[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: design sanity check

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Ben,

STOP!

I would "not" go with a "helical" coil on this secondary, especially the primary height you mentioned! You'll never achieve breakout because the primary will be arcing and burning up your secondary. Coupling is at 0.45 with the top of the primary placed 6" below the top of the secondary (as you mentioned). That's about 0.3 too high. You need to shoot for something in the neighborhood of 0.15. I would further recommend a flat primary. It will perform just as well, is easier to build, and will allow the streamers to go other places. Keep about 1.25" from the bottom secondary to the inner diameter of a flat primary for a coil this size.

Assuming a 4" minor dia. toroid (20.6pF, 20" major dia.), this flat primary would do well with your 4 awg wire.
Primary Coil Inputs:
3.25 = Radius 1
7.058 = Radius 2
0 = Height 1
0 = Height 2
8.38 = Turns (tap point for .01uF cap)
4 = Wire Awg
0.01 = Primary Cap (uF)

Build it for 10 turns (about 25 ft of wire). Note, I just guessed on the bucket cap value. Adjust accordingly. With this primary set even with the bottom secondary turn, the coupling comes in at 0.15 as mentioned above. BTW, the spacing between turns on the above primary is meant for 0.25" edge to edge.

Take care,
Bart

Tesla list wrote:

Original poster: "Ben Ziegler" <crossguy@xxxxxxxxxxx>

Hey all -
 I am halfway through construction of my first "junkbox" style tc.
Quick specs:
140 V variac, 15/30 NST, terry filter
two geek group bucket caps
24 AWG secondary, 576 turns (14") on 4" OD sealed pvc
topload of 4" minor diameter flex aluminum ducting

Using Bart Anderson's JavaTC, I get closest to resonance with a primary  of:
18 turns of 4 AWG copper, helical
6" diameter, 12" high

This puts the top of the primary about 6" from the topload. This seems like a good way to get a primary strike after very little operation. Since the secondary is complete, I can tweak the topload, power supply, and anything in the primary circuit. Any suggestions on the best way to lower the primary coil's physical height without going way out of resonance?

thanks,
Ben Ziegler