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St Albans South Signal Box

77302 Views 239 Replies 23 Participants Last post by  John Webb
Just a reminder to those interested in signalling that the preserved St Albans South Signal box, currently being restored, will be open to the public 10am-4pm Sat 7th and Sun 8th September as part of the national Heritage Weekend.
It is in Ridgemont Road off Victoria Street, close to the SW side of St. Albans City Station.
There will be a small 4mm layout demonstrating signalling principles, both semaphore and colour-light.

See the Events Calender for more detailed information.

John Webb
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Right - quite a lot has been going on since I last wrote.
LED Signals
The ones we're using are now mounted up - Four and three-aspect and the Junction Indicators ('Feathers'):

Also the GPL and the Theatre Indicator:

But of course they have to be supplied with power. We knew there was a duct under the entrance path - we eventually found it under the finial display in the above picture - temporarily covered by the slab that's visible. A view down the hole:

We couldn't get a draw tape through to our Location Cabinet (LOC) at first - digging up by the cabinet showed the duct run was not straight forward:

We're having to insert a new length of duct from the end of the old one direct to the end of the LOC on the right to give a direct pull through of the cable to supply the LEDs with 100 volts. The operating relays and their programmed circuitry have also been prepared and will be installed in a weather-proof box under the finials. Conduit runs buried in the flowerbed will take the power to the various signals.
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QUOTE (Bear 1923 @ 31 Mar 2016, 03:48) <{POST_SNAPBACK}>Neat John

When's the next open day?

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Telegraph Poles
For some time we've wanted to set up a demonstration pole run along the garden to show visitors how things were once done. We were offered a number of posts from a location near St Albans on condition we could provide a working party to load them onto the owner's vehicle and off-load at the box.
This was successfully done on a bright and warm day in April:

They were stacked up on site:

And have since been stripped of all the bits and pieces to allow them to be stacked closer together for convenience.

Two or three of the poles are a bit short, so we're going to use them to make posts for 'Yard lamps' to give better night-time lighting during evening visits. The first was erected this week:

This will give better illumination of the stairs to the 1st floor in particular.

We were given two Midland Railway bench ends - after careful preparation and the addition of new woodwork, we now have a nice bench to sit on and watch the trains go by:

The weekend of the 4th/5th June, we attended the large St Albans Steam Fair held in the grounds of Oaklands College:

We were next door to our friends and colleagues of the North London Society of Model Engineers, who were running their portable passenger rides track - there's a train just departing.
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For Bear 1923 (and anyone else!) next open days are 26th June, 10th and 24th July, 14th and 28th August (2-5pm on all those days) and extended opening 10am-5pm Sept 10th/11th for Heritage Open Days. We expect to have the new LED signals working by September if not before.
QUOTE (John Webb @ 18 Jun 2016, 17:13) <{POST_SNAPBACK}>For Bear 1923 (and anyone else!) next open days are 26th June, 10th and 24th July, 14th and 28th August (2-5pm on all those days) and extended opening 10am-5pm Sept 10th/11th for Heritage Open Days. We expect to have the new LED signals working by September if not before.

Thanks for that!
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Yesterday, three of us started prefabricating the cable runs for our LED signals. A general view:

Note the considerable growth of greenery since the photos in my post #121 above were taken!

A view the other way:

The Junction Indicators ('Feathers') are about to be connected up. The flexible conduits will be buried in the flower bed with additional protection against spades etc.

The LED signals will be controlled in a similar manner to our older colour light signal display. A PIC has been programmed to operate a number of relays to switch the 100volt supply to the various signal aspects. Because of the voltage involved, the control circuitry will be in a locked weather-proof steel box:

My colleague here is trying out the various components for size and accessibility.
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Earlier this year we undertook some civil engineering works in one of the flower beds. The result:

Now that the plants have grown, the train appears and disappears. As you might well presume, this is to entertain our younger visitors! (It's not yet fully signalled, I have to say.)
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QUOTE (John Webb @ 28 Jun 2016, 15:37) <{POST_SNAPBACK}>Earlier this year we undertook some civil engineering works in one of the flower beds. The result:

Now that the plants have grown, the train appears and disappears. As you might well presume, this is to entertain our younger visitors! (It's not yet fully signalled, I have to say.)
Is this age discrimination???
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QUOTE (Bear 1923 @ 29 Jun 2016, 23:51) <{POST_SNAPBACK}>Is this age discrimination???

You are as young as you feel, perhaps?
But there's no doubt the younger visitors tend to stand and watch the train going round with rather more attention than they give to many of the full-scale bits and pieces!

Anyway, on with items from yesterday's working party.
Second pole/lamp-post was erected near the lamp hut - more light on this area will assist us to clear up at the end of working days when the longer evenings are here, and also for evening visitors allow us to throw more light on exhibits that would otherwise go unseen:

Work continued on the LED signals - general view of the back of the 3-aspect while making the electrical connections:

And a close-up of the terminations on the 4-aspect; the links allow disconnection very quickly for fault-finding and maintenance:

(A bit different to fumbling about under a baseboard!)

John Webb
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LED Signals up and Running!

Today (6th July) saw the completion of the wiring of our LED signals after some six months of planning and working on them. Some views:

shows the 3-aspect at yellow and the 4-aspect at double yellow. The Ground Position Light signal (GPL) is 'Clear' and the theatre display (showing an 'R') is only partly visible through the greenery! (The GPL and theatre are not part of the main sequence, I hasten to add! They do their own thing.)

Junction Indicator ('Feather') 4 lit:

(And the GPL is 'On')

Feather 5 lit:

We have some 'fine-tuning' to do to get the tilt and viewing angles correct so our visitors get the best view of these signals.

They are controlled from an 'in-house' designed and built sequencer. This is located in a waterproof cabinet to which the flexible conduits to the signals have been terminated:

(The mounting board and the foam fill are to be painted black to minimise visual intrusion.

How the controller looked half-wired up half-way through the afternoon:

We're having to be careful as we can only run these signals at the standard 100volts AC, so the box will be kept locked!

Final view at the end of today with the system up and running:

The relay board on the left is an 'Off the shelf' purchase. The 12 relays in use have been labelled with their function. Each relay has an associated LED which is lit when the relay is energised. Top right is the 'PIC' chip which is programmed with the required sequences. Below that is a 12v power supply, and the transformer supplying it.
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QUOTE (Bear 1923 @ 7 Jul 2016, 15:09) <{POST_SNAPBACK}>

When can we visit?

Full list of 2016 open afternoons/days at

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Right - a catch-up on the last couple of months.
In late August we entertained a party of S&T (Signal and Telegraph) volunteers from the Bluebell Railway:

Here they are being shown our standard public demonstration by myself. After a pub lunch they came back and were shown two of our more complex demonstrations by one of my colleagues.

At the start of September we paid a visit to Harpenden Methodist Church's "Railway Fun Day", very much aimed at the younger enthusiasts. This was the largest layout present:

I don't know the make - the locos are battery-powered and haul short trains. They can be stopped in stations, and there are also points - but no signals! Towards the back there is a 'roadway' and also an aircraft that does take-offs and landings.

Then last weekend we had our extended Open Days as part of the national "Heritage Open Days" scheme. A few pictures:

Inside the tent we had some posters and a new display of photos showing the conversion of St Pancras to accommodate the HS1 trains. Also our model railway:

Note the signal shadows on the tent wall - from our model signal and lever frame set-up:

Finally a view of our museum room - unusually quiet!

Saturday was rather wet - we had 198 visitors. But as you can see from the photos the Sunday was lovely and dry and we had a further 364 visitors, totalling 562 for the weekend - slightly down on the last year or two.
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As a result of the Bluebell Railway's S&T visit in August, as pictured previously, we've been give a couple of fibre-optic platform indicators, "OFF" and a combined "CD/RA" for our collection.
A brief description of their use:
"OFF" - sited at one or more points along a platform so that platform staff are aware when the signal at the end of the platform is showing a clear aspect and therefore the train can be sent off safely.
"CD" (and "RA") - sited to be seen by the train driver. Can only be activated if the signal controlling the departure of the train is showing a clear aspect. CD = Close Doors, that is an indication to the driver that the doors can be closed.
"RA" - Right Away - informs the driver that he can move off if he thinks it safe to do so.

We've taken the "OFF" indicator first - seen here as lit by the 55watt car headlamp bulb normally fitted to this equipment:

Taken close up. Note the yellow colour; may indicate it was facing forward from the platform signal in case the head of the train was beyond it, as can happen.

Interior view from the rear - the lamp is housed on the left:

Note the neatly tied-up fibre-optic runs, looking very much like wires!

It has proved very easy to substitute a 12volt 3.5watt GU5.3 LED reflector lamp, as already used in some of our signals, for the original 55w lamp - this is the resulting view:

Not as bright as the original - we might go to a 5W LED lamp although even the above can be seen.

We're thinking of including these indicators into our 1970's colour light signal display, which is in need of some work after 5 years in action.
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Wild Life at the Box

No - not a party for swinging signallers! For the past month our Number 4 colour light signal, the one with a feather, had not been able to show a green aspect. Measurements had shown that while the controller was sending out the appropriate signal, it wasn't reaching the signal head. Only after the considerable growth of this year's greenery had been cut back was I able to access the duct containing the cables; this is what I found:

Clearly a small creature with sharp teeth had been employing them on the wires we'd so thoughtfully supplied! Here is a close-up after the wires were removed from the duct:

It was the severed white wire which normally fed the Green aspect relay in the signal head, hence we were only showing a double yellow at best. We were fortunate not to get a short-circuit - the white, blue and red individual wires run either at 12V or OV, depending on the selected aspect at any time, and the blue of the twin-core cable is always at 0V.
Anyway, the wires are replaced and have been given extra protection against this particular failure. We are planning a refurbishment of this demonstration, including a complete rewire, along the lines of what we did for the LED signals installed earlier this year, which will further rodent-proof the wires!
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Our Midland Railway "Pole Route"

Earlier this year we started collecting telegraph poles, as was seen in earlier posts. This was in the hope of being able to set up a section of pole route from one end of the garden to the other, as a visual part of railway history, since most such routes have been replaced by cable runs.
We had some external assistance from a knowledgable gentleman one of our members found for us. Our volunteers gave assistance in putting up the poles.
The whole pole run, seen from the North end of the box garden:

You will note that the end post has been stayed, as has the other end post. Two weights of wire have been used. Four of the wires are 150lb/mile, and the other four are 70lb/mile, if I have correctly understood the notes I was given!

This is a close-up of one of the pole before the work was completed - the bottom two wires are still to be fitted:

This was taken from the platform on the signal seen in the first photo. The insulators are Midland Railway ones - designed by William Langdon, at one time Telegraph Superintendent of the MR and known as Langdon Corrugated.

From one of the posts two wires run to one corner of the box:

These wires are on shackles patented by Brights at the post and on a variation of Langdon's insulator at the box.

Garden Railway:
Other work recently undertaken has included extending our garden railway:

Although it looks as though we're going to have to develop our own "Rail Head Treatment Train" to clear the line of leaves....

Partly to protect the track at the back from greenery, we've built a cover over the track and decorated the ends with a tunnel mouth:

Hopefully we'll try and add a few signals.

Regarding the 'Wild Life' in a previous post, having cut back more greenery this week, we were able to inspect more of the wood ducting. Another nest site was found, but there had been no damage to the wires, I'm pleased to say!

John Webb
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One job that's been going on all year has been improvements to the microswitches used to detect lever positions to allow the computer simulator to work things correctly.
Originally the 'Reverse' position of levers was detected by a cheap and cheerful system using cut and bent wire coathangers:

The bent wire is lifted up by the tail of the lever and thus operates a microswitch at floor level. Nicknamed "Heath-Robinsons" after the artist who drew weird and wonderful gadgets, they have given, on the whole, fairly reliable service.

But as part of making our systems more robust, we have built a new system of metal bars clamped to the lever frame to hold the reverse microswitches in place - we are part-way through installing these:

This shot shows one end of the lever frame where the replacement switches have been installed and the old ones removed.

Sunday 11th Dec saw our last Open Afternoon of 2016 with some 28 visitors, bring this year's total to 2,165 visitors. This is a couple of hundred down on 2015, the wet first day of the Heritage Open Days in September accounts for the majority of the drop!

Best Wishes to all for 2017 - do come and see us some time!

John Webb
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Great photo's John.
Merry Christmas to everyone at St Albans.
Hi John :)
Does someone have to rawl in under the interlocking to fit those new parts?
QUOTE (Bear 1923 @ 15 Dec 2016, 17:17) <{POST_SNAPBACK}>Hi John :)
Does someone have to crawl in under the interlocking to fit those new parts?
In part - the new items can be added from above, so mostly to remove the old parts and to wire up the new bits. I spent quite a few hours under there fitting the original microswitch assemblies!

Regards (and Seasonal Greetings!)
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