Woodworker's Journal 1982-6-6, страница 30
Geodesic Lighting Fixture This intricate network of connectors and chords is fascinating to look at and equally fascinating to build. The completed sphere is quite rigid, yet light in weight, and lends itself admirably to a hanging fixture, with or without an enclosed lamp. We made ours of mahogany, but most clear cabinet woods can be used including pine. Begin by making the hexagonal connectors (part A). Using glued up or solid stock, cut a workpiece of IVi" x 2" x 32 . Set your tablesaw blade at 30 degrees. Don't depend on the machine tilt scale but instead use a drafting triangle or a carefully cut cardboard or plywood gauge to set the blade. Use a flat (not hollow-ground) saw blade that cuts a kerf close to Vs" in width. With a 2" wide side of the stock riding on the table as a base, cut both corners off leaving at least V»" at the base. Use a push stick to feed the workpiece and another notched stick to hold it down and against the fence. Flip the stock over onto the other 2" side and repeat. Trim both left-hand side cuts (or right side cuts) until all sides of the hexagon are an equal V»' in width. With tne blade still set at 30 degrees, rip a beveled strip off a straight piece of scrap and tack this to an auxiliary fence as shown. Use the regular fence to rip a slight bevel off the corner of the strip as shown in the sectional views. Attach the auxiliary fence to the regular fence with screws and lower the saw blade (still set at 30 degrees), to cut a 3/16" deep groove along each corner of the hex stock. The fence must oe carefully set so that the grooves will be centered exactly on the hex corners for the full length of the workpiece. After grooving, set the blade at 0 degrees and use the miter gauge to crosscut the hex stock, like a loaf of bread, into 30 pieces, each V*" thick. When crosscutting, do not trap the pieces between the fence and the blade. Set a stop block against the fence, well ahead of the blade and ride off this. After cutting 30 pieces, you should have about 6" of waste left. Less than this would be unsafe to hold. The pentagonal connectors (part B) are next. Cut a work-piece to IVi x lVs" x 18". Again, use a prepared gauge to accurately set your tablesaw blade to 18 degrees. With a IVi" side as a base, cut off two base corners leaving a base width of V»". Tilt the workpiece counter-clockwise so that one newly formed side is a base. Adjust the fence for the next cut to make the base Vt" wide. Using the same fence setting, rotate the piece counter-clockwise and make your last cut to form the pentagon. Pull the 30 degree beveled strip off the auxiliary fence and replace it with one beveled at 18 degrees. This strip must also be slightly trimmed to clear the sawblade. Tift the sawblade to 36 degrees (this is not critical) and run grooves centered along the five corners of the stock, then set the blade at 0 degrees and crosscut 12 slices, each V*" thick. From V*" stock, rip strips just thick enough to fit snugly in the grooves after sanding. You will need 60 pieces cut to a full Ie_ngth of 43/s", mitered at each end at 18 degrees (part C), and 60 pieces cut to a full length of 3 Vt", also with ends mitered at 18 degrees (part D). Use a stop block on the fence to prevent binding tne pieces when the ends are mitered and make test cuts witn scrap to set the fence for the proper length of each part. To assemble the sphere, mark a 16V4" dia. circle on a flat surface and with the hex connectors (A) and 10 long chords (C), form a circle on top of this template (photo 2). Only a small dot of glue such as TiteBond is nee ded in the slots. When the circle is complete, take one hex connector and two C chords and form a triangle using two of the hexes on the base circle. Continue until five triangles are built off the base (photo 3). Using two hexes and three long chords, form an arc and connect two of the base triangles with this arc. Once added, you will see two connections to be completed between the last two hexes added (marked A in photo 4) and the top of one of the triangles on the base circle. Making these two connections, you will then see voids in the sphere that are pentagonal. These will be filled later. Continue with your long chords and hexes until all have been attached, then turn the dome over on a suitable support (I used an old towel in a doughnut shape). Build a mirror image dome on this side of the base circle, but rotate it one hex connector. In order to insert the globe and change burned-out bulbs, one hex connector at the bottom of the sphere should have its five chords glued to it but not glued to the surrounding connectors. To pull the joints together, use a tourniquet -X- rr
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