Hi Dean --

Thanks for the report on flexures.  After trying a pivot point, I'm now
sold on flexures.

One thing that bothers me is the possibility of oil canning.  I don't think
it is likely for a flexure to be free from this at microscopic scales, when
operated near zero strain.  I haven't seen a treatise on this but have
noticed it in my experiments.  A possible solution may be to not let the
flexures go through zero strain, but I'm not sure.  A positive aspect is
that when operated in a seismometer with active feedback such as the VBB
system, the change in stress during operation is minimal.

Another potential source of hysteresis is the clamping at the ends of the
flexures.  If the clamping force applied and the friction aren't enough,
the outer fibers of the flexure will slip under the clamp.  This would
dictate that the clamping be done far enough away from the bending zone
that the stress in the flexure at the clamp will be low.  Adhesives would
be much simpler than mechanical clamps, but the potential for hysteresis
due to cold flow seems much greater.

I have been experimenting with full-hard 0.003" thick 304 stainless shim
stock for flexures.  I would like to etch the flexures out of the shim
stock, as this would reduce the stress imparted during cutting.

Do you have any comments about these two problems or my choice of material?

Best regards,

Karl Cunningham
La Mesa, CA.
PSN station #40
karlc@.......

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