Thursday, 14 November 2013

A Question of Logic

I've had my thinking hat on again, in another attempt to synthesize Lanrhaiadr Mochnant and The Art of Compromise to produce a version that won't take up too much space in the office.

Point rodding in blue

Compared to earlier versions I'm planning to swap the viewing side over, so the goods shed will be at the front, as it is on Apa. Compared to the real LM the big changes are the replacement of the level crossing with a bridge and moving the main platform  to the down side of the loop. A quick reminder that in any case the model is going to be set both after passenger working ceased in 1951 and after LM became a terminus in 1952. Changing the level crossing for a bridge means I have to decide where to put the motley collection of sheds and the weighbridge. I suspect I won't reach a final decision on that until I place some mock ups on the baseboard. I don't think there is actually an obvious on scene location for the weighbridge that makes sense . A couple of other bits of the jigsaw have now fallen into place, including where the iron mink stood that was used for additional storage in the yard.

The jigsaw I'm not so sure about involves the points and signalling, because some of the edges of the puzzle are missing. Literally so when it comes to photos.

You might need a pen and paper for the next bit....

What I do know is that the LM lever frame had twelve levers, and Mike Lloyd records ten of them being in use at some point in time. I'm fairly certain that four levers were for signals. I know that three sets of point rodding ran along the downside of the line and I'm presuming two of those operated the points at 7 and 8. I'm guessing that point 8 at least had a facing point lock, which could account for the third rod, though the onlyTVR  FPL I have a photo of, at Llansilin Road, appears to have been operated off the same lever as the point.

Is it possible that point 7 didn't have a FPL because passenger trains wouldn't have used it in the up direction, or would it have had an economical FPL? In that case though wouldn't the FPL' for points 7 and 4 have been of the same kind, so why would they need rods from the lever frame?

Two rods pass under the loop, one of which then runs along the down platform towards the cattle dock siding. I think this continues to the catch point on the cattle dock siding. The second one, I presume, controls the catch point on the goods shed siding.

Three sets of rodding run alongside the up platform. One crosses under the loop at the end of the platform and controls point 5, so I'm guessing the remaining two control point 4 and its FPL.

That by my calculations comes to eight sets of point rodding, and four signal cables.

So the next question is what levers would have controlled what, and how would the interlocking have worked. Using TRAX 3 this is my best guess so far

It seems to work for most of the obvious movements and conflicts I can think of. When/if I get around to building it I'll be using DCC so at least I'll be able to amend things. Any advice and observations at this stage though would obviously be more than welcome.


  1. Just a thought for you to ponder.

    If you intend to operate LM as a freight only terminal, then the signalling and point control requirements will change considerably.

    It is possible that the line would be operated on the one engine in steam principle and the signal box just used as a ground frame with no signals to operated.

  2. Richard, Yes it is a good point. Llanrahaiadr was a tablet station, so I presume even in the heyday of the line that means the lever frame would only ever have had the status of a groundframe. I don't know enough about signalling to know if that means all the levers would have been locked by a tablet, or only those for the signals so that movements within the station would still have been possible
    By 1963 the photographic evidence I've seen suggests that not surprisingly the up starter was out of use and I can't see any trace of the down home, but even after closure the up home seems to have been in good condition
    My plan is certainly to operate it on a one engine in steam basis, though allowing myself discretion to run the odd passenger train when no one is looking.
    There are two reasons I want to understand how it would have worked in the real world. One is to get the point rodding at least roughly right, and the other is to make operation more deliberate, without, hopefully, getting to the point of being tedious.

  3. James,

    I'm quite happy to draw up a signalling diagram based on if you'd like. It might not be perfect, as it would be my interpretation of what is known,but you could then base your decision on the fact that the lines passenger service has only just been withdrawn so the station retains the signalling required for that.

    1. Richard, It would be a great help if you could. So far the only Tanat Valley diagram I've come across is the one of Llangynog Mike Lloyd included in his book.

  4. I'm so glad that you two are discussing this, I was going to suggest that Richard might be able to help. Afraid my knowledge of signalling isn't that great so it will be interesting to see what the pair of you come up with :-)

    Will you be taking the plunge and switching to EM this time around James, such a small compact layout would be an ideal introduction ?

  5. Geoff, Yes I don't see much point in proceeding unless I go with EM gauge. Not just because of the inherent increase in accuracy but also because of the knock on effect on other aspects of my modelling. It does feel like a big leap though and I've been staring at the contents of a C+L turnout kit for weeks without feeling in the right mood to start building it. However if I do mess it up then for this scheme I'm quite prepared to use SMP.

  6. James,
    I think you will be pleasantly surprised just how easy the kit will go together, just take your time and all will be well. If you haven't already joined the EMGS and don't have access to the manual then I will be more than happy to scan and mail you the notes on building a simple B6. Though the kits are ideal once you have more confidence then it's much cheaper to buy the components from the society stores.

    Do you have the necessary gauges ?

    1. Geoff, I hope so. I rejoined the EMGS after a gap of over 25 years, a few months ago.and I think I have most of the required gauges. What I need most is a quiet weekend without family and dogs, and with good light.

  7. I am sure all will be fine and you will enjoy the experience, I've put a post together on my blog. to show you how I go about things. Any questions then you know where I am :-)

    1. Geoff, Excellent. I've already read it a couple of times. So tht first point is accelerating up my to do list. It would be nice to have at least had a go before Warley so I can hold my head up high.

  8. Glad you found that of use, seeing as you have rejoined the EMGS you will find the method described with plenty of drawings in the track section of the manual CD. Once you have a clear plan of action then press ahead, I am assuming that your kit has both the crossing and switch blades prepared ?
    If that is the case then the most critical part of construction has been done for you but the blades will probably need a little honing to get a good fit against the stock rails. I'm not sure if you have Templot or are aware that it is now a free download with the option of making a donation ?

    Have fun,

  9. Geoff, Yes I've got Templot. Unfortunately the one thing it needs to be used properly is time. Every time I go back to it I've forgotten what I learned the last time I used it. That is part of the attraction of TRAX If only to get me to the point where I've got the plan to a workable stage, though it only does very basic sleepering.plans.