Tricks of the trade: Twisting wire bundles

A common problem that you may come across when building "a box" to do something-- whether a one-off gizmo or bona fide scientific instrument --is the rats nest of wires. A similar problem occurs when you need to run a bunch of basic wires out from your box to other devices. Unless there's a standard cable lying around that does exactly what you need, you can end up with messy tangles of wires outside of your box as well.

There are many well-known solutions of course, as varied as elegantly laced wiring harnesses, cable ties and teflon spaghetti sleeving, heat shrink tubing and cold shrink tape, and (possibly for the brave and/or insane) duct tape and paperclips.

One of the other basic methods-- well known to many people who build electronics --is to twist wire bundles with a hand drill and a friend. This is a quick and awesome trick that makes durable cables, short or long, exactly to your specifications, and shockingly fast.

Let's suppose that we need to run these four wires from point A to point B. They can be a mix of stranded or solid core wires, with different diameters an insulation types. The orange and blue wires in this bundle happen to be stranded copper wires with a particularly slippery PTFE jacket.

Twisting any length of these wires by hand is fairly difficult, because they don't tend to stay where put. Fortunately, we only need to twist the first inch or two:

Twist the first couple of inches of all the strands together and bend them over once.

Then, get the drill.

As we said, you need a hand drill and a friend to build these. If you don't have a friend, a bench vise will do in a pinch (pun intended). A standard electric hand drill works great, but I've also heard of occasional success with adapted cordless screwdrivers. Do not use any sort of heavy machinery-- drill press, lathe, or mill; it will not be safe.

Insert the bent-over twisted cable ends into the drill chuck, and tighten it down. (Keyless chucks help make this fast.)

Hand the loose cable ends to your friend, and stretch out the cables to their length. It's important that your friend keep a firm but not too tight grip. If something goes wrong, the wire should safely pull out of their hand.

Now, run the drill. Run very slowly at first, making sure that the wire does not whip around. You can speed up as it becomes stable. By the time that the wires stop looking smooth and just begin buckling, it's done. Don't overdo it, as the wires may begin to stretch in undesirable ways. Total time elapsed on this step is usually under 30 seconds.

Unchuck the wire, trim and pluck apart the ends, and there you go: a neat little wire bundle, ready to take on the world:

You can obviously do much more complex wiring as well. Wire bundles like these have internal tension and tend to stay together quite well.

Here is a much simpler example of the same technique. In our Drink Making Unit project, we had a central controller that had two wires each running out to the three separate motors.

Instead of running six loose lines, we instead made these three extremely effective and neat-looking twisted pairs. (Or more precisely, we made one long twisted pair and cut it into thirds.)

Twisted bundles like these are very well behaved-- not only do they look professional, but they feel good as well, with a natural springiness, and they seem to resist snagging.

So there you have it, a tried and true method, perfect making for simple one-off wiring harnesses, and making neat cable bundles to run between your devices.

It should probably go without saying, but this technique is very useful for general-purpose wiring, and is not for anything requiring special considerations. If your project requires high voltage, transmission lines, heater wires, or wires otherwise driven outside of normal parameters, you probably need to work with those wires separately and not collect them into a twisted bundle like this.