RE: [TCML] 8" Secondary Woes

["Phil Tuck" <phil@xxxxxxxxxxx>]

Greg,
I always use Acrylic with no trouble. Needs a new coarse hacksaw blade (HAND
saw, not jig saw), and I use the cutting oil that I use on the lathe. I
would imagine something like a liquid soap could be used instead.
I make a round wooden block that fits like a loose plug and push that up
inside near the cutting site, to support it internally. Light cuts take your
time.
Scoring around with a Dremmel cutting disc could provide a starting cut
maybe?


Phil
www.hvtesla.com


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Greg Peters
Sent: Tuesday, September 03, 2013 3:29 PM
To: Tesla Coil Mailing List
Subject: [TCML] 8" Secondary Woes

Hi all,

Well I've done something stupid. I wound a beautiful spiral primary with a
12" diameter inside turn on nice polycarbonate supports. I assumed that I
would be using an 8" (200mm) secondary and that 8" was a standard pipe
size. I was aiming for 2" between the primary and secondary. Never assume
anything! The nearest PVC water pipe OD is either 160mm (6") or 250mm (10").

8" OD tube is as rare as hens teeth in Australia. The only exception is 8"
acrylic tube which is difficult to cut and work with. I'm not a big fan of
acrylic, as I always seem to get my saw stuck, etc and I can see my
beautiful former being destroyed.

I have called nearly every pipe and plastics supplier in the country and I
am out of luck. No polycarbonate, styrene, PVC, polyethylene, polypropylene
or other plastic in 8" OD! I even called some of the gas pipeline suppliers
- I CAN get a length of blue 200mm LDPE pipe for about $500....not ideal
(expense wise).

I noticed that McMaster Carr has very cheap polycarbonate tubing in 8" OD,
and placed an order only to be informed that they will not ship to
Australia. There are a few other not so cheap US suppliers who may be able
to assist if necessary though they seem significantly more expensive.

Anyway, the closest thing I have found in Oz for a reasonable price ($200)
is a length of orange PVC electrical conduit at 225mm (9") OD.

So, my question to the list. Do I persist with trying to find an 8" tube,
possibly even from overseas, or settle on the 9" conduit and tolerate
having only 1.5" between my primary and secondary? I expect I will need to
lift the secondary quite a bit to prevent overcoupling and even flash overs
from the primary which will be running 24kV. Is anyone else running a
largeish coil with this kind of spacing?

This was meant to be a museum quality build and the idea of having to
significantly lift the secondary is frustrating, but realistically it's
looking like the only option! The coil has been painstakingly designed to
sit exactly in the middle of my shed space for maximum spark length in all
directions. Oh well, next time I will be more careful and assume nothing!

Cheers,

Greg.
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