An adjustable multi-gap (another abbreviation)

• To: tesla-at-pupman-dot-com
• Subject: An adjustable multi-gap (another abbreviation)
• From: Parpp807-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Thu, 23 Mar 2000 16:16:45 -0700
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi all,

This adjustable multi-gap (AMG) may be old stuff to experienced coilers.  

I had one 4 x 12 piece of G-10 leftover from building Scot's gap. This AMG is 
a variation using as many copper sweat couplings of whatever size that will 
fit your needs for power handling. I used five- 3/4 inch couplings which I 
placed in a vise to compress them just slightly into an oval shape. Wrap the 
couplings in a towel, or dado out two pieces of wood to hold the copper so 
the jaws don't put marks into the copper. Drill holes in the G-10 along a 
12-inch center line for 8-32 brass machine screws. With the screwhead under 
the slab, tighten a nut onto the screw. The screws should be long enuff to 
hold the copper
couplings at least an inch above the slab + the length of the coupling + 1/2 
inch. 
I used 3.5 inch screws. This is important to keep the heat load off of the 
base.  Drill the holes maybe 1/8 inch farther apart than the original 
diameter of the copper coupling.  The G-10 is not a must. Lexan or any other 
good dielectric can be used. You need 2 metal cleat washers for each copper 
coupling. You can buy them in a good hardware store. I cut them out of brass 
sheet so that each cleat is 3/8 wide and just a little longer than the long 
axis of the copper oval. Drill a hole in the center of each cleat to pass the 
8-32 screw. The bottom cleat is the shelf and the top cleat is the hold down. 
Put one 8-32 nut on each screw so the nut is
one inch above the slab. Put one cleat on top of each nut. Slip the copper 
coupling 
over the screw so it rests on the cleat, put a hold down cleat on top of the 
copper, and tighten the whole 
thing with a top nut. The entire AMG can be fine adjusted by setting the nuts 
and cleats.
The gap is easily set by rotating the oval couplings. I drilled and tapped 
some Lucite
rod for insulated mounting feet at the four corners.

This AMG is easy to build and inexpensive. The parts are not critical; many 
variations 
are possible.

Disclaimer: AMG is an abbreviation, it is not an acronym.   :-))

Happy day,
Ralph Zekelman       

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