Greenford East is the last remaining signalbox with WR lower quadrant signals in London. It controls
a triangular junction where the branch line from West Ealing joins the former GWR Paddington-Birmingham direct line.
I have now included a
hyperlinked diagram of the Greenford triangle
below.
This was the view of Greenford South Junction from South Greenford station on the branch line.
A train is signalled into the bay platform at Greenford,
which is cut into the eastern end of the Central Line island platform and reached via a separate chord.
The signal in the foreground, GE52/63, controlled Greenford South Junction,
while the one in the distance controls the entrance to the bay line.
It has since been replaced with a
new LED signal.
The rears of the up starters towards West Ealing
can be seen on the right.
A closer view of the signal that controlled the entrance to the bay platform, GE22/51 (also since replaced).
Because the embankment here is prone to subsidence, the signal post had had to be supported by scaffolding - note also the
additional support (painted white) for the signal in the photo above.
If the ground had been firm these signals would
probably still be here today. Thankfully, the
Gloucestershire-Warwickshire Steam Railway
have acquired them for future use there.
A face-on shot of the up starters towards West Ealing. The signal on
the left reads from the chord from the eastern junction, while the one on the right
has been cleared for a departing local passenger train.
Greenford East Junction. The viaduct in the background carries the Central Line,
which runs parallel to the ex-GWR line between North Acton and
West Ruislip,
over all three curves to Greenford South Junction.
A closer view of the up main starter, GE42.
This superb GWR bracket still carries the splitting homes for the eastern junction.
A long-range view towards Greenford from a bridge over the line towards Northolt.
On the left is the main ex-GWR (Wycombe) line, with the splitting up home signals for Greenford West Junction
clearly visible. Since the Marylebone resignalling, this section
from
Northolt Jct East
is now single track. The signals whose rears can be seen are not
the arms of a splitting signal, but are the down main innerhome and starter.
On the right is the Central Line; in the foreground, an Epping train approaches
Greenford, while one to West Ruislip can be seen departing from the station. The semaphore that
can be glimpsed over the station roof is the bay platform starter, pulled off for a train to depart.
A closer view of the bay platform and its starter, GE29. The platform line descends to go under
the westbound Central Line - the line
immediately to the left is its eastbound track. The backs of the same down main signals
can also be seen from this position, to the left of the Central Line viaduct.
A closer shot of the up main homes bracket, GE41/45. To the left, a yellow disc
controlling the exit from a disused siding can also be seen. The siding is in fact all that
remains of the former up platform line, harking back to the days when Greenford also had main-line
platform loops in classic GWR style. The main-line platforms were set somewhat to the west
of the present-day Central Line island, further to the left of where this photo was taken.
A rear view of the same signal.
A close-up shot of the yellow disc.
The down starter, GE50.
Greenford West Junction. The signal on the left is the down main innerhome.
To the right, the down starter can be seen, and the rear of the bay platform
starter glimpsed over the viaduct. The signalbox
nestles in the vee of the junction. The bridge carries the Central Line over the
branch chord.
28/7/07
The new colour-light to replace the two brackets affected by the subsidence problems has been erected, but - oh dear...
The up branch advanced starter, GE47, with the down branch home GE53 on the left
and Castle Bar Park station in the distance.
An up train approaches Greenford South Jct. This shot also gives a better appreciation of the relative positions of the two bracket signals.
Even the up branch starter hasn't been immune to the graffiti mongers. :(
17/7/10
Here are some photos taken on an official box visit organised by the
SRS.
First, a general view of the lever frame, diagram, and block shelf.
Red levers work stop signals; black ones are points, blue ones
facing point locks,
white are spares, and the yellow one works a distant signal.
There are no traditional
block instruments or bells, as all sections to adjacent boxes are worked by track circuit block (TCB).
At the far end of the block shelf are this nice group of lamp indicators, which tell the signallers whether or not
the signal lamps are lit.
Downstairs, beneath the operating floor, are the connections from the lever tails to the rods and wires
that drive the points and signals...
... and the mechanical interlocking that prevents conflicting moves being set.
A closer view of a part of the interlocking. The vertical tappets at the back slide
up or down as the levers are operated. The horizontal bars carry metal 'dogs' which can
fit into notches cut into the sides of the tappets. If necessary, working a lever may
drive one or more horizontal bars left or right - but this will only be possible if the
other dogs on the same bar can fit into notches on the tappets of associated levers. If any of those
levers are in the wrong position, the horizontal bar cannot move and thus the original lever
cannot be operated.
These boxes connected to the bottom ends of the tappets house electrical lever locks. These allow
point and signal levers to be locked by other equipment such as track circuits, eg to prevent a signal
being cleared when there is a train immediately ahead of it.
The left-hand end of the lever frame. The plungers you can see behind some
of the levers activate the electrical locking shown above, and must be pressed to release the lever - provided
the necessary conditions are met!
The lines at the top of the diagram are the main (Wycombe) lines from
Northolt Jct
(now controlled by
Marylebone Signalling Centre). Below are the lines from the bay platform at the station
towards the junction at the south corner of the triangle.
A selection of lever description plates. These levers control the signals on the up main line from
Northolt Jct towards Park Royal. The numbers below the horizontal bar on the distant lever 40 list the
other levers that must be pulled first before that lever can be - in this case these are simply the
levers controlling the adjacent stop signals on the main line. A good example of a constraint the
mechanical interlocking enforces.
The junction to the bay line as seen from the rear window of the signalbox. The line
in the foreground is the curve from the main line from Northolt Jct onto the branch towards South Greenford;
the one joining it from the right comes from the bay platform. The disc visible beyond the junction is no 27.
The view from the box towards Park Royal, with the down main innerhome
in the foreground and the East Junction in the middle distance.
The view from the opposite window, towards
Northolt Jct,
with the double-to-single junction.
The leftmost line is the chord from the South Jct.
You can see that the connection to the up siding has been plain-lined, though it is still shown on
the box diagram, the disc leading into it remains below the down starter, and the levers to control it remain in the frame.
Thanks to Andy Overton for this photo of the acceptance switch for up trains from
Northolt Jct.
Turning the switch clockwise to the Accept position allows Marylebone SC to clear the signal at
Northolt to allow a train to approach Greenford, provided the track circuits on the single-line section
(and an overlap beyond Greenford's
up main homes)
are all clear.
The electrical indicator on the right also repeats the setting of the switch for the signaller.
The lever plates for the two discs in the photo but one above. No 14 - the right-hand disc in the photo -
could be cleared either for a train to reverse from the up line back towards
Northolt Jct,
or (until recently!) a shunting move into the sidings.
The former, however, requires permission from Marylebone SC, who must operate an equivalent acceptance facility (numbered ME65)
to the one in the photo above before
Greenford can signal anything onto the single line.
This is enforced by an electrical lever lock, which will only allow the lever to be pulled if Marylebone has accepted
a train and the track circuits are all clear.
The need for a release from an adjacent signalbox is
highlighted by the white stripe painted on the signal lever. The same release is also required before the
down main starter can be cleared.
A closer view of the East junction, with the up main advanced starter beyond it.
The complete box diagram. The orange rectangles towards the bottom right are
the platforms at South Greenford; the East junction is towards the top right.
A closer view of the left-hand part of the diagram, showing the bay platform and the West junction.
The red rectangle towards the right shows the position of the signalbox. The two small red lamps
in the line to the right of the bay platform are a track circuit indicator, illuminated to show
there is a train there. The two letters above the lamps are a code used to identify that track
circuit - you can see a number of others at various points across the diagram.
A selection of indicator dials under the block shelf. The two on the
left relate to the up main distant (GE40); the right-hand one repeats the aspect the
signal is showing while the leftmost one indicates whether its main lamp filament is
lit or if one of its standby filaments has been activated. If its lamp is out completely,
the right-hand indicator will drop to 'light out'.
The indicator in the centre shows the state of Marylebone's acceptance switch. The one to
its right repeats the arm position of the
up main starter (GE42).
The plungers at the right are used to energise the electric locks and must be pressed
when pulling the levers below them. These are known as economisers because they avoid having
to energise the solenoids that release the levers locks other than when the signaller
actually wants to work that specific lever.
The signalbox. In case you are wondering why Greenford East signalbox
is situated at Greenford West Junction, the box name was originally Greenford East Station.
There were originally platform loops on the main line here, with Greenford Station West box at the far end of the station.
The latter closed in 1971.
You can see from
the brickwork that the original building has been extended; this was done in 1956 when this box
took over control of the South and East junctions.
After the visit I stopped off at South Greenford to take some shots of
the new LED signal at the South junction in action. Here it is cleared for a train to go into the bay
platform.
While I was there I also noticed that the up branch advanced starter had
been replaced with this LED signal since my previous visit.
Thanks to
Network Rail for allowing this visit, the
Signalling Record Society for organising it,
and in particular Danny Scroggins (NR) and Andy Overton (SRS) for their efforts in
making it all happen.
31/7/10
The starter from the Up and Down [East] Loop to the up main.
A telephoto view of the East junction from Perivale underground station. On the right is the up advanced starter.
A long-range shot from Castle Bar Park as a down train approaches the South junction.
The signal in the middle distance is the down branch home.
The last down automatic signal on the branch line, which also acts as the repeater for the down branch home.
The latter can be seen in the distance showing yellow, with the South junction signal beyond it at red.
The down branch home can be cleared irrespective of the aspect of the junction signal, provided there is a clear overlap
available beyond the latter, because there is a full braking distance from the home to the junction signal.
A short clip showing the signals in operation when
Chiltern
and
Wrexham & Shropshire
trains were being
diverted into Paddington due to engineering works. Chiltern trains were running roughly
half-hourly, and the double track section between here and Park Royal was being used as an
extended passing loop. Then the Wrexham & Shropshire came along...
For those not familar with the layout, here is a diagram of the area controlled from Greenford signalbox, which I hope will help put the photos into some context.
Just click on a signal, signalbox or other item to jump to the corresponding photo...
I have deliberately
excluded various technical details to prevent the diagram getting overcomplicated.
I have, however, included signal numbers where I know them - these are the codes in white on small black plates you can see in some of the photos.
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