[Part 1 of this story was featured in Copper#90 ; Part 2, in Copper #91—Ed.]
All of the brass points/receptor cups were designed to have cored-out cups so they could be filled with a lead/elastomer matrix. Using a urethane matrix eliminated the possibility of the lead shrinking away from the brass cups as it cooled.
The bottom of all of the cups were fitted with ¼” diameter steel ball bearings bonded into recesses machined into the bottom of the cups; therefore, assuring a three-point contact.
Here we see epoxy resin being blended with #9 lead shot in a Hobart mixer just before being poured into the undersides of the main plinth and drive motor support bases.
This is the underside of the sub-base for the VPI double motor flywheel drives, ready to be filled with the epoxy/lead matrix.
This is the underside of the main turntable plinth, ready to be filled with the epoxy/lead matrix.
The next step in getting the Minus K properly set up to support the weight of the turntable is to bond ½” thick high durometer rubber to the center top plate on the Minus K unit. It is being bonded down with a polyurethane elastomer adhesive. This adhesive will remain flexible after it is fully cured.
Initially it was my thought to install a pair of air pressure gauges, one for each of the Kuzma Air Lines and a vacuum gauge for the Sota vacuum pump. After thinking about it, I thought the gauges really serve no purpose and look out of place, as it made the unit look too industrial, so I ended up removing them.
After applying a layer of polyurethane adhesive to the top of the rubber blocks on the Minus K, I lowered into place the aluminum plate that will accept the plinth for the turntable. This plate has become part of the Minus K isolator.
Immediately after applying the adhesive, the plate was lowered and accurately positioned squarely on top of the rubber pads on the Minus K isolator. The adhesive was then allowed to cure. I might add the following; the thin sheet metal box that came with the Minus K, protecting the inner workings from dust, debris, etc., has been replaced by a number of ½” thick aluminum plates that will not only serve the same purpose but be much more aesthetically pleasing.
[We will conclude this story in the next issue—Ed.]