Automatic guards for reversing loops

[Andrew_au]

(Posted here rather than Controls, Signals and Electronics because it's DCC-specific)

Consider the reversing loop configuration in this post.

• Wye junction off the mainline
• Yards at the far end of the wye
• DCC automatic reversing section from wye to approach to yards. Reversing section has 3 entries - 2 on "branches" of wye (not on mainline) and third near the yards.

Two questions:

1. Consider the branches of the wye. Is it beneficial for the cuts to be close to the base (branches outside reversing section) or the ends of the branches (maximum length in reversing section)?
2. A traditional reversing loop naturally resists having multiple trains in the loop, since the single line leading to the reversing loop naturally supports only a single train. In this scenario, you could easily have a train operating on the yard end and a train entering or leaving the mainline, thus bridging both ends of the reversing section. What sort of interlock could be easily implemented to strictly enforce the "only one train" requirement.

 

[phils2um]

Hi Andrew,

This does not really address your specific questions but reflects how the wye and reverser controlled segment on my RR is situated. Two of the three entrances to the reversing segment are my mainline. And, the mainline rails on both sides of my reversing segment have matching "polarity". As a result the reversing segment also usually has the same "polarity" as the mainline (the DCC signal is phase matched). Thus, there is never a polarity conflict on the mainline. So long as no train crosses the wye branch leg boundary (causing the "polarity" to shift) it does not matter how many trains are in the reversing segment or bridging the two mainline boundaries.

I'm not sure this makes sense without seeing a picture of my layout which I don't have available at the moment.

 

[Greg Elmassian]

I have a wye entering my yard. The entrances are on two different boosters. I use a short detecting autoreverser.

I put the insulators right after the tracks "leave" the mainlines,which allows maximum train length in the yard.

Greg

 

[AlanL]

A traditional reversing loop naturally resists having multiple trains in the loop, since the single line leading to the reversing loop naturally supports only a single train. In this scenario, you could easily have a train operating on the yard end and a train entering or leaving the mainline, thus bridging both ends of the reversing section. What sort of interlock could be easily implemented to strictly enforce the "only one train" requirement.

Andrew, adding an interlock (if it would be possible) would be too complicated. It might be helpful if you can post a diagram of your track plan with the reverse loop. There may be a different position to install the reverse loop to protect your wye. As an example you can make the main line as the reversing loop

And the yard section can be connected to the original main line.


Ignore my note about the reverse loop activating, it was to help me visualize the operation and possible conflicts with 2 trains crossing the 'gaps'.

If the length of the reversing loop was a sensible length it would be difficult to cause any conflict with 2 trains, unless you drive your trains too close to each other, I'm sure that you don't. Of course it depends on your track plan.

Alan

 

[Greg Elmassian]

I agree, trying to enforce an "interlock" with that system is too much trouble. I'm wondering why/ Just to stop collisions, or are you "electrically worried"?

My yard is single-ended at this time, so, it's not actually possible to have 2 trains entering/exiting the reverse loop at the same time, they would physically collide.

Later this yard will have another exit (at the far end) and I will probably put a simple autoreverser in the power district it exits to, simple, no extra issues.


Greg

 

[Andrew_au]

I agree, trying to enforce an "interlock" with that system is too much trouble. I'm wondering why/ Just to stop collisions, or are you "electrically worried"?

The two failure cases I can see are "collisions" and "shorts" (two trains each bridging an end of the reversing section, but with opposite polarity).

It's more of a thought exercise. I know some people use dead sections, ABC, or auto-stop sections to stop trains entering turnouts or crossing removable bridges when they are not supposed to. I was wondering if it was possible to apply similar technology to an auto-reverse section, and how you would do it.

 

[dunnyrail]

The two failure cases I can see are "collisions" and "shorts" (two trains each bridging an end of the reversing section, but with opposite polarity).

It's more of a thought exercise. I know some people use dead sections, ABC, or auto-stop sections to stop trains entering turnouts or crossing removable bridges when they are not supposed to. I was wondering if it was possible to apply similar technology to an auto-reverse section, and how you would do it.

Well it would be quite easy to do what you need with switch control but I do not think you could manage it with an LGB or Massoth loop DCC unit.

 

[Greg Elmassian]

There are all kinds of ways, but I would graduate to a computer-controlled system that would allow arbitrary logic to be made, as your requirements are defined, refined and changed.

Hardwired logic is tough.

Perhaps you could have block occupancy, and then that triggers addin in a diode in the lead in track and then use ABC to stop the train short.

In my situation, I run the trains, so I don't need/want the layout helping me. If I had an automated layout, or people running it that would crash trains, perhaps I would consider having something.

Greg