Disc Construction

To: tesla-at-pupman-dot-com
Subject: Disc Construction
From: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Tue, 27 Apr 1999 18:33:08 -0600
Approved: twf-at-verinet-dot-com
Hello All,


As you know, I am presently constructing my SRSG. I have run
into a major problem: the disc material. The thickest G-10
(which I would like to use) I can find is only 1.5mm (0.059")
thick (being circuit board material). What I was thinking of doing
is taking 3 of these sheets for a total of 4.5mm (0.177"). As I
have a lathe, trueing the disc (sheets are square) is not a big
problem. Will this work and should I:

a.) just bolt them together? I will be using 4 or 8 electrodes
     (depending on the answer I get to my other post) and the
     disc will be bolted to a hub made from solid 306 stainless
     (which is a real pain in the butt to machine) via 8 more
     screws. This means I have sixteen screws (in two circles)
     total holding the 3 G-10 sheets together.

Or should I:

b.) Slightly rough up the inner surfaces and epoxy the three
     sheets together? The problem is I don愒 have a laminating
     press, so all I can do is pressure clamp them (while drying)
     between two pieces of thick sheet metal with normal C-clamps
     and two pressure bars. I can get the epoxy on pretty evenly,
     but I can愒 guarantee a 100% parallel surface (due to slight,
     but entirely possible, variations in the glue thickness. I would
     hate to have to true the front and rear of the disc.

c.) As these G-10 sheets are copper coated (35痠), could I
     etch a circle on the innermost and outermost surface
     (first and third sheet) to connect my tip holders? I will be
     using 5mm (3/16") thoriated tungsten tips and be mounting
     them in brass screws. I could cover the copper with solder
     to increase the effective thickness.

d.) Are the 3/16" TTRs (thoriated tungsten rods) large enough
     for 6kVA input power? I think so. If I use 4 rods, each rod
     would have to handle 1.5kVA (which is a lot less than they
     are rated for in TIG welding, esp. the thoriated ones) and
     with 8 electrodes, each would only have to handle 750VA,
     which has got to be underrated. The 5mm is a sort of
     compromise between VA handling and dwell time (motor is
     a 1500 rpm modified unit), although I think even the 4
     electrodes should be able to handle 8-10kVA easy enough.
     Oh, before I forget the disc will be 20 cm (~8") in diameter.

Coiler greets from germany,
Reinhard