Electrical connections

Never used MTH Realtrax but I have seen the problem you describe.

Wild guessing those MTH switches/turnouts have what we call a 'non-derailing feature'. If the turnout is positioned the wrong way, the switch will flip to the right way. This is easy to do with three rail track, you use one of the outer rails as part of a circuit. But to get this to work, you need a gap or plastic or plastic pins somewhere to isolate the circuit. Following so far? Then, when you connect two turnouts together, you get one isolated section on one side, and another on the other side, and bingo, electricity for the outer rail can't get thru.

Normally people don't like to break the common, it can confuse the crud out of you. Instead they would hook up the outer rails together, then put a plastic pin in the center rail, and that is what I do.

Would be good to know if you are using two separate transformers or one with two or more handles. I will describe the way its normally done.

So normally, we would put a plastic pin in between the switches on the center rail. Then we need to connect the outer rails of the two loops together. If you are using something like a KW, ZW, or an MTH Z4000, I believe the common is connected at the transformer. In that case you run the common, black, or U to a lock on to each loop. Then you run a second wire from the hot, red, maybe A or B of the transformer to the center rail of each loop. This stuff isn't like two rail track, you can run it anywhere to the loop. This setup solves the problem of 'phasing' the signals, so that you don't get a double voltage when the engine or lighted car goes over the junction.

When you have two separate transformers with two plugs, it gets a bit trickier, you need to phase them. New transformers have a polarized plug, and if manufactured correctly, the two transformers will be in phase if you connect the U or common to the outer rails. And ... some were not made right. And old transformers do not have a polarized plug, one blade thicker than the other. At this point you need something to measure. A voltmeter is one way, another way is to set both transformers to about the same setting and take a wire and see how big a spark you get.

Family beckons, maybe someone else can finish the description.

.......HOW BIG A SPARK YOU GET !!!!!!?????    Really?  No follow up as to just how big and what the size differential means.  Although functional I would be hesitant putting that level if instruction out on a public forum.  Kids that run trains on carpeting are known to be here.

Realtrax will work just fine for what you are trying to accomplish. There are a couple of thing you'll need to do:

1) Assuming you are using two conventional transformers, they will need to be phased. You can get more (PROPER) information about that here: https://ogrforum.com/...asing-transformers-2 This thread may not be using the same models as you but the procedures and concepts for phasing remain the same. Using a single transformer with multiple track controls (ZW, KW or Z4000) will pretty much eliminate this step.

2) You'll want to disconnect the center rail between the switches of the outer and inner loop. I have seen this done by bending or breaking the center rail connector on the bottom of the realtrax so that it won't connect to the next piece (only between one connection that connects the two loops together).  I would recommend connecting a short straight piece of realtrax between the switches and bending the copper tab on that instead of a switch. The switches are expensive whereas the standard pieces are much cheaper. MTH also makes and insulated track piece that will eliminate the bending or breaking of the center rail connector.

3) I would use multiple lock-ons on both loops. I usually space them about 8 to 10 track joints apart which (when using 10" track pieces) comes out to 7 to 8 feet apart.

One more recommendation, run your switches independently of track power. If the voltage on your track is low with the switch using track power, it may not throw properly.