Insulated switches shorting on DCC

[tuba1st]

I have come across a problem that is difficult to figure.  I have three switches in line on the main line.  These switches are older Atlas and they are all insulated.  With DC power and DC engines they are fine.  With DCC and DCC steam they short out as soon as the front truck comes into contact with the main line portion even before it reaches the frog.  The front truck does not short the track out in normal movement anywhere but at the switch it creates a short.  I was told to place a plastic rail joiner on one side of the main and on the curved portion of the switch to avoid this problem.  It didn't work as the engine does not even make it to the frog before it shorts.  Any suggestions or should I just replace these switches which will be expensive since there are ten switches off the main line.  I should note that I removed the electrical control from the switches as they were catching the 4-8-4 Daylight and my 2-10-2 by being raised too high.

[Joe Satnik]

Check the dimensions of both your engines and your turnouts. 

http://www.trainbuddy.com/Reference/nmra_gage.htm

Joe

[Chris350]

Check the dimensions of both your engines and your turnouts. 

http://www.trainbuddy.com/Reference/nmra_gage.htm

Joe

To expand on this, it's possible that the wheels are shorting either the back of the points or the guard rails.  You didn't mention in which direction the shorts occur.  So by checking that your wheels are in gauge and that the track clearances are correct and in gauge you can eliminate one possible source of the problem.

[jward]

how old are these atlas switches?

all of the custom line switches going back to the 1960s had insulated frogs. the switch point is the same as the adjacent stock rail so your wheel backs touching the points shouldn't cause the short.

on the oldest custom line switches, the frog consists of railswith just enough plastic on the frog to keep them from shorting on dc. on dc you don't notice a momentary shortof a wide wheel tread contacting both rails at the frog, on dcc it shuts the system down. these early custom lines are what i suspect you have.

later, starting in the early 1980s, the frog became a metal casting insulated from all rails with provisions for wiring the frog to a relay to switch its polarity. these are easy to identify as the frogs have little eyelets on eash side where a wire can be screwed to the frog.

if, as i suspect, you have the oldest version, you can paint the tops of the rails at the frog with clear nail polish. do this for no more than about 1/2" back from the frog, and it should take care of the problem. eventually the polish will wear away so you'll have to reapply it every so often.

[tuba1st]

The switches are quite old as they were given to me by a fellow musician who installed new switches on his layout.  I would guess they are at least 30-40 years old.  There is a plastic portion at the frog.  I do have to work on controlling the switches as the orginal housing for the switches interferes with the cow catcher on three big steam engines causing them to either stop or de-rail.  I'll try the polish.

[jward]

if the switch motor housing is interfering with your locomotives you have a couple of options. first is to use a lower profile switch motor such as the current atlas motor. atlas was wise enough to make the mounts the same for all of the code 100 custom lines, so the motors are backwards compatable. new motors come with a short plastic adaptor which you can use to move the motor further away from the track. i don't think they sell these seperately, but you'd have to checque atlas' web site.

http://www.atlasrr.com

they also sell an under the table switch motorbut installing those would mean drilling a hole through the subroadbed to accomodate the throw rod. the under the table motors are best planned from the start, rather than installed later.

[tuba1st]

I really appreciate the information given so far.  I spent more time on the layout last night and discovered my longer steam engines, 4-8-4, 2-10-2 coming out of a 22" curve before the switch causes the engine to be off center as it is entering the switch.  Its a little tough to fit myself down to the level to watch as the engines enter the switch but looking from above the engines are not centered.  I am going to try changing a 9" straight before one switch and see if that cures the problem. 
Any thoughts?

[tuba1st]

After a good skull session with my local hobby guy we decided to cut a small space in the track leading to the frog with a dremel tool.  It worked, all steam engines are making the trip without shorts.