RTV Considered Harmful (was [ATM] Re: Second ThoughtsonMirrorSupport)

[stuart452 at earthlink.net (Stuart Hutchins)]

James,

That is really interesting.  You also have an unusually thin mirror, so it
is a challenge.  For a simple rectangular beam, the stiffness scales as the
thickness cubed.
Regarding the "sling thing" Nils Olof Carlin was able to trick Plop into
modeling slings that induce out-of-plane forces.  See

http://w1.411.telia.com/~u41105032/sling/sling.htm

Stuart


----- Original Message -----
From: "James Lerch" <jlerch1@tampabay.rr.com>
To: "ATM" <atm@atmlist.net>
Sent: Monday, February 09, 2004 9:11 PM

> I'll quickly elaborate on the method used to evaluate the "Failed so
miserable"
> statement.  With the optic, whiffle tree, and wood cell propped up on our
test
> stand (supported only by the wood ring), Interferometry was impossible at
best.
> The gross amount of error present on the surface (irregardless of
orientation)
> made creating a reasonable fringe image nearly impractical.  In an attempt
to
> reduce this fringe data, it looked like nearly 19 waves of primary
astigmatism,
> mixed in with many other odd errors.  Rotation of the unit (Optic, Cell,
> Support) didn't change the orientation of the astigmatism.  However due to
the
> nature of the incredibly poor fringe images to work with, quantitive
analysis
> was impractical and skeptical at best.
>
>
> The sling we used contacted the edge of the mirror at 3 or more points.
Classic
> kinematics tells us that 3 points define a plane.  If the plane defined by
the
> sling, isn't coplanar (or at least parallel) to the plane established by
the
> whiffle tree support, Really interesting things happen!!!!  (like induces
> astigmatism, twisting of the optic, and jus hard to describe stuff!  (BTW,
we
> did all this testing with the interferometer at about 10 degrees
elevation)