My yokes came without the plastic centerpieces, and indeed they seem to be getting hard to find. I saw a Taylorcraft yoke, with centerpiece, on eBay and bought it thinking I could make a copy of the centerpiece. But when it arrived I saw the plastic was warped and deformed. So I was faced with making a mold from scratch.
I started with a 3inch styrofoam ball like is used by hobbyists to make Christmas ornaments. I cut the foam ball in half (Photo 2) on the band saw, sanded the radius slightly flatter on top, and then epoxyed it onto a plywood board. I cut three sections of broom handle and epoxyed them to the plywood in the position of the yoke spokes. Photo 3 shows the resulting plug.
After giving the plug 3 coats of wax, I covered it with fiberglass to produce the mold. (Photo 4) I wanted threaded inserts in the finished part so I made a core for the mold as shown in Photo 5. The core is a piece of 1/4 plywood cut to fit into the spoke cutouts in the mold. Three 8-32 screws hold 3 nuts in the correct position in the mold.
The layup procedure is to wet out two layers of glass in the mold, then pour 1/4 inch of resin with finely chopped glass in the bottom of the mold. Next the core is inserted. After the resin sets, the 8-32 screws are unscrewed leaving the nuts trapped in the 1/4 inch resin-glass layer.
The parts are removed from the mold, sanded and painted. The backing pieces receive no nut inserts but are drilled instead. Use the mold core as a drilling template. Photo 6
You can trim the edges of the centerpieces with a strip of vinyl electrical tape, then screw them in place on the yokes. Photo 7
The little aluminum inserts are made by clamping aluminum disks between two steel washers Photo 8, and then hammering the edge down around the washer. Photo 9 Then the insert (with its decal!) is epoxyed in place on the centerpiece. Photo 10
Link to Yoke Bearings, Decals, Fiberglass Molds
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