I thought I had it figured out but now I am unsure. I have identified the red track as a reversing section and labeled the gaps A to D. Am I correct? Is there a better way? I run a NCE Powercab with a SB3A and will use a Digitrax AR-1. I hope you can see the photo.
Scott
If it were my layout I’d move gaps A and B further down the loop (up in the drawing) to the initial turnout capturing both those sidings inside the reversing loop. But your plan will work.
You may find it nuisance if you’re running DC to have that one siding with main line polarity. For DCC it may not matter.
Also, only one reversing loop isn’t ideal. Once the train is reversed that’s it, you can’t traverse the loop again to reverse back. You have to back up through the reverse loop. I’d also put a second reverse loop inside the other return curve at the other end of the layout.
Can’t even see the broken image icon if Firefox. There is a sticky on how to post photos in the forum
if you read it, you missed the line Any site that requires a login won’t work, even if visibility is set to Public. Right there on your image is a big sign in button.
I took the liberty of copying your image and modifying it. No reversing is happening until you get to the black arrow I added. I would gap the straight and diverging route of that turnout. I also added the letter E and a vertical red line. You need to gap those tracks going into staging.
I think Henry has it right.
-Kevin
Edit: This post is incorrect as written. I leave it here in quotes instead of deleting because it illustrates another point I’ve tried to make elsewhere which I find useful. Think of reversing sections as separately powered blocks or power districts. If you look at these as “loops” you can easily miss crossing tracks that, like a figure 8 installed into an oval, create reversing sections. The correct solution is to remove the gaps at D as they are unnecessary. But you should just remove the gaps noted as A and B and instead insert the other set of gaps between the turnouts creating the actual reversing section where you need them.
'Well, if you’re going to do that then remove all the gaps except at D and insert a new gap just to the right of the turnout that actually creates a reversing section. That gets all of the mainline out of the reversing section.
Technically, the reversing section doesn’t begin until after that turnout. The only really usable reversing section is from D to the turnout."
As I say, the gaps at D can be removed as they achieve nothing.
I had thought that originally but then I noticed a second loop and that is why I posted the first picture. The picture below was my original thought but now I am even more confused.
Since this is DCC, and the length of the reverse section is not likely to be much of an issue, the only real reverse loop here is short section of track between the turnout at “A” and where it joins the staging yard ladder.
Consider the the whole loop the mainline and just put an auto reverser on that short section.
There is no second reverse loop, that section created the only reverse loop. Think about the layout if you removed that. There is no other way to reverse the train so there is no reverse loop without it.
Once you reverse the train, do you intend to back it thru the loop to reverse it again?
OR
Is there another loop on the upper level that I see a note about?
Sheldon
Ah… I missed that it was a DCC layout.
I think this diagram reflects what you suggested.
-Kevin
Yup.
The OP mentioned in his first post that he was using an AR-1 which is a Digitrax mechanical relay auto-reverser for a DCC layout. Identifying and isolating the reversing section is pretty simple in this example.
Rich
I don’t know I agree with Sheldon’s suggestion. Hard to tell dimensions but that looks fairly short. You could have metal wheels, helper locos or lighted cars in the reversing section and on both sides of it.
There is a lot not to like about that layout.
Yes, the proposed reversing section may be too short for lack of needed length.
Also, once a loco is reversed, there is no provision to turn it back into the former direction.
Another poor design is the use of two turnouts to join the yard to the mainline at the bottom of the diagram. The yard should be shortened a bit so that only one turnout connects the yard to the mainline.
Rich
I agree that is a possible problem. It would be good to understand the reasons for the this reverse cutoff in the design.
I also think Rich is correct about moving the one turnout. Or better yet consider a different track arrangement for the reverse loop all together.
Sheldon
Well, great minds think alike, even when they’re wrong.
The “second reversing loop” is an illusion. Fooled me easily.
Your proposed layout is a simple loop with an internal crossing track.
These can look like two reversing loops and they sort of are but they are a “special case”.
As pointed out by others (lots of others by now) the section of track where polarity actually must reverse if your train is to travel across it in the opposite direction (DC perspective, for DCC the term phase reversal is more useful but electrically speaking the two phenomenon are quite similar) is the crossing track.
My second response put the gaps in the wrong section entirely, treating that section as a regular balloon reversing loop which is what it looks like.
Technically, you need only isolate the crossing track. But then it will be too
I cannot visualize what you are proposing.
Please post a diagram.
-Kevin
To answer some questions. The track leading to the upper level has a balloon track for a reversing loop so that I can turn the train back to the other direction. It is stacked on top of the lower loop.
The cutoff track in the lower level is only 30" long, too short for a train to be completly isolated in the loop. Hence the reason to isolate a “section of track” as the reversing section.
The section I see as the second reverse loop is from where the staging yard starts at D and follows the staging, through the main line all around the layout and back to D. My understanding is that if a train can be backed up and then change direction it becomes a reversing section.
I am not sure how to proceed as all this track has been laid and I do not want to have to remove it. I will post a picture of the entire plan later on today to see if it will help.
I appreciate all the help thus far.
Scott
In fact, your original plan will work fine, now that I think it through better.
You need more than the minimum two sets of gaps required for a crossing track, as you’ve realized, and you have them. Gaps located as drawn and your layout will work fine.
Gap C is correctly located for what you are trying to achieve. No need to change that at all.
Gap C is all that is needed to prevent the circuit from shorting out. Gaps A and B are necessary to run a locomotive over the gap at C. It’s the locomotive wheels that short out the gap at C. Hence the need for an isolated section at least as long as the longest locomotive consist. But then there’s the metal wheels on the last car in the train which also short the gap at the other end of the isolated section. A normal DCC auto reverser will react to both shorting signals.
You do have options as to exactly where gaps A and B and D go but you don’t need to change them if you choose not to. You don’t need extra gaps at the proposed location E.
You can create a longer isolated “reversing section” using the sets of gaps more or less as you have done in your diagram. We have done this on our layout. You just need more than the minimum two sets of gaps, as you have discovered. You can move the gaps at A and B to extend the length of the “reversing section”.
You can also move gap D to where I suggested in my second “wrong” solution. You don’t need to move gap D but operations may be easier if you do.That’s the part that only looks like a reversing balloon loop but isn’t. It’s part of the main line continuous loop that runs through your staging yard. That curved loop back to your staging yard then stays part of the “main line” polarity. That’s what the solution proposed by Henry achieves but does not as easily isolate the part of the continuous loop you really need to isolate from gaps A and B to gap C. Steel whe
As you are fond of pointing out, only the OP needs to “visualize” anything.
[quote user=“Lastspikemike”]
In fact, your original plan will work fine, now that I think it through better.
You need more than the minimum two sets of gaps required for a crossing track, as you’ve realized, and you have them. Gaps located as drawn and your layout will work fine.
Gap C is correctly located for what you are trying to achieve. No need to change that at all.
Gap C is all that is needed to prevent the circuit from shorting out. Gaps A and B are necessary to run a locomotive over the gap at C. It’s the locomotive wheels that short out the gap at C. Hence the need for an isolated section at least as long as the longest locomotive consist. But then there’s the metal wheels on the last car in the train which also short the gap at the other end of the isolated section. A normal DCC auto reverser will react to both shorting signals.
You do have options as to exactly where gaps A and B and D go but you don’t need to change them if you choose not to. You don’t need extra gaps at the proposed location E.
You can create a longer isolated “reversing section” using the sets of gaps more or less as you have done in your diagram. We have done this on our layout. You just need more than the minimum two sets of gaps, as you have discovered. You can move the gaps at A and B to extend the length of the “reversing section”.
You can also move gap D to where I suggested in my second “wrong” solution. You don’t need to move gap D but operations may be easier if you do.That’s the part that only looks like a reversing balloon loop but isn’t. It’s part of the main line continuous loop that runs through your staging yard. That curved loop back to your staging yard then stays part of the “main line” polarity. That’s what the solution proposed by Henry achieves but does not as easily isolate the part of the continuous loop you really need t
The Atlas Wiring book explains all these variations in Chapter 5.
Figure 5.10 shows how to gap a single crossing track to extend the “reversing section”.
You have done this.
The trick to all this is the schematic as described by John Armstrong in his Track Planning for Realistic Operation, Chapter 8 page 96. Armstrong encourages us to draw a schematic of our layout, planned or as built. That way the true electrical shape of the layout is easier to see.
I’m not good at doing this but as I understand it you leave out the parts of the track that meander all over the place and just draw those as straight lines (or curves as the case may be). The important parts of the layout electrically are turnouts and crossings. The rest of the track is just two “wires” carrying power straight from one turnout to another. You really draw just the two wires, red and black, as those wires feed power to your track.
A continuous running loop of any length and any shape without turnouts is drawn as a circle schematically. Add a turnout and you have a circle with a stick projecting out (or in as the case may be). Connect the end of the stick to another turnout in the circle and you have either a passing siding or a crossing track. It is only when you connect that other turnout to the circle with a stick that you can create a problem.
When red meets black you have a problem.
