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RE: [TCML] 8" Secondary Woes

I found the same thing.  That is why I am doing a 10" coil as mentioned just
previously, because this was the next size available up in PVC stormwater
from 6" here in Australia.  I fell into the same trap - the pipe is marked
as 225mm but I don't know for the life of me where they take that
measurement from - the inside diameter is greater than that at just under
240mm, and the outside diameter (5.5mm thick PVC) is very close to

So you can't even trust the markings on the pipe itself!  Luckily for me I
haven't wound my primary yet.

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of Greg Peters
Sent: Wednesday, 4 September 2013 12:29 AM
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!


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