Catch or trap point, spur or nothing

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dclift
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Catch or trap point, spur or nothing

Postby dclift » Mon Jun 21, 2021 6:47 am

Regarding facing catch points, David Smith in “GWR Switch and Crossing Practice” page 74 states that “It was much more usual, in platform loops and at the ends of stretches of relief line which rejoined the main line, to provide a single connection, with a short spur leading to a mound of ashes or, without such a spur”.

I am currently building track for the station area of my layout based more or less on that at Chipping Sodbury on the Great Western main line to Wales. The track plan shown in Clark’s “An Historical Survey of Great Western Stations” shows neither a facing catch point nor a spur on the down platform road which was mostly used as loop on which to park goods trains to allow passenger trains to pass, the passenger service to this station being quite sparse.

Would be reasonable to infer that there was, in fact, no protection to prevent a train that ignored the platform starting signal at danger from proceeding over the trailing turnout onto the main line?
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David Clift.

martin goodall
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Re: Catch or trap point, spur or nothing

Postby martin goodall » Mon Jun 21, 2021 8:25 am

It would appear from this plan that no spur was provided at the exit from each platform loop at Chipping Sodbury, but in that case there would certainly have been a trap point (whether single-tongued or double-tongued*). This is unlikely to have been shown on a purely illustrative plan of the type shown above, but it might be worth trying to hunt down photos of Chipping Sodbury or other such stations, to see what arrangements had actually been made. A signal box diagram might also show the trap switch(es), which would have been located immediately in rear of the platform starting signal.

[* Until WW2, it seems to have been standard practice on the GWR to use only single-tongued traps, despite nagging from the MoT to provide double-tongues traps. I have noticed that on the DN&S, which which was substantially upgraded during WW2 to take much increased military traffic to the south coast ports, the GWR did provide double-tongued traps when making these alterations, but as the government was paying for these works, the Ministry of War Transport may finally have been in a position to insist on this.]

bécasse
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Re: Catch or trap point, spur or nothing

Postby bécasse » Mon Jun 21, 2021 8:49 am

Chipping Sodbury had a trap from the down platform loop by 1945, Badminton (the next station with a similar layout) didn't, which suggests that the one at Chipping Sodbury may not have been original and that one may have been installed later at Badminton. Both had run-back traps in the up platform loops, and the layouts at the London end of both stations were more complex with sidings and goods loops - and traps.

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Noel
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Re: Catch or trap point, spur or nothing

Postby Noel » Mon Jun 21, 2021 8:55 am

The 1921 25" OS maps don't show one, although that is not necessarily conclusive.
https://maps.nls.uk/view/109729519, https://maps.nls.uk/view/109729525
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Noel

martin goodall
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Re: Catch or trap point, spur or nothing

Postby martin goodall » Mon Jun 21, 2021 10:00 am

One small point. I wrote that the trap switch(s) would have been located "immediately in rear of the platform starting signal". In fact the trap would have been located immediately in advance of the platform starter, so that the loco could drive right up to the starter without running foul of the trap, but would then run amok on the trap if the starting signal were to be passed at Danger.

markdavy
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Re: Catch or trap point, spur or nothing

Postby markdavy » Mon Jun 21, 2021 12:37 pm

There’s a signal box diagram for Chipping Sodbury in George Pryer’s book ‘Signal Box Diagrams of the Great Western & Southern Railways – Volume 18 – GWR Lines : Swindon (excl) to Bath Spa and Branches’.

It’s undated but clearly shows catch or trap points at the western end of both platform loops. Also a spur at the eastern end of the down loop. The goods yard headshunt terminated in a sand drag.

David, I’ll send you a scan of the diagram by email.

Mark

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Noel
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Re: Catch or trap point, spur or nothing

Postby Noel » Mon Jun 21, 2021 3:12 pm

Regards
Noel

dclift
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Re: Catch or trap point, spur or nothing

Postby dclift » Tue Jun 22, 2021 5:16 am

martin goodall wrote:It would appear from this plan that no spur was provided at the exit from each platform loop at Chipping Sodbury, but in that case there would certainly have been a trap point..... it seems to have been standard practice on the GWR to use only single-tongued traps...
As far as I can see, Clark doesn’t show trap points where a platform road rejoins the through road in the track diagrams of the stations in his “Historical Survey” books, so their absence certainly doesn’t indicate that they didn’t exist. He does, however, show trap points, usually labelled “CP”, at the egress from sidings in many of his station plans. Incidentally, he references the Railway Magazine for November 1956, which I have in my collection, but all that I gleaned from that is that the line falls at 1:300 from east to west. I have tried to find photographs of the down end of the station but have failed to locate any that show the area where the main and platform lines diverge. I will assume that the safety point (another appellation used by the GWR) was single tongued, at least originally.

bécasse wrote:Chipping Sodbury had a trap from the down platform loop by 1945, Badminton ... didn't...
I checked Badminton which had a very similar layout to Chipping Sodbury, but Clark showed no trap, so it seems that its absence in this case reflects reality.

Noel wrote:The 1921 25" OS maps don't show one, although that is not necessarily conclusive.
Noel, thanks for the references to the OS maps. I spent quite some time on the NLS website last week but only succeeded in finding the 25” map of the up end of the station. The 25” map of the down end eluded me so I am grateful for the link. I also searched, unsuccessfully for a 25” map of Badminton, but it seems that it would not have been of much help anyway.

martin goodall wrote:...the trap would have been located immediately in advance of the platform starter....
Clark’s diagram shows the starter located some distance in advance of the platform end and adjacent to the section of track that is angled towards the main line. It seems to me rather odd that the trap point would be there rather than on the section of the platform road that runs parallel to the through road, but Clark asserts that his diagram accurately reflects the position of both down starting signals and I agree with Martin that the trap would be in advance of the signal. It would be absurd for it to be encountered before the signal was reached. Hence it must have been in the angled section. On the other hand, the SRS diagram that Noel posted this morning (Melbourne time) appears to show the starter closer to the end of the platform but this is only one way in which it doesn’t agree with Clark’s plan.

markdavy wrote:... a spur at the eastern end of the down loop.
I haven’t modelled this. My model is “based on” Chipping Sodbury and Badminton, but is not an exact copy of either. It seems that the spur at the eastern end was not part of the original layout but added between 1903 and 1919. I haven’t modelled the trap point at the western end of the up platform where, according to Clark “the line [originally?] ran beyond the platform to a dead-end, hence the tapering gap between platform and track”. I presume that this was a run away safety measure though the gradient of 1:300 is shallower than the 1:260 for which the MoT recommended them, at least according to Smith. Thank you for the promised scan of the signal box diagram.

The more I discover about this station, the more I realise how little I know. A site visit many years ago, pre Google maps, was rather depressing and, unsurprisingly, totally unhelpful, not that I really expected otherwise.
David Clift.


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