# DCC reverse wiring question



## Walman (Dec 18, 2011)

Hello all. I'm sure this is a basic question that has been answered before but I didn't run across it in the 25 seconds I searched  so thought I would ask. I attached a quick schematic (pdf) but in case you can't see it I'll describe it as well. This will be a DCC layout and I am running a Digitrax Superchief (8amp)

On one end of my layout I have an outer mainline loop. I also have a branch line (#1 for this discussion) that breaks off and parrallels the mainline for a time then crosses under it in a loop back towards the center of the layout where it will connect with the local line (at a 3-way switch). So in summary I have reversed back. 

To prevent electrical problems I assume I need to isolate the reverse loop right before I connect back to the 3-way switch, correct? I've indicated with a box on the diagram. 

So my questions are: Is it as simple as isolating as I have drawn? Do I need a reverse polarity device like the Digitrax AR1? Other issues/thoughts/considerations I haven't thought about? I will be running short trains that will completely fit on this branchline before it hits the isolation spot, if that matters.

Thank you.

Walman


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## Brakeman Jake (Mar 8, 2009)

Your drawing doesn't show any reversing situation yet so not even insulators are required.Depending how your middle track will connect to the other end will dictate if you need any reversing module or not.Not enough infos yet.


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## NIMT (Jan 6, 2011)

Totally agree that you either haven't given us enough info or you don't have a reverse loop problem.
More info would be helpful!


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## Walman (Dec 18, 2011)

*Re: "better" drawing*

Sorry I am at work and between meetings so just scratched out the rough layout in total. Does this help?


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## NIMT (Jan 6, 2011)

That helps a ton! Here's the answer!


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## Walman (Dec 18, 2011)

*Re: Thanks*

LOL. OK thanks. Now can I asked out of that chicken scratch of a drawing how you determined that was the key spot for insulators and not any other location (like my original concern area as just one example).

Thanks again,

Walman


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## Brakeman Jake (Mar 8, 2009)

Simple...just colour one of your tracks (wich track or colour not important) around the layout.Then follow your coloured track inside the trackplan...you'll end up finding a meeting point where colours don't match...this is the reversing point.


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## NIMT (Jan 6, 2011)

I have super "reversing track O Vision"... OK it's as Jake said!


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## Walman (Dec 18, 2011)

Brakeman Jake said:


> Simple...just colour one of your tracks (wich track or colour not important) around the layout.Then follow your coloured track inside the trackplan...you'll end up finding a meeting point where colours don't match...this is the reversing point.


OK yes that was my strategy. But going back to my "branch #1" example. If I colored the outside rail red on the branch just where it leaves the mainline and parallels the mainline then cuts under the mainline, when that rail connects at the 3-way switch the red rail is now on the inside rail of the 3-way switch. That is why I thought it was a reverse. I guess I'm not thinking of this correctly. Your placement of the isolation makes sense to me I guess I am struggling with why only there.


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## waltr (Aug 15, 2011)

On NIMT's diagram I am concerned that the isolated (AR1 driven) section may not be long enough for a full length train. What happens when the loco is existing and metal wheels cars are still entering that track section?


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## NIMT (Jan 6, 2011)

waltr,
The only problems would be if the loco's were spanning the gap on both sides. Metal wheels on the cars have never caused me an issue. The electronics in the AR-1 can reverse the section in a matter milliseconds and also has some fault tolerance! In order for there to be an issue you would have to span all 4 insulated sections of rails at exactly the same time, near to impossible!


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## Brakeman Jake (Mar 8, 2009)

Generally,as long as the reversing section (AR1 driven) is long enough to accomodate the length of the loco (or consist),there shouldn't be any problem as car trucks aren't conductive.However, there may be a problem with lighted cars for instance that would use their two trucks as current pick-ups,being electrically linked these could create a short while bridging a gap.

One could decide to have the entire inside trackage wired through an AR1,making this impossible,but then insulating both tracks is required at every place it connects with the outer tracks.NIMT's solution is the simplest though.


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