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| Signalling arrangements on the down main at Wem 13/11/2016 at 14:29 #87317 | |
TUT
507 posts |
I'm interested in the signalling practices on the down main at Wem when the area was worked by absolute block, prior to resignalling, as simulated in the Shrewsbury sim. At Wem, the down section signal WM32 was a 2-aspect colour light and the down home, WM33, was a 3-aspect colour light, with WM33R in rear of it - a 2-aspect colour light. What I don't quite understand is the rules for clearing WM33. In the sim, of course, you can clear it whenever you like, even if WM32 is on. Since there was a repeater, WM33R, instead of a traditional distant an approaching train would encounter green on WM33R, yellow on WM33 and red on WM32. Which is fine, but WM33 was not that far from WM32 - surely not full braking distance for a freight train. In traditional practice, you would of course have to bring a train nearly to a stand at WM33 and only then clear it up to WM32. The distant would of course be on. Were the traditional rules in force at Wem? That would make sense, but then it becomes harder to understand why a traditional distant worked from a separate lever was not retained (as was the case at Harlescott Crossing). It is evident that at some point the signalling at Wem was consciously altered to work WM33R from the same lever as the down home. And I don't really understand this? Was it possible to pull of WM33 for an approaching train, even with WM32 on, under certain conditions? Maybe for passenger trains with better stopping distances? Log in to reply |
| Signalling arrangements on the down main at Wem 13/11/2016 at 15:49 #87319 | |
headshot119
4869 posts |
I've had a flick through my notes from when I made the simulation. There's nothing specific in any of the instructions about bringing trains to a stand at 33 before clearing it towards 32 at danger. What I am wondering is if the aspect sequence chart I have is wrong. and 33R should only clear green if 33 and 32 are off. "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| Signalling arrangements on the down main at Wem 13/11/2016 at 16:27 #87320 | |
Andrew G
548 posts |
headshot119 in post 87319 said:I've had a flick through my notes from when I made the simulation. There's nothing specific in any of the instructions about bringing trains to a stand at 33 before clearing it towards 32 at danger.Or might 33 be approach controlled? Log in to reply |
| Signalling arrangements on the down main at Wem 13/11/2016 at 16:40 #87321 | |
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headshot119
4869 posts |
Andrew G in post 87320 said:headshot119 in post 87319 said:Quite possible, I've got someone looking into whether or not it does.I've had a flick through my notes from when I made the simulation. There's nothing specific in any of the instructions about bringing trains to a stand at 33 before clearing it towards 32 at danger.Or might 33 be approach controlled? "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| Signalling arrangements on the down main at Wem 13/11/2016 at 16:47 #87322 | |
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TUT
507 posts |
headshot119 in post 87321 said:Andrew G in post 87320 said:Thank you very much, it's an interesting one thisheadshot119 in post 87319 said:Quite possible, I've got someone looking into whether or not it does.I've had a flick through my notes from when I made the simulation. There's nothing specific in any of the instructions about bringing trains to a stand at 33 before clearing it towards 32 at danger.Or might 33 be approach controlled? 
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| Signalling arrangements on the down main at Wem 13/11/2016 at 16:51 #87323 | |
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headshot119
4869 posts |
TUT in post 87322 said:headshot119 in post 87321 said:Thank you for bringing it up, sometimes you get so used to how it works in the sim you just don't question why it's like that!Andrew G in post 87320 said:Thank you very much, it's an interesting one this :)headshot119 in post 87319 said:Quite possible, I've got someone looking into whether or not it does.I've had a flick through my notes from when I made the simulation. There's nothing specific in any of the instructions about bringing trains to a stand at 33 before clearing it towards 32 at danger.Or might 33 be approach controlled? "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| Signalling arrangements on the down main at Wem 26/05/2018 at 23:04 #108277 | |
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TUT
507 posts |
Some time ago I asked about the signal sequence on the down main at Wem. In light of this thread, I am quite keen to revisit the topic. On the down main at Wem were three colour lights. 2-aspect colour light distant WM33R, 3-aspect colour light home WM33 and 2-aspect colour light starter WM32. To be honest, I still don't feel I know how these and other, similar installations worked. There was some suggestion back in 2016 that WM33 was approach controlled. So how would that work? Say the section to Prees was occupied and WM32 could not be cleared, but we could still accept a train from Harlescott Crossing and bring it in to Wem station. Would we reverse 33 lever and then presumably it would be approach controlled so WM33R would be at caution and then WM33 would be at danger, but would step up to a single yellow as the train occupied T.11 track circuit? What about if, instead, we were able to clear WM32 with the train approaching, before it had reached WM33? Presumably WM33 would instantly clear to green (and so would WM33R if the train had not yet passed it). Presumably, if, on the other hand, we could clear all the signals, we would reverse 33 lever and then 32 lever and WM33R and WM33 would both clear immediately to green when WM32 cleared? Or was there no approach control and was it up to the signalman not to reverse 33 lever until the train was at, or nearly at a stand at WM33 signal? Or? Was none of this required? Was there full braking distance between WM33 and WM32. I ran the sim to see how it handled. I cleared WM33 which cleared straight away to a single yellow on the game and WM33R cleared to green. I then watched a freight train brake from 60 mph on F2. It began braking presumably when WM33 signal was sighted at yellow and it did stop with a nice steady rate of deceleration. It even went from 30 to 31 before braking back down to a stop at WM32. So in the sim it does seem like maybe 33 lever can be reversed with 32 normal and WM33 will clear to single yellow and there does seem to be sufficient braking distance according to the sim. But in real life, I watched the Video125 driver's eye view video of the area and it takes the Class 175 just 16 seconds to cover the distance. I would guess it was doing 70 mph? I think that's maximum line speed there, so that makes for a distance of approximately 500 metres between WM33 and WM32, which doesn't seem enough somehow. Log in to reply |
| Signalling arrangements on the down main at Wem 27/05/2018 at 10:31 #108286 | |
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Late Turn
696 posts 
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I don't know what the arrangements were at Wem, but I can give some of the detail of a couple of similar installations albeit on a different region. At Ketton, there's a 2-aspect colour-light distant (16R), a 3-aspect colour-light home (16) and a semaphore section signal (14), with much less than braking distance from 16 to 14, so not at all dissimilar to Wem. My recollection is that 16 was approach controlled with 14 at danger - you could reverse the lever, but the signal wouldn't come off (to a yellow) until the berth track occupied. Obviously, as a result, 16R wouldn't come off until both 16 and 14 were off. Ashwell is slightly different - a 2-aspect colour-light distant (1), a 3-aspect colour-light home (2) and a colour-light section signal (3) also acting as the IB distant, again without braking distance from 2 to 3. I'm sure that you could clear 2 (to a yellow) at any time with 3 at danger, but you certainly couldn't get 1 off until both 2 and 3 were off (enforced by, at least, the mechanical locking). Melton *does* have braking distance from the 3-aspect colour-light home signal (31) to the semaphore second home (30) with semaphore section signal (28) in advance, so 31R will clear as soon as 31 is cleared to a yellow, 31 then stepping up to green automatically when both 30 and 28 are cleared. Whatever happens at Wem, the distant certainly shouldn't come off to a green with the section signal at danger *if* there's not full braking distance from the home to the section signal. Log in to reply The following user said thank you: TUT |
| Signalling arrangements on the down main at Wem 27/05/2018 at 11:07 #108288 | |
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TUT
507 posts |
Late Turn in post 108286 said:I don't know what the arrangements were at Wem, but I can give some of the detail of a couple of similar installations albeit on a different region.This is really useful, thanks! The numbering makes me think this is likely to be a case of an approach controlled home signal. I suppose this arrangement where the distant and home are worked by the same lever with a 3-aspect, approach controlled, colour light home, is a way of automating the distant. A bit like in SimSig where it clears automatically. Log in to reply |
| Signalling arrangements on the down main at Wem 27/05/2018 at 14:15 #108291 | |
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kbarber
1712 posts |
One reason for eliminating a lever movement might have been to do with classification of the box. If it were close to getting an extra grade - or perhaps even if a sharp local manager saw the chance to reduce the grade - reducing the marks by a lever movement for every train that passed (and perhaps the equipment value as well - I don't recall quite how levers counted vs signals in the marking scheme) could be very handy. Of course, if the grade of the box were reduced the men working there would retain their old grade on a personal basis, so there would be few immediate savings, but it would still count for management brownie points.
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