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Re: 1256 variacs + questions

In a message dated 6/8/00 2:08:06 PM Central Daylight Time, tesla-at-pupman-dot-com 

<< Has anyone built any of their secondary structures with wood.  I am 
 designing a large coil and would like to make it an open air design (like 
 Greg Leyh's monster) but I am having trouble finding good strong materials 
 to build the framework.  If anyone has any wisdom in this area it would be 
 greatly appreciated.
Chris >>

Hi Chris,

No wisdom, but a little experience with the kind of wooden framework you 
My 1/2 - wave center fed bipolar is approx 21 inches of # 28 on 3 inch dia 
pvc. I have
15 KV-at-90mA NSTs and a 0.022 MMC. I can get the full 20-21 inches of arc 
between the 
two rabbit ears with 3/4 inch brass balls on the ends. The streamers and 
corona are
spectacular (to me). :-))

I have reached the limits of the insulation capabilities of the untreated 
pine frame. 
The vertical supports of 1 x 3 hold the secondary around 14 inches above the 
base. I
drilled and tapped pvc end caps for 1/4 x 20 bolts. Uh Uh. The steel bolts 
stuck into the end caps threw 8 inch streamers so I replaced the steel bolts 
with threaded 1/4 inch
acrylic rod. The secondary is wrapped with two layers of 1/32 inch silicon 
sheet. No power arcs but I get arcs running down the sides of the wooden 
supports to the
nails nearly 12 inches below the secondary. Great fun. I suppose treating the 
wood with
shellac and/or paraffin, etc., would improve things. I could also fasten some 
cleats along the supports to increase the arc path. Do not use wood.

I plan on doubling the size of this bipolar using G-10 or something similar 
for the vertical
supports. McMaster-Carr has Nylon bolts. So in MHO, do not use wood. And I 
like to know if any of the plastics experts out there have any suggestions 
for the use of 
other insulating materials more congenial to machining and the wallet than 

Hope this helps.
Happy day,
Ralph Zekelman