Regarding the length, there's a choice to be made. If you prefer (as I do) that the magnet and coil be mounted on the base, you need a long base like 36-40" or so. Lots of folks (including Lehman) just build a short base of 16" or so, let the boom hang over, and rest the coil on the floor. I like the longer base because you can get a finer adjustment of the level, also the relationship of the magnet and coil doensn't change when you adjust the leveling screws. There are enough things to fiddle with without worrying about that. (This is a case when one infinity is definitely larger than another, because both designs have an infinite number of ways to give you a headache). Regards, Ted Blank BOB BARNSon 12/30/99 01:04:46 PM Please respond to PSN-L Mailing List To: PSN-L Mailing List cc: Subject: Re: First time Lehman build Hi, I think that 1/2" or 3/4" thick aluminum base is gross overkill. My Lehman has a base 3/8" thick and is about 12" wide and 16" long. I think that this is plenty. Bob Barns Karl Cunningham wrote: > > Jim -- > > Just to add a note to what Ted said... > > As Ted said, the base should be pretty thick. One of the things about > Lehmans is the need to adjust the leveling of the base once in a while. > You will undoubtedly have leveling screws in the corners of the base > nearest the mass. It is extremely sensitive to even slight turning of the > leveling screws. The sturdier the base the easier leveling will be, and > the wider the base the finer the adjustment that can be made. > > You may think this is overkill, but I'd try to find at least 1/2" thick > aluminum, preferably 3/4" thick or more. And it should be at least 8 to > 10" wide. The wider the better. If you have room, make it 12" wide. > > As Ted suggested, check surplus metal outlets for the aluminum plate. If > you can't find a piece the right size, they might cut it for you for a few > dollars more. > > Good luck on your project. Be sure to post any questions you have to the > list, and let us know of your progress. > > Karl Cunningham > La Mesa, CA. > PSN Station #40 > karlc@....... > > At 10:37 PM 12/29/1999 -0500, you wrote: > >Gentlemen, > > > >My son and I are starting the process of building our first Lehman. I have > >visited numerous PSN web pages, and would like to thank everyone who has > >posted pictures and such relating to the construction. > > > >Would anyone out there care to supply me with just the basic dimensions of > >the frame, boom, and base. I will be using Larry Cochrane's electronics, > >and would just like to get a little help so that we can get this project off > >the ground. > > _____________________________________________________________________ > > 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) _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>