Co-acting semaphores - sky arms

[Rescars]

Following on from the thread elsewhere about current practices regarding banner repeaters and co-acting signals, perhaps there is room for a discussion about co-acting semaphores. AIUI these were typically two linked arms carried on the same signal post, with the principal arm at or near normal level, but with a co-acting arm placed vertically much higher to give better distance sighting, sometimes referred to as a sky arm. Surely the most spectacular installation of this sort was the famous "bedstead" gantry at Rugby, where all 22 arms were duplicated with 22 co-acting sky arms. This became necessary following the construction of the bridge carrying the Great Central across the LNWR, which destroyed the visibility of the original signals. IIRC the GCR had to fund the duplication. Are there any co-acting semaphores still operating on the national network or in preservation?

 

[norbitonflyer]

I was at Boat of Garten yesterday and noticed one there on the northbound

 

[MadMac]

In terms of NR, I believe the one at Greenloaning was the last in Scotland. Not sure about other parts of the country, but they must be pretty rare now.

 

[Fleetwood Boy]

Am I being really stupid, but why isn’t there the same sighting problem with colour light signals? Don’t think I’ve ever seen any repeated in the same way?

 

[riley1489]

Embsay, on The Yorkshire Dales Railway (preserved) has a co-acting starter signal at the end of the Bolton Abbey- bound platform. Or had the last time I was there, about 20 years ago.

 

[Ashley Hill]

Am I being really stupid, but why isn’t there the same sighting problem with colour light signals? Don’t think I’ve ever seen any repeated in the same way?

Semaphore co-actors were provided for poorly sighted signals where high speed required a driver to see the signals well in advance. The very tall ones that existed at Seaton Junction are a good example. There were two footbridges hiding the lower arms.
Colour light signals are sited to avoid the need for co-acting. I’m not aware of any but await to be proven wrong.

 

[AndrewE]

Semaphore co-actors were provided for poorly sighted signals where high speed required a driver to see the signals well in advance. The very tall ones that existed at Seaton Junction are a good example. There were two footbridges hiding the lower arms.
Colour light signals are sited to avoid the need for co-acting. I’m not aware of any but await to be proven wrong.

I think that colour light signals were always massively brighter than the earlier oil-lamp semaphores, so are much less likely to need extra clues to be provided for the driver. Weren't they originally called (or nicknamed) "searchlight signals" and installed specially for the reason of extra visibilty?

I thought that some [lower] co-acting signals were actually installed because the old pea-souper fogs meant that footplatemen couldn't see the upper arm sited for viewing well ahead, but needed to be able to read a signal close to them when they would have stopped at it in poor visibility. Aren't there stories of firemen climbing the signal post ladder to check or feel whether the semaphore was on or off?

 

[Gloster]

There were all sorts of reasons for co-acting signals, but they largely boiled down to situations where the driver could not see the signal continuously when approaching it. It might be an obstruction, such as bridge or a station canopy, it might be the curvature of the line, or possible obstruction by smoke, etc. It might also be the risk of the driver stopping at the signal and possibly mistaking the aspect because the arm placed well up is almost above him.

 

[King Lazy]

There are a lot of co-acting colour lights. A couple of examples are Lancaster which has a pair of ground level co-actors next to one another on the up main and platform 4.

Manchester Piccadilly Platform 14 has one too.

Here are some links to photos in the web.

Lancaster.

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Piccadilly.

Colour Light Signals

Regarding the original question. Helsby may still have its co-acting semaphore? I don’t think it has been resignalled and it certainly did have one.

 

[Sun Chariot]

I think that colour light signals were always massively brighter than the earlier oil-lamp semaphores, so are much less likely to need extra clues to be provided for the driver. Weren't they originally called (or nicknamed) "searchlight signals" and installed specially for the reason of extra visibilty?

I think searchlight colour light signals were of a single lamp lens, with rotatable filters for red, amber and green aspects. When I commuted along the Lea Valley to London, 1994-99, the Seven Sisters loop had such signals; and some between Bethnal Green and Hackney Downs.

 

[Sir Felix Pole]

Did the GW / WR go in for co-acting signals - they seemed to favour unusual placements instead to get round sighting problems? Thus the down starter at St.Erth is very low down to be visible under the (old) footbridge and against the rising gradient.

 

[Rescars]

Did the GW / WR go in for co-acting signals - they seemed to favour unusual placements instead to get round sighting problems? Thus the down starter at St.Erth is very low down to be visible under the (old) footbridge and against the rising gradient.

The GWR's preference for right hand drive resulted in a number of unusual placements so the driver didn't have challenges seeing round the boiler.

 

[Foxhunter]

Are there any co-acting semaphores still operating ... in preservation?

Ropley Down Main Starter on the Watercress Line. I know it's still there because I operated it last Wednesday.

(Also on approach to the Ropley Down Inner Homes the footplate crew see twin Semaphore Banner Repeaters. And the Yard Exit has a Yellow Shunt Dummy. A treasure trove of ephemera).

 

[341o2]

Am I being really stupid, but why isn’t there the same sighting problem with colour light signals? Don’t think I’ve ever seen any repeated in the same way?

A semaphore signal may not be in the preferred position because it is manually operated. No such restrictions regarding colour light signals

 

[Rescars]

Many thanks to all for their comments. It's good to know the species is not yet extinct.

As some of you appear quite close to this, some related questions if I may. As both arms co-act, they are presumably worked by the same lever in the box. But do the two arms have different numbers to identify them separately? Are they shown separately on the the signalling diagram? Are there separate indicators to prove their lamps are working etc? From an operating/maintenance perspective is one arm considered to be the principal which the other arm follows and, if so, is the sky arm the principal or the follower?

 

[4COR]

Believe the Bluebell have a co-acting outer home at Horsted Keynes (on the same post as the inner distant for even more complexity) - can be seen in an image on this page: https://www.bluebell-railway.co.uk/bluebell/pti/hkwork_archive3.html

 

[edwin_m]

Many thanks to all for their comments. It's good to know the species is not yet extinct.

As some of you appear quite close to this, some related questions if I may. As both arms co-act, they are presumably worked by the same lever in the box. But do the two arms have different numbers to identify them separately? Are they shown separately on the the signalling diagram? Are there separate indicators to prove their lamps are working etc? From an operating/maintenance perspective is one arm considered to be the principal which the other arm follows and, if so, is the sky arm the principal or the follower?

They would never intentionally be in different positions so I'd guess they are mechanically connected and worked off the same lever. I'd also guess that if the linking mechanism broke, the lower arm would possibly continue to work but the upper one would fall to danger.

 

[Taunton]

Did the GW / WR go in for co-acting signals - they seemed to favour unusual placements instead to get round sighting problems? Thus the down starter at St.Erth is very low down to be visible under the (old) footbridge and against the rising gradient.

The GWR/Western Region did not, as far as I am aware, have any co-acting signals. If there was a sighting issue for a signal ahead they would instead install a further double-arm one behind, which could show just the home clear to take you through to the starter, or home and distant clear to give the same assurance that a "sky arm" would do from afar, that it was clear as well. This led to more distants than there were block sections - through Taunton on say the Up line there were five such double-arm signals in succession with distants, but only three signalboxes, and some complex slotting. The several distants would have been On right back to the braking point for the Starter being On. It was not uncommon for a train, especially in the summer Saturday congestion, having been checked by the first distant, to have them being pulled off as it progressed through, and it could apply power and accelerate even before getting to the station, the section beyond having just been cleared.

 

[Gloster]

Co-acting arms should always be showing the same aspect, otherwise they are not co-acting arms. They are worked by the same lever and have the same number, which is actually the lever number. A driver only needs to say ‘I am at signal AB12’ as both are the same signal as far as s/he is concerned. Both arms have the same importance. There would be one sensor for each light, but in the box they might be shown separately or on the same indicator. For the signalman it doesn’t matter which lamp is out: he must apply the relevant regulations in every case.

To be clear: as far as the rules are concerned, co-acting signals are in just about every way exactly the same as a single arm/light signal and are really just one signal. They only have a second arm to make it easier to se them when the train approaches.