# Wiring a double cross-over for DCC



## TimW (Oct 20, 2018)

Is there anything special about wiring a double crossover (i.e., "X") for DCC? I am building a modified version of the Salt Lake Route layout that was in MRR back in 2010 except using primarily Code 55 flex track instead of Kato. I built the crossover using the parts list and information from a link I found on this site (since Atlas does not offer a double crossover), but it did not mention any special wiring to prevent short circuits. I am not doing any loop backs on my layout and my main lines are to be in parallel. Thanks!


----------



## MichaelE (Mar 7, 2018)

I don't believe there are any special wiring considerations for a double crossover. If I were to build one myself though, I would use turnouts with insulated frogs to cut down on possible problems.


----------



## timlange3 (Jan 16, 2013)

Never need special wiring for DCC, just wire as normal. As with DC, AC, or DCC, if you have live frogs you will need to insulate the frog rails.


----------



## DonR (Oct 18, 2012)

Tim 

Agree with the previous guys...there is no
difference in wiring a turnout for DCC or DC.

However, The placement of the double crossover
must be between two parallel tracks. Some twist
their oval in such a way that the Left side of the
oval is near the Right side and then place a crossover
to connect them. THAT does create a reverse loop
short circuit situation. Let us know if that is
your situation. 

Don


----------



## TimW (Oct 20, 2018)

DonR said:


> However, The placement of the double crossover must be between two parallel tracks. Some twist their oval in such a way that the Left side of the oval is near the Right side and then place a crossover to connect them. THAT does create a reverse loop short circuit situation. Let us know if that is your situation.
> 
> Don


No reverse loop in this layout. Everything is clearly designed in two parallel and independent loops. Thanks for the tip, though.


----------



## traction fan (Oct 5, 2014)

*Double crossover options*



TimW said:


> Is there anything special about wiring a double crossover (i.e., "X") for DCC? I am building a modified version of the Salt Lake Route layout that was in MRR back in 2010 except using primarily Code 55 flex track instead of Kato. I built the crossover using the parts list and information from a link I found on this site (since Atlas does not offer a double crossover), but it did not mention any special wiring to prevent short circuits. I am not doing any loop backs on my layout and my main lines are to be in parallel. Thanks!


TimW;

Peco does offer a commercial double crossover if you would rather not build one.
If, on the other hand, you prefer to build your own, then, considering the amount of work involved, I'd use metal, isolated, powered, frogs and wire the turnouts with the point rails insulated from each other, but with each point rail electrically connected to it's nearest stock rail. This is the turnout wiring option sometimes marketed as "DCC compatible", or "DCC friendly." These advertising terms are mostly bull, and it's quite true that ANY turnout will work with DCC. (or DC)

However, this wiring option prevents a possible, though rare, short circuit caused if a metal wheel happens to short the point, and stock, rails. If you are using Atlas code 55 N-scale turnouts they come already wired this way from the factory.

Remember that no matter what type of turnouts you build for your double crossover, both rails, of all four turnouts, need insulated rail joiners, or gaps, wherever the rails of one turnout butt up to the rails of any other turnout. Also the crossing, at the center of your double crossover, needs a good deal of insulating. Electrically, it needs to be identical to two pieces of straight track that physically intersect, but are electrically isolated from each other. Using a cut-down commercial crossing here could save a lot of work and possible frustration. I've built all-metal-rail crossings, but they need lots of gaps, and some sort of electrical polarity switching device. (I used switch machine contacts.)

I make my own turnouts, crossings, compressed yard throats, etc. My layout has several crossovers, but no double crossovers. I build my turnouts in the "DCC friendly" pattern just described . I figure that since I'm going to put in the same amount of effort, no matter what type of turnout I make, I might as well build all the mechanical and electrical reliability into it that I possibly can.

The attached file describes how I make my turnouts. The photo shows a crossover, and turnout, that I built using the method described in the file.

good luck & have fun;

Traction Fan:smilie_daumenpos:

View attachment How I scratch build turnouts new(8).pdf


----------



## CV-62 (Dec 9, 2018)

Isn't it true that the term "DCC Friendly" more or less evolved from the fact that on DC, most likely a momentary short between the stock rail and the point rail would not be a big deal, but in DCC the quicker acting circuit breaker would trip?

So, in a sense, something someone found that worked just fine in DC is not so "friendly" in DCC?

Still learning.


----------



## timlange3 (Jan 16, 2013)

CV-62, you are correct! But I would never consider a momentary short to be working fine. Long term it would hurt the equipment too.


----------



## traction fan (Oct 5, 2014)

*You're correct*



CV-62 said:


> Isn't it true that the term "DCC Friendly" more or less evolved from the fact that on DC, most likely a momentary short between the stock rail and the point rail would not be a big deal, but in DCC the quicker acting circuit breaker would trip?
> 
> So, in a sense, something someone found that worked just fine in DC is not so "friendly" in DCC?
> 
> Still learning.


 CV-62;

The terms "DCC friendly", and "DCC compatible", have been widely used, and misused, in advertising for a long while.
Over time, they seem to be more commonly directed toward the "isolated frog/point & stock rail jumpered" configuration I described both in this post, and in my "All about turnouts" pdf file. That doesn't mean that every commercial turnout advertised as "DCC friendly" is actually wired that particular way, even today. 

The point-to-stock-rail short circuit is extremely rare, provided all the wheels, and all the track (especially turnouts) are properly gauged. They should be anyway, of course, just to allow smooth operation of the railroad.

The tripping of a DCC system's breaker by such a short, would be annoying at least, and perhaps, with enough repetition, possibly even damaging, as timlange3 suggests; I don't know. But bear in mind that on a railroad with properly gauged wheels, and track, and particularly with the turnouts adjusted to all the applicable NMRA specs*, the short might never even happen in the first place.

Certainly it can't hurt to have your turnouts wired this way, (That's why I build my own wired that way) but I don't want to spread, "questionably-based alarm and despondency" (aka panic) among the proud owner/operators of commercial turnouts, over something that may not matter, or even occur. The advertisers of commercial turnouts may not be, shall we say, "quite as circumspect", since their function is to sell more turnouts.  Including selling " "DCC friendly" turnouts to get modelers to replace the good turnouts they already have. Nearly any commercial turnout can be easily brought up to NMRA specs. with simple plastic shims, but that ain't going to sell more turnouts.  

regards;

Traction Fan:smilie_daumenpos:

*As far as I know, no commercial turnout, including the otherwise excellent Peco, actually does meet all the NMRA's specs for turnouts. They all have their guard rail (and frog) flangeways too wide, for example. This can make it easier to let a wheel get into a position to cause the point-to-stock-rail short.


----------

