On 8/30/11 10:39 PM, James Hutton wrote:
Hello, so I was just wondering why no one uses helical coils with
insulated wire like this:
http://www.johndyer.com/MakerFaireJD06.jpgwhen building big static
gap tesla coils. I have seen tons of small sgtc's with a primary like
that, but it seems that with bigger sgtc's people always use copper
tubing and carefully space them in a flat or conical spiral. I don't
understand this. Helical coils with insulated wire are so much easier
to make, they cost less, their more durable, look better, and take up
much less space. Is it because helical coils are less efficient? I
need to build someone a nice looking tesla coil that is 900w
(15/60nst) and makes ~4ft lightning. I dont want the base looking
huge, and I can't spend a whole bunch of money on 50ft of copper
tubing. Should I still go with a pancake type primary using the usual
copper tubing? or can I just get a pvc pipe wider then my secondary
and wind an insulated wire around it/ and theres no way I'm air
winding a copper tubing helical coil :P I dont know how people have
the patience for that! thanks for the help!
You can use either kind of primary as noted by others.
Pancake primaries tend to promote better electric field
distribution... it acts like a flat plate at the "other" end of the
secondary from the topload, but you could easily use some other
conductive surface for that.
I don't know that the losses in the primary are all that huge, using
1/4" copper pipe is more from a structural convenience standpoint..
Bare AWG12 probably works about as well, but isn't as pretty.
Bare coils are much easier to move the tap on than insulated.
You'll need to be careful about overcoupling with a helical primary.
Space winding a coil is easy.. find something that you can wind in
between turns, wind the spacer and your wire/tube as a pair, then
remove the spacer. Rope works, a second piece of tubing works. heck,
a long red vine candy would probably work.
YOu can also do a spaced helix by winding it close spaced on a form,
then "stretching the spring" to get the inter turn spacing as you want.
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