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Re: 12" Secondary



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>



I make all my endplates of 3/4 inch plywood. Laminate top with Formica. Using a bandsaw or jigsaw, cut and tightly fit the plywood circular plate into the tube. Next, mark 8 evenly spaced points around the tube. 3/8 inch down drill into the tube and plywood with a #7 drill bit x 2.75 inches deep. Run in a 1/4 inch tap for 1/4-20 NC threads. Blow out the dust with an airgun. Continue around the tube until you have all 8 holes tapped and fitted with 1.5 inch long x 1/4-20 NC nylon fasteners. Endplates are flush with the ends of the Sonotube. Don't overtorque the tap or you will strip out the threads in the wood. I also squirt a bit of silicone into each hole just prior to inserting the fastener.

On the base end we use a 3/8-16 x 2.5 inch long brass threaded rod as the main feedthru. Attach the lower end of sec inside the tube and apply 3 separate coats of GE Silicone II allowing each coat to dry overnight --- gives a thick buildup. Then reinsert the endplate. Don't forget to install the interior anti-flashover baffles first!

Regards,

Dr. Resonance



2. If you happen to have the White Cap brand of 12" Sonotube(R), look for end closures that work beautifully: Cambro brand, #RFSCWC12, food-bucket lids. Made, it appears, from clear butyrate and available thru commercial restaurant-supply houses. They may also make them (cheaper) from that milky-colored plastic; I forget its name at the moment. Cambro has a Website; cambro.com but I'm not sure. If you want to do this & your "sonotube" won't fit, look for the White Cap brand at contractor-supply houses; it's cheap enough.

Those lids just snap right on--a perfect fit; you can hold them in place w/ beads of Si RTV. And first drill holes in their centers if you are to mount it on a lathe (see 4).

3. Here's what I did to provide space-winding if you should want to do that: First I wound on a tight layer of cotton twine of appropriate diameter; you could spray that w/ something convenient to hold it in place if you wanted. Then I wound on tightly a layer of 2'"-wide Teflon plumber's tape to "rigidize" the twine; but with varnish on the twine, perhaps that would not be necessary. Check McMaster-Carr for twine, tape & varnish.

4. Next wind on the wire using the spiral groove created by the twine to guide it. Tedious, of course--necessarily by hand and slowly, but if you make a perhaps-temporary motorized lathe as I did it would be a lot quicker.

5. Finally, apply the electrical varnish over the wire--mostly for the purpose, of course, of holding the wire in place.

And have fun: name of the game!

Ken Herrick
Oakland, CA

Tesla list wrote:
Original poster: Joe Smith <mailto:joesmith@xxxxxxxx><joesmith@xxxxxxxx>

Anyone know what the red liquid that is used in motor re-winding shops is called?
I'd like to know what to ask for when I go to my local motor shop.
I'm thinking this might be the way to go with my 12" cardboard tube(sonotube?)
Any comments welcome.
Regards
Joe Smith