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| Thingley Junction problem 22/02/2010 at 15:18 #755 | |
jrr
95 posts |
Running Westbury Diversion mayhem 6Z10 has come down from Chippenham to Thingley junction without a slot! F2 confirms it is at signal SN74. How? TEXT Log in to reply |
| Thingley Junction problem 22/02/2010 at 15:18 #6870 | |
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jrr
95 posts |
Running Westbury Diversion mayhem 6Z10 has come down from Chippenham to Thingley junction without a slot! F2 confirms it is at signal SN74. How? TEXT Log in to reply |
| Thingley Junction problem 22/02/2010 at 18:50 #6881 | |
Peter Bennet
5360 posts |
The Slot controls SN47 so is correct. However if I recall correctly there is a problem in that a train sitting at SN74 blockes the exit of an UP train. This has been cured in the next iteration by allowing UP trains to fall off earlier. Sorry about that. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Thingley Junction problem 01/04/2010 at 00:30 #8030 | |
mobster
8 posts |
Peter Hi, apologies I have been struggling with this and don’t really understand the response (old age, too much beer, not enough beer, get a life etc !), I have a background in control engineering and am interested in interlocking and wondered if you could throw light upon the arrangement. SN27> SN29> Up Chippenham ---------------------------------------------------- / Down Bath --------------------------------------------------- / <SN74 <SN72 / SN11> / Up> / Down < Melksham ---------- I can see the final turnout to the Melksham line is controlled from SN74 and is reliant on the slot request. The junction allowing access to the up Chippenham is controlled by SN29 (up) and policed by SN72 (down). If you are routing a down train through Melksham and allow it past SN72 you block the up Melksham which needs the crossover between SN74 and SN72 to gain the up Chippenham. Surely the interlocking is arranged to make trains wanting the Melksham slot stop at SN72 and only proceed if the onward route from SN74 is set for the branch i.e the slot has been given. Conversely trains requiring down Bath only get SN72 if SN74 is set for Bath. You may have implied this but the phrase falling off earlier is the one I don’t really understand as the offending trains come to a stand at SN74 which blocks the junction. Regards Log in to reply |
| Thingley Junction problem 01/04/2010 at 06:07 #8034 | |
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Peter Bennet
5360 posts |
Essentially you are correct in your analyses- the iteration you have allows Down trains to hove up to SN74 and thereby lock up the branch exit. There were a couple of elements to the solution as there were a few errors found (can't remeber what they all were) but the specific 'fall off'' one you query is a SimSig term for the train leaving the Sim. In your iteration the 'fall off' point is somewhere beyond SN74- so clearly it would never get there if a train was at SN74- so to aleviate the problem the trains now 'fall-off'' earlier infront of SN74 (or is behind?). Either way the lock-up problem is resolved. Remember this is out of your control area so the exact operation is not necessarily accurate but representative (in fact in the Sim it's just a single track right back to Wootton Bassett with no points (see below). #2 #1 Where 1 is the old fall-off point and 2 the new (roughly) Down Bath T-------------------T----------------------------------------------------------------------------------------------------------------------- Wootton B / <SN74 <SN72 / SN11> / Up> / Down < Melksham ---------- Hope that helps. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Thingley Junction problem 01/04/2010 at 09:58 #8039 | |
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mobster
8 posts |
Thanks Peter understood
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| Thingley Junction problem 01/04/2010 at 10:33 #8043 | |
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Peter Bennet
5360 posts |
Sorry, just seen that the plan I drew went all wrong- never mind you understood! Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Thingley Junction problem 01/04/2010 at 10:40 #8045 | |
GeoffM
6282 posts 
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mobster said:Surely the interlocking is arranged to make trains wanting the Melksham slot stop at SN72 and only proceed if the onward route from SN74 is set for the branch i.e the slot has been given. Conversely trains requiring down Bath only get SN72 if SN74 is set for Bath.No, because the interlocking doesn't know which way the train is going. It would be quite legitimate for a Bristol train to be held at SN74 so there isn't any way for SN72 to be held at red without affecting both routes adversely. Instead it is up to the signaler to prevent such situations happening (and there are plenty of real-world examples where they haven't!). SimSig Boss Log in to reply |
| Thingley Junction problem 01/04/2010 at 18:54 #8064 | |
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mobster
8 posts |
Thanks for the clarification Geoff.
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