Hi Friends
I have a question about designing turnouts on an spiral / transition curve with cant applied.
We have a case where we need to replace 2 turnouts and a connection, with 2 new turnouts and a connection. We can't move the turnouts location or change the design of the maintracks so we can't place the turnouts in a curve or on straight track.
It looks like the attached file with a grayscaled map behind. It is the turnout 05a and 05b we have problems with.
The Curve (red line) is radii 800 m with a cant of 125 and 140. Length of the transition curve (blue line) is 85 and 95 m. Green line is straight track.
One problem is that the transition curve has an different radii throughout the length of it - So what is the radii of the turnout foot?
And when we have 2 turnouts with one bench inside and another outside - how can we calculate the connection between these?
In BRT we can place the turnout on the spiral, but we cant use the Create Connection function. If we use the Connection Editor can we then trust the result?
Do anyone have any experience with the same problem we have? Please share.
Kind Regards
Martin Laursen
MANL@ramboll.com
Phone: +45 5161 7749
Yes, it will be much easier to maintain in the future.
When we move the transition to a straight then signaling and other needs to be moved - and the economy department says no for this...
Good decision - you remove cant issues from the task. You still have curvature and non-parallelity problems. Can't the turnouts be moved onto straight tracks (at least one oft them)?
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Thanks - We know that it isn't easy and we are not shure that BRT will calculate it correctly.
Today we (human people) basically dont calculate but trust the program to do everything for us - and that is my concern. 4x4=20...? OK... ;)
We were also concerned about construction of the turnouts and if the contractor could place it correctly.
So we have convinced the client to move both turnouts to a curve - much easier :)
But thanks for your answer.
It is not an easy task, especially when tracks are so close and not parallel. You have to place one turnout at start of one transition (turnout radius will be 265.2 m) and another one on second transition at the back position (turnout radius about 330 m). Both turnout radii are reversed to each other. Can they be connected with one piece of straight tangent to every curve? Good question and the answer probably is "no". But there should be a straight almost tangent to both curves. You need to check it in BRT by adding a straight after every turnout and checking angles manually. I think you can trust BRT.
Yes, and I know that this existing track solution is a huge problem when we design the track. The turnouts are from a time without computers and they just placed the turnouts doing the build.
1: The Turnouts are 1:9, 40 km/t
2: CL to CL is about 4.5 m
3: speed in transition is 40 km/t. The speed in the maintracks is 160 km/t
4: 3 grade parable
Since we don't have the track CL distance to place several different elements, I don't belive that there is a solution without having an alignment with a difficult geometry.
The cant is also a problem because it changes throughout the length of the turnout.