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Re: [TCML] 8" Secondary Woes



I might ask Greg, what power level are you running?  You might be able to
use the 6-inch and just draw the primary in, rather than going bigger...

Scott Bogard.


On Tue, Sep 3, 2013 at 10:29 AM, Greg Peters <greg.j.peters@xxxxxxxxx>wrote:

> 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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