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:

http://lahr.org/john-jan/psn/pivot.jpg

Here the above is a very good picture.  Another variation is also
shown on the same site:  http://lahr.org/john-jan/psn/horizvt.html;
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:  http://lahr.org/john-jan/psn/gldn_psn.html

Another picture site of the exact same pivot is also shown at:
http://www.geocities.com/ResearchTriangle/Facility/1739/page22.html
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
moment.

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

Take care,

Meredith Lamb


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