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| Dawlish Warren up loop 17/08/2016 at 19:29 #84137 | |
PeterDa
12 posts |
If I signal a stopping train (2F11) into the up loop (signal E21 to E123), I cannot signal the following express (1A84) through on the main line (signal E21 to E23) because of a message "No overlap available". Am I doing something wrong?
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| Dawlish Warren up loop 17/08/2016 at 19:59 #84138 | |
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WinsfordSaltMine
124 posts |
The overlap is the route that is left in till the train stops at the station, once the train comes to a halt you will be able to set the route on the UM.
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| Dawlish Warren up loop 17/08/2016 at 20:16 #84139 | |
Peter Bennet
5402 posts 
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There's a bit about overlaps here. Peter I identify as half man half biscuit - crumbs! Log in to reply The following user said thank you: PeterDa |
| Dawlish Warren up loop 17/08/2016 at 20:57 #84140 | |
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Danny252
1461 posts |
" said:once the train comes to a halt you will be able to set the route on the UM.Well, once the interlocking thinks the train has come to a halt. Log in to reply |
| Dawlish Warren up loop 17/08/2016 at 21:42 #84141 | |
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Stephen Fulcher
2078 posts |
That's pedantry at its best there Danny! PeterDa, basically a distance beyond a stop signal at red is effectively "reserved" in case that signal is passed at danger. The standard distance is 183 metres. In that distance beyond the signal, all trailing points will need to be set correctly, and all track circuits clear before the signal approaching the one that is at red can clear. Level crossings do not generally have to be down and clear. This is shown in SimSig by the white route "lights" being extended beyond the signal that the route is set upto. Obviously you do not want the overlap to be left there for all time in this instance, you need to be able to release it so that you can bring a train into the platform, and then pass one by on the main line like you are trying to do here. What happens in this case is a timer is provided on the last track circuit before the red signal, and the overlap will be released by the interlocking once that timer has run its course. The timer is set at the design stage to a time that it is considered that a train can be assumed to have stopped at the red signal. This is a technical exercise that will take into consideration the length of the track circuit being timed, the line speed, gradients and anything else considered relevant. This timer is set on the cautious side, so if you were watching both the panel and the train at the same time, it is likely the train will stop before the overlap drops out. Interlockings do not think, they are in the case of Dawlish Warren Interlocking, a BR Western Region E10k type Route Relay Interlocking, which are wired for each function to work as designed, but nothing more. Modern-day interlockings tend to be computer-based, but the principle is the same, they process inputs to give the desired outputs. The overlap is simply released when the train can be assumed to be at a stand based on the criteria set out by the designer. Log in to reply The following users said thank you: Richard42, postal, flabberdacks |
| Dawlish Warren up loop 17/08/2016 at 22:21 #84142 | |
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Danny252
1461 posts |
I had considered going into timers and whatnot, but thought that would be overly pedantic - but it seems all I had to do was tempt someone else to do it for me!
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