A Homebuilt Litz Machine
by David McNamee
"Jeez, Dave! That's crazy deranged, dude!" - Dave Draper, friend
This was designed and built as an experiment to twist up different samples and constructions of Litz wire, but the machine sat for over a year before it was actually tested, problems found and fixed, and samples run. At the Southern California Teslathon 2000 I used a secondary wound with Litz that was made on this rig (3x3 strands of #31, three twisted groups of three twisted together). It worked pretty good, and I may have set a personal best record for my coil, but I did not measure the distance to the tripod being used as a strike target. Rats.
During this period, I discovered that much finer wires are used to make Litz for frequencies of interest to Tesla coil fans, and this machine is too heavy-handed to use on those. I figure with massaging it might go to #34. Or someday I may have to build a coil that runs at 30 kHz! :^)The large round plate carries three carriages that are each equipped with a variable number of spools and a spinneret. The shafts the carriages are mounted on are hollow and provision made for a core strand; this option has not been tried as of this writing. As the plate turns, a belt arrangement on the rear of the plate causes these carriages to rotate in the opposite direction of the plate in a 1:1 ratio. The wires coming from the spools twist together at the spinneret to make a group. The tensioning on the individual wires has not been perfected yet and must occasionally be checked and adjusted. The three groups meet at a stationary spinneret at the other end of the machine where they twist together in a direction opposite the group twist. The newly made Litz cable then wraps around a rate idler, which also pulls it through the machine and the diameter of which determines how many twists per foot the cable ends up with. The cable then passes back through a bushing to a take-up drum clutched via pressure on some clamp collars and felt pads.
The entire operation is driven by one long belt, hand cranked by yours truly and friends. Most people ask why I didn't put a motor on it. Well, I was 95% sure it would work, but I didn't want to invest in a motor until I had really tried it out. And after making 1200 feet of that 9/31 at about one inch per crank, I'm ready to put one on it now!
Copyright © 2000 by David McNamee.
All Rights Reserved.
This part of this site last revised August 15, 2000.