On Friday 07 October 2016 09:46:22 andy pugh wrote: > On 7 October 2016 at 14:33, Gene Heskett <[email protected]> wrote: > > It all gets complex fast when dealing with alu and > > its instant oxidation. > > I have never found aluminium to be non-conductive. > Its a good conductor, IF you can achieve a 'gas tight' connection, AND maintain it for decades. But because of cold flow when dis-similar temps expansions are encountered, the average life of a crimp sleeve connecting your houses copper sticking out of the weatherhead, to the alu cable from the transformer on that pole across the street, is, IF the crimp is well done, perhaps 30 years. When I am on my roof for any reason, one of the things I always do is walk over and feel those crimped connections for heat buildup. Here, they are only 8 years old, but before that drop line was replaced because I had replaced a 60 amp service with a 200 in 2008, 2 of the 3 original connections made up in 1974 had already failed, one burning completely in two in about 1997.
I have also had the nominally 7" long aluminum jumpers from the meter socket, thru the wall to the service in a closet on the other side of that wall, try to burn my house down in the middle of a -15F Nebraska night in February, with the buzzing of the arc in the closet waking me up. That was the 2nd time that alu wire had tried to burn me out. I will not knowingly buy a structure with aluminum wire under the roof. I cut the seal on the meter and fixed it with some copper that wasn't heavy enough, but then went to the transmitter and "borrowed" about 8" of 6 gage copper to fix it right the next day. Cutting the meter seal is a felony in most locales, and its probably a good thing that I knew the head lineman at the power company, because when I called him to send somebody by and put a new seal on the meter, he had to have a good explanation as to why I cut it. The tv station, kxne, was a uhf, and was their highest billing customer at about 225 kw load during operating hours. Klystron amplifiers are hungry beasts. Alu, cut into with our cutting tools, oxidizes so rapidly behind the edge of the tool, that in .001 second, the film has achieved a 50 volt withstand. To make a connection, you must touch it with enough force to penetrate that oxide film. Since alox is the 2nd hardest substance we know about, its cutting dulls our tools much faster than when cutting other non-ferrous materials. > You could consider using one of these instead of a probe: > http://www.ebay.com/itm/CO-AX-INDICATOR-MILLING-MACHINE-COAXIAL-COAX-0 >005-/300841418164 I've not figured out how one of those works. The price seems decent though. > Thought, actually, with a bit of neck-craning and possibly the use of > a mirror you can centre a mill-spindle to a bore or round stock with a > generic indicator and an improvised mount. Thanks Andy. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
