Crossovers

What brand of track are you using?

The two paths will have to have their center rails electrically isolated from each other.

That may not help. I have had TMCC on the layout affect a test track that is on a different transformer across the room with no connection to the layout.

Huh?  If your concerned about the conventional loop you need isolation as mentioned otherwise your at full track voltage.

Let's clarify, we need input from the OP. If the trains being run on the conventional loop are TMCC / Legacy equipped then Chuck's concern comes into play. If not then it's safe.

The reason I asked about the brand of track was, most brands will need to have cuts made and a jumper soldered to separate the routes.

Big_Boy_4005 posted:

What brand of track are you using?

The two paths will have to have their center rails electrically isolated from each other.

both are using fastrak

I'm picturing your question as having the inner loop trains cross over the independent center loop track on to a third outer loop. Don't have a Fastrak crossing in front of me to verify, just make sure the center of the diamond is not connected to both center rails. If your engines can jump it, having neither connected is best as the two loops will most likely be at different voltages and the engine (or caboose, etc.) wiring becomes the jumper wire. An image of it maybe? 

I can not speak to Fastrack, but on a 90 degree tubular crossing there are tin plate steel strap that connects the center rails on opposite sides of the crossing.  These straps are connected in the center of the crossing.  If the two tracks are to be isolated, the straps have to be disconnected and a fiber shim inserted between them to insulate the two different routes.  On these crossings the rollers are carried through the center of the crossing on a piece of plastic, so there is no problem there. 

dawkil posted:

Big_Boy_4005 posted:

What brand of track are you using?

The two paths will have to have their center rails electrically isolated from each other.

both are using fastrak

FasTrack has a tab secured sheet stamping that connects the four center rails. You remove the base, remove that and solder jumpers N-S and E-W to isolate the two lines.

Moonman posted:

FasTrack has a tab secured sheet stamping that connects the four center rails. You remove the base, remove that and solder jumpers N-S and E-W to isolate the two lines.

Or you just wait for the crimps to corrode and you'll have your isolation!

thanks to all. i think i will just expand the two loops and not have them crossover. the KISS method (keept it simple stupid)

Larry, there is still the potential issue of TMCC/Legacy engines running conventional in close proximity to the command loop. As Chuck noted above, the signal radiates out well beyond the track to which it is applied, even without a physical connection.

To that end, when I want to clean locomotive wheels at my workbench, I need to turn the layout power off to get TMCC engines to work in conventional. If you are using conventional only engines, then you have no problem.

Elliot, you can connect the outside track of your test bench to earth ground, that will "nuke" any TMCC signal that is radiated.