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Axle Counters

Discussion in 'Signalling M.I.C.' started by hassell_a, Aug 9, 2008.

  1. hassell_a

    hassell_a Active Member

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    From the 'Why do Bulleids slip?' thread:

    ????!!!!! I think that you are getting somewhat confused here....

    Track circuits don't provide detection for points - that is done using point detection, regardless of whether the area is mechanically, TCB or axle counter controlled. A signal can just as easily be interlocked against a track circuit or axle counters.

    A track circuit doesn't do any more than detect the presence of a train on a section of track, which is what axle counters do.

    Maybe we need a new topic on this now![/quote:13fy1dbx]

    Not quite true, track circuits will lock points (hence why we have sealed releases at some locations) and will operate other kinds of signalling equipment for example signals that are released by approach control or are approach lit will be worked by the presence of a train on track circuits.

    Another topic in a signalling section might be more relevant for this.[/quote:13fy1dbx]

    Are you confusing axle counters with treadles?

    An axle counter counts the number of axles into a section of track and it will then show as occupied until all the axles are counted out of the other end of that section. While the section is occupied, points can be locked, routes help, signals approach control, or whatever else.

    A track circuit will show as occupied once one or more axles enter its section, due to the axle dropping the track circuit relay at one end. It will remain showing occupied until all axles are cout of the other end, allowing the track relay to pick up. While the section is occupied, points can be locked, routes help, signals approach control, or whatever else.

    Both systems are methods of showing a portion of track as being occupied - they deliver the same result. The difference is in how they can fail! And factors like track circuit clips not having any effect on axle counter sections.

    Neither track circuits or axle counters provide detection for points - that is proved using point detection boxes before a route can be set up. Track circuits AND axle counter may both be used to hold a route over a set of points once set up and once occupied by a train.
     
  2. Johnny_Cash

    Johnny_Cash New Member

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    ????!!!!! I think that you are getting somewhat confused here....

    Track circuits don't provide detection for points - that is done using point detection, regardless of whether the area is mechanically, TCB or axle counter controlled. A signal can just as easily be interlocked against a track circuit or axle counters.

    A track circuit doesn't do any more than detect the presence of a train on a section of track, which is what axle counters do.

    Maybe we need a new topic on this now![/quote:dyx33ed4]

    Not quite true, track circuits will lock points (hence why we have sealed releases at some locations) and will operate other kinds of signalling equipment for example signals that are released by approach control or are approach lit will be worked by the presence of a train on track circuits.

    Another topic in a signalling section might be more relevant for this.[/quote:dyx33ed4]

    Are you confusing axle counters with treadles?

    An axle counter counts the number of axles into a section of track and it will then show as occupied until all the axles are counted out of the other end of that section. While the section is occupied, points can be locked, routes help, signals approach control, or whatever else.

    A track circuit will show as occupied once one or more axles enter its section, due to the axle dropping the track circuit relay at one end. It will remain showing occupied until all axles are cout of the other end, allowing the track relay to pick up. While the section is occupied, points can be locked, routes help, signals approach control, or whatever else.

    Both systems are methods of showing a portion of track as being occupied - they deliver the same result. The difference is in how they can fail! And factors like track circuit clips not having any effect on axle counter sections.

    Neither track circuits or axle counters provide detection for points - that is proved using point detection boxes before a route can be set up. Track circuits AND axle counter may both be used to hold a route over a set of points once set up and once occupied by a train.[/quote:dyx33ed4]

    I see what you mean now, I was confusing their use and operation with other pieces of railway equipment, thanks for clearing that up.

    I haven't got any axle counters over a brand new piece of railway that I work on. I'm sure they have their uses but track circuits are still in great favour on some parts of the network (this returns the discussion back to the original point).
     
  3. hassell_a

    hassell_a Active Member

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    From some of the things that I hear about how recent large axle counter installations have gone, I think that track circuits are being more favourably considered for new works again.
     
  4. Johnny_Cash

    Johnny_Cash New Member

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    From some of the things that I hear about how recent large axle counter installations have gone, I think that track circuits are being more favourably considered for new works again.[/quote:25xw1ejj]

    One of the criticisms I have come across with axle counters is that they don't like OTP, OTM, trolleys and have to be reset after T3s incase any of the above have been used.
     
  5. boldford

    boldford Member

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    Axle counters v Track circuits.

    Humm. I think they've both got their own merits.

    Axle counters have to count exactly the same number of axles out as well as in to prove line clear. Very good where long/wet sections are encountered. They also dispense with the need to insulate various parts of points and crossings.

    Track circuits can be almost useless where the ballast/formation is very wet. (The tunnels under both the Severn and Mersey come to mind). They can also be a pain where very long sections are involved as they need to be split into a number of sections to control the shunt resistance. They are, however, rarely prone to wrong side failures.
     
  6. andrewtoplis

    andrewtoplis Active Member

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    On most 'modern' new signalling systems the train's position will be detected by the signalling system because they will be in constant contact (eg SELTRAC as on DLR). Axle counters are used as a back up to show they are clear of points etc. Once you move to a 'modern' system like this you dont need track circuits.

    Reliability is an issue though..
     
  7. Dan Hamblin

    Dan Hamblin Part of the furniture

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    Yes, the DLR seems to be suffering a lot of signalling problems at the moment. Mind you, we are fitted a variant of SELTRAC on the JNP lines.

    Regards,

    Dan
     
  8. andrewtoplis

    andrewtoplis Active Member

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    Hope you fixed it first then!!

    Mind you, I'm BCV these days, what do I care... 8-[
     

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