Re: copper tubing thickness?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

 > Not at all.  1/4" copper tubing is overkill for even a 12/60 although most
 > use it for high power NSTs (12/60 and 15/60) because its readily
available,
 > easy to use, and inexpensive.

1/4" nominal tubing (not refrigerator) is 3/8" od and is easy to work with..
1/4" OD tubing is quite small, and, having checked this afternoon at the
local hardware emporium, is actually more expensive. I think it's because
the wall is a lot thicker on the 1/4" OD tubing than on the 3/8" OD (1/4
nominal size) pipe. The 1/4 refrig tubing I saw was also a LOT softer than
the 1/4 soft copper pipe.

Actually, for a smallish coil, bare #8 solid copper wire is another
alternative.

Here's something else to consider, depending on how the primary is made.  If
you use real small wire (say, AWG 14, at around 0.07" diameter), the radius
of curvature of the wire is quite tight (0.035" in this case).. you could
start getting corona losses at around 3-4 kV.
Not so much turn to turn, because the gradient is less (only have a few kV
per turn), but at the outer or inner edge of the primary, where the voltage
relative to ground is high.


 >
 > I wouldn't go to 3/8" unless you are planning on using a small pole
 > transformer (3-5kva) in the near future.
 >
 > Also, make sure you make more turns than needed.  You'll always need some
 > room for tapping your primary when experimenting with different cap sizes,
 > different NSTs, and different
 > toroids.
 >
 > The Captain
 >
 >
 >
 >  > 1/4"OD is pretty small.. you might want to bump up to 3/8"..
 >  > Wall thickness is unimportant (thinner the better, because it's cheaper
 > and
 >  > lighter).. because the skin effect will push all the current to the
 > surface
 >  > anyway (why 3/8" might actually be better...)
 >  >
 >  > Be careful about "nominal sizes" vs actual sizes..
 >  >
 >  > "refrigeration tubing" is sold by actual OD
 >  >
 >  > Copper tubing (pipe) in various types (M, L, K, from thinnest to
thickest
 >  > wall.. M is what's used inside your house)) is sized more like iron
pipe
 >  > (but still different). There are two kinds, hard and soft, hard comes
in
 > 20
 >  > foot lengths, soft comes in coils..
 >  >
 >  > In L type, 1/4" tubing is .375" OD (3/8"), and .315" ID, 3/8" tubing is
 >  > actualy 0.5" OD, 0.430" ID, etc..
 >  >
 >  > ----- Original Message -----
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > To: <tesla-at-pupman-dot-com>
 >  > Sent: Saturday, March 01, 2003 10:00 AM
 >  > Subject: copper tubing thickness?
 >  >
 >  >
 >  >  > Original poster: "Dwight Harm by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>"
 >  > <dwighth-at-traxsoft-dot-com>
 >  >  >
 >  >  > I'm considering getting some 1/4" OD copper tubing, as that seems to
be
 >  > the
 >  >  > preferred primary coil material.  How significant is the tube
 > thickness?
 >  >  > This will likely be driven by a 12/30 NST for now, but I'd like it
to
 > be
 >  >  > able to handle something heavier (say 12/60) in the future.
 >  >  > Dwight.
 >  >  >
 >  >  >
 >  >
 >  >
 >  >
 >  >
 >  >
 >
 >