Signals for Glenmutchkin

[Portchullin Tatty]

Interlocked Lever Frame - Part 1; Experiments

 

One of the features I propose to include on my next layout Glenmutchin is an interlocked lever frame.   This is because one the most common “issues” now on Portchullin is driver error running signals or attempting to go over a turnout that is against it.  Glenmutchin will be a much more complicated trackplan and there will be a fair number of signals on it, so we are bound to have more operator issues!   The use of an interlocked frame is intended to be one of the means of controlling these – after all it is how the prototype did it!

 

Interlocking frames have been built before but they are not written about much – there are some pieces here, here, here or here if you want to look them up.  Whilst is it possible to do this electronically (and people have) I decided I wanted to go down the traditional route of locking tappits, so that if the road was not set correctly, the lever would not work and you knew you had a problem.   

 

Given that Glenmutchkin looks to be heading for a 45 lever frame, with a lot of interlocking I thought it would be a good idea to start on something simpler.  Thus, I have concocted myself a simple layout with a moderate amount of locking; this is what I have gone for:

 

And this is the locking chart that I think is right:

 

 

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!

[The Stationmaster]

Oooh, always nice to see a bit of interlocking.  You might find it helpful to set it out in the usual way 'f 'Locks' and 'Released By'  (although that does make noting the releases possibly more difficult.

 

So to begin at the beginning -

1 should be released by 2, 3

2 locks 4 (i.e. the point - the point and FPL numbers are transposed) 12, and 13,   releases 1

3 is released by 9 releases 1

4 Locks 2, 12, and 14 (in some schemes it would also lock 15) and releases 8

5 locks 4   Releases 2 and 12  

6 (should normally be at the far end of the frame - i.e. 6, 7, and 8 should ideally be renumbered), is released by 7 and 8

7 Locks 9  Releases 6

8 released by 4, releases 6

9 Locks 7, releases 6

8 is released by 4, releases 6

10 backlocks 9, releases 7

12 Locks 2, 4  released by 13, 14  (might lock 15 - depends on local needs)

13 locks 2, 3, and 4  Releases 12, 15 

14 Locks 13 both ways, Releases 2, 12

15 Released by 13   Locks 2, 4  (might lock 12 - depends on local needs)

 

I think that's about right - hopefully.

[Portchullin Tatty]

Oooh, always nice to see a bit of interlocking.  You might find it helpful to set it out in the usual way 'f 'Locks' and 'Released By'  (although that does make noting the releases possibly more difficult.

 

Humm, there are clearly some things I don't know then:

 

- the distant 1 would have been used even when the move was into the yard.  I thought it would make more sense for the train to approach no 12 at a caution so the distant would be held on?

 

- the distant 1 would only be used when both the home and the starter (2 & 3) are off - ie it would only be used on non stopping trains?

 

- I can see I had not conceived that the starters should also lock the loop turnouts and why they ought to

 

- the down levers should start at the right hand end of the frame and work backwards

 

Just as well I am doing an experimental frame/situation then!   My thoughts on Glenmutchkin are going to be even further off!

 

I will see if I can get my mind around the rest of what you have put up and revise the locking chart tomorrow.   I am making the interlocking in plasticard so that it is relatively simple to adjust for just this sort of reason.................

[RailWest]

>>>the distant 1 would have been used even when the move was into the yard...

 

No. As The Stationmaster has said, 1 would be released by 2 and 3, so I'm not sure how you would get the idea that the distnat would read for a route into the yard.

 

>>>the distant 1 would only be used when both the home and the starter (2 & 3) are off - ie it would only be used on non stopping trains?

 

Yes and no :-)  Provided that the train was not passing another train in the loop, if the signalman could get the road ahead to the next signal-box then he could clear all the signals - whether it was a stopping train or not is irrelevant. Incidentally, assuming that the single line was controlled by some form of physical 'token' (staff, tablet or token working), then - unless automatic exchanger apparatus was fitted - the exchange by hand would have to be done at slow speed anyway (typical <=10MPH).

 

In such circumstances the GWR took the logical view that, as the actual speed of the train therefore would be <40MPH (regardless of any actual line speed), the distant ought not to be worked anyway and therefore a 'fixed' distant would be provided instead. I do not know whether any other railway companies adopted the same approach.

 

Also - with some VERY rare exceptions (I can think of only one) - lever-frames were numbered from left to right. If, as you have drawn it, the frame was at the front of the signal-box, then the layout is numbered the wrong way round!

 

Levers 13 and 14 on the diagram seems to be 'swopped around' in the locking table. The diagram arrangement with 13 as the FPL seems more logical to me. As the point (14) locks 2, and 15 would be released by 14, then IMHO a separate lock by 15 on 2 is not needed.

 

Finally   there needs to be a trap point at the exit from the sidings. This would be worked normally by the same lever as the entry points.

[micknich2003]

It was Highland Railway practice on single lines where a train had only one possible route to have only "One Hole" in the point stretcher. For example your Points No5 would only be bolted in the Normal Position, likewise Points No10. Points No14 would have the conventional "Two Holes". 

 I have one or more signalling plans/locking charts that show this feature, but as always, finding them is another story. Mick.

[micknich2003]

I have several North Eastern Railway and Hull&Barnsley Railway Single Line signalling diagrams and most if not all show worked Distants, even into a Dead End terminus. Following the grouping it wasn't long before all Single Line Distants were made FIXED.

 The c1924 MoT Requirerments may give a clue. As all ready said, working distants on most single lines were little more then an expensive luxury. Mick.

[micknich2003]

Just a thought, would it not be better to have the Goods Yard connection as a "Trailing Point"?  It would also simplifie the signalling and interlocking and save a FPL, a lever and the associated roding run. See the two diagrams below, possibly the Highland did it as drawn by Mark. Mick.

 

 

[Portchullin Tatty]

Thanks for the various contributions; I will seek to have another bash at the locking chart tomorrow.

 

I did know about trap points I just forgot to put them in!  I also concur that the box (cabin to me) was reversed for the frame list - I have corrected this and also the numbering of the levers.

 

 

Mick, I deliberately went for a facing connection to the yard on the grounds that the purpose of the exercise is to test whether I can conceive (apparently I need help...........) a locking frame and then build it!  I am going to use the lever frame offered by the Scalefour Society; it is not a rendition of any particular manufacturer's but is a robust and useable frame.  This is largely done (but I have just gummed up some of it up with solder so it will need to be undone but this is a job for tomorrow) - pictures will follow.

 

 

[beast66606]

Levers 6 and 7 are missing ... 

[The Stationmaster]

On the Highland lines worked distants were used at crossing stations - and there was at some places (maybe all?) where there was a frame at each end of the station a second distant for the far end stop signal (which doesn't apply in this example of course).

[Portchullin Tatty]

Levers 6 and 7 are missing ... 

 

 

Oops, now corrected.

[Portchullin Tatty]

On the Highland lines worked distants were used at crossing stations - and there was at some places (maybe all?) where there was a frame at each end of the station a second distant for the far end stop signal (which doesn't apply in this example of course).

 

Now, I can answer these two points even if I am still not quite there on the locking chart.

 

Many of the Highland's stations did indeed have a pair of boxes (the Highland called them cabins); this is due to the length of the loops (which tended to be long as these were single track mainlines not branch lines).  As a result of this, the facing points at either end were to far to be operated from a single cabin; so the Highland put too in.  They did not provide two signalmen though; a fair amount of walking was expected in the job and latterly they did provide a bicycle (which I have modelled on Portchullin).

 

 

With regard to the distants, I am pretty certain that the Highland did not go in for fixed distants at all.  In addition, they used a second "distant arm" on the home signal.  This does not perform the function of warning what the next signal might be, it is an indication that the tablet exchange apparatus is going to be deployed.

 

Here is a picture (by Michael Westley and reproduced under a creative commons licnece, thank you Michael) of the down home at Achnasheen.

 

 

 

[Portchullin Tatty]

This is where we are at with the lever frame; the levers are now all there along with their release catches. 

 

 

This is based on the lever frame kit supplied by the Scalefour Society (3 no) and whilst it is not a replica of any particular manufacturer, it is durable and "feels right" to operate.  I have made a couple of modifications, the priovision of the plate to take a legend and an adaptation to provides some fixing brackets to take some slide switches.  The kit is concieved to take microswitches but as I may well wish to use point motors not servos, I need a double pole changeover.

[micknich2003]

 If I have it right, the Station Master's office was actualy the signal box/block post, that is where the Token instruments were kept, and again from memory there was also a set of levers contoling "Slots" on the Starting signals. The "East and West", or "North and South" cabins were Ground Frames. Somewhere, I have the drawings to prove it. Mick. 

[Portchullin Tatty]

At the risk of incurring Mark's wrath, perhaps two 'cabins' with separate locking frames would be seen as more prototypical??   There would also be the fun in devising working slots for signals with a 'starter' and distant on the same post.....  I have put 'starter' in quotes as in reality, it is not the signal controlling entrance to the next block section.  Then there is the question of were the two distants going in the same direction slotted as well.......??  I think I'll duck now! 

 

It certainly would be more prototypical (although not all stations on the Highland had the twin cabins and the LMS did rebuild a number with a single cabin after the permitted distances had moved out).  However, I only have one life........... this is only supposed to be an experiment too!  Mind you, it has convinced me that I want to simplify the Glenmutchkin signal diagram a bit too - so I will put something up in a moment on this thread.

 

Work in the lever frame has ground to a halt as I have run out of slide switches - so ebay to the rescue but it will now be a job for next weekend.  I'll load a picture up of the status in the morning when there is some light.

 

I have also confronted again the locking chart - having also made a few tidying arrangements to the signal diagram a few posts back.  This is where I am at:

 

 

And if anyone wishes to amend it here is a pdf of the word doc (so you can cut and paste from it).

 

Test Layout Frame list v2.pdf

[micknich2003]

Dear Mark, if you are modelling in Highland days, your Distant levers will be Green. On a signalling plan, Turnouts are Points, the signal engineer is only interested in the bits that move, not the complete assembly. Best Wishes, Mick.

[micknich2003]

Never come across Blue Facing Point levers, but I'm not going to say you are wrong, at one time there were over one hundred railway companys in the UK, and they all had their own ideas. For example although the North Eastern Rly painted FPL levers the usual Blue, they painted Clearance Bar levers what we would now call "Distant Yellow".

 Some years ago, I restored/rebuilt an ex Highland Rly locking frame, certainly all point levers were Black. Mick.

[Fay Singpoint]

I stand to be corrected, but dependent upon the era modelled, the levers for facing points are also blue, as per the FPLs. 

 

 

Never come across Blue Facing Point levers, but I'm not going to say you are wrong, at one time there were over one hundred railway companys in the UK, and they all had their own ideas.

 

From what I can gather the Midland Railway was an example as they painted their point levers Oxford Blue. 

[Fay Singpoint]

Hello Mark,

 

It's looking good. 

 

• There is no need to double count on some of the locking functions. As an example 6 already releases 9 and locks 2, therefore stating 2 locking 9 is superfluous and untestable.
• Providing point to point locking would simplify things further.
• 7 would not normally release 10 although (I believe) the LBSCR sometimes provided locking to ensure that any facing points were unbolted for trailing moves.
• The statement that 12 backlocks 11 is also superfluous as it's already a dead lock.
• Depending on how close they are, 6 may lock 3!!! Although this type of locking is probably a bit too late for the era you are modelling.

 

Also you have produced a locking table. A locking chart is the actual layout of the locking.

[RailWest]

Not aware of the GWR ever using blue for points, facing or otherwise. What you might find, however, would be levers that were blue/black, because they were either motor-points, or those fitted with an 'economic' FPL, in both cases both the point and FPL are worked by the same lever.

 

The GWR also used blue for level-crossing and wicket gate locks, but those became brown in BR days.

 

As you may have gathered by now, it all depends upon a mix of railway company and time period!

[The Stationmaster]

Hello Mark,

 

It's looking good. 

 

• There is no need to double count on some of the locking functions. As an example 6 already releases 9 and locks 2, therefore stating 2 locking 9 is superfluous and untestable.
• Providing point to point locking would simplify things further.
• 7 would not normally release 10 although (I believe) the LBSCR sometimes provided locking to ensure that any facing points were unbolted for trailing moves.
• The statement that 12 backlocks 11 is also superfluous as it's already a dead lock.
• Depending on how close they are, 6 may lock 3!!! Although this type of locking is probably a bit too late for the era you are modelling.

 

Also you have produced a locking table. A locking chart is the actual layout of the locking.

Point to point locking would obviously simplify things a lot but it depends how prototypical you want to be (you can even use FPL levers for the purpose as well - something the GW appears to have done in one or two instances in the early 1920s or thereabouts but which were quickly altered as you lose the security of the interlocking if the FPL lever can't be reversed for some reason).  In a similar fashion many locking designers - as was the case on the (G)WR - at one time would not use point to point locking as security of locking can be lost lost during disconnections (as would also be the case if 2 did not lock 9 and vice versa - as John Madeley very gently pointed out to me one one occasion ).

 

On standard locking (definitely by the 1950s but it could be found much earlier on GW frames for instance) 3 should indeed lock 6 as it is a conflicting route setting) but quite when that principle emerged is difficult to say and I think it would invariably be down to the Company or its contractors practice and also any particular conditions at the location.

[micknich2003]

From what I can gather the Midland Railway was an example as they painted their point levers Oxford Blue. 

 

 Seems logical, as most if not all Midland Rly Facing Points were fitted with Economical locks, Prince's pattern I believe.

 Whilst on the subject of lever colours, the North British Rly painted its Distant Levers red, unlike other companus who painted them Green. Mick.
 

[Portchullin Tatty]

Thanks for the various replies; which I will digest along with some helpful comments on the Scalefour Society forum. 

 

I'll do my FPL levers green; it is good to be different but still right!

 

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.

 

 

 

Sorry about any glare on the model; 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!

 

 

[micknich2003]

I'll do my FPL levers green; it is good to be different but still right!

 

 Mark, don't you mean your Distant levers will be Green? Certainly, the frame I restored had Blue FPL levers.

 Did you recive the M&H drawings I sent to you? Mick.

[Portchullin Tatty]

Mark,

 

Some photos taken 25th July 1977 which may interest you / be of use.

 

Kyle of Lochalsh signal box, which is probably about the correct size for Glenmuchkin.  Interestingly, it looks as it the frame is at the back of the box, so you might have to reverse your diagram again...??

 

 

Thanks for these, just a little after Portchullin is set when the 24/1s had been retired.  It looks to have been a typical mid summer's day for Scotland - drecht!

 

I did have in mind using Kyle's cabin for the basis of my layout.  Peter Bond (who built the two very fine cabins for Portchullin) wrote about the construction of a model of this cabin in last years BRM - August & September I think it was.  He has also prepared a drawing of the same that did not make the editor's cut for BRM but will be in a forthcoming Highland Railway Journal.

 

The Kyle cabin is currently undergoing a significant restoration by the Friends of the Kyle Line and will reopen at some point as a public museum.  I think they are going to put a model of the station in there to run "typical trains of the Kyle line" rather than show the signalling equipment.  The restoration has become quite substantial from what I hear; although this will be because they (and Network Rail) were so reluctant to fix the roof for so long..................................

 

 

the cabin in 2010.

 

Sorry Mick, I got myself muddled on what was green on teh lever front - it is still fund to be a bit different so the distant lever will go in green.  Yes i did get the last drawing, I will reply back privately.