On Tue, 18 Jan 2000 20:32:29 EST ChrisAtUpw@....... writes: >In a message dated 13/01/00 09:23:33 GMT Standard Time, >twleiper@........ >writes: snip.... > >Dear Mr.Leiper, > > This all sounds great, but what is the price of granite >engineering slabs >and how do you go about boring holes in them? snip In my case the price was ten bucks many years ago at a scrap yard. It is two by three and 4" thick and already had the leveling mechanism. All my attachment points are with PC-7 epoxy, so no drilling was required. The idea was to preserve the geometry of the components to the most rediculous degree possible over long term temperature drifts (days/weeks). I had tried all manners of insulation, stratified heating elements, baffles, etc. with less than ideal success. In addition, there is a principle in amateur seismology that states that the more you make the instrument immune to the environment, the more it is immune to YOU. Trying to experiment with it, ie; uncovering, adjusting, restabilizing and analyzing, becomes more of a pain in the ass. Since my vault is highly stable, I decided to focus primarily on reducing drafts (relatively simple) and preserving geometric integrity over long period temperature swings through materials selection. I am experimenting with bimetallic boom and support elements and hope to be able to preserve the geometry (and adjustments) over a twenty degree differential. I'll post something if it leads to anything worthwhile. One thing I would suggest if you don't have a complete machine shop in the garage...Make everything out of sealed particle board and other composites. My brother has a very high end custom furniture manufacturing operation in San Diego, and his tolerances with this material are getting down to the thousanths, and it is extremely stable. Like the Dobsonian telescope mount compared to an elegant German Equatorial mount, it promises excellent performance at a price attainable to the masses. I think my next project will be a complete seismometer and recorder constructed entirely off materials available at Home Depot and Radio Shack, so that great silent majority of teaming millions who want to become amateur seismologists can realize their unfulfilled dream... _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>