Templot Club Archive 2007-2020
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posted: 27 Jan 2016 01:55 from: Martin Wynne
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In some circumstances the dimension showing for the "smallest radius now" on a template (and possibly the flashing red warning) can be misleading. For example, suppose you have:
2_260848_580000000.png  Notice that the smallest radius is showing as 1052mm. This is the radius in the turnout road between the heel of the switch and the V-crossing. Now we apply some contraflexure: 2_260848_580000001.png  With the expected result that the turnout radius is eased, in this case to 1739mm. But now we decide that we want a "straight-over-straight" V-crossing instead of the curved V-crossing, so we insert a zero-length easement to straight transition at the end of the turnout curve: 2_260848_580000002.png  With the mysterious result that the smallest radius is back to showing 1052mm, despite there being no obvious change in the radius of the turnout. Zooming in we can see what is happening. There is indeed a short length of 1052mm curve, and Templot is correctly reporting it as the smallest radius on the template: 2_260848_580000003.png  The rail over the very short red section between the end of the transition zone and the end of the turnout curve is curved at 1052mm radius, because at that point the main road is beyond the transition zone and therefore straight. Corresponding to the very same section of rail in the first screenshot above. In practice of course such a short section of curve has no practical effect and it would not be possible to model it as such. But seeing the figure on the screen could be alarming when designing the track if you are not aware of what is happening. In the next program update I have changed the Templot code to ignore the radius calculations at the ends of the turnout curve section if they are close to a very short transition curve. But it is not possible to cater for every situation which might arise, so it's as well to be aware of the above effect. regards, Martin. |
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