At the new planetarium at Cal State in Fresno they have incorporated a sundial into the design of the building. I haven't seen it but I understand that there is some sort of aperture (a window, I presume) which will be joined, in time, by some kind of markings on the floor. The deisgn for the floor is all worked out but the best method to mark the floor is yet to be determined. Hopefully some of you with experience in this kind of thing will want to help them decide how to proceed.
Brandt Kehoe ([EMAIL PROTECTED]) is, i think, the designer of the dial and the person in charge of building it. He's on vacation until late July. He writes; > I would be glad for any and all advice on this.The floor is made > of granite tiles roughly 12" square. The granite is black > with a matte finish to reduce slipping. Originally our plan was to put in > a terazzo floor with the sundial pattern in the brass strips. That turned > out to be more expensive than we could afford so we went ahead with the > granite, figuring that we would work out how to do the pattern later. > > At that stage the architect decided the pattern was post construction and > not of interest to him so I have been working on ideas. > > Apparently there are a variety of ways of cutting patterns in granite - > sand blasting, high pressure water, routing, and possibly even lasers. > Most of these, however, are developed for use in a shop rather than at a > work site. > > There is a lot I don't know about these possibilities in this setting. > What any version of the pattern I can think of needs is grooves cut in the > granite to then be filled by whatever we use to make the pattern - paint, > brass, bronze powder in epoxy, or whatever. > > The curves in the pattern total about 450' in length. Whatever method is > used, thats a lot of pattern. My preference, based upon lots of ignorance, > is for a groove 1/8" wide and approximately 1/16" deep into which is > epoxied a brass strip. The brass is available for a reasonable price. > There would probably have to be thin gaps in the brass to allow for > differential expansion although the thermal contact of the brass and the > granite with the concrete slab and the ground suggest very limited > temperature changes, even should the A/C fail in a Fresno summer. > > The brass could be polished flush with the same grade of polishing compound > used to produce the matte on the tiles. One advantage of the brass over > paint or epoxy fill is that it would extend through the grouting. My > though for the grooves is to use a router with a diamond bit and make > plywood templates for the pattern. That preference is no doubt based on > the fact that I think I understand routers but don't really have a clue > about the other grooving techniques. One problem with the router, possibly > with other methods as well, is chipping in the granite which is, of course, > not of homogenious makeup. That would require some trials to see whether > it is a real problem. Tiny chipping should not be a problem if we use > black epoxy to hold the brass. > > Again, any advice or experience with such matters would be much appreciated. >
