# Wiring sidings in reverse loops in DCC



## Mike Nugent (Sep 22, 2021)

I am trying to understand reverse loop wiring. I have a copy of my layout which is very early in construction as in only the roadbed has been laid. I believe I have identified the reverse loop portion of the layout (in blue). The double slip switch was sort o throwing me off, but I think I have it now. Are the sidings (in red) associated with the reverse loops wired into the reverse loop district? 

See attachment


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## J.Albert1949 (Feb 3, 2018)

The two industrial sidings (in red) shouldn't have any relevance on the rest of the wiring.

It looks like you have TWO reversing loops there:

The first is obvious (in blue), starting/ending at the switch on the lower right.
The second (less obvious) is the loop beginning at the "leg of the wye" in the center/top (below the red siding).

That looks to be a double "crossover", NOT a "double slip" switch. It will need "insulation from the blue loop", I reckon.

That's actually a very interesting and versatile track plan.


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## MichaelE (Mar 7, 2018)

Yes, that's a great trackplan. It would be interesting in Swiss narrow gauge. Lots of mountains and valleys.


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## Lemonhawk (Sep 24, 2013)

I think there is only one. The blue part just after the Decatur Jct TO down to Fayette does not need to be included. I would put the upper red sidings on the same feed as the the reverse loop to keep the reverser from toggling un-necessarily. The double TO at Georgia Crossing I would put below the turntable, and terminate the reverse loop just before the TO to that bottom red siding. (elevation may interfere with this ). That keeps the double crossover and the bottom red siding from being in the reverse loop. This way there is only the one siding on the reverser. You should do the red and green pencil trick just to make sure nothing is hidden. Start some place and make the red the right rail and the green the left and start tracing around the tracks and see where red meets green on the same side, then you can figure out where to put the reverser to prevent the short. If the layout were a little more North, it would be nice to have an interurban or trolley track that connects all the small towns (Its not my layout, its yours so don't let put clutter on your layout!)


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## DonR (Oct 18, 2012)

J Albert is correct; There are TWO reverse loops.
You'll need two reverse loop controllers.

'A' loop is obvious; The track shown in BLUE.
Gap it as follows:
1. To RIGHT of DOUBLE CROSSOVER.
2. Just before the downward curve at mid point after
turnout at Hadley.
The Hadley RED spur would electrically be part of the iso section

'B' loop, as J Albert noted, is less obvious, but there none the less:
Gap it as follows:
1. To LEFT of Stone Mountain turnout (before entering tunnel)
2. At some point just below East Farms spur turnout.
The double track spur at Artemus and the
Single track spur at East Farms would electrically
be part of the isolated section.

It should be noted that the TURNTABLE is also a 'reverse loop',
however, some have a built in phasing circuit. If yours does not
you will need either a 3rd reverse loop controller OR a special
DPDT toggle switch circuit.

I have tried to make the isolated sections long enough for 
most lighted passenger trains. 

Don


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## Mike Nugent (Sep 22, 2021)

1. Thanks to all of you for the help. This feels like high school physics to me. i apply a formula, I get the right answer, I have no idea why.
2. I did the red line/green line activity. All it told me was two rails at two different points would conflict. Depending on where I started, the conflict could exist anywhere in the reverse loop. So I don't get the next step, hence my pursuit of your higher knowledge.
3. Attached another diagram based on DonR's suggestions. I have two quick questions. If I am not running a train with later lighted cars, like a passenger train, can I cut off the red reverse at the blue arrow? For that matter, if only my engines are going to be powered for any train, can I even make the loop as small as the orange arrow as long as I ensure it is longer than the consist of engines?

Again, thanks. New pic attached


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## Mike Nugent (Sep 22, 2021)

BTW Lemonhawk, I cannot move the crossover switch down to where you suggested as those tracks are at significantly different levels at that part of the layout.


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## DonR (Oct 18, 2012)

Mike

Mike

Yes, you could cut the isolated section at the Blue arrow. 
It would not be a good idea to cut it at the Yellow arrow
it would be too short in my opinion.

Actually, tho, there is no reason to have the isolated
section short. The 'reverse loop' controller will make
any operations thru the isolated tracks 'invisible'...it's
fully automatic and requires no action on your part
once installed...why do you want it short?

Don


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## DonR (Oct 18, 2012)

Mike

You've expressed a need to know more
about reverse loops, so here is some
explanatory chit chat.

It's just plain basic electricity. You have two wires for any
electric circuit. If you touch them together you short out the
circuit, sparks will fly and you could damage the components.
So you have insulation to prevent this.

Your layout track is the same as two wires. The RIGHT RAIL
may NEVER contact the LEFT RAIL. When the layout plan
causes the Right rail and left rail to 'touch' through a
turnout, you have a short circuit. (using the TWO colors representing
the two track rails is the tool that identifies the possible short)
To avoid the short, you insulate by setting up an
'ISOLATED TRACK SECTION'. The gaps or insulated joiners
prevent the electrical clash at the turnouts. A reverse loop
controller feeds power to the isolated section. It actually
flips the phase (polarity) of the iso track when the loco
crosses the gap.. therefore matching the phase of the main
track so there is no short. When the loco proceeds and crosses the 'exit'
gap, the loco shorts and the controller again flips the phase
thus matching the main again. All this happens so fast
that the loco does not pause, the light won't even blink.
To make the above work, you connect the output of
the reverse loop controller to the ISOLATED track. The
controller input is connected to your main power bus.
That's all there is to it. Usually, the reverse controller device
is mounted under the table near the section it controls. Once
installed you never need touch it again.

I hope these words will help you better understand
the reverse loop circuitry.

Don


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## Mike Nugent (Sep 22, 2021)

Thanks to all. I have mapped out 4 different return loops which will cause a change in direction on my layout. (This is basically the red/green line exercise.) Two of them go through the crossover which I had previously mapped out. 

Looking at the overlaps of the return loops, I came up with where the reverse sections need to be which is a combination of Don's and J.Alberts49's suggestion. As far as I can see, the Stone Mountain to East Farms misses one of the 4 loops leaving it without a return loop circuit which it would need and moving it to the Stone Mountain/Decateur "Y" solves that. 

I think I have it.

I have include a map of the 4 return loops but I would warn you, this is not for the feint of heart. To trace the loops, start at the color coded circle.

Thanks again to all.


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## DonR (Oct 18, 2012)

Mike

I'm afraid you are right...your drawing is not for the faint of heart.
But, am I reading you right?...you are saying that there are 4 reverse
loops...but I think you actually MEAN...there are 4 reversing ROUTES
your trains can take. On the Forum we tend to define any section
of track that turns a train around and requires electrical isolation
as a 'reverse loop'. By that definition you
still have only 2 'reverse loops' that require isolation
per previous suggestions. At least I didn't detect any track changes.

Don


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