Wiring standards part 3: feeder wires and track

In the last wiring post I covered the power bus terminals and feeders leading from the terminals. Now I'll cover the standards for connecting feeders to the track.

The first question is: how many feeder wires do you need per length of track? When you buy a starter train set with an oval of track you get one pair of feeders for the whole oval. But if you try to do that with a larger layout you'll probably run into trouble for two reasons:

1. Voltage drop, as mentioned before. The resistance of nickle silver rail is much greater than that of copper wire, so over a short distance of rail the voltage will drop enough to slow your trains.
2. Rail joiner problems. Rail joiners are designed to hold two rails in place and to pass electricity between the rails. However, over time some joiners will loosen or get dirty and eventually provide an imperfect connection. This will lead to even greater resistance (see point 1) or loss of connectivity altogether.

Now, this doesn't mean that every layout without power buses experiences rail joiner problems or large voltage drops. There are real life examples of layouts with long stretches of track where power is passed only by rail joiner and things seem to work well. However, in my experience every layout that relies on rail joiners for electrical connections has evenually experienced power drops. And this is why the power bus method is so widely recommended.

So, you may ask, we need to add feeders to the rails every few feet, but exactly how many feet apart? This is a matter of frequent debate on the model railroading internet forums. At one extreme are those who argue that rail joiners can never be trusted and thus each rail must get its own feeder. Not quite as extreme are those who argue feeders should be 3' apart, but don't require a feeder per rail in instances (like switch ladders) where many separate rails are used in a 3' span. At the other extreme are those who argue that spans of 10' or more are okay between feeders.

After reading what everyone said and thinking about my own experiences I tend to agree with those who don't see rail joiners as a long-term solution to connectivity, but I also don't see it necessary to space feeders every 3'. So, I decided to connect the feeders at every other rail joint. That is, feeders are attached at the rail joint, so every rail has a feeder, but there is only one feeder per two rails. This saves time and resources.

Alas, no solution is without controversy. By soldering the wire to the rail joint I am also soldering the rail joints, which is another big debate topic on the forums. Some argue that joint soldering causes problems because the metal rails will expand and contract with temperature changes. Soldering inhibits expansion, thus on hot days the rails will eventually bend out of gauge somewhere as a result. Others respond that they've never had this problem despite soldering their rail joints, and I'm in that camp. I solder all curved flex track joints and half of the straight ones, and in 2.5 years I've had no problems. I suspect there are as many as three reasons I've been so lucky:

1. The temperature variation in my room is not extreme -- from 60F to 85F at the limits. Even on our hottest days the room doesn't exceed 85F, and if it ever does there is a room A/C that is available, albeit almost never used. I suspect people who see problems often see greater temperature swings.
2. This is a very dry area, without great swings in humidity. Humidity doesn't affect the metal rails, but it can affect the roadbed and subroadbed depending on the material used. I have heard from many sources that Homasote -- a popular roadbed especially amongst those who hand-lay track -- is especially susceptible to contraction/expansion with humidity changes. It may be that the expansion/contraction problems some people are seeing have more to do with the roadbed than the track.
3. N scale may be less susceptible than HO and larger scales. I'm not married to this idea, as the rail sizes between the two gauges aren't that far apart (my code 80 in staging is not that different than code 83, which is the most common for large HO layouts). On the other hand, the track width for N is just over half of HO, and that might make a difference. However, for whatever reason I've noticed that it's rare for an N-scaler on an internet forum to complain about soldered joints causing track bendage due to expansion.

So, to make a short story long, I connect feeders to every other rail joint. Here's an example from the current staging construction:


As I keep mentioning, in staging looks don't matter. In fact, I personally like to have all the behind-the-scenes construction and wiring details visually evident in staging because visitors often find that stuff just as interesting as they find the sceniced portion of the layout. So, in staging I solder the feeder wires to the outside of the rail joint, thus avoiding potential problems with the wheel flanges hitting the wire on the inside of the rail. I'll describe the detailed procedures for soldering wire to rail, both for staging and the main layout, in more detail in a future post.

So, this post concludes the standards used on this layout to get power to the track under most circumstances. There are, however, a couple of exceptions yet to discuss. One is auto-reverse sections, and the other is track wiring for switches with "live" frogs. My next wiring post will cover auto reverse. I'll hold off on the discussion of switches with "live" frogs until I get back to construction on the main layout, as this doesn't apply to the Atlas code 80 switches used in staging.