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groundsignals as route indicators.

Discussion in 'Signalling M.I.C.' started by southyorkshireman, Sep 21, 2007.

  1. southyorkshireman

    southyorkshireman Part of the furniture

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    I can think of several instances (on preserved lines) where there is on the entrance to a loop controlled by a single main signal arm, then before the point there are a pair rather than a single ground signal, specifically indicating which route is set. In these cases, for a normal running move, can the ground signal indicate the route into the loop for a train or would the main signal signal arm dictate a specific route and the relevant ground signal for that route be cleared as necessary.

    Examples I can think of off the top of my head include Ramsbottom, and Swanage (run round, but it does have an indicator), though I think there maybe others
     
  2. kesbobby

    kesbobby Member

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    Assuming that the line is a running line and there is only one stop signal in advance of the points it could not possibly indicate a route on its own. It could only do so if, when cleared, some form of route indicator was also displayed to the driver.

    Clearing the main stop signal should be conditional on sequential locking in which:

    a. the points are set for the required route,
    b. the Facing Point Lock is in,
    c. the appropriate shunt signal is cleared.

    In that order.
     
  3. Tomnick

    Tomnick New Member

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    You'd normally expect some form of route indication at the running signal if it can clear for more than one route, irrespective of the presence of any preceding shunt signals in advance of that signal. As always, there's exceptions to the rule - for example, there's no route indication given on approach to Skegness station - with a choice of six routes from the inner home! I seem to recall something reasonably similar to the original post at Exeter West, though I can't recall the details - where there was no route indication given at the inner home, but instead it was taken from a set of ground signals in advance of it? It's a rare case though, if it is indeed true.

    In a good few cases, though I can't speak for the examples given, it's possible that the main signal would route only along the 'main' line, with access to the loop being for shunt moves reversing at the pair of ground signals and being routed accordingly from there. In that case, you'd need no route indication at the main signal, as there's only one route!
     
  4. sigsnguard

    sigsnguard Member

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    Under normal operations the Swanage inner home is (and can only be) cleared for a passenger train arriving into a clear platform face. We have a route indicator (ex-Weymouth) to show the driver whether the platform is 1 (the bay) or 2 (main platform). Two "running" dummies are between this signal and the buffer stop, the one outside the signal box being the one with the route indicator.

    The indicator was provided to re-assure crews arriving into the loop when a train was already in the platform. In this situation we bring them in "on the dummies" - so the inner home is not clered but the shunt signal at the base of the post is. On arriving at the signal box, there was nothing to show the driver that the route was indeed set for the loop so we added the "L" and "M" indicator to clarify this.

    At the other end, where the loco runs round, the dummy can only be cleared when the points are set to the loop, or when the platform is empty. If, for any reason, the loco is required to rejoin the train in the platform the signalman has a key release for the signal which is to be used only after a clear understanding has been reached with the loco crew.

    I think that it was only the GWR that "stacked" ground signals on the same post, each one indicating a specific route.
     
  5. Tomnick

    Tomnick New Member

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    I'm not sure whether 'stacking' of discs was unique to the GWR, but certainly the concept of an individual disc for each route isn't. We've got a couple of examples on the GCR of a number (two/three) of discs arranged horizontally, where each refers to a specific route. I'm sure this mirrors LNER practice - and I'm equally sure that I've seen discs where, although not on the same post as such, one disc is mounted behind another at a lower level, to create the same effect. The GWR practice of providing a disc for each route was probably more widespread though!
     
  6. gz3xzf

    gz3xzf Member

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    I remember seeing stacked ground signals at Llanfair Caereinion on the Welshpool, between the loop and the platform road there are two stacked one above the other, they appeared to be operated by one lever with an arranement at the signal to decide which road was set (detection from the turnout blades). I presume these work as with most stacked signals where the "Top Left" rule applies.
     
  7. craiggluyas

    craiggluyas Member

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    It was also midland practice, hence the 2 dollies at the top end of Embsay station, which were 3 originally.
     
  8. pseudonym

    pseudonym New Member

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    I think this is known as a Selective arrangement. Wasn't it popular on parts of the former Southern to economise on levers? The disadvantage was it could make the locking mighty complex.
     
  9. tuffer5552

    tuffer5552 Member

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    The DSR being set up to network standards has position light signals that work as point indicators. They do not show route indication but they prove A route is set. For normal running there is a theatre or diverging route indicator on the controlling signal. However if the points are usable for shunting, off a frame or auto points then it will tell the driver that the points are over, locked and detected.
     
  10. John Webb

    John Webb Member

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    LMS/BR(M) certainly used stacked ground discs. There was circa 1960 a three-high set on the Down fast at St Albans City controlling moves from Down fast to Up slow, Up Fast and Down fast sidings. We have a similar stack on display in the garden at St Albans South, albeit not yet in working order.
    John Webb
    (St Albans Signal Box Preservation Trust)
     
  11. guard_jamie

    guard_jamie Part of the furniture

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    The GW and LM used stacked discs as standard. The LNE generally put them side by side (up to five in some cases!) but as mentioned did sometimes put one behind another on a plinth. I am not sure of SR practice; they used a disc ulluminated by an overhead lamp rather than traditional aspects by night, which may have precluded such.

    The GW as far as I am aware were not averse to running discs, to prove a point. There are examples of this on Exeter West's diagram and real ones at Arley and Bewdley North on the SVR, the latter of which is a pre-preservation installation I believe. However in both of these extant examples you have one disc that needs to be cleared for both routes off the point, and it is a bracket signal in rear that indicates which route the train will take. I imagine therefore that these examples are purely to prove detection on the points (presumably to simplify the detection to the aforementioned bracket).

    However there are other examples on the SVR where it is the, for want of a better word, "main" signal that has all the detection on it. Two particular beasts are Bewdley North Dn. Main Inner Home to Shrewsbury and Bewdley South From Kidderminster to Dn. Main Inner Home. Both are right outside their respective Box but hard pulls because of the circuitous route the wire takes!
     
  12. Neil_Scott

    Neil_Scott Part of the furniture

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    I've got a disc on the Up main that requires to be puled for every movement towards Shrub Hill. It's of very little use apart from when shunting an engine into the goods sidings (which doesn't happen very often but I guess that's the point of having it). Shrub Hill also has running discs on Platform 1 heading towards the south.
     
  13. pmh_74

    pmh_74 Active Member

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    The GWR didn't always stack their ground signals - at Aberthaw for example there are single discs with multiple routes. There are also some double discs, and I'm trying to remember why (it's probably 10 years since I worked on that job...). I've a feeling it might be because some routes are/were worked by ground frame. Certainly in most instances the only route indication given to the driver is by him/her looking to see which way the points are lying.

    LU would have a single disc with a theatre sign indicating the route ('1', '2' etc., left to right). As LU practice is closer to SR practice than any of the other main line regions, I can well imagine they may have done something similar.
    There is, of course, the modern equivalent using a GPL and stacked miniature route indicators - I seem to recall that there's a particularly impressive (or, if you prefer, ridiculous) stack of these somewhere around West Hampstead. I'm unsure if the stack is in any particular order or if it's purely down to what's written on each indicator.

    We've done something similar at Swithland (Backing Signal to Down Main / Up Main, with the crossover detected via the running shunts. which are pre-set) but in this case the shunts are a stacked pair.
     
  14. Jamessquared

    Jamessquared Resident of Nat Pres

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    The Bluebell has a disc signal with theatre indicator that controls access from the Sheffield Park carriage yard headhunt into the carriage shed roads A, B, C, dock road (D) or platform 2, the route set being indicated on the theatre indicator. This is a new (2012) installation but our general signalling practice follows SR practice, so I assume that would have been the way the SR would have signalled that particular movement (i.e., rather than stacked discs). The fan of points that control access into roads A, B and C are hand controlled, but their position is detected and the signal can't be cleared unless they are proved in position; if an attempt is made to move one after the signal is cleared, detection is lost and the signal goes back to danger.

    Slightly OT, but in our museum we have this shunt signal - which was in position when the Bluebell moved in in 1960, but was retired after a while as it had become quite frail:

    LBSCR 'Tommy Dod' shunting signal Sheffield Park | Flickr - Photo Sharing! (not my photo).

    It's an LBSCR "Tommy Dodd", still in use on BR certainly up to the closure of the line. The signal displays two aspects: a red aspect with a white painted "Monty Python" hand pointing to the road that is blocked when on (not shown); and a green disc with a white cross for "off". When the signal is pulled, the whole head moves through 90[sup]o[/sup]. More photos and a description here: Southern Signals

    Tom
     
  15. Steve

    Steve Resident of Nat Pres Friend

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    Going OT, the reference to a 'Dodd' for a shunting signal is interesting. I first came across this use on the North Norfolk Railway. Had never heard it before. We always refer to them as a 'Dolly' here in Gods chosen County.. What terms do other people use?
     
  16. Neil_Scott

    Neil_Scott Part of the furniture

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    Disc!
     
  17. Jamessquared

    Jamessquared Resident of Nat Pres

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    Don't know what signalmen would call them, but loco crew on the Bluebell almost universally call them "dummies".

    I've read elsewhere that "Tommy Dodd" was used on the GER as well as the LBSCR - and maybe elsewhere too?

    I'm not sure of the derivation, but in the nineteenth century "tommy dodd" was rhyming slang for "odd" as in coin tossing (even or odd). You can imagine how a signal that could be on or off corrupts to heads or tails amongst railwayman slang. The common factor between the LBSCR and the GER is of course East London, so maybe the phrase arose there. There was a mid nineteenth century music hall song that went, in part, "Heads or tails are sure to win, Tommy Dodd, Tommy Dodd".

    Tom
     
  18. shedbasher

    shedbasher Member

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    As an Ex Midland signalman we called them Dummies
     
  19. The Saggin' Dragon

    The Saggin' Dragon Resident of Nat Pres Staff Member Moderator Friend

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    Seem to remember from when I drove at Llangollen that there was one at Llangollen Goods Junction.
     

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