Real Trax 3 rail

Two rail track, many possibilities. If you have been in DCC for some time you should be aware of most of them.

Three rail track. Should be no problem. Need more information. Just 2 rail, 3 rail, or both? Any reverse loops on the 2 rail or solid frogs or uninsulated frogs on the 2 rail? On the 3 rail, what kind of switches are you using, what kind of switch machines?

Al

just mentioned 2 rail ho as a comparison no issues with it sorry for the confusion

no reverse loops  3 rail

the issue is on the turn outs shorting when rolling stock crosses the frog

what ever frogs MTH uses on real trax...

but not on all of them

MTH real trax switches

Reading your first post you have written (-) in the middle (+) on either outside rail. I'm thinkin' that may be the problem.  The center rail is "hot"; the outside rails are common. This is all important to the switch.  You do not mention your transformer.

Please don't mention 2 rail if not necessary, some of these nice people get confused.

As far as I know the fact that you are using DC should not make any difference. Both outside rails are connect together unless there is some special circuitry in the turnout that I do not know about. The system is designed to run off AC but running it off DC shouldn't make a difference that big. Are you powering the turnout off track power or from a seperate power supply. On these switches there is some interconnection between the turnout power and the track power. If you are powering the turnout from an AC supply and running the track with DC then half the time the polarity of the turnout power will be wrong. This may or may not be part of the problem. HO turnouts do not have the auto align feature so it makes no difference what you power the turnout with. In order to work the auto align circuit requires a connection between the turnout control mechanism and the track. This could be a source of the trouble. Are you powering the turnouts from the same power supply you use for the track, if so try using a totally different transformer for the turnouts.

Al

Yes, what Al said (Thank-you Al). I beleive the non-derail feature of the switch may be giving you the problem.

I am not running MTH on dc...not sure how you got that..and I did make an error marking the center rail as (-)  it is (+) and the outer rails are (-)

turnouts powered off of track power and are manual switched 

Transformer is the Z750 also have a Z100 on standby

Does a certain loco or piece of rolling cause the problem?

Three rail wheel sets are not insulated, so no part of a wheel can touch the center rail.  On a  wheel set that is out of gauge(too narrow) the backside of the wheel can touch the center rail, especially going through the curved portion of a switch, causing a short.

That might be your problem. 

The turnout leads to a dead track used as a "spot" for parking cars..

shorts when every car travels across the frog...do not send locos since it is a dead end...they do not short on any other turnout

I am not running MTH on dc...not sure how you got that..and I did make an error marking the center rail as (-)  it is (+) and the outer rails are (-)

You say that you are not using DC, but you also say that you are supplying + and - to the track. This is a contradiction which is confusing some of the folks trying to understand your problem.  HO uses DC, our stuff uses AC.

If you are using AC, there is no positive or negative.   There is hot and there is common / return.

It sounds like a roller is touching an outside rail, or a wheel is touching a center rail, or a coupler "thumbtack" is touching the center rail. Those are the most likely ways that you'll get sparks while running over a switch.

Try disconnecting all power to the track, and isolating the section that's giving you problems. Then take an analog ohmmeter and attach it to the center rail and one outside rail. Watch the meter for a deflection as you manually roll your cars over the switch. Do it slowly enough so that you can correlate the wheel and roller positions to the deflections on the meter.