RE: Spiral and Helical Primaries

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Parpp807-at-aol-dot-com>

John C and Robert,

I probably missed a good opportunity to do some testing with  spiral coils 
on the twin bipolar. I can always go back for a revisit. I have so many 
solenoids from
the various bipolars that I have never made an Archimedes spiral. But I did 
learn how to wind large diameter solenoids. I can now see one or two spiral 
coils in the near
future.

My collection of solenoids consists of coils of many different diameters. The 
secondary has an OD of 4.5 inches. A solenoid primary of around 8 inch 
diameter
proved to be too close and the racers and arcovers were uncontrollable. 
Increasing the clearance between the primary and secondary to around 3 to 3.5 
inches is about as tight a coupling as I can control. Then I vary the 
coupling by raising and lowering the secondary which telescopes nicely over a 
piece of smaller diameter pvc. As I reported previously, this combo on the 
twins (Isis and Osris) gave a 73-75 inch spark with 2.25 kW input. Being ten 
miles from the nearest fire station convinced me to calm this down to a more 
controllable 65-68 inches.

I understand there was a lengthy thread on this same subject several years ago
with the general concensus being that there is no difference between the 
spiral and
helical primary. I suspect that is what I will find. I imagine the spiral 
coil as
producing an ellipsoidal B field with one end of the football going up the 
secondary
and the other end going down below the table. The solenoid should produce a 
parallel B field that cuts the wires of the secondary at 90 degrees. That 
sounds good
altho I can see how the coupling will be much tighter. Also, from what I have 
seen in various plans and read on the list, the usual space
between the flat spiral first turn and the outside of the secondary is 1-2 
inches.    
My experiments show that is much too close for a solenoid.

Slow learning in progress.

Happy day,
Ralph Zekelman
    









 Original poster: "John H. Couture by way of Terry Fritz 
<twftesla-at-qwest-dot-net>" 
> <couturejh-at-mgte-dot-com>
  Ralph -
>  
>  To my knowledge no one has ever made the proper tests to determine if there
>  is any advantage to the spiral compared to the helical primary for Tesla
>  coils. Both systems appear to work the same when correctly designed. You 
may
>  want to fill in this gap for coilers by making tests with the secondaries
>  you have available.
>  
>  There are no TC computer programs that I know of that takes the type of
>  primary into consideration. To find the spark length only the input watts
>  are used. The JHCTES Ver 3.3  goes a step further and uses the input watts,
>  power transformer secondary voltage, and the secondary inductance to find
>  the spark length.
>  
>  John Couture
>  
>  -----------------------------