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Liskeard distant signals

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

Liskeard distant signals

Unread postby colin1501 » Thu Jul 17, 2014 4:00 pm

Can anyone tell me when Liskeard box's distant signals ceased to be semaphores? I have a vague recollection of driving east along the A38 in 1980 and seeing a semaphore distant (the 'up') at the eastern end of Moorswater Viaduct. Also, I'm aware that there is (what I assume to be) a down outer home signal at the eastern end of Bolitho Viaduct. Was this always the case, or did this post originally carry the distant? Grateful for any help.

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Re: Liskeard distant signals

Unread postby Martin Shaw » Thu Jul 17, 2014 4:20 pm

Colin

The info I have suggests a date of 15-06-81 for introduction of C/L distant signals. Actually this was when the connection to the branch was made facing from the up road instead of trailing into the down. As far as I can tell the down outer home was as it was from at least 1915 at 995yds from the box, the distant was 1980 yds from the box and motor worked when semaphore. When the C/L distants were introduced they were moved out, up from 941 to 3620 yds, and down from 1980 to 2891 yds. Hope this answers your question.

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Re: Liskeard distant signals

Unread postby colin1501 » Thu Jul 17, 2014 4:39 pm

Many thanks, Martin, this is really helpful and ties in with the date that I observed the semaphore up distant. Out of interest, was there any increase in line speed when the C/L distants were installed, given the significant increase in braking distance available?

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Re: Liskeard distant signals

Unread postby Wilkinstown » Sun Jul 20, 2014 5:25 pm

Martin Shaw wrote:Colin

When the C/L distants were introduced they were moved out, up from 941 to 3620 yds, and down from 1980 to 2891 yds. Hope this answers your question.

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Why was the up distant moved so far out - were there additional stop signals provided at the same time ?
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Re: Liskeard distant signals

Unread postby Martin Shaw » Mon Jul 21, 2014 7:58 am

No. I suspect it will be to do with maintaining adequate braking distance on a steeply falling gradient, but I have no information to confirm that.

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Re: Liskeard distant signals

Unread postby Danny252 » Wed Aug 6, 2014 11:18 am

Seems likely - Up trains would encounter about 1.5 miles of falling gradients up to 1 in 58 before reaching Moorswater Viaduct, with the far end of the viaduct being 3/4 of a mile from the station.
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Re: Liskeard distant signals

Unread postby colin1501 » Wed Aug 6, 2014 7:33 pm

Interesting, but takes me back to my earlier question about whether line speeds were changed when the colour-lights were installed. Trains would have faced the same gradients when the up distant was a semaphore, but would have had significantly less braking distance between distant and home.
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Re: Liskeard distant signals

Unread postby John Webb » Thu Aug 7, 2014 12:12 pm

colin1501 wrote:Interesting, but takes me back to my earlier question about whether line speeds were changed when the colour-lights were installed. Trains would have faced the same gradients when the up distant was a semaphore, but would have had significantly less braking distance between distant and home.

Is it possible that the CL distant was moved out considerably because the previous distant-home distance in semaphore days had proved inadequate in adverse conditions on occasions?
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Re: Liskeard distant signals

Unread postby Mike Hodgson » Thu Aug 7, 2014 2:48 pm

I thought braking technology had improved over the past century. If it really was necessary to move the distant from half a mile to 2 miles away, surely the original braking distance must have been grossly inadequate, especially with loose-coupled unfitted freights - you might as well use 4-5-5 to offer them! Unless loading limits were unduly limited in steam days?

Was Reg 4A or even Reg 5 authorised here? I don't see that these would have helped much anyway here, but at least under Reg 5 the driver would have been cautioned before leaving the box in rear.
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Re: Liskeard distant signals

Unread postby John Hinson » Thu Aug 7, 2014 3:11 pm

Mike Hodgson wrote:I thought braking technology had improved over the past century. If it really was necessary to move the distant from half a mile to 2 miles away, surely the original braking distance must have been grossly inadequate, especially with loose-coupled unfitted freights - you might as well use 4-5-5 to offer them! Unless loading limits were unduly limited in steam days?

Was Reg 4A or even Reg 5 authorised here? I don't see that these would have helped much anyway here, but at least under Reg 5 the driver would have been cautioned before leaving the box in rear.

Braking technology may well have improved but so have train speeds. In steam days the line speed may have been much higher than the ability of trains but as diesel traction continues to get more and more powerful a greater distance is needed to stop. And once the decision to move a signal back is taken, there are all sorts of factors such as sighting and AWS location that cause a replacement signal to be far further back than might at first be thought necessary.

You would not use Regulation 4A or 5 in such circumstances. The idea is to keep trains moving, not to clobber them unnecessarily!

The maximum permitted speed between the Tamar and Penzance was 60mph in 1957 and I doubt it has changed significantly as the terrain imposes considerable limitations.

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Re: Liskeard distant signals

Unread postby Chris Rideout » Fri Aug 8, 2014 10:40 am

John Hinson wrote:The maximum permitted speed between the Tamar and Penzance was 60mph in 1957 and I doubt it has changed significantly as the terrain imposes considerable limitations.

John

On the subject of long braking distances, The signals at Botley were on a secondary line which carries a 70 mph limit. The colour light signalling was completed at the Eastleigh end in April 1977. The signals were spaced for 100 mph running! The down main had a 40 mph restriction approaching the points to use the single line to Fareham. Owing to the fact that the connection was about 130 yards long, trains would only need to slow down to 50 mph to pass the points in reverse to enter the single line section (Standard Tokenless Block).

Up trains at night would tear through the station on the up main and 3 figure speeds were known. It was rather hush-hush because the locomotives concerned were allegedly unable to exceed 90 mph but a stopwatch revealed the truth! I wondered: Was the layout at Liskeard signalled "just in case" trains ran considerably faster than 60 mph?
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Re: Liskeard distant signals

Unread postby Stuart Johnson » Fri Aug 8, 2014 11:26 am

John Hinson wrote:The maximum permitted speed between the Tamar and Penzance was 60mph in 1957 and I doubt it has changed significantly as the terrain imposes considerable limitations.


I can confirm that line speed through Liskeard remains 60 mph in both directions
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Re: Liskeard distant signals

Unread postby colin1501 » Fri Jul 7, 2017 4:47 pm

Martin Shaw wrote:
Colin

When the C/L distants were introduced they were moved out, up from 941 to 3620 yds, and down from 1980 to 2891 yds. Hope this answers your question.

Regards
Martin


Thinking a bit more about this, was the up home also moved further out when the colour-light distant signals were installed? Earlier photographs show a home signal just off the west end of the up platform, but this is not present in more recent views. If so, while still a significant increase on what was provided previously, the braking distance wouldn't be quite what it appears from the figures above. The fact that these signalling changes coincided with a facing connection being put in to the Looe branch from the up line also suggests that the up home would need to be moved further out. Can anyone confirm?

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Re: Liskeard distant signals

Unread postby roy hart » Sat Jul 8, 2017 4:11 am

The 1981 alterations at Liskeard were:
1. Recovery of up sidings
2.Recovery of down sidings
3. New facing junction to branch
4. Replacement of down distant (motor) and up distant (mechanical) with c/l

The up home was moved some hundreds of yards to the rear at a much later date (about 1999-2000, I'd say). It acquired a sighting board at the same time. The up home today is almost back to the site of the former up distant!
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Re: Liskeard distant signals

Unread postby colin1501 » Sat Jul 8, 2017 9:29 pm

Thanks Roy - that's really helpful. So interestingly, what we have on the up is a significant increase in braking distance when the c/l distant was put in, followed by a reduction some years later when the home was moved out. However, even if it had been moved out as far as the former semaphore distant, the braking distance from the c/l distant would still be 2,679 yards - more than adequate given the 60 mph line speed.

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