RE: Desktop Bipolar Coil

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

Original poster: "Ralph Zekelman by way of Terry Fritz <teslalist-at-qwest-dot-net>" <gridleak-at-bluemarble-dot-net>


Dave,



Dave,



Me thinks you are a bit optimistic on getting a spark length of 25.5 inches 
from a 24 inch bipolar. My efforts with a 24 and 48 inch bipolar convince 
me that the geometry of the coil must limit the spark length.



The problem is simply that the spark will always take the shortest path. I 
made the rabbit ear antenna arms adjustable so the spark length could be 
varied, but no contraption of hinges or ideas of plastic sleeving to 
increase the breakdown voltage at the base of the arms succeeded in making 
the spark longer than the length of the secondary. As the voltage will 
increase with the spacing, the quality of the insulation becomes a factor 
in the attainable spark length. While modern materials have increased the 
quality of the insulation, I have never seen a photo of a bipolar coil 
showing a spark length longer than the length of the secondary.  With 15 kV 
-at- 150 mA input,

the best I could ever get is 20 and 40 inches respectively for the 24 and 
40 inch coils.



An MMC combo will work just fine.



Good luck on your project.



Ralph Zekelman