# How do I wire the two reverse loops?



## MECRR (Aug 13, 2020)

I am adding on to my layout and it has two reversing loops but being new to doc and not wanting to use manual switches to reverse power I’m not sure how to do it , my turnouts will be switched using tortoise machines. Where do I have to put gaps in the rails and what do I use to switch the polarization of the rails?


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## cv_acr (Oct 28, 2011)

First point - you handle each one independently, the way you always handle a reversing loop.

Are you using DCC? (You said "being new to doc" which I assume is a keyboard auto-correct)

Reverse loops are actually pretty easy - you just need to reverse the phase/polarity on the loop. Three options:
1- manual toggle switch, but this requires the switch and the action to flip it which you don't want
2- using relays or auxiliary contacts on the tortoise machine (built in), but this requires some careful thinking and making sure that it switches the right way and is probably not going to be possible to work right for the loops you have drawn. This can work well for the tail of a stub wye, or a loop that only has a single switch leading into it, but your loops connect at two ends to different switches. Not a major problem, but kinda make option 2 "difficult"
3- automatic reversing unit like a Digitrax AR-1, requires a more expensive electronic piece, but is dead easy to wire in, and is totally automatic. You don't need to think about it when running trains after it's wired in.

Gap both rails of the loop, at both ends of the loop, just past the switches.



https://dccwiki.com/Reverse_Sections


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## cv_acr (Oct 28, 2011)

Also, unless the turntable is a "split-ring" power supply design, you'll need to handle that as a reversing track as well.


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## MECRR (Aug 13, 2020)

cv_acr said:


> Also, unless the turntable is a "split-ring" power supply design, you'll need to handle that as a reversing track as well.





cv_acr said:


> First point - you handle each one independently, the way you always handle a reversing loop.
> 
> Are you using DCC? (You said "being new to doc" which I assume is a keyboard auto-correct)
> 
> ...


Thank you for the reply . Yes I am running DCC . So I do like the auto reversing idea , where would I put say the Digitrax AR1‘s and where would I have to gap the rails? The turntable reverses it self. Thank you again for your help.


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## MECRR (Aug 13, 2020)

Also I guess what really has me confused is the double cross over , is that a big problem ? should I take it out?


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## DonR (Oct 18, 2012)

The double crossover does not create any phase/polarity problem the way
you show in the drawing. It requires no special wiring. Just make certain
the right rail of the upper track is the same polarity as the right rail
of the lower track.

For the upper 'reverse loop', place gaps in both rails after each turnout that
creates the loop. Is this loop long enuf to hold your longest
lighted passenger train?

For the lower 'reverse loop', place a gap in both rails to the right of the double crossover
and a gap in both rails just after the turnout that creates the loop on the left. This
loop is very long and should accomodate most any train on your layout.

By all means, use automatic reverse loop controllers such as the AR1. 
You'll need 2, one for each 'loop'. Don't even think about using
manual switches, you'll end up with very awkward operations, constant short circuits and
train stoppage. You could not sit back and watch a continuous running train.

It's easy to wire the reverse controllers. Your track bus is connected
to the INPUT of the controller. The OUTPUT of each controller goes to the
rails of it's assigned isolated section. 

Once set up, the reverse loop controllers need no attention. They
are usually mounted under the table near the loop they control.

Don


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## mesenteria (Oct 29, 2015)

The double crossover doesn't need special wiring or polarity control as long as it is wired in series along with the tracks that meet it at the four ends. 

A quick precis on reversing sections:

a. They should be the sections reversed in almost all instances, not the rest of the layout at large;
b. They can only be reversed if they are gapped, or separate, from the rest of the powered layout;
c. The gaps for a reversing loop-back are almost always best placed at the ends of the two exits of the turnout that holds the loops 'ends';
d. It is a good practice to not have the gaps right across from each other. Have one at place X, but the opposite rail's gap should be about 1/8" further out;*
e. Typically, your whole train should be within the loop, between both sets of gaps, before the reversing process, but it doesn't have to be the case;**
f. Auto reversers are a gift from engineering, but they cost about three times what a decent boxcar costs these days.

The reverser is wired in series with the rest of the layout, but only the reverser provides power to the rails between the two pairs of gaps that cut off the loop. This way, only the reverser detects and corrects any phase (not polarity, phase) conflict. Think of it like a pair of feeder wires up to the rails. The reverser is wired exactly the same way, but its outputs, and only its outputs, feed the rails in the reversing loop.

* The reversers have to be 'tuned' to the layout. They react quickly, sometimes too quickly. A way to ensure they're not going to get two signals within 1 millisecond as any one axle with metal tires crosses the pair of gaps is to ensure only one tire can send a signal at a time, and we do that by displacing the two gaps so that they are not perfectly transverse...not directly opposite each other.

** You can make your trains longer than the gapped reversing track, but once again, you must stagger the gaps slightly AND you need to make a second pair of gaps distant enough that your longest car truck with metal tires and pickups (some cabooses are lighted, as are passenger cars) fits between the double gaps. This configuration again ensures the reverser isn't getting successive, rapid, and repeated conflict messages telling it to reverse the phase of the gapped section. 

I know, this must sound horribly confusing, but if you ponder it a bit, and keep reading, you'll eventually see how it works.


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## CTValleyRR (Jul 26, 2014)

Does SCARM have the capability to export to a jpeg (picture) file? If so, that's a better way to post than a photo of your monitor, which has poor contrast and lower resolution than a jpeg or other image format.

Definitely go with the autoreversers. They are so much better than the other options that the cost isn't a consideration. They are extremely simple to wire. Just install it in the feeders between your bus and the tracks (all feeders to the isolated sections must come of the autoreverser.


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## MECRR (Aug 13, 2020)

The blue lines across the track is where I was going to insulate for my reverse loop the green are where I am powering my frogs does this look good or am I missing something ?


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## MECRR (Aug 13, 2020)




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## cv_acr (Oct 28, 2011)

MECRR said:


> View attachment 561832


The bottom loop is incorrect. You don't want to include the parallel tracks with the double-crossover. That does not isolate the loop. You need to isolate the reversing section from all other track.

Move the "upper" set of gaps to the right of the crossover switch. The "lower" one stays in the same place.

The top loop is good - it's very simple.


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## DonR (Oct 18, 2012)

If you are using Electrofrog turnouts your
Tortoise motors can be wired to power the frogs. As you
indicate with GREEN, you DO GAP ONLY the FROG rails of
each turnout. You DO NOT gap the the
other turnout rails. It may be necessary to
add track drops to the track where gapped.

Don


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