most important, the two curves must not intersect (cross over). Even if extended to a full circle, they must still not intersect. This is the usual cause of problems using transition curves.

Here for example at first sight it seems reasonable to want a transition link between these two curves:

2_100824_210000000.png2_100824_210000000.png


But when the curves are extended, it becomes clear that they intersect (black lines):

2_100825_400000000.png2_100825_400000000.png

Which means a transition curve between them is mathematically impossible.

The solution is to adjust the radius of one or both of the curves, or move the templates, until the curves do not intersect. For example as the white line, when the radius was reduced from 1400mm to 1318mm.

To see if they intersect, you can simply extend the length of the template (F4) because it is very likely a dummy template which is going to be discarded and replaced with the transition curve template.

If you post a screenshot or box file of your problem, I will make a video clip showing how to resolve it.

cheers,

Martin.

posted: 10 Nov 2020 13:46

from:

Graham Long
 
 

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Thanks for replies. I will have another go tommorow. It is late at night now.
best wishes

posted: 11 Nov 2020 13:16

from:

Graham Long
 
 

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Thanks. I now understand.

Regards
Graham



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