Simple Rules for Producing Longest Sparks Using Minimum Power Input  !

( John Freau -1998  )

More about TC efficiency theory at John's homepage:

http://hometown.aol.com/FutureT/page5.html

From:  FutureT@aol.com [SMTP:FutureT@aol.com]

Sent:  Thursday, August 13, 1998 5:49 PM

To:  tesla@pupman.com

These rules may be helpful for some who may wish to experiment with sync-gaps at low break rates.

In a recent posting, I showed the better efficiency I obtained using these methods. It is important to have

a well matched system when using sync-gaps. These rules are based on my 42" and 64" spark TC's.

It should be possible to scale the results up or down, by following these rules. These rules are just a

rough guide, and some slight non-linearities may be seen with up or down scaling. Results will be

affected by transformer losses, design techniques, etc. These rules are based upon a square law for

power versus spark-length scaling, which seems to fit well with empirical results.

1, Quelles est la long, d'étincelle voulue

1,22

m

2, La long, d'étincelle/2,5 donne approx, le dia du tore

0,49

m

3, Diviser la long, d'étincelle par 10

0,12

m

donne la grosseur du tore

(Approximative)

4, Puissance de l'alimentation

798

watts

5'.  Mains Power frequency f =

50

Hz,      BPS = 2*f =

100

breaks per second

5. (Watts/BPS)/1.5= Joules/bang (the1.5 factor covers losses)

5,32

Joules/bang

6. Minimum rating for transformer = power input (watts) from (4)

above, for non-shunted transformer. (approx)

798

watts

7. Voltage on capacitor, Vc = input voltage times 2.22 times

transformer nameplate rms voltage rating

( =

8

kV  ),

for resonant charging with some losses thrown in. (approx)

17,76

kV

9. Capacitor size; C = 2 J/Vc^2 (joules from (5) above) (approx)

0,033748

uF        =

33,75

nF

10. Spark gap; synchronous rotary,

100

BPS

11. Primary and secondary coils; use traditional designs.

...but learn more at John's homepage:

http://hometown.aol.com/FutureT/page5.html

12. Inductive ballast; adjustable as needed.

Let's try an example, and aim for an 80" spark. 80/2.5 = 32" toroid dia.  80/10 = 8" = toroid thickness.

(80/1.7)^2 = 2215 watts. (2215/120)/1.5 = 12.3 Joules/bang. Minimum non-shunted transformer rating = 2215watts.

Voltage on capacitor, (assuming 14.4kV transformer), Vc = 14.4kV * 2.22  = ~32kV.

Cap size = (2 * 12.3)/32^2 = 0.024uF.

For a small coil, aiming for a 20" spark: 20/2.5 = 8" toroid, 20/10 = 2" toroid thickness.

(20/1.7)^2 = 138 watts. (138/120)/1.5 = .77 Joulesper bang. Minimum non-shunted transformer rating = 138 watts.

Voltage on capacitor, (assuming 10kV transformer), Vc = 10kV * 2.22 = 22.2kV.

Cap size = (2 * .77)/22.2^2 = 0.003uF.

For a tiny TC, aiming for a 5" spark: 1/2" by 2" toroid, 8.65 watts, .048 joules/bang, assuming a 6kV transformer,

Vc = 13.32kV, C = .00054uF. It is unknown if these rules will track "linearly" down to the small TC levels above.

Enjoy!  ( John Freau 1998)

New spark length formulas, as of April 27th, 2000:

inches

cm

Spark length (inches) = 1.8*sqrt power input (wallplug watts)

51

129

Spark length = 5.8*sqrt power input / 4th root of the bps

52

132

Spark length = (3.9*16th root of the power input*sqrt power input) / 4th root of the bps

53

134