How to braid cables

Braiding methods

The general description of a braid is multiple strands of material woven together in an interlocking fashion; such that it is not possible to untwist the assembly, nor to pull any one strand apart from it (without breaking it outright). Each strand should also cross between both sides, such that its average coordinates remain at the center of the braid (otherwise flexibility would be impaired).

There are many, many possible braids, although not all are sensibly applicable here given that wires are less flexible than fabric (for example); finger-weaving, for example, will involve too much bending to be practical. I won’t even attempt an exhaustive listing of the methods that could work for wires; you can find the rest yourself (or elsewhere on the Web).

Properties which contribute to the suitability of a braiding technique:

• Symmetry – not just for aesthetic appeal; keeping a symmetrical form is also good for ensuring that the braids handle flexing and twisting in opposite directions with equal comfort.
• Uniform element usage – some of the more ‘ornamental’ braids have groups of elements used in different manners. In general, those are not what I’m after; they’re generally more complicated than their merit (if any) warrants, may require different lengths of each, and may involve greater bending in one of the groups. Braid forms using all elements equally are generally more practical (and all of the types listed below are in this category).
• And last but not least, ease of formation – if it takes a year to make, then it’s a bit hard to regard as ‘practical’, right?

That said, maybe you can find a cable with some thick and some thin wires, for which some non-uniform (or ‘complex’, I suppose you could say) braid works well.

Plait

The simplest braid (and the only one you can really make with 3 cores); simply transpose cores from alternating sides over to the center. (Over 1 for 3 cores; over 2 for 5 cores; over 3 for 7 cores; etc.)
These are flatter than their width (a little over half), which may serve as a happy-medium between round cables and ribbons.

With an even number of cores, there is no true center position, so you will have to pick one side of the center and stick with it along the braid. This will produce a somewhat asymmetrical result (especially with 4 cores) which will not handle flexing to both sides equally.

When you make half a lock (after as many transpositions as there are wires), the core arrangement is mirrored from where it started; this can be useful in some places. A full lock returns the cores to their starting positions (and this should be the case in any valid braid).

Extra-flat plaits

If the number of cores is a multiple of 4 plus 1 (9, 13, 17, 21 etc.), there’s a technique to make them flatter still (but wider):

With 9 cores, pass the outside strand over 2 then under 2, repeating from alternating sides again. (For 13 cores, over 3 under 3; 17 cores, over 4 under 4; etc.)
You can try with other numbers of cores if you alternate the passing counts: For 11 cores you could try over 3 then under 2 (or over 2 then under 3), and if you have an even number of cores you will again have to accept asymmetry; for 10 cores you could do (over 3, under 2) from the left then (over 2, under 2) from the right, for 12 cores you could do (over 3, under 3) from the left then (over 3, under 2) from the right, etc.

Technically, this method can also be applied to 5 cores (over 1, under 1); but that’s effectively the aforementioned finger-weaving, so requires more bending than is comfortable with wires. It’s also possible to extend the technique further (say, over 2 then under 2 then over 2 for 13 cores), but by that stage it gets excessively fiddly to weave and if you need wiring that flat, it’s probably better to use a ribbon cable.

Square braid

You can make these with any multiple of 4 cores (although it becomes hard to coordinate with more than 8 or 12).
The 4-core version can be seen as two interlocking twisted pairs (in opposite directions).

With the start and ends horizontally arranged, these go (from alternating sides again):

• 4 cores: Over 2, back under 1
• 8 cores: Over 5, back under 2
• 12 cores: Over 8, back under 3
• 16 cores: Over 11, back under 4

etc. However, getting square braids to begin and finish neatly can require applying an exception at the start:

With 4-in-a-row connectors like the peripheral “Molex” or FDD “Berg” (or the modified Molex KK on PWM fans), naïvely following the basic rule tends to produce a sideways bias.
To start them off properly, cross wire #1 or #4 under one then over one of the middle two, without turning back. Then proceed as normal, starting from the other side. This has the additional benefit (as plaiting gives by default) of allowing you to mirror the cores (as between the peripheral and FDD connectors) within the braid itself, rather than having to twist the cable or transpose the cores in a separate stage.

For a 4-pin square connector like the ATX +12V, you should start by placing one diagonal pair of wires (#1 and #4 using the official counting method) to the left, the other pair (#3 and #2) to the right.

Or alternatively, you can use a slotted disk, in which case the starting positions are readily apparent and the wires will be transposed like this.

Hexagonal braid

Uses 6 cores, I recommend using a slotted disk to hold the ends (you can buy them, or cut your own from cardboard).
Essentially, you take one triangular trio of cores and transpose their ends 120° clockwise, then take the others and transpose their ends 120° counterclockwise, and repeat these two steps until done.

However, if you do it with the start and ends in a flat plane, then the cores go over 4, back under 1 and over 1.

Practicing

While fabric cords are sufficient for checking that the basic braid forms are valid, this won’t give you a feel for how they work on wiring.

For realistic practice material, I suggest using output cables cut off from a failed (or gutless wonder) PSU; especially the main ATX cable (19 to 27 wires, depending which variant and how many sense lines are included) will allow you to try out many possibilities.

Overall

My preferred techniques so far are the square braid for 4 or 8 cores, hexagonal for 6 cores, and (to be realistic) plaiting for any other count.

Is braiding a practical way to bundle wires? I’ll leave you to judge for yourself.
That said, if you braid your hair (which I don’t), then I would consider this at least as good a use of the time (and you probably won’t have to do it as often).

If automated for manufacturing, then I’d hardly doubt in the practicality; and if anything it would seem easier to manufacture than the common woven sleeves.
(Although it’s presumably come down to the woven sleeving being already available, rather than needing new machinery set up.)

I can definitely attest that a competently braided wire bundle is more flexible than with sleeving. If anything it’s more stylish too (not that I weigh looks above practicality).

Pages: 1 2 3 4