How to handle overlapping return loops?

[nickelplate759]

The structure of my plan devolves to something pretty simple - a loop with internal tracks making a sort of figure 8. The internal crossing is just a crossing, not a double-slip or anything fancy.
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I know I need reversing sections, but I'm told they need to be as long as the longest train.  So either I run really short trains (not what I want) or somehow my reversing sections need to overlap.       I want to be able to reverse about the longest train that will fit without crashing into itself.  How can I pull that off?  Can have more than two reversing sections for the entire train?

I've labeled the 6 blocks of the loops.
So - if A and B are the reversing sections, they are too short for my taste.
Even A+F and B+E  is short than I want.
I'd really like to be able to run  trains as long as (the shortest of) C+A+F or E+B+C or D+A+E or D+B+F.

If I give each section its own reversing controller (that's 6 total), am I in good shape? Is that more than I really need?

Suggestions (other than run only short trains, or switch back to plain DC) welcome!

[hoyden]

I have a similar situation on my layout. I put sections A, C, D on an PSX-AR auto-reverser. On my layout section B is quite a bit longer and is fed directly. Sections E and F are also fed directly.

[John]

one reverser .. for the C & D tracks.. all you need ..

[nickelplate759]

one reverser .. for the C & D tracks.. all you need ..

Doesn't that assume that either my trains will fit in C or D, or that no cars in the train with electrical pickup (like a Kato passenger car with lights for example), will still be block A when my engine enters block B via Block C?
If C reverses polarity when the engine goes from C to B, what happens when a lighted (with pickups) car on the same train goes from A to C at the same time?

Or is simpler than I fear?

[mmyers]

If you are worried about train length, just add either A or B to the reverser with C and D.

Martin Myers

[nickelplate759]

If you are worried about train length, just add either A or B to the reverser with C and D.

Martin Myers

That won't work, I think, because C and D are both part of both the A loops and the B loops.  I'm thinking that a series of cascading reversers would do what I originally thought of,   but apparently that's not how they work and they'd just fight with each other.

I was thinking of this behavior:
Start in block F
Enter block A, reverser-A aligns with F. 
Proceed to block C and reverser-C alings with A but reverser-A does not change.
Proceed to block B, reverser-B aligns with C.
etc.

This would some kind of require logic coupling between reversers, and it probably requires them to know (or infer) the direction the train is moving. I gather reversers are simple devices and can't do this.

[mmyers]

Isolate C and D on the left side of the crossing. B, E, and the right sides of C and D and the crossing are fixed phase. Balance on the left side- F, A, left C and left D go on the reverser output

[nickelplate759]

Isolate C and D on the left side of the crossing. B, E, and the right sides of C and D and the crossing are fixed phase. Balance on the left side- F, A, left C and left D go on the reverser output

Like this?
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[wcfn100]

I think you can leave it like this but use two reversers, one for A and one for B.


Jason

[jagged ben]

That won't work, I think, because C and D are both part of both the A loops and the B loops. 
...

It would work just fine.  And I think it's the best.    Say your reverse section is A+C++D, and you're going from C through B to D, that is not a problem because the polarity will match at both ends of B.  If you're changing direction instead of doing the figure-8, then you're train can be as long as B+E or B+F. 

You could pick any arrangement of three contiguous sections such that the reverse and unreversed sections are at least two sections long on any route, and that would substantially address your train length concern.
A (or B)+C+D
A+E+C or any mirror opposite
A+E+D or any mirror opposite
A (or B)+E+F

Martin's suggestion that you drew up in your last post would also work, but the gap locations in the middle are somewhat arbitrary. It's simpler just to include all of either D or C. 

EDIT:  If you look back at your original post, you kind already had it figured out.

...
I'd really like to be able to run  trains as long as (the shortest of) C+A+F or E+B+C or D+A+E or D+B+F.
...

Pick the shortest (or longest) of those combinations you mentioned and make it the reversing section. 

[mmyers]

Like this?
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Yes, like that gives you about the longest train possible.

I suggested the gaps at the crossing because I am assuming a standard crossing that is already jumpered. Either all of C or all of D could be used but the crossing would need to be isolated from the other route. More work for about the same result.

Martin Myers

[nickelplate759]

Thanks all!  So, not as hard as I'd feared.

[nickelplate759]

So here's the real plan.   Based on advice received, I think I should hook up the red (coral where hidden) tracks to the reverser.
Black tracks are "normal" (non-reversing), white tracks are hidden "normal". Not that it matters to DCC, but the outer track at lower right goes up a  2% grade to get over the hidden tracks.

I have two questions:
1. Should I attach the yellow section to the reverser or the non-reversing feed?  I know it would work either way - I'm looking for opinions on which would be better.
2. How do I handle the crossing (not a double slip) at A?  I expect to use an Atlas code 55 crossing.  It has insulated frogs, but I suspect I'd have to cut gaps in it somehow to be able to run the reverser through one leg and not the other.
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[davefoxx]

George,

If I'm interpreting your plan correctly, just put the whole crossing in the reversing section, because you have another reverse loop coming out of the bottom of that crossing (technically, out of the turnout at the crossing's 11 o'clock position) that goes around the inner loop around the roundhouse.

DFF

[jagged ben]

Your plan isn't as simple as you let on in the original post.  I think it works as you've drawn it up, but I also agree with Dave.  You can include the crossing and the industrial spurs north of it to get a longer reversing section.

I believe the two tracks of the atlas crossing are electrically isolated, so you should have to cut any gaps on account of it.    If that turns out to be wrong you can end the reversing section at whatever gaps are necessary.