PSN-L Email List Message

Subject: Re: Lehman construction
From: "Frank Cooper" fxc@.......
Date: Mon, 10 Jan 2000 19:49:33 -0600

Hi Jim,
You might try John Cole's ball bearing method.  Look at his web site at
or mine at   I  increased the period of my
seismic pendulum from 12 to 16 seconds quite easily by using his method.
Frank Cooper, Friendswood, Texas

-----Original Message-----
To: PSN-L@.............. 
Date: Monday, January 10, 2000 7:03 PM
Subject: Lehman construction

>Well, things seem to be going along quite nicely,  but I think I've hit a
>roadblock.  I can now setup the boom for a very repeatable 11sec period,
>but I just can't seem to coax anymore out of it.  I've tried tilting the
>base with the front screw and bringing the rear boom pivot point closer to
>the vertical plane of the wire pivot.  Just doesn't seem to want to slow
>down any more than about 11sec.
>I am using a 1/2" dia.  threaded brass boom,  with a sharpened point on the
>pivot end.  This point is pivoting in a VERY small dimple at the end of a
>3/8" bolt.  I even tried applying a small amount of lube to the pointed
>pivot,  in an attempt to reduce any friction.
>Any suggestions?
>Jim Martin
>Public Seismic Network Mailing List (PSN-L)
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Larry Cochrane <cochrane@..............>