Enough has been written over the years about Lionel wiring to fill volumes. Not so much for American Flyer, though. Fortunately, when it comes to Lionel vs American Flyer wiring, there’s a lot of similarity. Most of the advice you find about Lionel wiring applies.
Prewar vs Postwar American Flyer
It’s important to remember that prior to World War II, American Flyer used 3-rail track just like Lionel. From a wiring standpoint, all advice regarding Lionel wiring will apply to 3-rail American Flyer.
Differences in terminology
The major difference between the two is terminology. What Lionel calls “common,” American Flyer calls the “base post.” These are both synonyms for the white wire in household AC wiring, what electricians frequently call “neutral.” People frequently also call it ground. If you confuse the base post with ground on a train forum, someone will correct you. You can count on that. It’s also likely someone else will come along and tell that person making a big deal of things like that is why he’s not much fun at parties. Or something to that effect.
The important thing to remember is “common” and “base post” isn’t the hot, live wire. The wire coming from the other post is the live wire. And if you bridge the two with anything but a train or accessory, you create a short circuit.
Similarities in Lionel vs American Flyer wiring
Electrically speaking, Lionel and American Flyer used similar voltages and amperages in their transformers. The math regarding voltage drop is the same for both. That means 18 gauge wire is about the minimum useful wire size for running power to the track, with both systems.
The favorite trick of running loops of wires under the layout and running feeder wires up to the track works with 2-rail American Flyer too. You can share the loop connecting to the base post with every loop of track on your layout. Accessories can all cheat and connect to the base post loop too.
Peter Riddle’s book Wiring Your Toy Train Layout explains these tricks. It also takes command control into account, if you use modern trains with one of the many command control systems on the market, such as TMCC or Legacy.
Most importantly, any advice you find regarding electrical connectors, organizing your wiring, or making it look nice applies to both systems.
Differences from Lionel wiring
The major difference in wiring comes from the lack of that third rail. With Lionel you can cheat and insulate one of the outer rails much of the time, then use a passing train to electrify the insulated rail to activate a nearby accessory. One common use of this is to activate crossing gates. You can’t do that with two rails. You can insulate a small section of the rail connected to the base post to achieve the same thing, or use other tricks like reed switches to detect the presence of a train. It’s doable, it’s just not quite as easy.
Reverse loops are the other major difference. With a 3-rail system, you can loop back on a switch to make the train turn around. With a 2-rail system, you’ll create a dead short if you do that. If you want a 2-rail reverse loop, you have to add circuitry to reverse the polarity. Gilbert provided the AF 695 reverse loop relay for this purpose. To have a reverse loop in 2-rail, you need either an AF 695 or a modern equivalent circuit. Lionel books won’t talk about that.