Live Frog Switching with N-scale Peco Turnouts
The ins and outs of "wiring around" the points on electrofrog turnouts
When I first encountered "live frog" terminology in model railroad magazines, I must admit that it merely brought back bad memories of high school biology class. The model train hobbyist's literature was either slow to point out the need for amphibious cogitation or I was slow to pick up on it—I suspect the truth lies somewhere in between. Anyway, since my first encounter with the "frog" term, I've had ample model railroading experience to make me realize the need to not only understand what all this frogspeak is about but to act on this understanding as well. In simple English, appropriately dealing with frogs can have a lot to do with how well a model railroad operates and how much frustration is involved in the hobby. Especially, it has to do with avoidance of that activity hobbyists dislike most of all: points and track cleaning.
Before I go on I should say that the only kind of turnout I use is Peco N-scale electrofrog turnouts because I don't like the way slow-moving trains run on Peco insulfrog turnouts or the way you do wiring when you use them, but I do like the way trains run on electrofrogs and the way they route track power as well as trains. (See wiring books for details.) So everything that follows is exclusively about this type.
Frogs are the frog-legs-shaped rails towards the wide end of a turnout and they get power from the points (the moveable rails that you switch with switch motors—see either P in fig. 1). Look at the two outside rails on a turnout (I and J in fig. 1). Nothing about throwing a turnout's throwbar (T) to switch the points affects these rails. But ALL OTHER rails (that aren't outside rails) on Peco turnouts are affected by throwing the switch. When the throwbar is halfway between the two points, XYABCDEFKLPP in fig. 1 is all dead track; when it's thrown to the left against the GIW rail, GIW and XYABCDEFKLPP are all one conductor, or all "south" or all "plus" or however you want to describe it; when it's thrown to the right against the HJZ rail, HJZ and XYABCDEFKLPP are all one conductor. Check it yourself with a continuity tester.
Note that it is only the fact that the points touch the outer rails that gives any power to the inner rails at all. So that means the points/throwbar assembly is in reality an electrical switch. And that's the problem. Any dirt at the contact points means all inner track is dead. And we all hate train stalls—especially because it suggests we're about to have to clean track (ugh!). Cleaning the dirt out of points will usually solve the stall problem, with three main exceptions: (1) Even though oxidized nickel-silver still conducts electricity—which brass track users cannot say—dirty track in general rather than dirty points specifically can still be the cause of the stall; (2) the loco can have dirty wheels or brushes or a loose wire; and (3) cleaning points can sometimes slightly bend them so that they make poor contact, so don't rule out bent points as the culprit.
Kiss Points-Cleaning Goodbye
The solution to the stall problem is to cease using points/throwbar assemblies as electrical switches. Use Tortoise switch motors and use the built-in accessory switches they supply to switch the current going to the frog. Then having dirty points won't lead to stalls, and you won't accidentally bend points during cleaning, and you'll have less problems and more fun in your future.
You'll have to solder a wire to E (fig. 1), making sure you solder to the outside of the rail and not the inside where the wheel flanges go. And you'll have to remove the Peco's spring (Circuitron doesn't recommend that you use their Tortoises for switching frog power if you leave the spring in; it's because of short circuit problems). And you'll have to make sure that you follow all the recommendations in the wiring books about how to wire layouts using power-routing turnouts. Vital areas to understand are where to put insulated joiners and where to put feeders. I'll assume that you know how to do this right from here on. If needed, consult Kalmbach's Easy Model Railroad Wiring, by Andy Sperandeo.
One Solder Per Turnout—Or Three?
All the diagrams in the books seem to indicate that for frog powering you need to solder in overly-delicate areas on turnouts and that you have to solder three wires per turnout. Luckily, neither of these is quite true. If you're like me and desire to minimize your intake of soldering fumes, you'll be happy to hear this. Maybe the books have said it somewhere and I missed it, but I can't remember seeing anywhere that the best way to get connections (for frog power switching, using accessory switches) to outer rails is (in many cases) when you install feeder wires. I also never saw it mentioned that you can avoid delicate places on turnouts when you solder.
Here's what most books say to do: solder wires near G, H and B and let the accessory switches on your switch machines do the frog power switching instead of your points. Perhaps some books assume you'll mess up if you try to combine feeder soldering operations with live frog switching operations.
Anyway, it's time to clarify the point: if done right, feeders are a good way to get two of the three needed frog-switching connections made, as long as you only use this method for the first turnout after the feeder and do NOT use the feeder wires on any consecutive turnouts following the first turnout after the feeder. This means that, for the first turnout after a feeder, you can tap into your track power feeder wires and use those to connect to two of three connections to your Tortoise's accessory switch for the live frog switching. The third connection will always be soldered to E regardless of circumstances.
The reason you can't use the feeder wires for accessory switch connections beyond the first turnout after the feeder is that you'll short-circuit your track, and it won't work. When an electrofrog Peco operates, it transmits North and South power (North to one rail and South to the other) to all track beyond it (on the frog end of the turnout) on one side of its trackage and either all North or all South to all rails of all track beyond it on the other side of its trackage. The former is good loco running power; the latter is no power at all—things can't run without North on one rail and South on the other. In fig. 1, if North goes into G and South goes into H, because the point (L) is touching the H rail you'll get all of (the inner rails) XYABCDEFKL as South power, and that means that Y and Z will both be South because HJZ is one continuous rail and I've already said that H is getting South power. But GIW is still getting North power, so the fact that X—as part of the inner tracks—is getting South power means that the WX side of the turnout's trackage is good loco power: North and South. Additionally, all trackage and turnouts that come after YZ will be similarly cursed with nothing but useless all-South power (as long as the trackage is in the same block). So if you were to try to use accessory switches on turnouts (after the first one after the feeder) to power live frogs with feeder wires, you'd be sending North to South or South to North half the time—a short circuit. But if you power the frog from the rails of the turnout itself, you'll merely be harmlessly sending South to South.
Since it's likely that over half of the turnouts on an average layout are the first one after the feeder, the ramifications of all the above are that you'll be able to avoid 2/3 of the soldering on over half of your layout's turnouts by tapping off the feeder wires.