Single Cross-over with opposite polarity?

[KB02]

I have been thinking of adding in a single cross over to a section of my layout, but I've determined that wiring it in may be a bit of a pain. My layout is, when all is said and done, a big loop. What looks like a double main line is actually dedicated east and west bound track - meaning the inside rails share the same polarity. I know that I would need an auto-reverser, but how would I go about wiring it in? I've tried drawing it out, but that confused me even more. Is ther a simple schematic somewhere that someone could point me to to help with this?

 

[Iron Horseman]

I have been thinking of adding in a single cross over to a section of my layout, but I've determined that wiring it in may be a bit of a pain. My layout is, when all is said and done, a big loop. What looks like a double main line is actually dedicated east and west bound track - meaning the inside rails share the same polarity. I know that I would need an auto-reverser, but how would I go about wiring it in? I've tried drawing it out, but that confused me even more. Is ther a simple schematic somewhere that someone could point me to to help with this?

So it sounds like the layout is a dogbone or water wings type. Pretend the cross over is the main track and ignore the 2nd "main line" part. That should then look like a normal reversing loop, and can be wired as such.. The only difference is that there will have to be an additional set of insulated rail joiners on the 2nd main line that we just ignored.

 

[KB02]

Yes, dog bone style, essentially.

And actually, the more I have thought about it, it will be easier than I though. If I am using two turnouts to create the crossover, all I would have to do is isolate one of the turnouts and wire it through an auto reverser. As long as the isolated section is long enough to accommodate my longest consist of locos (maybe three?), that should cover everything electrically, right?

 

[tootnkumin]

We have a similar setup through a middle divider, only it will hold 4 long SD's or 5 GP's, but the tracks would be a foot or so apart. It's got a manual polarity reverser. Once all the locos are between the isolating joiners,(at each end of the connection piece) the reverser gets thrown and they carry on through the turnout on the other side. The turnouts and their diverging bit stay connected to the tracks on either side. To use only the length of track available through a normal crossover, might be a bit tight, although you could possibly extend the isolated section back along the approach tracks a bit maybe. Some thought required on feasability.

 

[Iron Horseman]

And actually, the more I have thought about it, it will be easier than I though. If I am using two turnouts to create the crossover, all I would have to do is isolate one of the turnouts and wire it through an auto reverser. As long as the isolated section is long enough to accommodate my longest consist of locos (maybe three?), that should cover everything electrically, right?

Generally yes, but .... Do your cars have metal wheels? If so the "gaps" have to be bigger than the potential contact area of the wheels. Also any lighted caboose, FRED, or passenger cars could cause problems. It is usually safer to make the isolated section as long as the longest train.

 

[crusader27529]

On a club layout long before DCC, I wired it quite differently.

The layout was just a long loop that sort of looked like a double track dogbone, so I wired it like it was a double track mainline, and only had to worry about polarity issues ONLY at the loop parts of the layout(both ends). That allowed amazing flexibility in adding crossovers and the like, because since it was a double track mainline, the crossovers didn't cause a polarity reversal.

Think about it.......

 

[KB02]

On a club layout long before DCC, I wired it quite differently.

The layout was just a long loop that sort of looked like a double track dogbone, so I wired it like it was a double track mainline, and only had to worry about polarity issues ONLY at the loop parts of the layout(both ends). That allowed amazing flexibility in adding crossovers and the like, because since it was a double track mainline, the crossovers didn't cause a polarity reversal.

Think about it.......

Interesting... I'm not sure that would work with the way my layout is currently wired, but I like the idea.

 

[tootnkumin]

With the way you want to have it, with the auto-reverser in the middle of the crossover, and to get enough track for a couple or more locos to fit inside the reversed length of track, will be to extend that length into the tracks leading to each side of the crossover i.e. move the insulators further away from it. I don't think there's any hard and fast rule that says they have to be right at the joins on the ends of the turnout's rails.

So..as I figure it (disclaimer here again, in case someone disagrees) measure how long the longest loco consist you will want to put through the crossover will be. Measure that distance back from the middle of the crossover rails, along the approach/departure rails on each side, and put insulated connectors in those tracks there (or a bit more, or even the closest existing joint). When the leading loco triggers the reverser, all the locos will be within the track affected. (If someone says it won't work, I'll salute and go down with the ship)

 

[tootnkumin]

Thinking on a bit, you would need isolation gaps at each end of both sections of the straight through rails and probably with plastic inserts in them wide enough to guarantee that the wheels of following cars could not bridge the gap when passing over them. I would also suggest electrofrog turnouts as well, no power routing through the point rails. One of the problems we have at the club.

 

[trailrider]

Got a similar arrangement, except both sides of the dogbone are close together. My crossover uses #8 Atlas turnouts. But, my layout was designed for DC operations, and is divided into blocks that are fairly long. Each block adjacent to the crossover is controlled by DPDT toggle switches. I have signals adjacent to the xover. Before running a train through there, I throw one of the toggles so the red-over-green light goes to green-over-green, that tells me the polarity across the turnout is correct. (Actually, these are tied in with the switch machines, so throwing the turnout routing switches, also adjusts the polarity.) Works with DCC as well.