Re: [ATM] PLOP Calculations

[Andy Saulietis <iss@pvtnetworks.net>]

Nils Olof writes,


>I get the impression you plan to eliminate friction forces in the tangential
>direction - I'm not sure but I believe those forces are pretty innocuous.
>What I am sure isn't as innocuous by far is forces in the axial (parallel to
>the optical axis, pulling part of the edge forward-backward:
>http://w1.411.telia.com/~u41105032/sling/sling.htm
>So I believe the bearings at the edge should roll in the direction
>towards/away from the mirror front.

I thought the sling has to be in the plane of the CG of
the mirror perpendicular to to optical axis..allowing the
sling to move in that direction (along OA) would
not be desirable?


>Perhaps a (moderately but sufficiently heavy) sling of steel wire (easier
>than a chain), strung with small ball bearings at suitable distances (with
>spacers in between) would do the trick - suspended to touch the mirror at
>the level of its COG.

I used a 5/16" plastic coated steel cable for the sling on the
36"f5.2 2" thick currently nearing completion..showed little
if any astigmatism. Another thought is to use small Teflon
disks strung thru the cable, maybe with a thin plastic band
around the edge to reduce the friction with a ground pyrex surface.
Something like this for the primary rear support points might be
easier than the radial bearings.





Andy Saulietis
ISS Enterprises
10 Milky Way
Mayhill NM 88339


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