Wiring Stub Terminal Passenger Station

[Flagler]

I have a Stub Terminal Passenger Station that can be entered through a wye of the Double main line.I have a DCC layout,Use kato unitrack and use 3 X over . I also run 8 ft long lighted passenger trains. Two of the double x over are used on the west and east side of the wye on the main line and the third is used within the passenger station stub area as the leed into the station.

[GaryHinshaw]

Do you have a question?

I'm guessing you'd like to know how to configure the reversing section.  It would help a lot to have a reasonably detailed diagram of your configuration with dimensions, and some indication of how busy the terminal will be.  In a situation like this you can easily run into difficulty with one or two trains spanning both ends of a reversing section simultaneously, which can give the reverser fits.

[Flagler]

Thanks for the reply. I will post a picture of the track arrangement  Tuesday. I know that the reversing loop needs to be as long as the lighted train. If  Have the entire station tracks blocked off and a train is moving out bound while a another train crosses the start of the reverse section will this cause a problem or  do you have a problem only when two trains cross the insulated areas at the same time?

[GaryHinshaw]

Ok, a photo would be good.  Until then, the following cartoon might be helpful.  This shows a very simplified segment of track where there are two fixed polarity sections (red is the north rail, black is the south) on either end of a reverser section (grey) which has no fixed polarity.  From top to bottom, there are 4 different reverser states shown: 1 - Indeterminant, i.e. the polarity it was left in from the last train passage. 2 - The gaps on the left are bridged by metal of any kind (e.g., metal wheels, a loco truck or a lit passenger car truck), then the reverser will set the top rail to N if it was not set already.  3 - The gaps on the right are bridged by metal, then the reverser sets the top rail to S.  4 - Both gaps are bridged by metal; now the reverser cannot cope because no polarity choice avoids a short.  In this last case, it does not matter if the wheels at either end are part of the same train or a different train; they simply cannot be simultaneously bridging both gaps.



Now imagine a slightly more complicated setup where the reverser section has a turnout that splits it into two tracks on the left side that then join two tracks with fixed polarity (north up like above).  In that case you could have two different trains bridging the two sets of gaps on the left and not have a problem because north up in the reverser section would be compatible across both sets of gaps.

With these principles in mind, we can have a look at your terminal and decide what kind of arrangement gives you the most operational flexibility.

[Flagler]

These are some pictures

[GaryHinshaw]

Thanks for the photos.  A few quick questions:
* Have you placed any insulating gaps anywhere in this track configuration yet?
* Is this glued down already, or are you still free to put new gaps anywhere?
* Do the crossovers have any built-in gaps in them (save for the frogs) or are they one electrical unit?  Maybe an equivalent question: is there only one pair of feeder wires for the entire (double) crossover?

[RBrodzinsky]

Using the double crossover before the terminal coming off the wye is setting yourself up for potential problems. Since you can, easily, run two trains in/out along the outside tracks, you always run the risk of two units trying to trip the reverser at the same time. In a "normal" wye, converging into a single track, in this configuration you would just isolate the diverging tracks from the single track, and let all the terminal tracks flip as necessary. You can do the same here, as long as you ensure two trains do not leave/enter the terminal at the same time.

The third side of the wye is too short to even consider adding the reversing section there.

Gary- the Kato dbl x-over is fully insulated. Only the two outside tracks are continuous. You need feeders on all four legs

[Flagler]

The track has not been isolated .I cannot  isolate until I decide where to Isolate,hence the discussion. That being said the track arrangement is not glued down. If It were glued down it would be with white  Elmers glue, this allows for eazy changes when combined with Unitrack and blue foam board.The beauty of the design. My basic question has been answered.I just need to make sure that any
two trains do not cross the Isolation locations at the same time. This will provide a good location for a switch tower

[GaryHinshaw]

Ok good.  I think the simplest solution is to place the gaps between the stub-lead crossover and the two wye tracks, then put the terminal tracks under the reverser.  As noted, you cannot run two trains in and out of the terminal simultaneously, but having a tower there helps reinforce that restriction.  I was trying to think of an alternative scheme that would be less restritive, but nothing simple comes to mind.

[Flagler]

Thanks Gary, What if I allocate more than one AR15 to the Area? I have a surplus.If two trains are in the opposit curves  of the wye they could not be  X of in the X over or a collision would occur.Do you think this might work?

[RBrodzinsky]

The problem there is the double crossover, since the outer two rails are continuous.  If you never crossed over, there would be no need for reversing at all, just two unconnected sidings. It is only if you want to cross over:  then you want to ensure that whatever terminal track is active has the same polarity as the in-use exit track. Multiple reversers won't help in this situation; just one that controls the x-over and the entire terminal.

[GaryHinshaw]

I thought about that possibility, but it raises a question I have never found a good answer to (see below).   I think what you are proposing is something like this:



where the black tracks are fixed polarity and the blue and green are two separate reverser blocks.  Assuming the Kato crossover is isolated as shown, I think this would work.  As Rick notes, if no train takes the crossover, it would definitely work: trains could come and go willy nilly, and indeed no reversers would be required.  The question is: if you take the crossover and the two reversing sections have opposite polarity, which one switches when you cross the gap?  If you had a "fast" and a "slow" reverser, then the fast one would switch first and things would probably be fine.  But I don't know in practice what would happen. You could try it...

[Flagler]

Has anyone had two reversing sections  in tandem. If you are in one section controlled by a AR15 and go into another section controlled by a AR 15 would only the AR 15 section being entered fire off if needed ?

[RBrodzinsky]

Has anyone had two reversing sections  in tandem. If you are in one section controlled by a AR15 and go into another section controlled by a AR 15 would only the AR 15 section being entered fire off if needed ?

No, that's the problem. Unless they have significant differences in speed (Gary's "fast" vs "slow") and then who knows what would happen (I guess someone could hook up a PM42 and PSX-AR in tandem and tell us).  But mostly, they would fight.

[wcfn100]

Instead of auto reverse can you use power (phase) routing from the wye legs? 



Jason