Re: [ATM] PLOP Calculations

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

Andy,

>
> I'm also thinking about using a heavy roller chain for the
> sling, with the refinement of adding short shafts every
> few links in the spaces between the chain links..each shaft
> end would carry a small bearing that contacts the mirror
> edge..the idea is that if there's differential expansion between the
> chain and the mirror, that the bearings would eliminate the stress.
>
> Also, each of the 27 cell support points could be a small
> bearing alined so the axle is perpendicular to the radius
> of the mirror at that point..thus allowing the supports to expand
> or contract relative to the glass without adding stress.
>
> What U guys think about this??

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.

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.

Nils Olof


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