It seems to me that there might be considerable friction losses in the
supporting points because of the weight that they bear-could this be a
factor?

-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@...............
On Behalf Of John or Jan Lahr
Sent: Monday, February 09, 2004 9:51 AM
To: psn-l@..............
Cc: bromberg@.........
Subject: Different pendulum design

I've built a prototype horizontal-pendulum seismic sensor using a design
that
Brady Romberg, a School of Mines student, came up with.  This still
needs
a lot of work, but I thought the mechanical design was quite
interesting.

I've posted a seismogram and some photos here:
http://jclahr.com/science/psn/romberg/

The weakness in this design is the vertical rod and it's attachment to
the
horizontal plate.  I think flexure in the rod and/or attachment is what
limits
the period to about 2 seconds.  Perhaps the mass needs to hang from a V-
shaped support rather than a single rod.

Cheers,
John

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