Thursday, January 1, 2009

The Wire Tracker

Happy New Year to you all.

One of the more troublesome aspects of aviation electrical work is the fact our wires are usually NOT color-coded. That means you can have a bundle of twenty wires and before you can do any useful work you will need to figure out which one of the twenty at the equipment rack is the frayed one you've spotted behind the instrument panel.

How to do it? The good ol' fashioned way, which I described in an article some time ago, is to use a continuity tester. That is, a hunka wire long enough to run from here to there, a couple of flashlight batteries, and a flashlight bulb. You know you've found the correct lead when the bulb lights up. I even described a do-it- yourself tester based on an old-style Navy flashlight.

Alas, while 3 volts ain't all that much, you could be connecting those 'unimportant' three volts to a meter-circuit that blows it's top at two volts.

Whatcha REALLY want is a cable tracker.t

A cable tracker is a little oscillator that puts a warbling TONE on the wire under test, which you can then hear by waving a matching receiver at the other end of the wire.

Harbor Freight's gottem. Item #94181 about $20 US, probably less if you can find a Sale. (But Santa brought me this one :-)


1 comment:

Ernest Christley said...

Time-Warner has cancled my newsgroups, so I had trouble posting this on RAH, but this will do.

I'm going to make a suggestion without really having a clue what I'm talking about, but here goes... Why not make headfins like a modern radiator? Maybe even oven braze it.

The way I imagine it being done is that a fairly thick walled head (sans fins) is cast and machined close to the correct shape. A sheet metal aluminum fin is cut with the appropriate OD, but with a hole slightly smaller than the OD of the cylinder. Two steel plates are cut to support the fin, with a hole somewhat larger than the cylinder. One of the plates are cut in two.

Clamp a fin between the steel plates, then press the head into it, deforming the ID of the fin. Remove the steel plates (the reason one was split), and fill the valley formed between the fin and cylinder with oven brazing paste, or TIG it to the cylinder head. Push the cylinder through another fin, etc. The steel plate serves as the spacer. There are companies that will do "dip brazing", also.