# Reverse Loop/ Crossover Best Practices



## Thelic (Jan 10, 2018)

Hi Everyone,

I'm looking for guidance for the crossover/reverse loop combination shown below in yellow.

If you draw the track diagram its really a dogbone with two crossovers, and one of the lobes has a double loop for staging. Potentially looking to squeeze in a 3rd loop for additional staging as well.

Leaving it at 6 switches, you get all the options, you can access either loop from either track, either direction. You can also run trains in the continuous loop mode without having to manage an additional shared track.

I can reduce this to 4 switches by removing the double track bridging the two crossovers. I'm not sure if its worth it though.

I guess the other thing is DCC auto-reversing, I think I can get away with 3 sections? One for each yellow loop, and then one somewhere on the rest of the track, probably on one of the green staging leads? 









Any input would be welcome, I'm still in the process of adding spurs, industries, roads etc. to the plan.

If anyone is interested, this is really just an evolution from the plan in the linked thread. I recently got ahold of Track Planning for Realistic Operation by John Armstrong. What a great book. This layout is a going to be considerably easier to build, has a longer visible mainline run and has considerably better grades and hidden track access. Plus I think it will actually look like its going somewhere rather than in a loop.

L Shaped 8'x8' Layout | Model Train Forum 

Thanks,

Thelic


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## mesenteria (Oct 29, 2015)

I can only see one reverse-requiring section, and that would be the section in yellow. I would keep the utility of the two crossovers (they're 'double' if the overlap, which these do not). I don't seen anything else needing reversing, even at that crossing at lower right. If it's a DCC-friendly crossing, the central portion will be dead, so it will only impede very small engines with maybe only two pickup axles set within 2.5" of each other. If you power the central diamond, which a reverser would handle, you would be able to run small locos like a docksider over it. Even if you make it a double-slip switch, a DCC-friendly Peco or Walthers, or a hand-made one will do well.


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## DonR (Oct 18, 2012)

Wow, this is quite a layout and is another way that a DOUBLE CROSSOVER
has been used. I had to draw out the layout
using Red and Black for the track rails to determine how to wire the track. 

There are two reverse loops.

1. The DOUBLE TRACK section in YELLOW in upper left. 

2. The SINGLE track section in BROWN (or RED) in the upper left.

For 'loop' 1. Use gaps in BOTH rails in the single YELLOW upper track to the left of the DOUBLE CROSSOVER .
You'll also need a gaps in BOTH rails between the YELLOW single lower track before the DOUBLE CROSSOVER.
This isolated YELLOW DOUBLE TRACK section will be fed by Reverse loop controller #1. NOTE that
both tracks are wired as a DOUBLE TRACK. The turnouts that create the YELLOW double track will
be a part of the Isolated section.

'Loop' 2 is more simple. Use a gap in both rails to the left of the turnout that creates the SINGLE BROWN track,
You'll also need a gap in both rails of the BROWN track to the left of the turnout at the entry into the yard.
This isolated BROWN SINGLE section would be fed by Reverse loop controller #2.

Both reverse controllers would use the DCC bus for input.

NOTE that the Double Crossover and the double track section to it's RIGHT must
be wired as a DOUBLE TRACK, The TOP rail of BOTH upper and lower tracks
of the double crossover and tracks connected to it's RIGHT will take the RED DCC bus wire.
The BOTTOM rail of BOTH upper and lower tracks will take the BLACK wire of
your main DCC bus. All other tracks would take the main DCC bus.

Don


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## MichaelE (Mar 7, 2018)

From an operating standpoint, yes, you will be able to operate more than one train, but not in opposite directions unattended. There will have to be a switchman present to make sure trains pass one another without an accident. Or, you'll be starting and stopping trains on passing sidings to allow another train through.

This is fine if you want to dig in and operate the railroad. For rail fanning, not so much.

There is not much of a yard lead to speak of at either end and the main will be fouled at the upper left while assembling or breaking up trains while another train is running on the main. It's longer on the lower right, but still rather short.


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## 65steam (Dec 18, 2019)

This looks like an interesting layout, but I don't think that your yard is located optimally. Too much of your yard tracks are on curves, which will make it difficult for you to uncouple and couple your cars. Is there a way that you could relocate it to have straight tracks mostly?

You have staging in the rear, so I encourage you to locate those tracks behind a backdrop so that they are hidden from view.


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## Thelic (Jan 10, 2018)

Great feedback, much appreciated!


The era modeled will be modern, thus far I only have Kato ES44ACs, so not too concerned with electrical pickup.
I've shoehorned a smaller, straighter yard in, I also think it balances the A/D track better. The only parts that are not straight are not in the switch clearance. You can pull a cut of cars the full length of any of the yard tracks and reshuffle using the A/D track. The leads allow enough room for about eight 50 foot cars. The MAXI-Is are too long to fit more than one, but they are only ever through traffic in the prototype. I'm *CONSIDERABLY* happier with how this one looks.
I now have a ton of room in the middle for scenery!
The staging on the dogbone lobe along the back is actually all under the table. The two long leads from the bottom avoid having to stack reverted loops and bring both track to the same grade which also allows for a continuous run mode via the crossover.
For scenery there's a mountain ridge that runs along the back of the table, with more substantial height gains in the lobes.


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## OilValleyRy (Oct 3, 2021)

There’s a lot of promise there. Looks exciting. The only thing that I see possibly being problematic is that diamond in the lower right, which appears to be a curved diamond. Unless you’re planning on making it custom, I doubt you’ll find that works. Diamonds are notorious derailment sites. It may be better to eliminate that… Unless it is an over/under bridge? It’s difficult to discern which is intended.

Also, what scale and radius are the curves?


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## 65steam (Dec 18, 2019)

Much improved, nicely done!


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## cv_acr (Oct 28, 2011)

mesenteria said:


> I can only see one reverse-requiring section, and that would be the section in yellow. I would keep the utility of the two crossovers (they're 'double' if the overlap, which these do not). I don't seen anything else needing reversing, even at that crossing at lower right.


The crossover(s) turn both ends of a dog bone into reversing loops. If you head out clockwise from the crossovers you'll eventually end up back there in the opposite direction.

OP is correct to turn the yellow loops into reversing sections, and I would make the opposite end reversing section the red loop under/over the yellow ones.


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## cv_acr (Oct 28, 2011)

OilValleyRy said:


> There’s a lot of promise there. Looks exciting. The only thing that I see possibly being problematic is that diamond in the lower right, which appears to be a curved diamond. Unless you’re planning on making it custom, I doubt you’ll find that works. Diamonds are notorious derailment sites. It may be better to eliminate that… Unless it is an over/under bridge? It’s difficult to discern which is intended.
> 
> Also, what scale and radius are the curves?


Yeah, my assumption is that based on the way those lines cross, and where the tunnel entrances are drawn, is that those lines at the back are rising at different grades and the red curve is above the other one.


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## Thelic (Jan 10, 2018)

Yes, that's correct lots of grade changes here. I'm still shuffling the grades around to get the best access to hidden track and reduce the ruling grade.


N scale
Modern equipment clearances
Minimum visible radius is ~16.8", minimum hidden is 14.9"
Max grade 2.5%
75" passing sidings
Continuous run and point to point capable
9' 5" (darn drywall) x 8'


I've started some mock up of the benchwork. I really need this to be modular, I probably only have a few years left in this house before more bedrooms will be needed so it needs to be able to break down into reasonable sized sections. Obviously the sheets will need some weight saving holes added. Add a 3/4" sheet of birch plywood atop the framework.


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## DonR (Oct 18, 2012)

cv acr

You usually are correct that a double crossover can result in two
reverse loops. However, in this track plan if you trace the two tracks
leaving the crossovers to the right you'll see that they join together
in the bottom right by a turnout that changes to a single track that
does not form a loop. That track that eventually does return to
the crossover..but from the left.
The result is the tracks to the left do become 'reverse loops' but
the double track leaving the crossover from the right are simply
a 'double track' and does not require gaps.

Don


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## 65446 (Sep 22, 2018)

I Don't know about all the amendments that have been made..I'm sure they are for the best. 
But I just had to respond to *OVR*'s post #7..
Diamonds are *not* "notorious derailment sites" any more than any other train-routing device such as switch or turntable ! Leave alone the OPer has made this a grade separated event, no longer a diamond (if it was)..


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## OilValleyRy (Oct 3, 2021)

I hadn’t previously seen the tunnel portals. So that clears that up.
I stand by my assertion that diamonds (along with turnouts) are high on the derailment culprit list. But as it is an over/under crossing, in relative terms it doesn’t matter.


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## mesenteria (Oct 29, 2015)

cv_acr said:


> The crossover(s) turn both ends of a dog bone into reversing loops. If you head out clockwise from the crossovers you'll eventually end up back there in the opposite direction.
> 
> OP is correct to turn the yellow loops into reversing sections, and I would make the opposite end reversing section the red loop under/over the yellow ones.


Yup, you're right. I did a more thorough tracing using a piece of paper with two coloured dots, one red, one black, and started at the rightmost crossover with the black dot outward, north. Then, twisting and turning the paper with the curve, I can see that the rightmost crossover closes a loop, and so does the leftmost, as I could see easily earlier. Thanks for pointing that out. So, any sizeable portion of either loop could be controlled by a single controller/reverser, and the length of train would never present a problem unless it runs into 50 (?) cars or more.


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## 65steam (Dec 18, 2019)

You might consider curving the front edges of your base to avoid having so many sharp corners, which might not make good visuals.


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## Thelic (Jan 10, 2018)

Lets call them the "staging loops" and "main loop".

The "Staging loops" are everything left of the crossover, might be many concentric loops.
"Main loop" is everything to the right of the crossover
The most logical place to put an auto-reverser on the "main loop" is anywhere where there is a good long stretch of single track. I would think one of long leads around the right side of the table would be ideal, and only one is required since they are actually part of the same loop. You are quite right though the tunnel section on the left would also work, plus both ends would then be visible for troubleshooting...hmmm...

We can run the staging loops with a single unit as well, but we would have to ensure that only a single train is moving across the crossover at any given time. Alternatively we could add a reverser for each of the concentric loops and then we can pull a train into staging while having one pulling out at the same time which is possible given the way the switches are oriented. Given that I would like block detection and transponding I should be able to put a Digitrax BXPA1 on each staging loop and call it good.



My original question though is what's the best track arrangement for the crossover and reverse loop leads. Consider we have lots of room to play with.










Red works, but I think yellow has it beat.
Currently my preference is yellow, I think it has the least potential of issues because it limits the S-bends. It also
Blue uses 2 less turnouts, but restricts traffic. It would have to be changed ever circuit to run in continuous mode.
Green doesn't have all the destination options and would have to be excessively long to add the full double crossover.
Or something completely different?


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## Thelic (Jan 10, 2018)

65steam said:


> You might consider curving the front edges of your base to avoid having so many sharp corners, which might not make good visuals.


Plan is to cut the straight sections back and spline them with 3/16" plywood or hardboard.


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## OilValleyRy (Oct 3, 2021)

Yellow.


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## 65446 (Sep 22, 2018)

[*Re: post #14*] 
*Oh !! Now it's turnouts too*, notoriously "high on the the derailment culprit list" !! 
Neither of those were ever know to be "notorious" for derailing anything !! If yours do then yours are installed wrong or just el cheapo !! Everyone experiences derailments as part of the nature of RRing in real or in miniature..
But no one talks or thinks like that about these two ultra important track elements based on their supposed (ehem) "notoriety" for causing derailments !! Where did you dig that up, sir ?!!


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## DonR (Oct 18, 2012)

Mesenteria

This usage of a double crossover is quite different from that in many
other track plans shown here on the Forum. Very often, it is true, that some usage does create
a 'reverse loop' on both sides. However, in this track plan 
the 'reverse loop' approaches the crossover from the left. Look 
again at the 'double track' departing the crossover to the right
(clockwise). The double tracks become single track thru 
a turnout at lower right. At that point there is no ability to
turn a train around, thus no 'reverse loop'. However, if you
continue to follow that resulting single track it will become
a reverse loop which can be isolated by gaps in the obvious
curve section in the upper left area.

Don


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## cv_acr (Oct 28, 2011)

Thelic said:


> My original question though is what's the best track arrangement for the crossover and reverse loop leads. Consider we have lots of room to play with.
> View attachment 569806
> 
> 
> ...


Red and yellow both work fine and allow all the movements between all tracks. S-bends aren't really an issue, as the only S-bends really created in either version are just the crossovers themselves which are always naturally a form of S curve. (But the key word is "avoid SHARP S-curves".) The way you have the crossovers oriented in the red design, a train coming off the bottom side of the loop passes through at least a full car length or so of straight track in the first crossover switch before taking the front-to-back crossover at right, so there shouldn't be any problematic curves here. A train coming off the upper side of the loop into the first crossover is more or less navigating a continuous right curve into the start of the crossover.

Blue as you noted creates a bottle neck, and green really doesn't do what you want it to do. It just makes it "look" complicated with the diamond crossing without really accomplishing anything quite as useful and it sacrifices a crossover from the bottom track to top track when travelling to the right.


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## OilValleyRy (Oct 3, 2021)

Telltale, 
Banish derailments on your model railroad | ModelRailroader.com

Don’t hijack the OP’s thread though. If you want to discuss derailment causes in another thread I’m fine with that, but not in Thelic’s layout design thread.


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## cv_acr (Oct 28, 2011)

telltale said:


> [*Re: post #14*]
> *Oh !! Now it's turnouts too*, notoriously "high on the the derailment culprit list" !!
> Neither of those were ever know to be "notorious" for derailing anything !! If yours do then yours are installed wrong or just el cheapo !! Everyone experiences derailments as part of the nature of RRing in real or in miniature..
> But no one talks or thinks like that about these two ultra important track elements based on their supposed (ehem) "notoriety" for causing derailments !! Where did you dig that up, sir ?!!


No, you're right. It's sections of straight track with no special work that are the most likely to cause track-related derailments. 🙄

Don't be obtuse.


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## 65446 (Sep 22, 2018)

*cv_ac**r *
Thanks ! That is precisely what I had in mind as well !! I've seen more derails on straight and curve track throughout decades and decades than on switches and crossings !.Maybe it's because there are no guard rails that TOs and X-ings have, which tend to keep trains properly railed through them..!
The only real question with TOs are the *points*; if they are tapered correctly, are level with stock rails, and are snug in place in each position..Those 3 factors, if sound, are about all that's needed for smooth ops thru them..


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## Thelic (Jan 10, 2018)

Thanks for the input guys, I think I'll continue with the yellow version. It has the simplest(?) switching logic. For addressing I'm thinking:

Red and yellow operate as a pair to access staging or open the mainline loop. I could break these up to maximize traffic, but I may be asking for trouble in a hidden area if I try dispatching and receiving at the same time.
Green and Orange always work together (tie to same address).
Blue and Purple always work together (tie to same address).
But then purple and orange also only ever act together? So If I were to ever throw orange I would need purple to close and vice versa, which would also close blue/green, which I guess isn't a problem...Is this an issue solved with routes in DCC?

Also, there must be a way to use the additional switch on the slow motion switch machine to provide interlock protection for trains attempting to enter a switch that isn't thrown their way. A short section of track on the ends of the yellow, red, and blue with one rail tied to through that turnouts switch machine?

So for instance:

Tracks left of the yellow would only receive power if the yellow switch was thrown for them, AND the green one was also.
Tracks left of Red would be dependent on only itself. The orange/green addressing protects trains from running through an un-thrown green switch.
Tracks to the right of Blue would be dependent on only itself.
Purple and orange would be protected by the route logic mentioned earlier.










Hopefully I have this right...


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## DonR (Oct 18, 2012)

I assume you mean a stall motor (Tortoise) when
you say 'slow motion switch machine'. If so the stall
motor would need voltage long enuf for it to
complete it's change of the turnout points. That's normally
done by a DPDT toggle switch. You would need some
sort of 'sensor' and relay to do that automatically and the
relay would have to hold until stall motor is done.

Don


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## Lemonhawk (Sep 24, 2013)

Typically the voltage to a stall motor switch machine is left on all the time. A DPDT wired like a reversing switch is used to change the point position. Stall motors are designed to "stall" when they have moved and hit something and not burn out. Unlike solenoid type switch machines.


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## DonR (Oct 18, 2012)

Yes, Lemonhawk is correct...that is the reason that you may
face a complicated sensing and current control circuit for
each turnout if you pursue the 'auto throw' idea. If those
were twin coil turnout motors the 'auto' system would be
much simpler and less costly.

Don


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## Thelic (Jan 10, 2018)

I might have been unclear, after doing some research what I'm referring to is called a braking section. I'm not looking to automate the switch throws.

I believe I can use the extra SPDT switches on the switch machine to add or remove power from the approach tracks if the arrangement is not set for them, or one step further route a "set speed to zero" function from the programming track. This crossover is hidden in staging so I really don't want to be collecting trains off the floor after they run through a switch not set for them.


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## DonR (Oct 18, 2012)

thellc

Wow, your explanation sure makes more clear what you are
looking for.

You don't need any switches, you can do what you want 
with the use of turnouts with POWER ROUTING...for example...
The Peco Insulfrog. You place a gap or
insulated joiner in the frog rail of the approadh tracks about
2 feet back from the turnout. With the Insulfrog set wrong, that tradk
section would go 'dead' electrically and the loco would stop. Simply then
set the turnout points correct and the train would continue. No special
gadgets or complex wiring needed.

Don


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## Thelic (Jan 10, 2018)

Thanks Don,

I've already got a collection of electrofrog turnouts, but your solution is certainly has an elegance of simplicity going for it! Essentially what I'm suggesting is the same thing except using the switch machine to do the routing.


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## Magic (Jan 28, 2014)

Electrofrog turnouts are also power routing so you can use what you have.
You just have to gap them right and I think (always a problem.) that using 
them the way Don suggested would work just fine without any extra gaps.

Magic


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## DonR (Oct 18, 2012)

Yes, the Electrofrog turnouts can be made
'power routing' to be used to create a 'safety dead section',
as Magic suggests. However the the isolation gap in
both FROG rails would be
2 or so feet AWAY from the turnout instead of at it. That
creates the controlled 'safety' sections.

The way it works:

Consider the divert FROG rail to be PLUS, it's other
rail MINUS. When points set to divert the Frog rail
gets PLUS current, thus track goes 'live'...loco moves.
When points set to straight that Frog
rail gets MINUS...thus no circuit..track dead...loco stops..

Note: While I used DC + and - in the explanation above 
the Electrofrogs work just the
same on a DCC AC powered layout. The Frog changes
the PHASE. Same result.


Again, this is the easy way to avoid locos running
into points set against them..no special devices or
wiring needed.

Don


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