Re: [ATM] ?Glued Mirror Cell

["Jan and Rod Shea" <jnrshea@comcast.net>]

Thomas,

Thanks for the info.  I would love to see pictures if it is not too much 
trouble.  It is good to know someone has made a cell like the one I want to 
do.  Do I understand that you made the collimation bolt - bar pivot point by 
basically countersinking the mirror side of the hole through the bar, and 
RTV'ing the ? flathead machine screw into the hole by gluing the screwhead 
into the countersink?  In effect, you are hanging the bar from the 
screwhead?  Seems like you could back it up by putting a locknut on the 
underside of the bar spaced a little way back, and glued to the bar as well.

Thanks,

Rod


----- Original Message ----- 
From: "Thomas A Simmons" <tasimmons@raytheon.com>
To: <atm@atmlist.net>
Sent: Monday, September 13, 2004 1:29 PM
Subject: [ATM] ?Glued Mirror Cell


>
>
>
>
> Hey Jan and Rod,
>
>  FWIW, I have a full thickness 12.5 inch mirror done up much as you
> propose. It's bounced down dirt roads and such without coming out...yet.
> So yes, it will work, and yes, you HAVE to be a genious (smile).
>
>  What I did different than your proposal was to drill and countersink from
> the backside of the bars, and then RTVd the screw to the bar. To tell you
> the
> truth, I'm not sure it was necessary. With proper prep of the mating
> surfaces
> and no gap save for a thin film of RTV, it just might work.
>
>  Oh, one thing I did do wrong. With a forstner bit I drilled out a 1 by
> 1/8 inch
> depression in the bar for the RTV to fill, which gave a roughly 1/4 inch
> pad (total)
> the thick pad allowed for the mirror to shift and therefore lose
> collimation as
> the tube rotated horizontal to verticle-
>
>  If no-one gives you pictures, write me off line and I'll snap a
> couple-it'll also
> motivate me to get into the miror box for "just one more improvement on
> that dang scope"
>
> Date: Sun, 12 Sep 2004 16:15:20 -0700
> From: "Jan and Rod Shea" <jnrshea@comcast.net>
> Subject: [ATM] ?Glued Mirror Cell
> To: <atm@atmlist.net>
> Message-ID: <001901c4991e$62048af0$6401a8c0@NOTHALDESKTOP>
> Content-Type: text/plain;            charset="Windows-1252"
>
> I am designing what I hope to be a very portable lightweight 12.5" dob,
> likely made from aluminum.  I'm willing to bite the bullet and glue the
> mirror to the cell, and make a compliant hinge cell using RTV.  I am
> thinking about a six point cell, PLOP derived, either Richard Schwartz
> right angle style or conventional.  Would simply RTV'ing bars to the tops
> of collimation bolts work, as long as the tops don't rotate when
> collimated, and I used very wide topped bolts (? ~ 1") or machine screws?
> Alternatively, some type of bearing could connect the glue pad and the
> collimation bolt, but that kinda defeats the purpose...  Seems like the
> glue should be GE type 840, about 1" in diameter, and 1/8" thick.  Has
> anyone made a cell like this?  Can someone point me to pictures?
>
> Thanks,
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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