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Worked distant semaphores

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Worked distant semaphores

Unread postby B.P.Mills » Sun Jan 24, 2016 11:13 am

Can anyone please confirm an e-mail address for contacting the editor of the extensive site entitled British Railways Signalling-Mechanical and Fog signals. The address [removed] and others does not connect.
I wish to point out to the site editor (for the benefit of modellers and the layman) that due to mandatory slotting, a worked distant signal could not be raised or lowered if the stop arm was reading danger above it. One of his inset illustrations shows the distant 'off' for GW, LNER and SR types, with the stop arm at danger which is of course, an error.
Regards, B.P.Mills
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Re: Worked distant semaphores

Unread postby John Hinson » Sun Jan 24, 2016 7:38 pm

Hello,

I suspect the site is dead - Norton Security lists the site as dangerous.

As an aside, I have removed the email address from your post, it isn't good policy to publish email addresses on the web (even if it is dead) and if anybody can help it would be best if they contacted you with a new address therough the Private Messaging.

Finally, I am moving this to Signalling - Current as I think that is a better place for the subject and you may generate some discussion even if you don't get contact information.

Best regards,

John
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Re: Worked distant semaphores

Unread postby B.P.Mills » Sun Jan 24, 2016 8:55 pm

Thanks for your prompt response, John. Having raised this issue, to my surprise, I see that Mike Hodgson has an inset mini-jpeg on his post showing a raised (i.e., cleared) upper quadrant distant arm below a Stop semaphore at danger. Is that a fluke? I didn't think that that situation was possible in modern-day UK semaphore signalling. Rightly or wrongly, I assumed from 50 years of signalling association, that a worked distant if not motored, was not connected to a signal box lever, only its slot which was controlled by the stop signal with its relevant distant slotting arrangement and slot release from the ’box in advance. Likewise with a motored distant semaphore, the motor control is interfaced with the working of the danger (stop) arm and action by the signaller in advance.
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Re: Worked distant semaphores

Unread postby Mike Hodgson » Sun Jan 24, 2016 10:45 pm

My photo had to be taken within a window of no more than a couple of seconds. The stop arm was worked directly by a wire and when the lever was replaced behind the train, that arm returned pretty much instantaneously. The distant below was motor-worked, and as the stop arm was restored the electrical contact acting as the slot was broken. So the distant immediately also started to drop back, but the back emf in the motor and the inertia of the gearing mechanism slow it down. The distant therefore takes that much longer to return to the on position. I was only able to get the timing right because I was in the box at the time (on an official SRS visit, I should add!) Apart from the fact that another train should not be even be approaching, let alone following that closely behind, it would be obvious to a driver that both signals were in the process of going back, and it was not a wrong-side slotting fault.

It required the combination of a manually worked stop over a motored distant, a situation which whilst not very common, was not all that exceptional. The box in question has now gone.
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Re: Worked distant semaphores

Unread postby Fast Line Floyd » Mon Jan 25, 2016 5:10 pm

I have also seen a GW signal with the stop arm at danger and the distant OFF underneath, this one at Kensington South Main was caused by the down rod to the stop arm coming detached from pin on the back of the spectical casing after the split pin wore away, hence when the stop signal lever was pulled the slot bar was as lifted which is why the distant arm came off but the stop arm stayed ON.
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Re: Worked distant semaphores

Unread postby Russell Maiden » Mon Jan 25, 2016 11:08 pm

In another case of a wrong side failure (as opposed to the delayed replacement where a motored distant arm does not instantly follow the stop arm) I recall a case of an upper quadrant lower arm Distant being in the Off position with the stop arm above at Danger at Bollo Lane Junction (South Acton's Up Distant beneath BLJ's Up (From Gunnersbury) Home). This was found to have been caused by extreme wear in the balance-weight crank fulcrum allowing one weight to sit on top of another in the slotting arrangement.
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Re: Worked distant semaphores

Unread postby Chris Rideout » Tue Feb 16, 2016 1:47 pm

Mike Hodgson wrote:... It required the combination of a manually worked stop over a motored distant, a situation which whilst not very common, was not all that exceptional. The box in question has now gone.

At Southampton Central, a similar situation could be observed. The Up Main Advanced Starting (no. 11) was at the tunnel mouth and had an automatic distant underneath because there was a short section of TC block between those signals and Northam Junction. The next signal ahead was an automatic 3 aspect colour light. When I was working there, a fault developed on the distant motor and it took about 20 - 25 seconds to touch the repeater "on" contact after no. 11 was replaced. It led to delays pulling off any of the Up Starting signals for a following train because the arm proving prevented the electric lock from freeing the lever.
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Re: Worked distant semaphores

Unread postby Stuart Johnson » Tue Feb 16, 2016 9:27 pm

I remember that distant very well- watching operations from above the tunnel mouth in the late 70s, it was quite common to see the arm go up, and instantly drop back, and go up, and drop back, several times before a train came along to put a stop to the process. TC problems in the tunnel?
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Re: Worked distant semaphores

Unread postby Pete2320 » Wed Feb 17, 2016 1:44 am

Stuart Johnson wrote:I remember that distant very well- watching operations from above the tunnel mouth in the late 70s, it was quite common to see the arm go up, and instantly drop back, and go up, and drop back, several times before a train came along to put a stop to the process. TC problems in the tunnel?

With a Westinghouse motor, this can be caused if the "hold off brake" becomes worn or contaminated (a damp morning can do it). The motor runs to the clear position and cuts out and the arm should be held off by the brake but that slips so the arm drops back towards "on" until the motor cut out contact is made again. The BPRS/GRS motors do the same when the holding resistor burns out.

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Re: Worked distant semaphores

Unread postby Mike Hodgson » Wed Feb 17, 2016 9:16 am

A broadly similar explanation also applies to level crossing barriers that exhibit a tendency to '"twitch" periodically when in the raised position, although different technology is involved.
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Re: Worked distant semaphores

Unread postby Stuart Johnson » Wed Feb 17, 2016 1:29 pm

Pete2320 wrote:
Stuart Johnson wrote:I remember that distant very well- watching operations from above the tunnel mouth in the late 70s, it was quite common to see the arm go up, and instantly drop back, and go up, and drop back, several times before a train came along to put a stop to the process. TC problems in the tunnel?

With a Westinghouse motor, this can be caused if the "hold off brake" becomes worn or contaminated (a damp morning can do it). The motor runs to the clear position and cuts out and the arm should be held off by the brake but that slips so the arm drops back towards "on" until the motor cut out contact is made again. The BPRS/GRS motors do the same when the holding resistor burns out.

Pete


Pete, thanks for the explanation. I've been meaning to ask about that for nearly forty years- it's nice to get there in the end!
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