A Highland Miscellany

[LesGros]

Mark Tatlow

...If people out there think there are errors in this; especially the locking chart (locking logic is a bit mind twisting) then please pipe up as I will be building it soon! ...

Mark,
I am not qualified say if you have errors in your design, but would recommend you download "Sigscribe" from the Modratec website (http://www.modratec.com/ ) and have a play. It is free software used to design and test the interlocking lever frame kits which are supplied by Modratec. The program protocols are based on UK practice; it includes a means of simulating the action of the lever frame, so it could be used to explore your design.

cheerydoo.

[grovenor-2685]

Well, I was just about to do a table for this when I found you had asked the same question on RMweb. As I have been out the people there who sit at their computers all day have already provided you with answers so I won't. I do agree with the Stationmaster that the more usual table has a "released by" column rather than the "releases" you have used, they are of course the converse of each other but the "released by" is easier to get right, some engineers provided both, but using the 'releases' column on its own is less common.
I am less convinced by Michnich's suggestion that the fpl going into the yard would be a 2 holer, I would think it quite likely that the bolt would only be required for the running line move as passenger trains would not be admitted to the siding, in fact its unlikely anything other than a light engine would arrive directly into the yard, since you cannot shunt with the engine trapped inside.
You might like to add a 'call on' signal under signal 2 and another shunt on a right bracket as the siding entrance is to far from the box for hand flag waving, if you put the box close to said siding entry then shunt signals could be avoided and the shunting done with flags.
Trains heading left to right and wanting to shunt the yard would have the engine run round and shunt from the back of the train so would need the call on to rebuild the train before departure (the loco would also need to get back to the front hence the signalled move wrong road, at the box end he could be flagged back onto the train. (If you moved the box to the other end for proper supervision of the shunting, then you would not be able to flag the loco back on its train so would need a couple of shunt signals at this end)
Trains heading right to left could shunt from the front and not need a run round but would still need the wrong road move to get back to their train as its unlikely that the whole train could be put in the yard unless its much bigger than it appears.
Regards
Keith

[Mark Tatlow]

Hi Mark,
Interlocking is a mind twister and takes time and quiet, your locking chart is a long way from complete,

Err yes, this is dawning on me now! Thanks for the help and also Keith's; I will be producing a revision to the chart later but I want to get some "building" done first.

This is where we are at with the lever frame:

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This is made up of three of the society kits with a few modifications. The legend plate is obvious and I have also introduced brackets to take slide switches. Whilst the kit is conceived to be compatible with microswitches I need at least some double pole changeovers, so I am carrying out this adaptation.

[Tim V]

I would agree about a frame imposing on the operators the possibility of them getting the operation correct. Mind you, you can still get the operators who defeat the locking!

The original concept of Clutton was to include frame locking so that operator error was reduced. It worked, it's a pity the staging roads cannot have have the same rigour imposed within them. In fact it's the staging roads where mistakes are now made

[Chris Mitton]

Hi Mark

I was going to suggest SigScribe to you but Les beat me to it - it is fun!

Like you I aim to have Stowe Fen fully interlocked with tappets and sliders - none of this fancy electronics! Although probably years rather than months in the future, I've more or less worked out my own interlocking - whiling away the hours spent in hospital waiting rooms! - so out of bravado and at the risk of being shot down in flames by the professional signal engineers on this forum I spent a few minutes adapting my chart to suit your test layout - result below. I'd appreciate your thoughts, and anyone else's, to see if my thinking is on the right lines. [I'm assuming that Glenmutchkin is set in the period of Absolute Block working.] Maybe I'll get round to posting Stowe Fen's on my own workbench thread.

A couple of questions for the above-mentioned experts. First, shouldn't you have, at least in the Down direction, an advanced starter? Otherwise, it's impossible for a down freight to back into the goods yard without "blocking forward" to the next box on the left.

Second, am I right in assuming that, even in a wholly mechanical environment, there would be some kind of electrical lock to prevent a starter signal being cleared until the signalman in advance had pegged "line clear"?

Third - this is somewhat counter-intuitive - are FPL levers interlocked in the frame with the switch levers they relate to? It seems blindingly obvious that that is their purpose: however, if this were so and the locking mechanism at the switch blades broke, the signalman might be led to believe the points were locked when in fact they weren't, in violation of fail-safe principles.

I do agree with Keith that it would be more sensible to put the signal box at the other end, where there are more pointwork and signals.

GlenmutchkinLockingChart.jpg

Look forward to seeing the completed frame!

Regards
Chris

[Mark Tatlow]

Aghh Chris that is very good of you!

I have to say I tried to download Sigscribe and got obgged down with it. I have a feeling I may have a corruption of it as when I close the programme it says some odd things to me! I had better have another go.

In the light of some direction from RMweb, I have made a number of amendments to both the signal diagram and also the locking chart. These are here:

Test Layout Signalling Plan v2.jpg

Test Layout Frame list v2.jpg

I'll settle down and compare this with yours, I can see one query already........

I think I am getting closer so that will leave the real layout plan to do. This has also gone through a bit of gestation:

Glenmutchkin Signalling Plan.jpg

[grovenor-2685]

I'm not sure you have correctly interpreted the Stationmaster's input onto your new plan, and there are a few significant errors, duplication of locks should be avoided, both to reduce the number of locks to be made, and more important to be able to test the locking fully, a duplicate lock cannot be tested to confirm correct installation.
Also the home signals, eg 2, must be released by the fpl(s) as it is a requirement to have the points locked.

I have a modified chart ready but its to late to post it tonight as I want to compare with the Stationmaster's version as he is probably not as rusty at this as I am.
So tomorrow.
Keith

[grovenor-2685]

For now here is an extract from the IRSE 'Green book' on Interlocking, note how the layout ensures that the sidings are connected by a trailing point.

(h) - Single Line Passing Loops

Fig. 10. This shows a station on a single line with a loop so that trains can pass each other. If a train is running with No.2 signal into the up platform, a second train cannot be permitted to run into the down platform with No.14 signal as there is not sufficient overrun ahead of 3 or 13 signals, and no facilities are available for diverting the trains clear of each other.
Since all trains travelling in the up direction pass over 8 points in the normal position, 7 facing point lock will only bolt 8 points normal and 7 lever will lock 8 lever. Similarly 10 will bolt 9 points in the normal position only. It should be noted that the points at either end of the loop should be set normally in the position shown on the diagram, so that in the event of a train running past 2 or 14 signals at danger, it would continue on the correct line.
No.2. This reads to the up line so must be released by 7. There is no need to make it lock 8 as this is done by 7. 2 will also lock 5.
2 must not be pulled at the same time as 14, so that 2 can lock 14, but this is usually effected by making 2 lock 10. The reason for this is, that if there is a train waiting at 2 while another train is being let into the down platform, 10 will be reversed for 14 signal and cannot be replaced until the whole of the train has passed over it, so therefore 2 cannot be pulled until 10 has been replaced and by the time that can be done, the down train will have come almost or quite to rest. If 2 locked 14 directly, it could be pulled immediately 14 was replaced.
For a similar reason 14 will lock 7.
No.5. This is released by 9 in order to give a complete road.
No.8. This lever operates a clearance bar in addition to the points in order to prove that a train on the up line is not standing foul of a train running on the down line. This is provided because the signalman has not a good view of this end of the loop.
Note. No. 13 must not lock 9, nor must 3 lock 8, in order that two trains may leave the platforms at the same time.

IRSE single line.jpg

Keith

[grovenor-2685]

OK, I have had a good look at the Stationmaster's suggestions, I think he must have been having a bad day as there are some real oddities there. Also I think you have carried through one or two of his suggestions without allowing for your change of numbers.
So far as the numbering goes, it is usual for the fpl/point numbering to be symnetrical at each end, your right hand end is the usual so really you should swap 4 with 5 and 6 with 7.
However, on the attached table I have kept to your numbering. Incorect entries to be removed are shown in green and crossed out, missing entries required to be added are shown in red. NB. I left your heading in place, it should be Locking table rather than locking chart.

frame.jpg

frame.pdf

Regards
Keith

[John McAleely]

Simple newbie question please: what is a 'clearance bar'?

[grovenor-2685]

what is a 'clearance bar'?

Mechanically it is the same as a facing point lock bar but it is connected to the points rather than the lock bolt. The bar sits under the flanges and rises above rail height when moved, hence if the signalman pulls on the lever when there is a vehicle over the bar he would be trying to lift the vehicle. The effect in this case is that the tail end of an arrived train sitting on the bar will prevent points 8 being reversed for a train to depart.
Regards
Keith

[Mark Tatlow]

Thanks Keith, I will digest over the forthcoming week! It is certainly pretty intense for the uninitiated!

As of the moment, work has stopped on the frame pending getting some more slide switches and 10 BA nuts. I have got the pull rods and switches in on the first 6 levers so you can see how it works. There is a cradle that slips over the end of the lever and is then attached to a pull rod; thus, as the lever moves the cradle and the pull rod rock back and forth. I have found that it is important to make the joint between pull rod and cradle secure, as they can break. The toggle of the slide switch has a hole drilled through it and the pull rod is passed through this but with a 10 BA nut slipped on first. A second nut is then offered up to the free end and they can be set to act as the limits of movement on the pull rod. As it moves back and forth it takes the toggle of the slide swith with it and you have a simple and durable DPDT switch for the lever frame.

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Sorry about any glare in the pictures; it might have to do with the shiny yellow thing int he sky but I am not certain it being that long since we have seen it!

[Terry Bendall]

what is a 'clearance bar'?

Mechanically it is the same as a facing point lock bar but it is connected to the points rather than the lock bolt.

Kieth is that the same as a fouling bar which from your description seems to be the same?

Terry Bendall

[grovenor-2685]

Yes, depending on your viewpoint, it is either detecting something fouling or proving that it is clear, so really two words for the same thing. mostly they were replaced by track circuits and electric locks over the years, as of course were facing point lock bars. In more complex layouts the bar would occasionally have a lever to itself.
Regards
Keith

[Terry Bendall]

Yes, depending on your viewpoint

Thanks Keith. Something new to learn every day.

Terry Bendall

[Mark Tatlow]

As a diversion from the lever frame, I have made a start on the first bit of civils required for Glenmutchkin. To segmentalise the layout and create more room for descrete vistas and cameos, I intend to introduce an overbridge in the throat of the station. This will mean that you can not see what is happening at the station approaches/loco shed end from the platform end and vice versa.

The bridge is in fact modelled on the one at Killiecrankie, but there were very similar ones at The Mound, Kyle of Lochalsh, Keith amongst others. Heres a picture of the Kyle one:

Kyle_of_Lochalsh_2_Station_geograph-2194733.jpg

The advantage of using the Killiecrankie bridge is that I had previously modelled one for a layout of this station and whilst the abutments are still firmly attached to some mothballed boards, the deck could be reused. The deck has a nice skew to it to make it a bit more interesting and utilises lattice girders; which few seem to bother modelling. This is what it looks like:

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In terms of abutments, most Highland (and indeed this is common to most scottish lines) had bridges with curved wingwalls swept back from the face of the abutment. To give the layout some locational character, this was something I wished to produce. This is where we are at presently with the abutments:

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Typically, the random or dressed stone ranges from Wills are my favoured mediums but seeing Andy G making a good go utilising Slaters 7mm coursed stone I thought I would have an experiement with this. This is because many of the later bridges on the Highland used the same coarsely dressed stone; like this one at Dalwhinnie:

078compress.JPG

And these show the bridge deck on the abutments as they stand:

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[DougN]

Mark they look really good. The bridge is certainly a feature to any layout. The curved abutments certainly add an architectural charm. This is certainly one of the charms of the scottish and english railways. There was a level of pride on the workmanship and finish to what some would think is mundane infrastructure.

[Terry Bendall]

Yes very nice Mark. What is the material with the holes in it that you have used for the structure of the wing walls and the abutments?

Terry Bendall

[Mark Tatlow]

Yes very nice Mark. What is the material with the holes in it that you have used for the structure of the wing walls and the abutments?

Hi Terry,

It is just plasticard with a lot of 3mm holes drilled in it (and I have the swarf all over the spare bedroom to prove it - best sort this out before it gets noticed.....)

I have done this because the Slaters stone sheet is vacuum formed onto a master and when you look at the rear side for every projecting stone to the front there is a cavity to the rear. As I am worried that liquid solvent would get trapped in these cavities, I have incorporated lots of ventilation holes.

I have still had one or two stones where the vent hole did not cover the cavity and in the week since the first section of sheet was attached the plastic did go mushy locally. I have just drilled little pin pricks in such areas and this has cleared this up.

[Terry Bendall]

It is just plasticard with a lot of 3mm holes drilled in it

Thanks Mark. Sounds like a good solution to me. I thought that you had found a new material.

Learn something new everyday.

Terry Bendall

[Mark Tatlow]

The bridge is coming along and is now close to finished (constructionally).

It has taken a lot of time with plastic filler to get the stones to meet neatly at the corners and also to be coursed sensibly at the corners. Having said this, I am inclined to think it is one of the more important parts of modeling structures and buildings. Cracks or missing sides/ends on a building are just a total no no and even an untrained eye (I am a chartered surveyor so it is worse for me!) spots the error immediately.

This is where we have got too:

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_DSC0268 (3) Compress.JPG

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I am not happy with the string course at the moment, it sticks out too abruptly and possibly the same for the copings to the top of the parapet - so more filing and sanding.............

However, it does look like a bridge and I doubt the civils guys will condemn it!

[Mark Tatlow]

With a lot of help from Keith Norgrove (thanks Keith) the locking design for the lever frame should now be concluded. This is where we are at:

Test Layout Signalling Plan v3.jpg

Test Layout Frame list v3.jpg

Locking chart plan - test layout v2.jpg

The lever frame is also ready to receive the beginnings of the locking frame; so guess what i am doing this weekend........... (after a trip to Wakefield of course!).

Just to save anyone pointing this out; I am told that the Highland did paint thier distant levers green.

[JFS]

Hi Mark,

Good stuff!

There are many ways of laying out the locking of course, but I think there might be a few simplifications possible in the layout - for example, both 2 and 9 are released by 4,6 and therefore these could be combined on the same bridle. This would remove those two releases off bridle "F" then 9 and 10 released by 7 could be combined with 9 locks 10 by providing a butt under tappet 9 between bridles J and F. I think that saves one bridle and 6 nibs and notches which, when you are hacking them out by hand, is worthwhile

I will be demonstrating my approach to mechanical interlocking at Wakefield so if, by the remotest chance, non of the above makes sense, I would look forward to talking it through with you.

Best wishes,

Howard.

[Jim Summers]

Mark said:
"Just to save anyone pointing this out; I am told that the Highland did paint their distant levers green".

Maybe I can still usefully point out that so did pretty well everyone else in pre-grouping days (and I believe Ireland continued to do so until power signalling).

Distant signals themselves were red, of course, but the green on the lever goes back to the days of time interval and handsignalling. White meant clear, green meant caution because the full time had not elapsed, and red meant stop and stay.

Jim

[Mark Tatlow]

Hi Howard,

I am going to be in Wakefield on Saturday and I will definately stop by.

As of this evening my mind is not up to the challenging of my/Keith's locking (I have been getting grief/suggestions on RMweb http://www.rmweb.co.uk/community/index. ... try1018576) so a chat about the rights and the wrongs will philosophically welcome!