PSN-L Email List Message

Subject: Re: Lehman construction
From: meredith lamb mlamb1@..........
Date: Wed, 12 Jan 2000 17:06:30 -0800

Hi all,

With specific reference to the pivot area, I would really recommend
the variety like used with a number of professional instruments like
the Sprengnether horizontals.  Probably the best I've ever seen is
John Lahr's home brew variation:

Here the above is a very good picture.  Another variation is also
shown on the same site:;
except the diagram doesn't match the picture, and it wouldn't
work as is.   John's complete web site related to amateur
seismology is:

Another picture site of the exact same pivot is also shown at:
Here the pivot is photographed with 3 additional views.

An additional mention should be made in regards to the connection
wires in the photographs.  As is they create a slight drag, on the
boom.  Copper wires looped to create a visual effect of a spring
like Sean-Thomas suggested some time back, will help alot here.
A lesser alternative, is to create a high looping copper wire
connection to lessen the drag.

The wire used is piano/music wire, available at a variety of
hobby shops.  Sorry, but the exact size escapes me at the

One could install terminals on the round pivot assembly for this
"spring" copper wire connection; between the mass and the

Take care,

Meredith Lamb


Public Seismic Network Mailing List (PSN-L)

[ Top ] [ Back ] [ Home Page ]

Larry Cochrane <cochrane@..............>