Hi Rick, Hay Jan-- call me kuz we need to talk. Rick, I designed my Lehman base because I wanted to use some scrap aluminum plate I got from a salvage yard that was kind of small. It needed to be bolted to something because the unit would not have worked if It wasn't. The mass would have just sat on the ground after the pipe uprights tipped forward. I settled on the 50/50 cement sand mix because that is what my dad taught me to use some years back for making castings. During the PSN meeting Robert Uhrhammer, of the Berkeley Seismological Lab mentioned that the Broadband network uses a 50/50 mix as Jan just posted earlier and they just sit their equipment on the slabs. He also said they sometimes just sit them on window glass to eliminate even more expansion. It turns out that a 50/50 mix has the best stability / expansion ratio due to the ratio of elements and density. He also said they never use any ag-rock in it. Of course I just knobbed my head in agreement as Bob explained all this and acted like I always new that... and told myself something about having dumb-luck. All in all, the design works real well for me. I was even able to put a second slab around the mounting cube and keep an air gap between them so I could stand next to the device and work on it without too much extra effort. Later, I also added 3-inch insulation to the sides and tops of the covers. I only checked them from time to time after that through a window in the top. About once a year the upper wire would rust and break and about every 2-3 months I would tweak the 4-40 screw to center the boom. By the way, I think I said this before, did I mention SPIDERS!!! Never just reach down into the darkness... One night I came up with the biggest blackest angriest fattest spider at the end of my elbow you ever saw. Regards, Steve Hammond PSN Aptos, California -----Original Message----- From: Rick BittoTo: PSN-L Mailing List Date: Tuesday, January 18, 2000 5:54 PM Subject: Re: Lehman base material? >I had thought of pouring a concrete base from scratch with threaded >inserts cast in place. I too was wondering what drawbacks this base >would have (other than weight). > >Rick > >_____________________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email listserver@.............. with the body of the >message: leave PSN-L _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>