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Ashton Moss South Junction - Crowthorne Junction

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

Ashton Moss South Junction - Crowthorne Junction

Unread postby John_S » Fri Feb 24, 2017 7:28 pm

Here is the signal box diagram for Ashton Moss South Junction, after it assumed control of Crowthorne Junction about 1970:

http://www.lymmobservatory.net/railways ... th_q65.jpg

I also have another plan which gives distances and TC lengths (not scanned), from which we learn T3 was 440 yds long, T5 was 220 yds and T9 440 yds.

I understand the lengths for T3 and T5 - Absolute Block clearing points for semaphore and colour light distants, respectively. But what is the reason for T9 being 440 yds? It sounds like an AB clearing point but is not (unless Crowthorne acquired a colour light 8/9 before closure..)
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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby John Hinson » Sat Feb 25, 2017 11:14 am

Hmmmm, with no other suggestions arising I'll pop an idea into the melting pot and suggest that it was planned to convert the home signals to three-aspect colour-light signals either then (and then ideas changed) or for the future (whether it actually happened or not).

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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby John_S » Sat Feb 25, 2017 11:25 pm

Thank you John, although I'm not sure I follow you: if the signals at Ashton Moss South itself were converted to 3 aspect colour light, how would this require a 440 yard overlap at signal 8/9? For what it's worth, 8/9, 69 and 70 were all 3 aspect colour lights, according to my information.
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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby John Hinson » Sun Feb 26, 2017 11:58 am

My intended inference was that as colour-lights they could be worked like multiple-aspect signals, in other words you could clear 2 or 5 in advance and they would show a yellow to allow a train to roll down to 8 with the overlap clear. The same could be achieved with a distant arm below 2 & 5 semaphores. But there wasn't . . .

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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby John_S » Sun Feb 26, 2017 12:24 pm

Thank you John, that's clearer!
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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby Mark Lamb » Tue Feb 28, 2017 9:38 pm

Though I haven't got an answer for the query of why T9 was 440 yards long, I have some suggestions that may be relevant. It may be that signal sighting had something to do with it: there are quite a few bridges between Ashton Moss South and Crowthorne, and it could be that it was difficult to position 8/9 signal closer to the junction. Also, the approach to 8/9 is on a falling 1 : 122 / 100 gradient. Not all colour light overlaps were 200 yards - on the West Coast modernisation scheme that gave us Carlisle PSB, the overlaps over Shap were (still are?) shorter than the standard 200 yards when climbing, and longer when descending.

The two factors may have combined to position 8/9 where it was, which fortuitously (though with no real reason) gave an overlap of 440 yards. Purely conjecture on my part, though.

Regards,

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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby scarpa » Wed Mar 1, 2017 5:59 am

n the diagram R 70 appears to have position 1 and 4 route indicators.Is this a mistake or am I missing something? Signal 8/9 appears to have the route indicator applying to the Branch which seems odd assuming the points set for the branch would be normal and the higher speed.
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Re: Ashton Moss South Junction - Crowthorne Junction

Unread postby John Hinson » Wed Mar 1, 2017 8:36 am

R70 signal was back at Guide Bridge - Stockport Junction's Home. Position 4 applied to this line, position 1 to Denton Junction and of course neither for the main line towards Manchester Piccadilly.

I'm not sure offhand what the speeds were at Crowthorn Junction but probably not much different for either destination as this was not exactly a high speed route. These days I suspect you would have a feather for either route.

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