--OK here's the thing: I can get 8 gauge aluminum ground wire
in coils that are pretty tightly wound; i.e. about 8" dia. What I
*need* are dead straight pieces, maybe 10 to 12ft long. I'm thinking
if

Fab up a roller straightener. See ebay item 7527787746 for a not-great
picture of one on a Eubanks wire cutter/stripper, on the front left
corner of this machine. These use 4 rollers over 5 rollers followed by
4 rollers beside 5 to straighten in both planes, with a screw to set how
close the rows of rollers are to control how much the wire gets bent
back and forth. On our Eubanks I aim for maybe 1/2 the overall wire
diameter deflection when feeding 14 ga insulated wire and it comes out
pretty straight. More deflection would be straighter but the pulling
resistance gets out of hand and we don't need it any straighter :-).
For a quick-and-dirty setup just use some small pulleys, maybe .75-1"
diameter, and start with just one plane, to see if it will do your job.

--
Regards,
Carl Ijames carl.ijames at verizon.net