Brooks (brooksmoses) wrote,

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Some observations from installing a car stereo

So I was working on installing suzanne's new car stereo today. It all went reasonably smoothly -- unlike larksdream, I already had the soldering iron and wire strippers and screwdrivers and so forth, from previous projects, and so didn't find myself needing to go buy them.

On the other hand, I did discover a few bits of craft in how to join wires together, and some of that may be worth sharing (and writing down so I'll remember for next time).

These are stranded copper wire, about 16 gauge (i.e., the bundle of strands is about 1mm in diameter), and the idea was that I would solder them together end-to-end, so that I could then easily seal over the joint with a bit of heatshrink tubing.

The first lesson, learned last time I did this, is that it is very important to put the heatshrink tubing over the wire before soldering the wires together.

Somewhat less obvious is the best way to put the wires together before soldering. The first attempt I made involved simply pushing the ends together, so that the wire bundles sort of interpenetrated. This worked quite badly on multiple levels. First, the connection had no structural rigidity, necessitating four hands (one for each end of the wire, and one for the solder, and one for the soldering iron) to do the work, and unfortunately my feet are not that prehensile and I am not equipped with a tail. Second, this causes all of the ends of the wires to splay out, and there is no way to successfully convince them to not do so -- it's quite easy to push them in place with the soldering tip, but of course one cannot hold them in place until the solder cools that way. And then, with the ends all splayed out, one gets a rather iffy looking joint that the heatshrink tubing will not even begin to slip over.

With a bit of considering and improving on practice, I came up with the following process: Start with about 5/8" ends of the two wires. Cross these at a right angles in the middle. Wrap the ends around the opposing wire tightly, using a pair of flat-face pliers to get the ends down snugly. This results in a twisted connection (which doesn't splay the ends out), with a bit of a kink in the middle. Since the wires themselves are pretty straight going through this kink, bending the kink back so the whole mass is straight causes the wires themselves to bend sharply around each other, producing an interlock that is sufficiently solid to hold itself together without being otherwise held while one solders it.

The second trick involves the heatshrink tubing. An easy way to shrink the tubing is to hold it over a candle flame. However, one wants to avoid getting the tubing sooty.... I discovered that the trick to this is obvious. See, the visible yellow flame is in fact incandescently-hot soot. If one holds the tubing-covered wire in the flame, all of this soot gets cooled off and deposited on the tubing quite thoroughly. On the other hand, if you hold the tubing just above the tip of the flame, the soot has all burned up at that point, and it stays clean. I only got one wire really sooty before this obvious fact occurred to me.

So, anyhow, I got all the soldering done, and bolted it in, and it seems to work quite nicely. And suzanne is happy.

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