Amersham To Harrow Signalling - 1962

AWESOME!!!

Thanks Harsig ;D ;D ;D ;D

Yes, Your a genious! I have uploaded it to IDSME's space to get ound te bandwith issue sir...

This doc can also be found at here.

Now there is a man who wants to be a signalling CAD operator...

What's a signalling CAD op then?

Sorry to be a pest but what is C.A.D?

Well what else am I going to say except "Thanks Harsig"!!
Those signalling diagrams have answered a whole bunch of questions I was going to ask, so you've saved me a lot of potential keyboard tapping. Nice one.

On the subject of CAD, that used to be something that one posh bloke would call another, as in....
"You sir, are a cad and a bounder!"
(if he thought the bloke was an a**hole!!) ;D

Hi
Thanks for posting the diagram - I have been busy studying it trying to learn more about LU signalling practices. As I have previously said before I think, my background is with BR signalling so would welcome some clarification on some of the LU signals. Apologies if I am asking pretty basic questions as usual.

Firstly regarding Chesham. Was this a mechanical box with a lever frame working colour light signals, manual semaphore and shunting signals? In addition were the points mechanically worked by rodding or were they motorised? If mechanical did points 7 and 8 have any form of FPL? Signal JV3 controlling entry into plats 1 or 2 leads onto JV4 at the end of plat 2 which I am reading to be a semaphore stop signal. In BR practice this would generally be fixed at stop with a shunt signal below it reading past it to allow access to the sidings and run round loop. I am assuming that this is not the case on LU - am I correct in this?

Another query regards the single line towards Chalfont. The diagram shows JV 7 as being slotted by Chalfont 69. Would it not be better for the signals on the ends of the platforms (JV16/18) to be slotted instead as they control entry onto the single line (with JV17 being abolished)? I am thinking that maybe it is possible for a train to be on the single line from Chalfont and a train at Chesham allowed to draw up to JV17 or would there be controls in place to prevent this. I can only think that JV17 is provided to allow a train to shunt from plats 1,2 or the run round loop as far as JV17 and then set back again with any incoming train being held at JV2. Looking at Chalfont now - howcome Chesham does not slot the entry signals to the single line (JT80 and JT84) or JT83 as the last controlled signal towards Chesham? I will admit to not being familiar with the regulations concerning single lines on LT.

Looking now at Croxley. Some of the signals are shown as slotted- B6 slotted by JJ59, B18 slots JP 136 (of Watford) and B1 slots JP 101 (again of Watford). Again using my BR logic I can see no reason for the slotting.

Next point- several locations (Watford, Northwood Park, Pinner and North Harrow) have what is described as a Yard Control Lever - what is this?

Most of the yards seem to feature handpoints but some are also described as having switchlocks - are these to detect handpoints in certain positions?

Finally Harrow on the Hill box (JB) seems to slot a lot of its own signals - is there any reason for this?

Again aplogies for asking so many questions and also if they are basic. As I have said my background is of BR signalling and i know it differs in a lot of respects from LU practice. I have picked up the basics - basically by reading and asking a lot of questions- but find that there are still some 'odd' things that stump me. I would be grateful for any assistance that anyone could give me and look forward to hearing from you.

A long and interesting series of questions which I shal now attempt to answer



Chesham box was a mechanical box. The diagrams as posted show the arrangements following electrification of the line which was also the occasion when colour light signals first appeared there.They were provided only for those moves involving passenger trains with the existing semaphore signals left in place for all other moves.


As regards the points the following are two extracts from the relevant signalling notices

My understanding of the term electric track locking is that this means that the relevant point lever is electrically locked normal or reverse when a train is occupying a track circuit reading over the points. The originla signalling notice diagram does also show the points as being fitted with a facing point lock but since no separate lever no is shown these were presumably worked from the same lever as the points.
The second qoute relates to No. 7 points

No. 7 crossover (and the bay road) was a new addition at the time of electrification, hence the provision of electro-pneaumatic operation.



It would seem to me that you are correct in reading the diagram. As far as I can tell No. 4 signal was indeed a semaphore which could be worked to admit trains to the yard. This should not however be taken as evidence of what is standard LUL practice as I strongly suspect it is just that no alterations were ever caried out to the arrangements at this end of the station.



I'm pretty sure that the signalling was set up to allow shunting on the single line at Chesham while another train was in section between Chesham and Chalfont. Remember any such train could just as easily have been going away from Chesham as towards it. The original signalling notice shows that JV17 had an overlap of 721 feet and JV 2 had an overlap of 615 feet ( the gradient is falling towards Chalfont) the combined distance between the two signals being 1498 feet. (the overlap is measured from the trainstop rather than the signal, hence the distance between the signals is slightly greater than the combined overlap.)



This arrangement basically means that the single line is entirely under the control of the signalman at Amersham and he is able at any time to send a train towards Chesham, while the Chesham man can only send a train towards Chalfont when it has been accepted by the signalman at Amersham. This would seem to be a standard way of arranging the control of single lines on LT where there are separate signalboxes at each end but I should state that the number of examples is and always has been extremely limited so it may not be safe to draw such a conclusion.
Years later of course when Chesham Box closed it was a simple matter to give the signalman at Amersham control of the starting signals at Chesham by extending the slot control to include JV18 which was renumbered JT69^A while JV 17 became JT69^B.



With the exception of B18, I would say that all the other examples are to do with ensuring the availability of a suitable overlap at the next signal in advance.
e.g. before JP103 can be cleared a suitable overlap must exist in advance of signal B2 and this will not be the case if Nos 7 or 8 points at Croxley are reversed, therefore the JP103 is slotted by B1. Likewise before B2 or B13 or B6(to the southbound road) can be cleared a suitable overlap must exist in advance of JJ60 and this overlap may be fouled by a train shunting out from Croxley Tip Sidings hence JJ59 slot lever prevents this move from taking place at the same time.
B18 allows JP136 to do double duty as Croxley's Advance starter. It would seem that LT practice at this time was generally to provide a controlled stop signal at any point where they wished the train to stop before reversing back. This is presumably also why Watford was given control of signal JP103 with the slot by Croxley rather than just making the signal B1.



TheOneKea has already quoyed my previous explanation on Yard Control Levers. With regard to switchlocks these are basically handworked points which can be locked in the normal position by the signalling system. They are also detected when in this position thus allowing signals that read over them to be cleared. Handworked points Z7 and Z19 at Watford could also be locked and detected in the reverse position. Once the yard control lever is reversed any switchlocks are unlocked and the points are free to be moved. With the exception of the points already mentioned at Watford these points are not detected in the reverse position and in general an electric lock on the yard control lever will prevent it from returning to the normal position unless the hand worked points are deteted in the normal position.




Finally we come to my favourite Signal Cabin. There are in fact three signal cabins at Harrow On The Hill. They are Harrow North Junction, Harrow Station and Harrow South Junction. Harrow North and Harrow South are controlled remotely from Harrow Station Box and they are not normally manned. All signals controlled from all three boxes carry the same cabin code JB but because they are also in relatively close proximity there is innevitably a certain amount of slotting between the boxes. In general slot levers in the 12n range are located in the south box, those in the 13n range are in the station box and those in the north box are in the 14n range of numbers.

Hi The OneIkea

Thanks to yourself for your comprehensive reply to my epic question. I find this forum invaluable for learning about LU signalling and the members ever helpful. I am always keen to find out how our LU signalling colleagues work their boxes and what signals and equipment they have available to work the levels of traffic that I never encountered during my signalling career - even on the WCML. You are the unsung heroes of the system and deserve credit for the excellent job you do- it is appreciated by me at least. Since reading the posts on here I have certainly kept a good look out for signals when I get to travel on the Underground (which is not often as i live in the Midlands) and like to think my knowledge of them is increasing. I look forward to learning more. Now if I can only find a copy of the notice dealing with Hammersmith (H&C) box/station - required for personal interest as I have an interest in terminal stations

Hi Dave

I was just repeating what was said on the DVD Metropolitan Main Line - honest guv ;D I would suspect that the Aldgate area could be a bit of a challenge at times too.

I would agree with you though that Earls Court does look a busy place - again how the signalling staff manage to work this god only knows. I used to work on a BR main line and still had time to sit down in between often large gaps in traffic - even used to cook myself an evening dinner. Those who work Earls Court I would have thought do not have that luxury...

It's not my reply, it's Harsig's - I just dug it out to save him the trouble of retyping it.



Heheheheh, you would get along quite nicely with stephenk then ;D ;D ;D

The only problem I can see with Earls Court are the missing crossovers and the absent diveunder for the eastbound HSK route.

The change took place in July 1960 and was one of the later stages of the Amersham re-signalling as it allowed the abolition of Absolute Block Working between Amersham & Great Missenden. First Supplement to Traffic Circular 28/1960 'Alterations to Signalling Great Missenden - Amersham' refers.
From your post I infer that you have or have seen Supplement to Traffic Circular 9/1960 which as you say does show the signal as Gt Missenden No 5, but even this diagram already clearly foreshadows the change as some of the track circuits shown on the up line approaching Amersham are already named 983^C, 983^D, 983^E & 983^F which falls in line with LT's standard track circuit numbering for track circuits controlling an automatic signal of the same number.

Thanks for the reply - I hadn't noticed the 983 T/C numbers! Yes, I have 9/1960 with a couple of others - but without knowing what the missing portions are - a bit of patchwork is needed to get the full picture!

Would I be correct in assuming that A983 and associated T/Cs were removed when Gt. Miss was closed?

Greg.