There are a lot of electronic components out there, but the one we tend to forget is the most basic: the wire. Sure, PC boards have replaced wire with copper tracing, but most projects still require some form of wire somewhere. If you need any wire, there’s a good bet you’ll need a long wire, and that means connecting one wire to another. Easy, right? Not really. There are different ways to connect cables, and which one you use depends on what you want to do and the type of phone you’re using.
If the wires touch, good enough, right? That’s not the case. You need enough contact area for the current you draw through the wire to flow. It is also good if the splice can survive a certain amount of mechanical stress, vibration, and survive repeated heat and cold.
Usually, after connecting, you would like to sell the connection, although depending on the application, you don’t always see that. At the very least, you may want to wrap it with electrical tape, use heat shrink tubing, or seal the bare wires and perhaps provide mechanical support or strain relief.
Remember that there are connection options, whether mechanical, solid, or soldered, that allow you to avoid pieces. Soldering on a terminal strip, for example, or sewing wires into the terminals will get the job done. So does a butt joint, wire nut, or WAGO connector. But sometimes, for whatever reason, you just need to attach two wires to each other. It’s been done before.
The Gold Standard
Undoubtedly, the best way to join two strong wires of the same size is the Western Union splice, or the lineman’s splice, which goes back to at least 1915 when the book. Functional electrical wiring (PDF) explained. It will work with stranded wire, too, if you twist it tightly and, even better, wire it first.
You bend each wire around the other wire and wrap each wire around the other wire. There are several options regarding how to handle the middle section, as you can see in the adjacent image.
This is not difficult to do, but it depends a little on the skill and patience of the splicer. On the other hand, they are very mechanically strong.
NASA’s work document (NASA-STD-8739.3, PDF) encourages you to avoid fractions and choose controlled processes such as crimps, where the tool produces repetitive connections. However, in testing, Western Union soldered parts were found to be stronger, often stronger than the surrounding wire.
Other Common Spaces
Perhaps the most common splice is the rat or pig tail splice. This is where you simply twist two wires together. If you don’t need to survive mechanical stress and you have solid wire, this works well and is what you usually see inside electrical boxes in North America, either made or with a wire nut.
These are quick and easy, but without something like a wire nut, the least suspect. They tend to loosen over time, especially under vibration.
Another problem is when you have big, stiff wires that don’t work for twisting. That called for the breakup of Britannia. Here, you put two thick wires at the ends and tie them with a thin wire. You don’t see these very often, although you may see them in some useful situations. Often, you would cut the connector at the edge to join the two main wires. Note that the binding wires wrap both the wires and the common part where the wires touch.
A similar splice is what is called a fixture splice, where a smaller wire wraps around a larger wire. This is another situation where you can almost always eliminate this with some type of mechanical connector, such as a telephone nut.
Sometimes you need a splice that is not much larger than the actual wire. You can do that with a scarfed splice. This usually only works for large, strong wires. You cut each wire to a point (using, for example, a file) and join them together like a scarf joint in carving. Of course, you have to sell or fix the wires somehow, since there is no mechanical connection. This takes a lot of work and skill to get right.
Special spaces
Sometimes, you want to connect to an existing wire to form a âTâ or tap. It is possible to make a tap joint by removing the residue from the main conductor and wrapping the wire around the bare metal. Usually, you will tie a knot in the tap wire before wrapping to try to improve the grip of the machine a bit.
However, these are not particularly powerful, and you must be careful to remove the insulation so as not to damage the main conductor and weaken it or reduce the current capacity.
If the main wire is tied, another alternative is to carefully divide the main conductor into two segments and pass the tap wire through the center before wrapping it as before. Although this may be a little practical, it is still not a good replacement for the red tap or the three-wire connector.
Connecting multiconductor cables can also be a challenge. Of course, with a light bulb, it’s as easy as making two pieces. But in wires where the pair is balanced, it is often not possible to maintain the spacing and twist of the wire. It’s best to get a cable of the right length.
Maybe Others
There are probably as many ways to make a splice as there are people who make frames. Some are smart, some are bad, and a few – like the Western Union splice – have stood the test of time.
Most of the time, you want to avoid pieces where you can. Try a terminal block, a solder sleeve, or a crimp connector. Even a wire nut, while technically a nut, will give you some adjustment benefit just by twisting the wire together.
We like Western Union splice with a good coat of solder. Ultimately, the “right” piece is the one that matches the electrical load, the mechanical demands, and the environment you expect it to live in. A quick twist may work today, but a well-grounded frame will still work years down the line.
Which way are you going? Let us know in the comments.
