Ground and Fixed Signals
From quite early on it was realised that the standard
signal, mounted on a post and visible at considerable distances, was
not required when shunting. Also it helped if the train driver could
see which way points had been set as he approached them.
Various
types of small signal, mounted next to the track and called 'ground
signals' were developed. One less common name for these was
'dwarf signals' and the signal man at my local station told
me the railway staff called them 'Dolly' signals.
The
first ground signals were simple discs mechanically linked to points
so as to indicate which way the points were set. If the disk was
facing you it was set for the turning, if edge on it was set for
straight ahead. Then came oil lamps, fitted with two lenses and
mounted on a pivot so that either the red or the white lens could be
turned to face the driver. To aid day-time working it was a common
practice to add a large red painted plate or disk of metal round the
red lens, but this was not universal.
Some companies,
including the GWR and LNWR, tried very small semaphore type ground
signals, again with a lamp behind to give a clear indication at
night, however these proved difficult to see.
Fig___
Examples of early pattern Ground Signals
Early ground signals were operated by the point
blades themselves. The danger is of course that the points might not
have fully closed, so 'independent' signals were developed.
These appear the same to the train crew but they are operated by a
separate lever from the signal box or a local lever via wires and
pulleys. The point mechanism was fitted with a hole and pin
arrangement such that the signal could only be moved to the all-clear
when the point blades were fully home. The photograph of the double
ground signal (Fig___) shows the locking mechanism which is always
mounted beside the relevant point as it is operated directly by the
blades. In the shown example the mechanism is very close to the
signal but it could equally be some distance away. The mechanism
consists of a plate about eighteen inches (45 cm) square with a rod
leading to the point blades and two rods running parallel to the
track. The signal control wires are connected via the two rods and
these can only be moved when the bar to the point is in the correct
position.
Fig___ Ground signal interlocking mechanism
At about the time of the First World War a new
design appeared, consisting of a more or less circular plate perhaps
a foot in diameter, usually painted white with a red stripe across
the middle.
The disc was pivoted in the centre so it could
rotate, on early examples the disc was bolted to the arm of the
miniature semaphore signal. When the red stripe was horizontal it
meant stop, when at forty-five degrees it meant all-clear, for night
operation small holes with coloured glass lenses were fitted to the
plate and an oil lamp mounted behind to give a clear
indication.
These rotating disk signals could be either upper
quadrant or lower quadrant depending upon the preference of the
owning company.
Where the original pivoting oil lamp signals
still existed (the LNWR had quite a few of these for example), two
separate discs were sometimes added to the two faces of the lamp. One
plate had a horizontal red stripe, the other had a diagonal stripe,
representing stop and all clear respectively, these plates had a hole
in the centre for the original oil lamp lens. Some of these modified
oil lamp signals survived into the 1960's.
There were
variations in the design of disc signals, the LMS and the Southern
Railway both had rotating discs consisting of fractionally more than
half a circle with a flat bottom, the SR type had a slight dip along
the lower edge, the LMS had a straight bottom edge. There were a
couple of the LMS type still in use in 1997 at Stockport railway
station south of Manchester. The GWR started with a similar flat
bottomed shape (they only cropped off about the bottom third of the
disk) but then used a full circle, and I believe this latter type
became the standard for British Railways. The LNER standard upper
quadrant ground signal was a full disc. These disc signals did not
replace all the older designs, examples of the LNWR ground semaphore
type remained in use into the 1970's and possibly the early
1980's, however where British Railways replaced ground signals
they fitted the disc type.
Ground signals were only used for
shunting purposes so the prohibition of two arms for different tracks
on a single post did not apply, hence you will see disc signals
'stacked' two, three or even four high on a single short
post. I believe there was a single example of a five disk signal
(five disks mounted one above the other on a single post). The three disk type shown below was at the entrance to the DMU stabling sidings at Stockport, south of Manchester.
Fig___ Three-high disc type ground signal
As
with the multiple home arms these are read from top to bottom as
referring to routes from left to right, hence on a two disk signal
the top disk refers to the route to the left and the upper disc that
straight ahead or to the right. Multiple pivoted oil-lamp signals
could not be mounted on a single post and where there was
insufficient room for these to be placed side by side they were
mounted separately one behind the other, with the rear lamp mounted
on a longer spindle to show over the top.
The convention is to
mount the signal, of any type, to the left of the track it
controlled. Where a single disk was mounted between two sidings and
it would be unclear which track it applied to a small white painted
metal plate with a black arrow was added below the disk to show which
track it referred to.
Ground signals showed red for danger and
green or white (prior to 1893) for all-clear but, due to the
proliferation of red ground signal lights in crowded yards, several
companies used a white light for danger from about the time of the
First World War. In the late 1920's the LMS and possibly other
companies began using yellow lights and yellow miniature arms on
ground signals which might be passed at 'danger' for
shunting purposes.
Modern British Railways disc type ground
signals have a small electric lamp in a housing to the upper right of
the disk which illuminates the disk at night. The reverse side of the
disk signal has a simple white semaphore arm, although this is only
of real use where the rear of the signal is visible from the local
signal box.
Fig___ Disc type ground signals
Ratio offer a kit of the later GWR/British
Railways rotating disc signal in a pack of four single discs, these
were unobtainable for a while so I made some up using a leather punch
to make 2 mm diameter disks from 20 thou card.
To do this
punch several disks with the punch, these will 'back up'
inside the punch tube. Insert a panel pin into the punch and operate
the mechanism to push the cut discs out of the tube. You may then
need to put them between two sheets of metal (I used thick washers)
and squeeze them flat with pliers or a gentle tap with a hammer. The
discs were then stuck to a 6 mm length of 30 x 30 thou Slaters
plastic rod. The lamp was a 2 mm length of 1 mm diameter round
section rod carved about the top to represent the chimney. For the
double disk type use an 8 mm high support and use 2 mm length of the
same 30 x 30 thou rod to represent the square bodied lamps.
The
ground signals in use at Stockport station on the London-Manchester
line are an LMS design dating from the 1940's. The frame is from
pressed metal and there is a small lamp on an arm which illuminates
the front face of the signal. These signals were designed for use
with the standard LMS cropped circle disks but the mountings are
arranged at an angle so that on multiple disk signals full disks can
be fitted with the top of the lower disk overlapping the base of the
one above. In the 1990's all these signals retained the original
cropped LMS disks.
Fig___ Photographs of disk type ground signals in 1997
Fixed signals
Some
signals would always remain in one position, for example some
'distant' signals at the approach to a difficult junction
were fixed at the danger position. On these the arm was simply
screwed to the post. The arm often carried no spectacle plate with
its coloured glass, instead the lamp itself was fitted with a green
or yellow glass, where upper quadrant signals were used the spectacle
plate could be retained as shown in the sketch..
In this
category we also find 'whistle' signs, which told a driver
to sound his whistle. These were mounted where there was any danger
of a train surprising someone, such as un-gated level crossings on
light railways and industrial lines. If a shunting line passed under
a bridge or through an arch in a viaduct a 'whistle' sign
might be mounted so people on the far side of the obstruction would
be warned of the trains approach. Most common was a simple board with
the word WHISTLE painted on it, the GWR used a circular board painted
red and with the letters SW painted on it. British Railways used a
circular board about eighteen inches in diameter with a red ring
around the edge and a black 'W' on a white centre.
Other
fixed signals include the speed restriction sign, used to warn
drivers of reduced maximum speeds across viaducts and bridges, when
approaching unusually tight corners or where track was likely to be
below the normal standard perhaps due to maintenance work. As far as
I am aware the SR and LMS did not use fixed, permanent, speed
restriction signs however the GWR employed a circular board with the
maximum speed. The LNER employed numbers cut from steel plate and
this design was adopted by British Railways. These consist of cut-out
steel numbers approximately eighteen inches high mounted on a metal
post about five foot high. The LNER painted the numbers white but BR
favoured yellow (I believe this change was introduced in the mid
1960's as it was at that time that British Railways research
indicated that yellow was an easier colour to see than red). When
these are placed between tracks where confusion might arise they have
a cut-out metal arrow welded to the support post just below the
numbers.
Following privatisation Railtrack adopted a circular
white plate about two foot (60cm) in diameter with a red ring around
the edge and the speed limit in black numbers. These are virtually
identical to the speed restriction signs used on the
roads.
Temporary speed restrictions were sometimes imposed,
notably where work was being done on the track. The start of the
restriction was marked with a portable sign showing either the letter
C or the maximum speed, the end of the restriction was marked with a
similar sign showing the letter T. I believe most such signs were
square as shown however the GWR used a circular C sign. According to
Glanville Carlton the early BR "C" and "T" signs
were, in fact, stencils, which were slid into special oil lamps which
had a large 2ft (?) cowl, fitted with an opal white plastic 'glass'.
The end result was surprisingly visible at night.
To warn
drivers that a temporary restriction lay ahead an arrow shaped board
about three feet long was positioned further down the line. The board
had two holes, about two feet apart, behind which coloured lights
were mounted. The board was positioned about half a mile behind the
works (that is half a mile before the train would reach the work
area) and displayed a green and white light. According to Glanville
Carlton the early BR (and possibly immediately pre-nationalisation)
arrow boards were painted yellow and had two yellow oil lamps mounted
behind the board, however, according to my notes British Railways
initially used a green painted sign as shown in the sketch (into the
1960's) but one seen in the late 1980's was painted white
with two flashing yellow lights (presumably the standard battery
powered type used on roads at that time).
Beside the track
there were, and are, the gradient posts. Short posts with two arms
pointing along the track, one in each direction, giving a simple
indication where the gradient changed. These were quite small,
perhaps three foot high with two foot long arms. The post and arms
were painted white and the actual gradient was painted on the arms in
black.
Finally with the introduction of electric and diesel
multiple units British Railways introduced small signs, usually
attached to lamp posts, on the platforms indicating where the driver
should stop for various coach formations. These were black, about a
foot high by eight inches wide with white lettering. With steam
hauled trains there would usually be either just a couple of coaches
or quite a few, so the driver either stopped somewhere about the
waiting room or at the far end of the platform, the DMU and EMU
drivers must have found it difficult to judge where to stop. There
would typically be one of these small signs for a four car unit and
another father along the platform for a six car unit.
Fig___
Some typical fixed signals