Hi gang,
  Here is some info (via Google) about hinges.

  For the rolamite hinge:
http://www.rexresearch.com/wilkes/1wilkes.htm

  See Fig. 4 for a rolling hinge in:
http://www-civ.eng.cam.ac.uk/dsl/TSR_hinge.pdf

  A good discussion from our own archives:
http://www.seismicnet.com/psnlist/990909_123918_1.html

  For pics of the Geotech 220 (up to 30 sec. period, 8" boom length,
boom mounted with crossed flexures.)  I got this via ebay, where else?
http://mywebpages.comcast.net/ROYB1/  (my web site)
  I have not yet put this in service--still using my big, old, ugly
home-made Lehman.
Bob
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