I'm sure at some point in time we've all felt like the young modeler above. Wiring is not generally the favorite aspect of the hobby for most modelers. However, since wire is the pipeline that takes electricity from its basic power source to a particular device, its helpful to gain an understanding of the basics.
In this short section we'll look at:
 | Wire size (gauge) |
| Stranded vs. solid wire |
| Connecting wires to 'something else' |
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Wire Size/Gauge
Just as water pipes come in a variety of diameters, wire does as well. The diameter of the wire is labeled by an acronym called AWG (American Wire Gauge) or 'gauge' for short. Each wire diameter has its own distinct awg number. For reasons that totally escape me, wire sizes are in reverse order. That is, the smaller the wire, the higher the awg number. In other words a 10 gauge wire is much thicker than a 24 gauge wire. For a typical HO or N scale model railroad application you will generally use wire in the size range of 12 awg on the large end of the spectrum to perhaps wire as small as 24awg.
Why chose one size of wire over another? Two reasons. First, the larger the wire, the less drop in voltage over longer distances. Imagine breathing through a straw. The wider the straw (or wire in our case), the more air (or electricity in our case) you can draw through. So, if you are transporting currents over longer distances a larger wire would result in a lower drop in your voltage. Thicker wire, less drop in voltage over longer wire runs.
Since larger wire creates less of a voltage drop, why not use it all of the time? In this case practical matters (such as the size of your fingers) come into play. If you are wiring a small device, such as a crossing flasher or track feed it becomes physically difficult, if not impossible, to accomplish the task with a wire as thick as a pencil. You need something smaller.
Here's a quick and dirty suggested wire size chart for various applications:
| Main Power Buses and long accessory buses: 12 awg or 14 awg. I generally use 14awg except in cases where the wire run is very long (say over 50ft) in which case I might use 12 awg. |
| Track Feeder Wires: 18 awg (track feeders are the wires that connect the main power bus to the track rails) |
| Switch Machine and Toggle Wiring: 20-22 awg |
Shown above are some common wire sizes. The 14 gauge wire on the left is good for most power buses, the 18 gauge for track feeders, and the 22 gauge for wiring switch machines and accessories.
Stranded vs. Solid
For any given wire size (gauge), you have the choice between stranded (many tiny wires inside the insulation) or solid (one thicker wire). Choosing one over the other often comes down to personal preference and the task at hand. Stranded wire is more flexible. It also tends to look neater in that it is less prone to small kinks. On the down side, when you strip stranded wire you have to deal with all of those little strands which can be messy. In most cases I opt for stranded wire due to its flexibility. The strand issue can be dealt with by stripping off a 1/2" or so of insulation and tinning the strands with a small amount of solder.
Stranded on the left, solid on the right. Both are 18awg
Connecting Wires
When it comes to connecting a wire to 'something else' else you have a few choices.
| Solder the wire to the other 'thing' |
| Use a mechanical connector |
| Combination of the above |
Which method you use depends on the application. Lets look at a few examples:
Soldering. Areas I use direct soldering for connections are: attaching track feeds to the rail, attaching wires to a switch machine, and attaching wires to a toggle switch. First, a 1/2" or so of insulation is stripped off of the wire and the wire is pressed firmly against the rail or wrapped around the appropriate terminal. Next, a tiny drop of flux is applied to the area. Finally, a soldering iron is applied firmly to the point the wire meets the attachment point. Solder is touched to the attachment point until it flows like water around the area. For more details see the section on soldering.
Mechanical Connectors. I rarely use solder anymore for a wire to wire connection. Why? The availability of a nifty mechanical device that takes the pain out of the process, is just as reliable, and provides built in insulation. They are called by a variety of names such as suitcase connectors, tap connectors, or the nickname '3M' connectors. You simply insert the two wires in each end of the connector, crimp a clip down from the top, and the two wires are mechanically connected. After crimping the connector, a firm tug on each wire will tell you if you've got a good connection or not. If one of the wires pulls out, obviously you don't have a good connection! These connectors are labeled by the size of the wires being connected. For example, a 14-18 connector will connect any two wires that are with the size range of 14awg to 18awg. A larger wire won't fit in the connector and a smaller wire will slip out. Some hold the belief that a soldered connection is somehow more reliable or more solid than the tap connectors. After using, literally thousands of the tap connectors I don't share that belief.
Radio Shack is one source of connectors. They call them 'Wire tap-in squeeze connectors' and their part number of 14-18 connections is 64-3052. These work absolutely fine but some of the more expensive brands such as 3M are easier to work with.
In this photo, electricity is transferred from the main power bus (14 gauge wire) to the track rails with a connector wire called a 'track feed' or 'feeder'. The feeder wire is connected to the power bus with the small blue clip called a tap connector (aka suitcase connector). The tap connectors slips over the main power bus wire, the 18 gauge track feeder slips into the hole and a metal clip crimps them together.
The photos above show the simple process of connecting an 18 gauge track feeder wire to a larger 14 gauge main power bus. In this case a 14-18 gauge connector is illustrated.
Mechanical/Solder Connection. The final method of connecting a wire to a device involves slipping a spade or ring connector over the end of a stripped piece of wire and then hooking the connector to a terminal. A common use here would be attaching your wires to the terminals of a power supply. In theory you are supposed to be able to simply crimp the ring connector over the wire and it will hold. My experience has been that sometimes the crimp doesn't always hold and the connector slips off of the wire. To prevent this, I add a touch of solder to the point where the wire touches the connector for added insurance.
So, there are some of the basics. That wasn't so bad was it? Next time you're at a cocktail party you can impress the locals with a line such as "Since my power bus was only thirty feet long I went with 14 gauge stranded. I didn't feel the run was long enough to create enough voltage drop to warrant going with 12 gauge. I followed that up by dropping some 18 gauge stranded feeders tapped into the bus with 14-18 suitcase connectors". That should get you invited back to the next party :)