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Signal boxes - Great Harwood loop line

British signalling of the past (UK, excepting Northern Ireland)

Re: Signal boxes - Great Harwood loop line

Unread postby Pete2320 » Mon Mar 6, 2017 5:09 pm

andyhunt873 wrote:Hi everyone,

I know this is not really concerned with signalling, but I thought someone might be able to help.

My friend Bernard wants to give a talk about people using the trains during "wakes weeks" and going to Blackpool for their holidays.

Has anyone got / know of copyright free photos that Bernard could use during his talk / or with your permission?

Just thought I'd ask, as you've all been very helpful to me.

Thanks,
Andy.

No, not really a subject for this Forum! However it does remind me that the L&Y routes to Blackpool were well provided with small section splitting boxes, some of which survived until fairly recently.
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Re: Signal boxes - Great Harwood loop line

Unread postby Chris L » Mon Mar 6, 2017 5:27 pm

Pete 2320 wrote:
No, not really a subject for this Forum! However it does remind me that the L&Y routes to Blackpool were well provided with small section splitting boxes, some of which survived until fairly recently.


.....not to mention the multitude of mechanical IB signals, some worked from such boxes! (see: https://signalbox.org/diagrams.php?id=711 ). However, we're wandering off topic again.....

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Re: Signal boxes - Great Harwood loop line

Unread postby andyhunt873 » Wed Mar 8, 2017 7:18 am

Hi Chris,

Thanks for that, I know I wandered off the subject.

So here's one on signalling.

I was once again looking at the OS 1912 map, and was asking myself how accurate is the map, I was following the track on the map either side of Simonstone station trying to gauge where the distant signal was for the up line.

I now know that a distant signal was placed a minimum of 440 yards before the home signal to allow the train to slow down and break for the home signal in time, but if the map is correct, I measured it at well over 700 yards - could that be right?

The line gradient is stated at 1 in 90 along this section, and I know that in placing a distant signal, gradients and breaks were taken into account, so could 700 yards be correct?

Thanks,
Andy.
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Re: Signal boxes - Great Harwood loop line

Unread postby JRB » Wed Mar 8, 2017 8:08 am

It could.
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Re: Signal boxes - Great Harwood loop line

Unread postby kbarber » Wed Mar 8, 2017 9:29 am

Could often be very much more than 700 yards too... all depends on not only gradient but also maximum permitted speed (and perhaps what the sighting constraints are, possibly other factors too). At St Albans South https://signalbox.org/diagrams.php?id=151 the down distants were some 1035 yards from the homes (the line is climbing at that point) whereas on the up (with a downgrade assisting the train) it was 1760 yards.
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Re: Signal boxes - Great Harwood loop line

Unread postby Chris L » Wed Mar 8, 2017 10:02 am

In 1960, Simonstone's Up Distant was 950 yards from the Home signal and its Down Distant was 942 yards from Down Home 1.

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Re: Signal boxes - Great Harwood loop line

Unread postby Danny252 » Wed Mar 8, 2017 10:29 am

Is 440 yards the minimum for a distant? I thought that it was 800 yards for lines with negligible gradients in "later" days (i.e. I don't know what the rules where in, say, 1880!).
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Re: Signal boxes - Great Harwood loop line

Unread postby Bob Davies » Wed Mar 8, 2017 10:39 am

The distance between a distant signal and the first (next) stop signal is determined by the speed of the line, the gradient between the two signals and the type of traffic using the line.

Here is a nice explanation of how braking distance is worked out, with some examples -
http://dickthesignals.co.uk/onewebmedia/29%20calculation%20of%20service%20braking%20distance.pdf

Aandyhunt873 wrote:I now know that a distant signal was placed a minimum of 440 yards before the home signal to allow the train to slow down and break for the home signal in time, but if the map is correct, I measured it at well over 700 yards - could that be right?

I think that you are confusing the distance with the block clearing point. The line speed would have to be very low for 440 yards to be an adequate braking distance.
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Re: Signal boxes - Great Harwood loop line

Unread postby andyhunt873 » Wed Mar 8, 2017 12:57 pm

Thanks everyone again!

Yes, that's me getting the block section confused with signalling again :roll:

Interesting to read about the distances of the signals at Simonstone, Maybe I will never really know which signals are which from an old OS map, but obviously at stations (either side of) they must be (whatever they are know by) stop signals.

And from looking at the examples of the block sections, signals next to boxes (either side of) must also be stop signals (home and starting signals), and the one to the rear of the home signal - a distant one?

I've been reading a BR 1960 publication for the central lines, it has lots of fascinating details about each line, are there any online documents / publications / sites with signal locations / details etc?

Thanks,
Andy
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Re: Signal boxes - Great Harwood loop line

Unread postby Mike Hodgson » Wed Mar 8, 2017 1:47 pm

You should be circumspect in using old OS maps to determine historical signalling. These maps will be accurate as at the date of original survey. Subsequent changes are unlikely to be shown unless there is a complete resurvey, but that was infrequent. Also they show signal posts regardless of how many signals or what type are on the post; and to avoid confusion they do not necessarily show all the signals.
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Re: Signal boxes - Great Harwood loop line

Unread postby Chris L » Wed Mar 8, 2017 8:18 pm

John has very kindly put my 1960 diagram sketch of Simonstone on the main Signal Box site - see https://signalbox.org/diagrams.php?id=1145.

Hopefully that will help answer some of your questions, Andy.

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Re: Signal boxes - Great Harwood loop line

Unread postby Stuart Johnson » Thu Mar 9, 2017 9:46 am

Looked at in more general terms, Simonstone is an almost perfect example of what might be described as the classic British double track station layout, with crossover, slip connection to sidings, and trailing outlet at the other end. It has the standard signalling necessary to get Board of Trade approval post-1889, and no more.

There were many examples of this layout all over the country, and examining the differences between the various companies' approach to signalling it has produced lots of discussion over the years. However, this is the textbook version!
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Re: Signal boxes - Great Harwood loop line

Unread postby Mike Hodgson » Thu Mar 9, 2017 11:01 am

Stuart Johnson wrote:Looked at in more general terms, Simonstone is an almost perfect example of what might be described as the classic British double track station layout, with crossover, slip connection to sidings, and trailing outlet at the other end. It has the standard signalling necessary to get Board of Trade approval post-1889, and no more.

There were many examples of this layout all over the country, and examining the differences between the various companies' approach to signalling it has produced lots of discussion over the years. However, this is the textbook version!


One further feature of this layout which Stuart might have mentioned is the total absence of facing points. To clarify the term Slip Connection in case you're not familiar with it:
You can cross a train between Up and Down Lines by pulling 6 lever to reverse the crossover.
If you pull both 6 and 7 levers you can cross between the UP Main and the yard.
But you cannot get directly from the Down Main to the Yard at that end - you would use 10 instead.
Note that in both cases the arriving train would always back into the yard.
You can't pull 7 on its own; the locking will require 6 to be pulled first.
The reason that a single slip is used, rather than a double slip (which would have allowed Down trains to run directly into the yard) is that this would constitute a facing point and the Board of Trade strongly discouraged provision of facing points on running lines wherever they could reasonably be avoided as they had frequently been the site of derailments in the Victorian era.

Whilst it is possible to get from the Down main to the Yard at the Great Harwood end, the train would have to back over the crossover 6 onto the Up Main and then go forward with 6 and 7 levers reversed. This is undesirable since it not only involves more movements and takes longer, it unnecessarily blocks both running lines in the process.
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Re: Signal boxes - Great Harwood loop line

Unread postby andyhunt873 » Thu Mar 9, 2017 11:25 am

Chris / John / Mike.

Chris,
Thank you for sharing the Simonstone track layout, it does indeed answer many questions for me.
Can you tell me what the abbreviations AR, LR, ALR mean please? also what W: 12 and S: 4 means?
I've seen this on other track layouts. Lastly (and I'm sorry I ask a lot of questions), by the two distant signals there is a square box with a cross in it, what does that denote?

John,
Thanks for taking the time to amend the website to include the Simonstone layout, I know it's not a quick thing to do!

Mike,
Thanks for the detailed explanation of the workings of the points, I have been puzzling over why the sidings at Gt. Harwood / Simonstone and Padiham where against the flow of traffic - but you've explained it perfectly to me! and the more I look at the map, the more I see it.

Thanks,
Andy.
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Re: Signal boxes - Great Harwood loop line

Unread postby Mike Hodgson » Thu Mar 9, 2017 12:30 pm

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