Re: 1256 variacs + questions

[Parpp807-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

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

<< 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.
Thanks,
Chris >>

Hi Chris,

No wisdom, but a little experience with the kind of wooden framework you 
reference.
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 
rubber
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 
plastic
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 
would 
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 
G-10.

Hope this helps.
Happy day,
Ralph Zekelman