Re: ATM Doormat cell?

["Bill T." <twentiethwave@hotmail.com>]

Try it out!  I could probably think of theoretical reasons so nay-say, quote 
disagreeing authorities, do discouraging calculations, cite negative 
precedents, etc. etc.  But it just might work.  Please let us know!  I've 
used similar materials (ok - BubbleWrap) for "temporary" mirror cells, and 
the darn stuff works perfectly well, even without good ventilation.  Cheap, 
quick, and/or dirty solutions to basic problems often work out, like for 
instance the Dobsonian telescope form factor.

Bill T.


>From: "Scott Berfield" <sberfield@xbox.com>

>Since I think I have a shot at actually finishing my mirror in this
>decade, my thoughts are turning again to the mirror cell. I have a full
>scale design for a 6 point cell all laid out and ready to go, but the
>more I think about it the more it seems like there should be a better
>answer than all that aluminum.
>
>I have searched the archives and found many references to using
>astro-turf type cells and these seem to be a very neat solution. The one
>complain I see anywhere is that the air flow around the mirror would be
>limited.
>
>I am currently polishing on a bed made from a Home Depot plastic "grass"
>doormat. This is covered in stiff plastic "blades" which are arranged in
>small circles. When polishing, even with considerable weight, the mirror
>does not shift appreciably on this mat. Like a bed of nails, the
>hundreds of support points add up to very even support.
>
>Since the mirror is held some distance off the substrate, and since the
>mat has regular perforations (app. 1/4" holes regularly spaced), it
>seems that airflow to the back of the mirror could be ensured by
>mounting the whole thing on a stiff perforated backing plate. A fan
>could be used to either blow or suck (not sure which would be better)
>air across from the sides or up through the middle. The mirror could be
>retained at the edge using clips or RTV. The whole thing would be light
>and cheap and very quick to construct.
>
>Are there flaws here I am missing?
>
>Scott



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