From: Fredmoreno@aol.com
Message-ID: <fbc5ae90.36bb2cec@aol.com>
Date: Fri, 5 Feb 1999 12:39:56 EST
To: lancair.list@olsusa.com
Subject: Crushed Tungsten source
Mime-Version: 1.0

          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
          <<  Lancair Builders' Mail List  >>
          <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> 
>>
	Several years ago I ordered 25 pounds from:

Hi-Temp Specialty Metals, Inc.
Industrial Park
P.O. Box 2188
Willingboro, NJ  08046

Sorry, couldn't find the phone number. Another source I used when I needed
more:

Exotech, Inc.
2077 N. Powerline Road
Pompano Beach, FL 33069
305-960-1770, Mike Gussack.


 The material is apparently a waste product from tungsten carbide manufacture.
My cost was about $3.00 per pound.  Ask for the fine grade which is like beach
sand or a bit coarser.  The density of the "sand" (including voidage) is about
equivalent to lead when you add epoxy to fill in the open space, or about 20
times denser than dry pine which I used to make master forms for aileron
weights.  I recall about 0.4 pounds per cubic inch, but make a sample and
check before going forward.  I made pine forms, weighted them, calculated the
equivalent weight in tungsten epoxy, and then cut the pine down t size until I
got what I needed.  

	I mixed up a batch of epoxy, then stirred in the tungsten (you need a tough
stick or an old stainless spoon) until it looked like wet, slightly runny
sand, and then formed it into plaster of Paris molds derived from wood that I
shaped to fit the spaces I wanted to fill.  For ailerons, these end up being
long tapered sections with triangular cross sections. 
	Once hardened you break the shapes out of the mold, clean up, then bond in
place and cover with 1-2 BID.  You can sand the tungsten/epoxy shapes on the
belt sander to get rid of rough spots, but what you are doing is ripping out
tungsten grains from the matrix, and your sanding belt will get smooth in a
hurry.  When you cast your shapes, be sure you get very near to the final
shape because that's the way it's going to be.
	I used a different approach for the elevator counterweights.  After I
finished and primed the elevators, I cut a hole on the inside surface of the
counterweight horn about 4 inches back from the leading edge, and then spooned
in the gooey mix of epoxy and tungsten (preweighed), and left the elevator
nose down until the stuff hardened.  Then I patched the hole. Easy, painless,
and a lot easier than fussing with lead shapes.  I also think the excellent
fit (self forming) in the counterweight area provides a slight weight
reduction because you are getting maximum density all the way to the front. 

Hope this helps, 

Fred Moreno