Ted,

One comment on that paper, not related to the design you were 
discussing:  It also describes  the 'Balance-like physical pendulum' and 
the 'Off-center or Nearly balanced physical pendulum'.  Both these designs 
can have almost zero restoring force and hence very long periods.  However 
they also have almost zero sensitivity to linear acceleration forces and 
are therefore pretty much useless for sensing ground motion.  That 
limitation wasn't made very clear in the paper.

Though I guess in that respect they do act a bit like using feedback, in 
that you trade reduced sensitivity for an extended lower corner 
frequency.  However, they would exhibit none of the response-flattening 
that you would see when using feedback.

Regards,

Brett


At 08:06 AM 9/20/2008 -0600, you wrote:
>Hi Folks,  This is one approach I have not 
>tried. 
>http://www.phy.mtu.edu/~suits/PH3110/pendulums.html
>Has anyone built one, as a mock up to see the results?
>If someone would suggest some dimensions, I would like to try it, to see 
>how it would work and the period possible.
>Ted


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