Subject: Toriod Sizing
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Wed, 9 Aug 1995 01:04:00 GMT
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Quoting Ed Sonderman:
ES> My secondary is built on a 6.0" dia pvc pipe - probably
ES> 6.25" od. It is covered with 5 - 6 coats of polyurethane.
ES> The wire is #22 formvar covered magnet wire - then covered
ES> with another 6 coats of polyurethane. I believe the winding
ES> length is 27" (my records are at home and I'm at work).
ES> There is approximate 960 turns. Primary is 15 turns of 3/8"
ES> copper tubing wound on a plastic coil form at 30 degrees
ES> (saucer shaped). Toroid is 40" in dia and 5 or 6" thick.
ES> Spark gaps are one rotary with a static gap in series. I
ES> haven't checked the frequency since I built my newest
ES> toroid. With my 33" toroid, I believe the frequency was
ES> about 130 khz.
Quoting Phil Mason:
PM> I assume that that toroid (40"x5-6") is optimised for your
PM> system (having followed your previous postings). Is the
PM> dimension simply related to the coil dimensions or is there
PM> a more complex relationship involving operating power and
PM> frequency etc?
I can help a bit here as I assisted with some design details
during the step by step peaking of the system.
The same coil operates fine at lower powers, higher frequencies,
with a smaller toriod. I simply guestimated (remember I hate
math) on the size toriod the coil could handle based on primary
turns and capacitor value. Call it intuition, honed by
experience. I don't think I worked out a single number on the
system since the secondary was completed.
Ed was kind enough to work up on my hunch, and with the upgraded
commercial capacitor and the new toriod, he hit to within two
turns or so of the primary inductance we were both seeking.
The balance is very complicated and tricky, as we found out when
Ed ran a series of tests on the primary ballast. Frequency,
coupling coefficient, spark gap performance, peak power, even the
toriod height above the secondary have to be just right for the
system to function well with this much toriod loaded on the coil.
But judging from the descriptions of the spark, boy does it
I have to extend a huge amount of credit to Ed for the fine
construction practices and diligence in building this system from
nothing but text files. In my experience nobody has pushed so
hard on a six inch coil and produced this much spark. This
includes anything I have seen Richard Hull do in 1/4 wave work,
or anything that I have been able to accomplish on a relatively
simple six inch diameter 1/4 wave coil. Usually to bump up to
these power levels the coiler goes to an eight or ten inch
diameter secondary. Ed has stuck to his guns and has shown that
the six can be coaxed to really big coil performance...