Seventy years of main line signalling in London #2

Seventy years of main line signalling in London #2

The Central Section resignalling scheme which we looked at in the first part of this feature was conducted in a number of stages between 1950 and 1955 and it covered the main lines out of both London Victoria (actually Pouparts Junction) and London Bridge (actually Bricklayers Arms Junction) towards Purley where there was already colour light signalling towards Brighton. The idea of the scheme was to fill in that missing gap and ensure both these important and intensively used main lines had the most modern signalling systems throughout. It also meant the last vestiges of semaphore signalling were taken out of use on the Southern Region’s two main lines towards the coast.

Stage four of the scheme was brought into use on May 8th 1955, but it did not have the concrete gantries used in stages one, two and three that are the main discussion here.

The above map showing stage four of the scheme and how it linked to the south coast mian lines (via Redhill/Quarry and via Oxted.) We can see from this the first section of the Oxted lines indeed received this upgrade as did both the Caterham and Tattenham Corner branches. It however didn’t mean every single main line from East Croydon to the Sussex coast was operated with modern colour light signals. The Oxteds at that time (both via Uckfield and East Grinstead) continued to have a considerable amount of semaphore signalling, but again these were not intensively used and the levels of traffic encountered meant it would certainly be decades before both had fully modernised signalling systems – and that would only be after these lines had been cut back to their current termini.

In fact the modern enhancements on the longer Oxted branch came about largely because of considerable rationalisation, including single line working and the removal of surplus infrastructure such as junctions (that at Groombridge), rationalisation of stations (such as Edenbridge and Uckfield) and removal of one major level crossing (again this is Uckfield.) If the plans for restoration of the line Lewes did ever come to fruition it would be a whole new ball game because it would entail a massive upgrade of around forty miles of route (South Croydon to Lewes including replacement of a missing seven miles or so of railway) – but let’s not dwell on that because that’s a lengthy article in itself altogether!

Whether the Oxted lines were upgraded or not, it would have benefited anyway from the 1950s signalling scheme between London and Purley because the greater efficiency achieved by that upgrade alone must have been worth its weight in gold as the trains on the further flung parts of the system could in turn be more reliable, and really that was the whole point of the 1950s scheme – not to increase capacity but to enable the services to run more efficiently.

The different stages in the 1950s resignalling scheme. Stage one is the phase with most infrastructure still present.

As a matter of fact a new fact regarding the 1950s signalling arose on Twitter although I do not think the person posting the information realised there was anything other than the information being dispensed thus. What it means is we now have further details of the re-signalling in question by way of a circuitous route (pardon the pun) – and that is the electrical work that was undertaken at the same time.

Switchgear (for the traction power supply of course!) Source: Twitter

What the person posting this didnt say (or realise) is the new electrical system was fed by Deptford power station – in fact the power station was upgraded by way of building an extension and the old power station became known as Deptford East. In fact especially for the railway’s power supplies new 52.5MW machines operating at 50Hz were installed at Deptford East. At the same time the power to the traction current supply was changed from 25 cycles to 50 cycles.

The main power source is marked on this drawing at the top as Deptford. Source: Twitter

Although the above diagram does not denote these, several of the nodal points for the Southern’s resignalling scheme can be seen where the power would have been distributed and these include Wandsworth Common, Streatham, Brockley, Penge, Selhurst and Croydon. It must be remembered not all the railway routes were followed in terms of dedicated 20KV to 50Kv power supply routes, clearly some followed roads even which is why the map barely represent the actual railway network in this part of London.

If one thinks about it the London Transport power stations at Lots Road and Greenwich were not anywhere near tube lines – they had to be built on land that was available at the time and more importantly located by the river for easy delivery of coal by ship or barge. Thus the main power cables had to be threaded through London’s roads to the locations where the power would then be rectified into the 630 volts needed for the tube system. In fact the main electrical supply installed during the 1960s for the Victoria Line threaded its way entirely through London’s streets from Lots Road power station to Coburg Street! Obviously the answer here is to use the shortest possible power supply route even if it has to be dug along the roads.

Deptford (East) was the first power station in Britain to supply a main line railway – the LB&SCR in 1909 and subsequently it was responsible for the powering of the SE&CR’s system in 1920 – which at the time the biggest suburban electric railway system to be found anywhere. (Source.) It is said the three Deptford power stations combined were at one time the largest such complex in the world.

The two nearest chimneys belonged to Deptford East LP station and where the electricity for the Southern/British Railways’ 1950s resignalling scheme would have originated. Source: Twitter

Evidently the new colour light signalling also needed power too since the old system had either been manually or pneumatically operated and substantial new signal boxes were provided where there had previously been none, such as at Bricklayers Arms.

The power supply for the new signalling was in fact taken from the substations for the traction supply system and this means the new 1950s signalling scheme was being powered from Deptford East!

Plans for the signalling scheme were perused and from those I drafted a scale based drawing, simplified of course, to show the general design of these special concrete pillars and the signals that were placed upon these. I just wanted to keep the dimensions simple, thus its just the main aspects of those that have been given here. I excluded also the ladder that was built up the the pillar itself as well as the steps that are built into the top of the cantilevered section. The steps were of course to ensure engineers and signal cleaners had full and easy access to the top of the cantilevered section as well as to access the signals themselves and clean their lenses.

Anyhow we will see more of these pillars in detail later but for now one can see the main image at the top of this page and how the structure was generally built. The difference here is the modern LED signals introduced for the Brighton Line resignalling a decade or so back are placed directly on the cantilevered section itself and that is evident by how the signals have been sited behind the railings themselves. Originally the signals were set on brackets that extended out ahead of the railings which meant the front of the signal was clear of all obstructions. The design of the railings it seemed varied between locations as those at Anerley are not quite the same as in the diagram I have.

Diagram I drafted to show the general dimensions of the wider span concrete signal gantries for the 1950s resignalling scheme.

Lets compare the drawing with one of these actual signal gantries in question! Factually the only one of these that can be viewed up close is that on the down platform at Anerley and the next tthree pictures depict this particular one.

General view of the Anerley gantry with a London Overground service departing for West Croydon.

Close up of the concrete signal gantry pillar at Anerley.

Basically the structure is overall as those found on the engineers drawings. There are differences though. Instead of a dedicated tubular channel at the side through which the cables were threaded (and which has obviously been dispensed with) the modern answer is to simply place the cables themselves up the side of the structure itself. The structures had fixings for smoke deflectors but I don’t know if these were ever used. Several of the pictures in the first part of this article (including one with a steam locomotive at East Croydon) do not show any smoke deflectors in use – which means these might have been dismissed as part of a cost cutting exercise.

The ladder itself isn’t the original those were somewhat narrower. This one is a later job probably seventies or eighties for all we know. A hole can be seen to the right of the ladder towards the top. This is a 2 inch diameter hole threaded with a steel tube and these enabled the railway’s civil engineers to hoist these gantries into place using rail based cranes and a special steel bar for the purpose.

The next picture I took over the top of the bridge parapet at Anerley and is made from two images merged together in order to show the full extent of the cantilever section of the gantry.

Image showing the top of the gantry itself.

The most obvious feature of this is the makeshift brackets that have been employed to secure the signals themselves. As mentioned earlier proper brackets were manufactured for the 1950s signals but obviously these were no longer fit for purpose. Compared to the original work its all a bit Heath Robinson these days! The other interesting feature that can be seen are the steps up the sloping part of the cantilevered section. These were cast as part of the pillar itself. One can also see how modern day signal engineers have simply strung the cables along the base of the railings!

Good view of the gantry with a Southern train about to depart from Anerley for Cousldon Town.

In this last picture one can see clearly the general appearance of the signal gantry itself including the two inch hole that was for the civil engineers’ use. After seventy years of use these structures are now looking a bit tatty but they must have been very smart when first introduced.

Several of the stations have these gantries quite close to the platforms such as at Forest Hill and Penge West but none on the platform itself these days except Anerley and the reason for this positioning is because of the adjacent road bridge. The ‘check signal aspect’ can of course be found at a number of locations across the railways including the New Cross to Norwood Junction line but here its quite critical because of the tight location.