# Reversing loop wiring



## riogrande51 (Aug 24, 2012)

This poor drawing is a one line drawing of a loop on my layout I have isolation joints at the 12.5 crossing and on the turnout from the main line the diversion route.
The problem is if I remove the isolation joints it creates a direct short at the switch. 
I have added a auto reverse mod from Digitrax which you can hear the relay clicking when the loco tres to cross the diversion switch leg but the loco just stops moving.

Please look at this and see if I need another isolation joint of if I have them in the wrong place
thanks


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## sstlaure (Oct 12, 2010)

That doesn't look like a return loop with the crossing. If the track literally loops back on itself (goes into and through the loop and exits the return on the exact same track it entered the loop.) Looks like yours goes through the loop then crosses the entrance track. Am I missing something?

Best bet it to pick +/- rail designations for your inboard/outboard rails. Put your finger on the + rail (doesn't matter which one) and run your finger around the track. If your finger as it goes through the rail changes sides (going from outboard rail to inboard rail) that's where you'll have a short.

In this example you can see how the RED (+) rail loops back onto the Blue (-) rail causing a short. The black lines are where the breaks should be. The round part is the part that needs to have the reverse loop circuit wired in. You should isolate both rails.


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## cv_acr (Oct 28, 2011)

I'm not sure what's going on to the right of what you've drawn, and it also doesn't show where you've attached feeders, but the the reversing section does NOT look to be properly isolated. The insulated joint in the crossover should be on the loop track to the left of the switc.

Take a highlighter or different colour pen and starting at the insulated gap by the diamond crossing trace over the track in the loop. Keep highlighting until you hit another gap and see if you can see the problem.


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## riogrande51 (Aug 24, 2012)

*shorts on layout*

Here is a plan of the whole layout I have tried all day to gt it to work but I just chase the short from one place to another. 
Please review and see if you can tell where to place the gap and if I need a auto reverse

thanks


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## NIMT (Jan 6, 2011)

This should you fix you right up.


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## riogrande51 (Aug 24, 2012)

Do I need a auto reverse?
Thanks


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## riogrande51 (Aug 24, 2012)

went and tried it but I got a direct short on the left switch on the track going on the straight any ideas?
Thanks


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## NIMT (Jan 6, 2011)

Your going to have to be more specific about which switch you mean? 
And yes you'll need an auto reverse unit to run the yard!
Did you isolate both rails on both sides?


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## riogrande51 (Aug 24, 2012)

Yes I did both rails The switch that is the top most the straight track going from it know has a dead short Is there a way to see if the auto reverse is working I not sure I haven't burned it up
Thanks


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## riogrande51 (Aug 24, 2012)

The program I drew the layout only has a short on the upper left turnout that you tagged but nothing else


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## sstlaure (Oct 12, 2010)

If you look at the small dwg I attached you would only get 1 indicated short as well, but you have to isolate a loop at both ends so that your train can enter the loop and completely clear the mainline short of the loop so that the auto reverser can reverse the polarity of the mainline.

In this example, your train takes the RH side route into the loop, the train smoothly passes into the loop, once completely in the loop, the reverser switches the polarity of the mainline (lower pic) so that as the train comes around back to the mainline, the polarities are now aligned properly to allow the train to pass without a short


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## cv_acr (Oct 28, 2011)

Riogrande:

If you erase all of the yard and stub tracks from your diagram, your basic schematic is a double oval with a reversing track cutting across the middle. This is what you need to do to isolate that reversing circuit:










(compare this closely to your diagram, and you will see why NIMT suggested those locations for the gaps.)

You cannot isolate ANY reversing section with only one pair of gaps. Both ends of the reversing segment need to be isolated.

The Wiring to the reversing section must also be completely isolated, or you defeat the purpose of it.

In order to not short out when an engine crosses over the gaps into the reversing section, you must be able to reverse the polarity of the rails, either with a toggle switch, or using an auto-reverse circuit (generally only available for DCC). Otherwise, your track will be isolated, but will still short out when the engine crosses the boundary, because the engine is now completing a circuit between two isolated rails.

If your track is properly isolated, and you are still getting shorts, you need to look at your wiring because you probably have something wrong below the table.

The other thing to watch out for when building a layout, is whether you have any switches that are what are termed "power routing", which selectively route power through the frog based on the direction the switch is set. What this actually does, is set the polarity of the frog, and both frog rails, so one branch of the switch has opposite polarity on both rails (and therefore an engine can complete the circuit and operate) and the branch the switch is not lined for both rails are the same polarity, so no complete circuit can be made. This is fine as long as the track is a dead-end spur. If this track forms a double ended siding, or there are power feeders attached anywhere beyond the frog, this will also absolutely cause a short (but only, and as soon as, the switch is thrown in a particular direction. (in the case of two switches facing each other, like in a siding, this will actually depend on the position of both switches))


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