Originally Posted by DonR
Sometimes metal wheels will short at
a narrow turnout frog if their tread is too wide.
You can often remedy this by using a tiny
dab of clear fingernail polish on ONE rail
of the frog where the are near each other.
Others have filed down one frog rail.
To check what is actually shorting, get down
very close to a turnout that has shorted,
have DIM lights...run your cars as slow as they
will go over the turnout. When you see a tiny
spark, STOP. That is where it is happening.
The advice Don gave you about using nail polish to insulate one of the frog rails is good. Filing down any part of the frog, as Don says "others have done", is, in my opinion, not good at all. In fact it may make the problem worse instead of better. You said this is happening on Atlas turnouts. Atlas actually makes two different lines of turnouts, "Custom Line" and "Snap Switch."
The Atlas "Snap Switch" type has two metal rails, of opposite electrical polarity, directly under a thin layer of plastic in the frog. (I don't know if the "Custom Line" turnouts have this same setup or not.) Filing will only remove more of the plastic, expose the metal rails, and increase the likelihood of a short circuit.
By all means, do the test Don suggested to find out where the short is happening. Like Don, I also suspect you will find that the problem happens when a wheel is on the frog. The nail polish fix will help temporarily, but eventually the polish will wear off. Of course you can always apply polish again, but there is a more permanent solution.
The area between the metal running rails (that the wheels ride on) and the plastic guard rails, just inside the running rails, is called a flangeway. There are also flangeways in the frog. Commercial turnouts usually have flangeways that are too wide to meet NMRA specs. You can use an NMRA gage tool to check this, and many other important things on your railroad. If you don't already have a gage, you can order one from www.modeltrainstuff.com
So why care if those flangeways are too wide? Because having the flangeways, and the wheels of your cars & locos set at the standards built into the NMRA gage will cause the wheels to move over away from the area where the short is happening. This will also decrease the chance of derailments on the turnout. Building up the frog, with a thin piece of styrene, will be a long lasting version of the nail polish fix.
The frog flangeways of commercial turnouts are also too deep. Gluing a strip of styrene into the bottom of the flangeway will eliminate bouncing of cars as they pass through the turnout. Some folks have tried filing down the tip of the frog point in an attempt to cure this "wheels drop down into the frog and then bounce back up" thing that makes the cars run roughly through the turnout. Again, a bad idea. Don't file down a frog. It does no good, and can do plenty of harm.
The attached file "Improving Atlas turnouts" explains these fixes, and more. The other file "All about turnouts" has lots of additional information on turnouts.
Let's take things one step at a time.
1) Do Don's test.
2) If it shows a short at the frog, try the nail polish fix.
3) If the nail polish works then, at your convenience, read the "Improving Atlas turnouts" file and decide if you are having additional problems with your turnouts, besides the frog short.
4) If you are having other problems, like derailments, on your turnouts, use the information in the files to either improve the Atlas turnouts you now have, or replace them with the better turnouts recommended in the "All about turnouts" file.
Improving Atlas turnouts pdf version.pdf
All AboutTurnouts rev 4.pdf