I have a DCC layout and recently purchased a Walthers Shinohara double crossover. It is the newer DCC Friendly type with the yellowish-green sticker on the box. I need to wire the crossover to a DPDT switch to reverse polarity when an engine crosses over from the northbound track to the southbound track since the double crossover leads to, and provides the return from, a loop.

I have wired the crossover incorrectly because the layout shorts out when an engine tries to crossover from the northbound track to the southbound track with the polarity reversed by the DPDT switch. However, with the DPDT switch thrown in the other direction for normal polarity, the engine passes through the crossover (remaining on the same track) without creating a short.

When I wired the double crossover, I wired the four rails on the loop end of the crossover to the DPDT switch and wired the DPDT switch to the bus wire that supplies power from the DCC controller. I used insulated rail joiners on the four rails on the other side of the double crossover.

Any advice that you could give me would be most appreciated.

-- Rich Jurgovan (redking56@aol.com), January 22, 2005

Answers

Rich,

This is a difficult problem to troubleshoot over the Internet. I'm not sure I have a good mental picture of how you wired it. There are possibly several places you could have gone wrong. While it may be possible to get what you have working, it is just difficult to do over the Internt. Let me suggest a simple arrangement that has a limited opportunity for trouble.

1. Put four insulated joiners on the ends of your double crossover that is going to the loop.

2. Wire your double crossover up normally. Don't worry about reversing any polarity on the crossover.

3. Wire your DPDT up so that the only thing that reverses is the loop itself.

That should do it!

-- Allan Gartner (wire4dcc_admin@comcast.net), January 22, 2005.

Rich,

Thanks for making the drawing. The drawing indicates that you have several things wrong. Also, it tells me that you may be trying to do something different than your original question posed.

If you want to reverse the loop:

1. The insulated joiners should be on the left side, not the right side. They should be insulating ONLY the loop on the left.

2. Your DPDT switch should ONLY be going to the loop, not your double cross.

Now regarding whether you are trying to do something different than you originally posed:

You show the polarity of the two sides of your double cross over reversed. You also show the tracks arriving at the double crossover from the right reversed. Is your layout one big oval? If so, then it isn't the loop you want to reverse - though we may have to reverse part of it to make things work.

-- Allan Gartner (wire4dcc_admin@comcast.net), January 23, 2005.

Rich,

Looking at your drawing, your layout is a big oval. By putting in the double crossover, you will need a reversing section. While the only part of the layout that is at issue is the double crossover, a rule of reversing sections is that it must be at least as long as your longest train - or at least longer than your longest locomotive if you are not using any lighted cars or cars with sound in them.

Looking at your drawing of your double cross over, you will need to reverse the bottom half (looking at the drawing), part of the loop (or all of it if you want to AND the track leaving the lower right of your double cross over. Remove the joiners that you show connected to the lower right turnout on the double cross over and connect that track to your double cross over. Now you will need to put insulated joiners at the end of the track segment that connects to the lower right cross over turnout.

YOu will need to have your DPDT thrown one way when you cross over onto the double crossover. After your entire train (or locomotive if it is the only thing drawing power) is on the reversing zone, flip your DPDT. Things should work now.

-- Allan Gartner (wire4dcc_admin@comcast.net), January 23, 2005.

Rich,

To test polarity, the easiest thing to do is disconnect your booster and hook up a 9V battery in its place. Then just a DC meter to check polarity.

You don't need insulated joiners on the upper right of your crossover. ONLY connect the DPDT switch to the bottom half of the crossover. The top half of the crossover should be powered from the same bus that is powering the rest of your layout.

Look at the color drawing you sent me. If you follow the colors through the crossover, you will see the short. You need to reverse the polarity of only 1/2 of the crossover. Look at my drawing of my crossover on my website. http://www.wiringfordcc.com/switches_walthers_old.htm#a2 Notice that on my website, the colors cross through the crossover without red meeting blue or blue meeting red. That is what you need to have happen.

Don't worry about cutting your outside rails. That has nothing to do with your problem.

-- Allan Gartner (wire4dcc_admin@comcast.net), January 23, 2005.

The double crossover is constructed such that both main tracks should be of the same polarity. If you are using it to turn a simple oval track configuration into something resembling a figure 8, you are creating a polarity reversing section right at the crossover. It is not made to do this. Instead of trashing the crossover I suggest looking at the track loop. Wire up your mains to be of the same polarity. Put insulated joiners only at the 4 rail ends leading into the track loop. Wire up that track loop through an auto-reverser. If the track does loop around in both directions [simple loop --> figure 8] wire up the crossover section with fixed polarity and wire up the track loops at both ends as separate reversing sections, each with their own auto-reverser.

There are tight clearances at internal frogs on the crossover where some wheel treads may touch rails of opposite polarity. My solution was to flip all 4 turnouts to the same position, either straight through or X, using 4 Tortoise motors wired together.

DonV

-- Don Vollrath (dvollrath@magnetek.com), January 24, 2005.