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1940/50/60s UK Power Boxes with 'GRS' 'NX' Panels

British signalling of the past (UK, excepting Northern Ireland)

Unread postby Keith » Sat Oct 11, 2008 10:48 am

Richard Pike wrote:Sorry for the slow reply on this one. I had seen a Potters Bar diagram on my travels and it took a while to track it down. I guess this panel is one i wont be rebuilding...

http://richard2890.fotopic.net/p54182772.html

I may upload it as three images if anyone wants better detail..

So many catch points! Derailing a train towards the other fast line looks a bit risky - as discussed here recently - even if that's one of the sections with a very wide ten foot.
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Unread postby Richard Pike » Sat Oct 11, 2008 7:57 pm

I note that 21 and 23 position lights are both in place but there is no reversing siding and just what is 29 position light?


http://richard2890.fotopic.net/p54195438.html
http://richard2890.fotopic.net/p54195430.html
http://richard2890.fotopic.net/p54195432.html
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Unread postby SDL » Sat Oct 11, 2008 8:02 pm

just what is 29 position light?

It's a two-tier position light. The top signal comes 'off' for the Up Siding; bottom signal for the Up Slow.
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Unread postby Richard Pike » Sat Oct 11, 2008 8:42 pm

Next door...

http://richard2890.fotopic.net/p54196844.html

showing a few of the Potters Bar signals on the right.. How were down slow trains offered on the down main? Was there a special code?
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Unread postby Richard Pike » Sat Oct 11, 2008 9:02 pm

SDL wrote..

It's a two-tier position light. The top signal comes 'off' for the Up Siding; bottom signal for the Up Slow

But everywhere else has route indicators... I wondered if it was co acting for sighting?
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Unread postby SDL » Sat Oct 11, 2008 9:19 pm

Richard Pike wrote:But everywhere else has route indicators... I wondered if it was co acting for sighting?

No, that was entirely typical: A two-tier PLS for signals with two routes, a single PLS with a route indicator for signals with three or more routes.
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Unread postby StevieG » Sat Oct 11, 2008 11:48 pm

Keith wrote:
Richard Pike wrote:Sorry for the slow reply on this one. I had seen a Potters Bar diagram on my travels and it took a while to track it down. I guess this panel is one i wont be rebuilding...

http://richard2890.fotopic.net/p54182772.html

I may upload it as three images if anyone wants better detail..

So many catch points! Derailing a train towards the other fast line looks a bit risky - as discussed here recently - even if that's one of the sections with a very wide ten foot.

Unusually here, the 'ten-foot' was (& is) indeed much more; must be more like twenty feet, thanks to the three tunnels : This was created during the 1950s quadrupling between Potters Bar station north end, Mimms (location of signals, 4, 14, 15 & US13 on Richard's drawing), and Greenwood (sigs. DF10 & DS10).
Prior to, the Up Fast and Up Slow used to be the Up & Down Mains, and the two down lines here and their tunnel bores were new for the quad'g, and the separation between the pair of bores of each tunnel is quite wide.
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Unread postby StevieG » Sun Oct 12, 2008 12:32 am

SDL wrote:
Richard Pike wrote:But everywhere else has route indicators... I wondered if it was co acting for sighting?

No, that was entirely typical: A two-tier PLS for signals with two routes, a single PLS with a route indicator for signals with three or more routes.

Definitely a two-tier signal - no co-acting.
They applied in the usual 'top-to-bottom; left-to-right' way (from "UP SIDINGS" on the drawing); -
- Top for straight ahead into the up yard (to "UP SIDING" to the right of 49 points on the drawing);
- bottom out to the Up Slow.
It will be noted there was no signal protecting 49 points from moves out of the yard ("UP SIDING").

This little set up worked in an interesting way (I'm pretty sure I'm remembering this correctly).
The normal situation with 29 was that, with 49 points detected Normal, 29 top was 'off' without the signalman having called any route, thus allowing unrestricted to and fro shunting.
[ Presumably it was up to anyone acting as shunter to check that 29(top) was 'off' before calling any move out of the yard over 49s, trailing, in the opposite direction. ]
When a signalled move was needed over 49 points Reverse, the signalman called the required route, (from 29 to 5, or 26 to "UP SIDINGS"), in the normal way (twist and push).
Straight away, 29 (top) went to danger, then nothing happened for a while (presumably the customary 30-second approach locking on 29 operating).
Only after that, and if the requisite track circuits were still clear, did 49s go over to Reverse, and 29 (bottom), or 26, come 'off' according to which route had been called.
When the required move had gone clear of the TCs through 49s (S15 and S17), and the route cancelled by normalising the set route's eNtrance switch, then after a few seconds - could have been 10 - 49s motored themselves back to Normal and 29 (top) auto-cleared.
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Unread postby StevieG » Sun Oct 12, 2008 12:51 am

Richard Pike wrote:Next door...

http://richard2890.fotopic.net/p54196844.html

showing a few of the Potters Bar signals on the right.. How were down slow trains offered on the down main? Was there a special code?

Not sure I understand this question.

(Ignoring Marshmoor's independent distants) on the Down Fast, the possibly relevant signals were PB10, (PB41 DS->DF 'turnout' points), 'Auto' sig. M28, and (M)22 semaphore home.
On Down Slow, it was PB20, (PB41 points), and (M)29 semaphore home.
The DF was fully track-circuited and worked by TC Block.
The DS was not TC'd beyond the end of PB20's overlap, north of PB41 turnout, and was always worked by AB (as were the other three lines whenever Marshmoor was switched out).

So the DF trains were described under TCB from PB to Marshmoor by bell, whether they came straight down the Fast, or S->F via PB41s.
Trains which ran DS from PB through to Marshmoor had to be offered from PB and accepted by M in the usual way, with PB20's 'straight' route aspect released by 'Line Clear'.

Hope that answers the query.
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Unread postby Richard Pike » Sun Oct 12, 2008 8:42 am

Thanks for the replies regarding PB. We need to get thing's down in writing while we still have people round who knew these boxes. I was 10 years old when the last ECML boxes closed. My memories of the boxes i did see are now a little sketchty and i didn't fully understand what was going on. I have a 100+ ECML diagrams to upload in the next few weeks. I know i need to improve the quality of the images on my site and this is something i'll work on in due course. Any requests as to my next upload?
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Unread postby StevieG » Sun Oct 19, 2008 10:56 pm

Richard Pike wrote: ..... Any requests as to my next upload?

As (I don't think) you've had any direct response to this one, do you have Goods & Mineral Junction?
There are some possibly interesting points(!, sorry) to relate about there.
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Unread postby Richard Pike » Mon Oct 20, 2008 9:20 am

G & M and Five Arch Bridge are two i haven't come across yet. I will keep looking as i'm sure they are about.
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Re:

Unread postby StevieG » Fri Oct 30, 2009 9:34 pm

In Sept. '08, Richard Pike wrote:Was Potters Bar a MetV GRS installation? This came my way last night..
http://richard2890.fotopic.net/p53659724.html
Note that it shows double track to Greenwood.
In case of interest although not that sharp, dug out these photos, bought (without caption or attribution) years ago at some railway/transport show/day.
They show, probably the same panel facia as that through Richard's link, for the box's first (pre-1959) layout, when the quadrupling works had been completed, going left-to-right, from just north of the station to just north of Potters Bar Tunnel, but from there through to the then fringe box, Greenwood, was still double track.

Image

Image
Last edited by StevieG on Fri Oct 30, 2009 11:14 pm, edited 2 times in total.
BZOH

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Re: 1940/50/60s UK Power Boxes with 'GRS' 'NX' Panels

Unread postby Richard Pike » Fri Oct 30, 2009 10:21 pm

I've now finally located the official book of words on the Potters Bar resignalling.

Quote..
There are twelve crossovers including two double slip and one single slip, one triple ended and two single ended layouts comprising twenty-nine point machines in all.

I can't see two double slips anywhere so are they referring to two ends of the same slip?
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Re: 1940/50/60s UK Power Boxes with 'GRS' 'NX' Panels

Unread postby StevieG » Fri Oct 30, 2009 11:35 pm

Richard Pike wrote:I've now finally located the official book of words on the Potters Bar resignalling.

Quote..
There are twelve crossovers including two double slip and one single slip, one triple ended and two single ended layouts comprising twenty-nine point machines in all.

I can't see two double slips anywhere so are they referring to two ends of the same slip?

I can't reconcile some of those figures either.
The only track layouts I know of are as shown on your original facia plate, plus the quadrupling-completion one that was the same except for the doing away with the superfluous 2-ended 54s and triple-ended 55s, plus, at some time, the south FLs trailing xover 51 disappeared, and a GF-operated FLs facing xover alongside signal PB6 arrived instead.
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