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LNER / BR(ER) TCB 'In-Section' Ground Frames

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

LNER / BR(ER) TCB 'In-Section' Ground Frames

Unread postby StevieG » Wed Sep 10, 2008 9:50 pm

[ A 'branch' from a 27th Aug.2008 (@ 23:01) post by Keith, in the thread - >> Signalling - Current >> Facing Point Lock levers ] :

Keith wrote:..... Actually, we have a fairly near equivalent with ground frames. These can either be released remotely from the controlling signal box or using a key which the traincrew take with them. The majority have disappeared now, mainly because of loss of wagon-load traffic and closure of the sidings, but the few remaining sidings (plus new ones installed as wagon-load has been on the increase again) these days tend to be controlled directly from the modern signalling centres, where these have replaced the more traditional signal boxes.

...Not to forget a third way of releasing ground frames, although I fear all may now be extinct :
This was the LNER/BR(ER) 'in-section' GF in Track Circuit Block sections of automatic signals, where the GFs (often quite extensive ; e.g., I believe the master* GF at Rayleigh had at least 11 levers), had individual control levers for each signal protecting the connections that it controlled (directly or indirectly*).
For those unfamiliar, I understand that their operation was :
That they had no remote release of any kind, and the signal levers could be moved from their normal (usual) Reverse position to the backlock position, replacing their signal if 'Off' to Danger, at any time.
The track circuiting in the running lines, the protecting signals' approaches, and the point connections, was quite comprehensive.
The signal lever backlocks would only release, allowing the lever to go fully normal, when :
1. either the signals were free of approach locking (no approaching train on the approach side of any signal whose aspect would step down to a more restrictive one), or
2. any train within that distance had been proven by TC occupation/timers to have stopped on the approach side of the signal, or
3. an arriving train needing to work sidings or cross to the other line, had arrived under clear signals to the right position ready for the next move, and the correct combination of TCs was either clear, or occupied long enough to show that the train was at a stand in a correct place, waiting to shunt.

I think GF-operated shunting signals were also provided where necessary.

Once the moves were finshed, and all the GF connections were restored to normal and were not to be used further, the protecting signal levers could be Reversed, and the signals assumed the correct aspects according to TCs being occupied or clear.

*At some places (I believe former GER-route locations at Billericay, Hockley and Rayleigh were all examples), there was more than one GF; one being the 'master' and having the protecting main signal control levers, the other/s being what might be considered 'subsidiary/ies'. Once the master GF was free for use in one or both directions, it could in turn give an appropriate release to a 'subsidiary' GF.
One such case was, I was told, at Billericay, where the main GF was at the London end of the station and included a trailing crossover amongst its functions, while there was a sub-GF beyond the country end of the platforms, working a second trailing crossover.
Ironically, I believe I recall that latter day rationalisations, loss of sidings and yards for example, and perhaps the dislike of points on curves, had some odd end results, with the pre-1990s resignalling remnants at Billericay consisting of the master GF retaining only its main signal control levers, plus a release for the country end GF - whose crossover was the sole remaining pointwork around the whole station area.
Addtl. info. added 11/09/08:
The 'master' GFs (at least) were blessed with a limited illuminated diagram : I think I recall from briefly seeing Rayleigh's one day, that this featured TCs in the immediate area, and indications of when the signal lever backlocks were free for the lever to be placed fully Normal.
Rayleigh's GF was in the open with the diagram 'hooded'. I think the 'master' at Billericay was in a hut.
On re-thinking, I reckon Rochford also had this type of GF(s) arrangements, and that was where it had been mentioned there having been an 11(+?) lever 'master' GF.
Last edited by StevieG on Thu Sep 11, 2008 9:52 am, edited 2 times in total.
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Unread postby Keith » Wed Sep 10, 2008 11:25 pm

Interesting - I don't recollect ever coming across such an arrangement, but it makes sense.
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Unread postby Peter Jordan » Thu Sep 11, 2008 7:08 am

And then, of course, there was the system installed on the 'tokenless block' sections of the Salisbury - Exeter line where the ground frame was released by a track circuit at the site or a special block instrument. The system is described in Kichenside & Williams 'British Railway Signalling.'

Do any of these ground frames still exist and see any use? I suspect not.

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Unread postby Chris Osment » Thu Sep 11, 2008 8:09 am

...... on the 'tokenless block' sections of the Salisbury - Exeter line where the ground frame was released by a track circuit at the site or a special block instrument.


AFAIK it was not 'OR' - the GFs were released by TC at the location and there was a 'repeater' block instrument at the site which was used to clear/occupy the block.

Do any of these ground frames still exist and see any use? I suspect not.


Thinking about it, I believe they have all gone now. AFAIK the only GFs to remain are the 'station' ones at Gillingham and Honiton (is that still there?). Has the one at Chard been recovered?
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Unread postby StevieG » Thu Sep 11, 2008 9:49 am

(Additional info. just added to my post here of yesterday.)
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Unread postby Richard Pike » Thu Sep 11, 2008 4:33 pm

The tokenless block between Chippenham Junction and Dullingham had a ground frame release for the Dower Woods siding at Newmarket. Another unusual feature was the level crossing repeater at Wood Ditton crossing. I have it somewhere and i'll post a picture if i find it.

I think the ground frame on the Luton single line at Welwyn Garden City was released by track circuit occupied for two minutes i believe. There was also an instruction about not restoring the levers to normal with no vehicles left on the main line..
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Unread postby ferroequine » Thu Sep 11, 2008 5:40 pm

Chris Osment wrote:
...... on the 'tokenless block' sections of the Salisbury - Exeter line where the ground frame was released by a track circuit at the site or a special block instrument.


AFAIK it was not 'OR' - the GFs were released by TC at the location and there was a 'repeater' block instrument at the site which was used to clear/occupy the block.

Do any of these ground frames still exist and see any use? I suspect not.


Thinking about it, I believe they have all gone now. AFAIK the only GFs to remain are the 'station' ones at Gillingham and Honiton (is that still there?). Has the one at Chard been recovered?


Can't answer the last part Chris but the method of GF release by occupation of a track circuit was quite common on WR mas schemes although in that case I believe tc occupation only allowed the Annets Key to be part turned (to position 2), the remainder of the release was given by the Signalman.

But, as you say, the release on Tokenless Block was controlled solely by track circuit occupation with a delay (normally 1 minute) before the Annets Key was free to be turned from No 2 to No 3 position. At GFs where a train could be shut in a 'shut in plunger' and a block repeater were provided - effectively the plunger carried out the same function as a 'Train Arrived' button on the block instrumen and the repeater and plunger were wired into the block circuit making it effective however long the section in use happened to be and whether or not various signal boxes were in or out of switch.
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Unread postby Richard Pike » Sat Oct 18, 2008 9:03 pm

Finally found the diagram i wanted.. Horns siding, Welwyn Garden City, released by a track circuit on single line.



http://richard2890.fotopic.net/p54348420.html
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Unread postby Keith » Sat Oct 18, 2008 9:45 pm

Richard Pike wrote:Finally found the diagram i wanted.. Horns siding, Welwyn Garden City, released by a track circuit on single line.

No shutting in of course, but how was the release cancelled? TC going clear? That could be risky if the local kids start fooling around as the train moves away. :shock: "One pull" would have its own problems - one mistake and the train has to go away and come back!
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Unread postby Richard Pike » Sat Oct 18, 2008 10:04 pm

Yes i think finding the diagram has posed more questions than answers..
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Unread postby ferroequine » Mon Oct 20, 2008 1:43 pm

Keith wrote:
Richard Pike wrote:Finally found the diagram i wanted.. Horns siding, Welwyn Garden City, released by a track circuit on single line.

No shutting in of course, but how was the release cancelled? TC going clear? That could be risky if the local kids start fooling around as the train moves away. :shock: "One pull" would have its own problems - one mistake and the train has to go away and come back!


The 'local kids' at a certain location on the GW mainline discovered exactly that sort of 'fun' and became quite adept at turning the key at just the right moment as a train passed and then retiring a safe distance to await the arrival of the Techs. Eventually the circuitry was modified... :)
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