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DCC wiring and gaping the rails

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  • Member since
    November 2009
  • 6 posts
DCC wiring and gaping the rails
Posted by mailman51 on Wednesday, November 14, 2012 6:57 PM

New guy question. I understand the process of having gaps in the rails,and feeding power to switches from the point end of the switch. With DCC do I need to gap both of the rails on the frog end of the switch or just one rail and why?

  • Member since
    February 2002
  • From: Reading, PA
  • 30,002 posts
Posted by rrinker on Wednesday, November 14, 2012 7:25 PM

 Depends on which ones you are using. With Atlas - no gaps. Gaps at the frog end and no feeders there is for power routing and live frog turnouts. In fact, with my Atlas turnouts, I have feeders on all 3 legs. On a power routing turnout, the frog will change polarity depening ont he position of the points. You need to gap both rails coming from the frog for this type of turnout so that you don;t get a hort.  Bottom line - exactly the same as DC. If the turnout needed gaps in DC, it needs them in DCC. If it didn;t need gaps in DC, it doesn't need them in DCC.

           --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
    October 2005
  • 1,047 posts
Posted by betamax on Wednesday, November 14, 2012 7:25 PM

Yes, both rails.

Are you handlaying the switches or are these commercial units?

If handlaid, check out the Fast Tracks template library, they show the gaps cut at the frog. If the frog isn't gapped on both rails, a short may occur when a metal wheel bridges the gap. 

DCC "Friendly" switches usually have the point rails connected electrically to the adjacent stock rail, so gaps are needed to prevent a direct short, and both must be gapped to prevent a short when a metal wheel bridges the gap between the frog and the point rail. If the frog is "live", the position of the points controls the flow of power to the frog.

  • Member since
    July 2008
  • 1,206 posts
Posted by mfm37 on Wednesday, November 14, 2012 9:38 PM

Elevtrically, DCC works the same as DC. So if they need gaps for DC they need gaps for DCC. A short circuit is a short circuit.

Whether a gap is needed depends on the switch. Personally, I gap both rails on every switch and then feed power with feeders as needed. Avoids problems later and if the feeders happen to be hooked up wrong, they can be corrected under the layout.

  • Member since
    December 2004
  • From: Pa.
  • 3,361 posts
Posted by DigitalGriffin on Friday, November 16, 2012 4:12 PM

This question is quite complex

With older DC, typically you would only power the route your train was traveling on, so you used power routing turnouts.  You didn't need to worry about the gap so much with these turnouts.

However with DCC, all tracks are powered all the time so you can run more then one train at once.  So you drop feeders to every track section.  And you use DCC friendly turnouts in which the inner rails are isolated already, so there is no need to gap them.

You can tell them apart because the frog is usually isolated at each inner rail end.

 

Don - Specializing in layout DC->DCC conversions

Modeling C&O transition era and steel industries There's Nothing Like Big Steam!

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