Bodmin Parkway signaling

[whole diary]

[inspector_blakey]

For loadsa pictures of proper signals have a look at Adrian the Rock's website.

Pah!

Far too much lower quadrant rubbish in there 
For the uninitiated, lower quadrants are the ones that drop down to show "off", as opposed to upper quadrants which go up. As ever the GWR^▸ (Great Western Railway) went its own sweet way with these things (along with other peculiarities such as using a standard of 25 inHg for vacuum brakes on its trains when the rest of the country used 21 inHg, head and tail lamps with the bracket on the side instead of the back, and they even took a lot of persuasion to adopt the same gauge as everyone else!) and used lower quadrants right up until the bitter end at nationalization (and BR^▸ (British Rail(ways))(W) continued with them). The other three companies, particularly the LNER^» (London North Eastern Railway - about), had changed to upper quadrants.

The GW^▸ (Great Western) lower quadrant signal arms at Yeovil Pen Mill were replaced upper quadrants by Network Rail recently. They do look a bit odd...
http://philmason.fotopic.net/p53203323.html

[super tm]

Hello

The colour light at Liskeard (LD4) is a two aspect stop signal. The next signal is the repeater for the signal at St Germans on the Up line - so it has no yellow aspect.
 

If it is a repeater then it must have a yellow aspect.  Unless it is a banner repeater.  Colour light repeaters will be Green / Yellow.

[thetrout]

The colour light at Liskeard (LD4) is a two aspect stop signal. The next signal is the repeater for the signal at St Germans on the Up line - so it has no yellow aspect.

Fair enough, I might have been thinking of somewhere else then my apologies for the confusion

[winterbourne]

Oh no Yeovil ruined.  Same fate as East Usk years ago. Just as long as the rot doesn't extend into Cornwall. We'll be on the border armed with pitchforks & hot oil!

[inspector_blakey]

The LNER^» (London North Eastern Railway - about) realized that upper quadrants were the true way 80 years ago...you could think of it as an upgrade 

[eightf48544]

Apparently at Shrewsbury they've recently replaced some upper quadrant signals on the line from Crewe (ex LMS^▸ (London Midland Scottish - 1923 to 1948)) with lowere quadrants because the total number of lower quadrant signals in the Shrewsbury is greater than the number of upper quadrant. Not sure i understand the logic but it but it came from a reliable source.

[Chris from Nailsea]

I think there was a chap called Pythagoras, many years ago, who also summed that up quite neatly?   

[Zoe]

Why are there no semaphore distant signals in Cornwall?

[inspector_blakey]

I don't know the answer for definite, but I can have a guess.

In the old semaphore system of signalling, in many respects the distant was much the more important signal for the driver to see (if he missed the distant at caution, by the time he saw a stop signal "on" it was waayyy too late to stop!)

Semaphore distants had a couple of disadvantages: firstly there was usually about 1 - 2 miles of wire running between signal box and signal post, making a very heavy "pull" for the signalman. More importantly, in fog (and before the days of AWS^▸ (Automatic Warning System)/TPWS^▸ (Train Protection and Warning System)) they had to be "manned": the local track gang would be called out and stand by the signal showing a yellow or green handlamp, and clipping a detonator to the rail when the signal was at caution. The combination of ear-splitting bang from the det and a yellow light made sure the driver could not miss a signal. Incidentally, even though the GWR^▸ (Great Western Railway) had long ago installed an in-cab warning system at distant signals (ATC^▸ (Automatic Train Control)) they still used fogmen (see for example Signalman's Twilight by Adrian Vaughan).

Colour light distants did away with both these problems, being much more visible in fog. The distant levers in signal boxes became nothing more than electrical switches and actually had their handles cut down to prevent the signalman forgetting himself and yanking them over with a mighty heave! BR^▸ (British Rail(ways)) Western was installing colour light distants in semaphore areas (but leaving the semaphore stop signals) in the 1960s, which I would guess is why there are very few (or even no...?) semaphore distants left.

[eightf48544]

BR^▸ (British Rail(ways)) Western was installing colour light distants in semaphore areas (but leaving the semaphore stop signals) in the 1960s, which I would guess is why there are very few (or even no...?) semaphore distants left.

One of the numerous wastes singling the line West of Salisbury was that the Southern Region Signal Engineer had been busily installing colour light distant signals at most boxes on the route during the previous 5 years. The reasons as per inspector_blakey post. One thing he didn't mention was if there were no fogmen available the signalman had to work double block. So he could not accept a train from the box in the rear until he had received the Train out of Section from the box ahead rather than accepting it when his clearing point had been passed by the  previous train. Thus if a train missed the distant signal and passed one or more of the stop signals at danger the section into which the train ran would be clear.

One of the jobs I had was helping the Special A amend the signal box instructions for any box with a colour light distant signal. Although the General Rules did away with fogsignalling and use of fogmen when a colour light distant was installed there was an exception.

It's imprinted as I read so many times.

"During fog or falling snow when single line working is in operation on the Down/UP line between A and B fog working must be introduced."

This was because the distant signal was focussed for right line running if the train was on the wrong line and it was foggy there could be the chance of the driver missing it plus the AWS^▸ (Automatic Warning System) ramp would not be there.

Overcautious? Very unlikely to happen, yes, but it was there just in case. So that should the need arise single line working could be introduced during fog or falling snow the signalman would know whether the fogmen were in positon or whether he had to work double block.

Then the rules and regulations were designed to keep the job moving (safely) not like today when at  slightest sign of trouble it's "Stop the Job" whilst we work out what to do.

[winterbourne]

This is interesting stuff. We do have two semaphore distants in Cornwall - alas they are fixed ones underneath section signals for the next box. One at Par, one at St Blazey.

47704 at St Blazey. The section signal sharing a post with Par's distant is visible.


Short section applies here, & the fogmen rules are long gone.

[Zoe]

Are they ever going to replace the remaining semaphores in Cornwall and install track circuit block west of Truro?