Re: Ground Shunt Signals
- From: WZR <invalid@xxxxxxxxxxx>
- Date: Wed, 4 Jun 2008 19:41:38 +0100
On Tue, 03 Jun 2008 20:08:07 +0100, John F Kappler wrote:
A couple of years ago (I think) all the ground shunt signals I saw in
the south of the UK were changed so that at "danger" they displayed
two red light instead of the previous one red and one white.
However, in Glasgow recently I noticed on the approach to Central the
ground signals there still display the red/white combination (despite
all the normal signals being modern LEDs).
I was even more surprised to see one at Shields Road that not only had
the red/white combination but that the unit appeared new and the
lights were LEDs.
I understood the original change was for safety reasons so did the
change only apply to parts of the UK - Was Scotland exempt?
JohnK
To add to what has already been said, the 'pivot' aspect (the permanently
lit one) of the new LED signals can display both red and white through the
same aperture, meaning that it is possible to wire the signals to display
either RW/WW or RR/WW. There is allegedly a requirement that thou shalt not
mix aspect displays in the same area, though I have seen this flouted in a
few places. This requirement probably accounts for the Shields example you
saw.
A common method of replacing the signals, to conform with the above, is to
replace the heads progressively over a few weeks, maintaining the old
aspects, then once they are all LEDs, go round and reconfigure the aspects
in a single weekend.
Glasgow Central still has (AFAIK), a number of examples of stacked multiple
heads, rather than single ones with a route indicator, so having 'all reds'
might have been considered to have been potentially confusing in these
instances.
With regard to the elevation of the heads, mentioned elswhere in the thread,
this is a recent practice implemented for a couple of reasons:
It makes the signals easier to see, since a true ground mounted head can get
'lost' in amongst high ballast shoulders - especially when read from a train
length away during propelling movements, and covered in brake dust and other
contamination;
it makes maintenance easier, you don't have to grovelling in the ballast on
your knees to get the back off (more relevant for non-LED heads where lamp
replacement is required on a regular basis).
--
WZR
.
- References:
- Ground Shunt Signals
- From: John F Kappler
- Ground Shunt Signals
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