Upper Quadrant/Lower Quadrant...whats the difference?

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desperate modeller
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Upper Quadrant/Lower Quadrant...whats the difference?

Post by desperate modeller »

Could somebody please enlighten me on the difference between the two and explain their uses?.......thats the trouble of trying to build an accurate model, you got to learn first!!

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Post by richard »

Both are horizontal for Stop / Danger.

Upper Quadrant move up (into the quadrant above horizontal) for "Clear".
Lower Quadrant move down (into the quadrant below horizontal) for "Clear".

Most of Britain's railways started with lower quadrant but eventually changed to upper quadrant for safety. The GWR kept to lower quadrant throughout its life.

Re. safety: Imagine what happens if the connecting levers fail, or the arm is weighed down with snow & ice. An upper quadrant signal would fall to a "Danger" position. A lower quadrant would fall to a "Clear" position.


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Post by Ben »

Just to complicate matters, the Great Northern Railway used somersault signals which pivoted at the centre of the arm through 90-45 degrees to show the 'off' or clear position.

After safety issues arised with lower quadrant signals, counter balences were added to ensure the signal returned to danger is the cable was to break.

Lower Quad:
Image

Upper Quad:
Image

Somersault:
Image

Thanks

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Post by Bullhead »

The GN (most notably at King's Cross) and GC (for example at Immingham) also experimented with three-position upper- and lower-quadrant semaphore signals: the arm - which was red with a vertical white stripe, like a conventional two position semaphore stop arm - was horizontal/displayed a red aspect for "stop"; inclined at 45 degrees/yellow aspect for "caution"; and vertical/green aspect for "clear". A number of proprietary manufacturers offered these systems, which are illustrated in my former colleague Sandy McLean's book, "A Pictorial Record of LNER Constituent Signalling" (ISBN 86093-146-3).

Of course, the logical next step was to dispense with the semaphore arms completely and simply have colour light signalling. And, interestingly, it remains the convention on monochrome signalling layout plans to show the aspect(s) capable of being displayed by colour light main aspect signals by using vertical, diagonal, and horizontal lines (or combinations of these).
So - did anyone dare tell Stephenson, "It's not Rocket science"?
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Graeme Leary »

Just curious - when did NER (if before 1923) or LNER (after) replace Lower quadrant signals with Upper Quadrant?

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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by StevieG »

Graeme Leary wrote: Wed Jul 13, 2022 5:23 am Just curious - when did NER (if before 1923) or LNER (after) replace Lower quadrant signals with Upper Quadrant?

Graeme Leary,
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Unlikely the NER replaced any Graeme Leary.
The IRSE (Institution of Railway Signal Engineers; the professional body for said engineers) only came to consider the subject of upper versus lower quadrant signalling in the 1920s.***

The post-Grouping companies (other than the GWR) then did not launch an intensive (& expensive) programme to replace LQs with UQs in a short time : For one thing a great deal of the LQs still had many years to go before becoming life-expired.

They had to be far more frugal, and so UQs (including those of the LNER) would've probably tended to come in with new significant works, or piecemeal when replacement of LQs became necessary through wear or damage, etc.
Many such LQs were still working past 1948 into the BR period, probably thousands. There were still some ex-GNR somersault signals on the East Coast Main Line in the 1950s, Many LQs were still going into the 1960s (though tended to be more on secondary and branch lines), some made it into the 1970s.
And there is still one 'celebrity' much cared-for Midland Railway LQ in service today on the Peterborough-Leicester line.


*** - [ Apart from safety measures already mentioned to make signal arms working in the lower quadrant fail-safe, certainly the GWR and I'm pretty sure the other companies, by the 20thC. had their LQ arm spectacle plates/frames (the holders of the coloured glasses) that were made to be of a weight heavier than the signal arm. Thus also as far as possible, ensuring that an arm would return to Danger even if entirely disconnected from its operating mechanism.
( The first UQ signals already mentioned appear to have originated in N. America, and usually, or often, were designed to be capable of giving the three indications, hence the first few in the UK at locations mentioned previously (plus a few others, like the Ealing & Shepherd's Bush Railway), were also UQ signals, which also readily distinguished them from the then standard LQ operation of all others signals.
I believe that Distant signals becoming yellow rather than red emerged at around the same time.

Anyway, the IRSE's consensus for the future of semaphore signals was that the UQ 2-position should become the default standard.
( They also expressed a preference of the daytime colour light signal rather than semaphores as the way ahead, and the possible creation and use was pointed out of what became the 4th UK aspect of double yellow.]
BZOH

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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Graeme Leary »

Many thanks StevieG - certainly explains the situation and details very clearly.

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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Atlantic 3279 »

Something suggests to me that there was still a somersault signal at Havenhouse or Thorpe Culvert on the line to Skegness in the 1990s or later. As has been said, even when the desirable new features of signals had been agreed, replacement of existing ones was piecemeal. If there wasn't an overall modernization scheme for that particular line or district (with the object of saving money and/or improving traffic handling?) then only damaged or worn out items would be high priority for replacement, unless say there was a bit of re-signalling for an altered junction. I imagine too that in some cases, replacement signals in "lesser" locations could conceivably be suitable older types (or at least parts threof) recovered in good condition from other places
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Dave »

Graeme.
If you don't have this book by NERA you should get a copy, it will help you a lot.

A History of North Eastern Railway Signalling.
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Horsetan »

Just to muddy the waters a bit, the Cheshire Lines Committee occasionally re-used lower quadrant arms and spectacle plates, but inverted to make upper quadrant arms at almost no extra cost.

Example here

The South African Railways did much the same thing as the CLC.
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Atlantic 3279 »

On TODAY'S lunchtime BBC regional news (Look North, E.Yorks and Lincs version) there was a fire report from Boston, and visible at times in the coverage were both a traditional level crossing with wooden swing gates, and I believe a SOMERSAULT SIGNAL by the quirky octagonal building next to the level crossing.
Viewers were informed that the fire brigade had stopped all road traffic and trains owing to the precarious state of the adjacent fire damaged multi-storey building. As I suspect the rail line in question may be only the link to Boston Dock, I'm not sure how much rail traffic has been stopped...
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Horsetan »

Atlantic 3279 wrote: Wed Jul 20, 2022 6:39 pm On TODAY'S lunchtime BBC regional news (Look North, E.Yorks and Lincs version) there was a fire report from Boston, and visible at times in the coverage were both a traditional level crossing with wooden swing gates, and I believe a SOMERSAULT SIGNAL by the quirky octagonal building next to the level crossing.
Viewers were informed that the fire brigade had stopped all road traffic and trains owing to the precarious state of the adjacent fire damaged multi-storey building. As I suspect the rail line in question may be only the link to Boston Dock, I'm not sure how much rail traffic has been stopped...
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by Atlantic 3279 »

The very one.
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by PinzaC55 »

I think a common time when NER signals began to be replaced by LNER upper quadrants would be 1937. There is an interesting set of photos in Kew PRO showing early colour light signals between York and Darlington and these also date from 1937.
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Re: Upper Quadrant/Lower Quadrant...whats the difference?

Post by majormagna »

Indeed they began to be replaced by that time, but several lower quadrant signals were still i use on branch and secondary routes in the NE Region in BR days, the Stainmore line was especially noted for having a mix of all three NER Division pattern signals, as well as LNER/BR upper quadrants!
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