PSN-L Email List Message

Subject: Pivot paper
From: "Randy Pratt" rpratt@.............
Date: Thu, 23 Oct 2008 09:15:09 -0500

Hi All,

        It does. The axis tilts as the spheres roll sideways, or the 
> plane rolls on the sphere. If the mass is lower than the centre of the 
> rolling axis, this adds to the stability. If it is above this, it can 
> detract from the stability.

CRP - I argue that if the angle of the flat plates of the pivots are
parallel to the real axis of swing (based on the center of locus points
being found in our XLS pgms, then there is essentially no twist because then
the pivot is "rotating" about the center of the locus with essentially no
circular arc curvature error therefore there is no effective change of
length of the suspension or boom and therefore the bob is describing a
circular arc whose plane is set by the tilt of the vertical support and
thereby the period of the pendulum.

RP - Let's take a pendulum with axis north south.  Tilt the axis to make a
Lehman i.e. vertical axis and north south boom.  Rotate the axis 90 degrees
and you now have an east west pendulum.  I would have to agree with Chris.



Public Seismic Network Mailing List (PSN-L)

[ Top ] [ Back ] [ Home Page ]