Hello and signals

[acook]

Hello everybody,cracking site,local history meets industrial archaeology.
Being the tender age of 52 i was a child when steam ended,but still love the engineering behind it all.
I was at the AVR gala saturday and enjoyed it enormously ,as I managed to see 5043 come into BTM ,and see it go out on the way back.
Now,being a big kid and refusing to grow up,i am building a model railway.
I have got to the signalling stage and have encountered a problem that the world wide wait does not seem to mention.And this would probably be the best place to ask this.
So,semaphore signals in an unoccupied block,home cleared,distant cleared,as the train passes the distant signal does the arm move to caution,or does it continue to mirror the cleared home?
Both scenarios seem right ,and wrong at the same time.I'm hoping a wise old head here could help me .
cheers,alan

[jolly47roger]

When a home and a distant are on the same post then, if I remember correctly, they always return to level together. But maybe it's not the same for a lone distant.

[BristleGWR]

This illustrations on this page I think answers your questions:

http://www.signalbox.org/signals/semaphore5.htm

[acook]

Thanks for the input,the signal box was one of the places visited .
It confirms the case of a combined home/distant returning to level together
when the train passes,which would imply that a lone distant when passed would not continue to mirror the relevant home signal.however,in the case of a long block,and the distant being a braking distance in front of the home,is it possible the distant would not level until the home leveled?I ask this because it would almost halve the gubbins I need to make to actuate the signals.

[BristleGWR]

I'm not a signalling expert, so I might be completely wrong, but my understanding is that the lone distant and the home are operated from the same box using two separate levers and are interlocked with relevant points/other signals and also interlocked together such that the distant can not be set to clear unless the home is set to clear first. Working in reverse order, with these same interlocks in place, I would assume that the distant would need to be set to caution before the home could be set to danger??? Thoughts anyone?

[jules]

I would assume that the distant would need to be set to caution before the home could be set to danger??? Thoughts anyone?

Generally, semaphore interlocking prevents the signalman clearing signals - it does not prevent any signal at clear being returned to danger, even before the train has passed - as might be required in an emergency situation (though this sort of thing gives drivers brown trousers!)

Therefore, the distant most certainly does not have to be set to danger before any associated stop signal can be set to danger. What if the train has passed the distant but not the stop signal and an emergency develops? In this case the stop signal must be operable to danger regardless of the distant's position - after all, it doesn't matter - we know there isn't another train in rear that will see the distant still at clear ...

Of course, the distant cannot be cleared before all associated stop signals are cleared, with the normal course of events being that both the distant and the home signal will be returned to danger when the train has passed both signals, though technically a separate distant can be returned to danger before stop signal once the train has passed it - not something you might be able to see though - until you can see the actual train approaching.

Through slotting on a stop / distant combination, the distant arm will never show clear until the stop signal has been cleared, even if the distant has been pulled off by the controlling box. Normal sequence of events would be for stop signal to be cleared, followed some time after by the distant controlled by the box in advance as their block section clears. It can happen that the distant is already cleared by the box in advance but is held at danger by the slotting - in this case, the stop and distant arms will appear to come off together. This might happen when the box in advance is switched out (i.e. all its through signals are at clear), or where the signalman in advance is a little faster than his counterpart and he has a clear block section available (notably where there is a route divergence, a train has been shunted off, looped or terminated leaving a through route).

One more thing - having gone "out of course" and reversed a stop signal at clear back to danger before the train has passed but after the train has been accepted and entered section, the electrical interlocking will give you absolute hell before you can clear that signal again. Best to have a damned good reason if you don't want fisticuffs with the train crew too!

Note that throughout this reply I have referred to stop signals, rather than home or starter signals. The definition of the positioning of a distant when combined with a stop signal is that it should be at the "section" signal of the box in rear, which will normally be the starter - not the home. This depends on braking distance to the first stop signal (home signal) of the section in advance. If that distance is insufficient, then an outer distant would be provided at an earlier starter signal or at the home signal of the box in rear.

I hope I've got all this right - it's been many years since I was taught the darker arts of sempahore signalling. To protect the guilty, I won't say where I learned

[BristleGWR]

Thanks jules for the reply, and correcting me, I wasn't sure how the interlocking worked in reverse.

To help answer Alans question could you please advise/confirm the following:

If there is sufficient distance between the distant and the stop signal and the signalman has means of detecting that a train has passed the distant the distant could be set to caution before the train reaches the stop signal. i.e. the distant would go to caution before the stop went to danger. In an emergency or where the distance between the distant and stop signal is relatively short the distant and stop signals would go to caution and danger respectively at the same time.

[jules]

If there is sufficient distance between the distant and the stop signal and the signalman has means of detecting that a train has passed the distant the distant could be set to caution before the train reaches the stop signal.

Yes that is absolutely correct, but it not compulsory. Sometimes, a treadle is provided, connected to a bell that announces the arrival of the train in section. But the above has little to do with the distance between the signals. The distance between the distant signal and the first stop signal in the next section is absolute - it must be sufficient for the fastest train to stop at the stop signal having passed the distant at caution. This depends on many factors - the maximum line speed, the gradient, maximum weight of trains on the route etc.

In an emergency or where the distance between the distant and stop signal is relatively short the distant and stop signals would go to caution and danger respectively at the same time.

When the starting (or section signal) goes to danger and the train passes out of section, because of the slotting on the same post, the distant will automatically go to caution when the box in rear sets their starter/section signal back to danger, regardless of whether the box in advance has operated the lever to put the distant back at caution or not. (Frequently they won't have, as they might not yet have seen the train).

Where the distant is not slotted and is on its own post, logically the signalman would replace the distant followed by his home signal once the train has arrived in his section. Don't forget that another train cannot enter the section until the previous one has completely cleared it or otherwise been accommodated.

As per above, the distance between the distant and first stop signal cannot be "relatively short" - it is an absolute distance. If the local conditions dictate that the distance between a starting signal and the stop signal in advance is insufficient for the fastest / heaviest train to stop, then an "outer distant" will be provided at a preceding stop signal. This could be the home signal or any other intermediate stop signal, or in exceptional circumstances an "advanced outer distant" in rear of the home signal (very rare).

Bear in mind that for the box in advance to clear their distant, they must clear *all* of the relevant stop signals in their section, meaning the train will pass through to the next section, without possibility of being stopped (except in emergency) ...

If signalman needs to slow a train down, it was very common practice to leave distant at caution and home signal at danger, then clear the home signal just as the train approached it.

Another point to remember was that guards were also responsible for seeing that signals were not passed at danger, so it didn't pay to be overly prompt at returning signals to danger in case a guard misread the situation ...

The whole point is that there sure can't be a following train until your section has cleared and you have accepted a following train, so it isn't that important to immediately return signals to danger, as there sure won't be anyone along to see them not at danger - therefore, a common misconception

[BristleGWR]

Thanks jules

[acook]

Thanks for all of this, I think the important point here is the signal box itself,has control over the local area that the train is in,and what was confusing me initially is the modern experience of automatic signals being tripped as they are passed.
In my case of 1940-55 it would seem the distants and homes can move together,just need to make more signal boxes!
At the risk of opening another can of worms, the Great Western . org site has the distances between boxes on the various routes and generally this is only 1-2 miles.There are several boxes almost adjacent to each other, and i wonder about the ringing of bells must have been almost constant.
Not an easy job and i have new respect for the men who did this job.

[jules]

Thanks for all of this, I think the important point here is the signal box itself,has control over the local area that the train is in,and what was confusing me initially is the modern experience of automatic signals being tripped as they are passed.

Yes, that is a colour light phenomenon - with semaphore, apart from the supervisory interlocking, the signalman had complete control over all signals and points and operated them with sheer manual graft.

In my case of 1940-55 it would seem the distants and homes can move together,just need to make more signal boxes!

Post your track layout and signals here if you'd like it checked over for signaling!

There are several boxes almost adjacent to each other, and i wonder about the ringing of bells must have been almost constant.
Not an easy job and i have new respect for the men who did this job.

True indeed. It is easy to forget that up until the 1950s nearly everything went by rail and the UK's railway system was an extremely busy place, 24/7

[acook]

On the grounds of a result about signalling,does anyone know what the locos and rolling stock would have been travelling the severn beach line late 30s to the dmus of the early 60s. I know the midland ran excursions to svb so i can justify a black 5,and there was mention on here of metro tanks in the 30s,but I have no idea of what ran inbetween.

[stantheman]

On the grounds of a result about signalling,does anyone know what the locos and rolling stock would have been travelling the severn beach line late 30s to the dmus of the early 60s. I know the midland ran excursions to svb so i can justify a black 5,and there was mention on here of metro tanks in the 30s,but I have no idea of what ran inbetween.

I lived next to the Severn Beach line at Shire' for several years. I didn't really have a deep interest in trains at the time, but I used to spend a fair amount of time at Hung Road bridge watching the comings and goings.

Most trains consisted of Prairie or 'Matchbox' locos with 2 or 3 suburban in tow. Occasionally a 'GWR' railcar (with or without a single suburban would be seen and very,very occasionally a twin railcar with a coach between.

I used to catch the train from Shire' to Clifton Down going to school. If I arrived at the station 15 minutes early I could catch a train which consisted of a tender loco plus 5 or 6. On Friday I deliberately caught a later train home as it was a railcar, but the guards always made us schoolkids ride in the coach behind.

There were also the 'monkey specials' which worked from various parts of the country (mainly South Wales) via Pilning to the Zoo at Clifton. These were longer trains (7-9) with tender engine.

The majority of the freight workings were 4w petrol tanks or 4w vans (banana with white circle marks). In addition there were regular visits to Shirehampton coal yard with coal for the two main merchants (Lowell Baldwin was one of them). All these freights were normally pulled by the Prairie/Matchbox locos.

There may have been other locos used but alas I had no knowledge of class types at the time.

[acook]

Superb, the exact answer i was hoping for.
On t'net the metro tanks are class 455 240's,matchboxes would be 57xx pannier tanks, the tender loco is possibly a 260 43xx, or 2251 collet 060, and as for the railcars, these would have been the swindon built style, with the slab ends.its a shame the earlier streamlined ones were not based in bristol as i think they just look much better.
as an aside, gwr archive mentions twin set nos 35&36 being destroyed by fire at st annes park in 1956, does anyone know any details about this?
It seems fire accounted for five units out of the38 built, which seems rather high .
and finally?, these units had 2 aec bus engines onboard, did they sound like a class101 or similar heritage dmu?
Thanks everybody for the info, this place is magnificent.

[AndyK]

Superb, the exact answer i was hoping for.
On t'net the metro tanks are class 455 240's,matchboxes would be 57xx pannier tanks, the tender loco is possibly a 260 43xx, or 2251 collet 060Thanks everybody for the info, this place is magnificent.

I'm not old enough to have more than the vaguest memories of the line in steam days- I can remember a standard tender loco coming through Clifton Down on a freight - presumably a 73xxx or a 75xxx. Otherwise my knowledge is from books.

I have seen pictures of a 43XX mogul on passenger duties; prairie tanks seem to have been the 4575 (sloping tank) variety; I expect the standard Class 3 82XXX tanks would have been used quite frequently. 28XX freight locos could be seen on Monkey Specials.

When the line between Ashley Hill and Kingswood was still open for passengers the service was operated by ex-Midland 0-4-4 tanks.

As for freight, I suppose virtually any class that was used in the Bristol area generally coulod have been seen on the Avonmouth line - not forgetting the Somerset & Dorset 2-8-0s.