On Tue, 18 Jan 2005 14:22:54 -0600, Don Foreman
wrote:

How many resistors do you plan to make? I have some projector
arclamp carbons, copper-clad, about .223 dia x 6" long. "As is" they
measure 6.23 milliohms end-to-end. (Kelvin bridge measurement:
millivolts with known 1000 mA flow) You could grind or etch (ferric
chloride) off some copper to get .033 ohms, probably in an inch or
two.

They can definitely "take the heat". I'd terminate with clamps of
some sort rather than soldering wires to the copper; the solder would
probably melt.

I'd be happy to send you one or two of them if you'd like. Email me
if interested.

Post script: I removed 1" of copper. Was going to etch it, but
after taping all but one inch I thought I'd shine up the exposed
copper a bit in the beadblast box. Well, that copper was gone in
about 3 seconds!

The resistance is 0.055 ohms for 1 inch, dia is .218". You're still
welcome to a projector carbon or two, but 3/8" or even 1/2" dia
welding carbons might better suit your 30-watt .033 ohm need. From
this experiment, I'm guessing a 1/2" dia welding carbon would exhibit
about .010 ohm per inch of stripped carbon. 3" x 1/2" would have
enough area that I don't think it'd get too terribly hot at 30 watts.
The old Ungar 35-watt soldering pencils had elements of about that
area.