Also, the reason the research coil needed 33 turns on the primary
is because it had a large high inductance secondary with about
1500 turns, and at times I used a larger toroid. It needed 33(?) turns
to tune. But for the newer TT-42 coil, since it has a smaller
secondary with fewer turns, and lower inductance, and also
the larger capacitor, then it needed much fewer primary turns.
I assume you're familiar with Bart Anderson's Tesla coil
program, " JavaTC"? It's excellent for determining how many
turns are needed for the tap point with a certain number of
secondary turns, secondary size, toroid size, capacitor size,
etc.
John
-----Original Message-----
From: Futuret via Tesla <tesla@xxxxxxxxxx>
To: tesla <tesla@xxxxxxxxxx>
Sent: Wed, Mar 1, 2017 7:53 pm
Subject: Re: [TCML] 42" Sparks 12/30 - John Freau
I looked over those specs. I had forgotten about that earlier version of
the TT-42 coil. The specs you gave were of my old "research coil". I had
forgotten about the 6" diameter secondary and the 34 turns on the primary,
but yes that was the research coil. Then I decided to make a more
compact coil that I called the TT-42. TT stands for Table Top. This
newer coil is smaller and uses a 4.2"diameter secondary with 19" winding
length of 28awg heavy formvar magnet wire (about 1300 turns I think).
The primary is tapped at 13.5 turns, and uses 12awg solid pvc insulated
telephone ground wire (gray). This was very tricky to wind. It's a flat
pancake primary. The inner diameter of the primary winding is 6.5". It's
close wound. I use a 1.5" x 6" toroid directly above the secondary, and
a 4" x 13" toroid above that, and the 120 bps sync rotary gap. Such
rotaries have to be phased in by either rotating the motor in it's cradle,
or using an electronic phase shifter. The tank cap is 0.015uF.
Of course you can build the design that you mentioned. Either way
will work, there's a lot of flexibility for these projects. It's better to
use the larger tank cap because it keeps the voltage lower. I'm surprised
the research coil worked as well as it did considering the small cap value.
This is all I have at my website at the moment, mostly VTTC stuff.
I can't find the photos of my TT-42 coil. I'll take new photos and
put them at the website. You can find my sync gap and phase shifter
circuit at this website.
https://sites.google.com/site/jfuturet/home
John
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