Re: [TCML] 8" Secondary Woes

[Stan Gray <wsmg@xxxxxxx>]

Hey Greg,

They don't carry any 8" pipe? That should be pretty common I would think. It would be 8" id and around 81/2" od.
If you end up using acrylic melt your cuts smooth and heat up a drill bit or rod to treat your holes also to get them smooth, that's suppose to prevent crazing or cracking. My Sparky Matic coil is 8" pvc pipe and is under 9", my space between the primary and secondary is 2 tite fingers one way and 3 the otherway, and around 11/2" to 2" above the primary. (1st winding) I haven't measured it lately, I'll check it later when I go to town, I don't have it here right now it,s near were I'm having the teslathon.

Good luck,
Stan




________________________________
 From: Greg Peters <greg.j.peters@xxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> 
Sent: Tuesday, September 3, 2013 9:29 AM
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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