RE: [ATM] RTV question

["MATTHEW SIMMONS" <msimmonsmcse@msn.com>]

I guess I would say I am using the "all six points in the 70% zone" design. 
Im really not that good with PLOP. I just did the auto-design feature and 
went with it. Looking at it, I guess you could say its more of a hexagon 
configuration.

As to the springs, the are not there to support the mirror. My current 
configuration is as follows:

Steel bar with 3/8" hole in middle
3/8 Stainless machine bolt through hole
Side of bar opposite mirror has nylon washer, then spring, then another 
washer.
Bolt goes through hole in 1" thick Y frame
Then another washer and a clamping knob

To collimate the scope, just turn the 3 knobs, the springs keep everything 
in tension, so the tilt of the mirror is very responsive to a slight turn of 
the knob.



Matt Simmons





>From: "Richard Schwartz" <richas@earthlink.net>
>Reply-To: richas@earthlink.net
>To: "MATTHEW SIMMONS" <msimmonsmcse@msn.com>
>Subject: RE: [ATM] RTV question
>Date: Mon, 14 Jun 2004 09:00:48 -0700
>
>I guess I was the guy who started all this silicone noise.   The orthodox
>believers totally reject it because it does not appear in any of their
>books.   Please keep this note private.
>
> > 13.1" f4.5 Plate glass mirror, 1.5" thick (Discovery)
> > 6-point PLOP designed cell
>
>You did not specify WHICH 6 point cell you are using.    One version has a
>point in the center and five points at about the 80% zone.  The other has
>all six points at about the 70% zone.     You might look into a SEVEN point
>flotation.  It is a hexagon pattern with a center point.   Of course, if
>you have a cassagrain, this is not possible!
>
> > 3 3/16" steel bars
> > 6 1" x .25" thick RTV pads
>
>This sounds OK, but I would make the pads a bit thinner, more like 3mm
>thick.   I would make the bars of aluminum to minimize weight, corrosion,
>and the work of cutting them.  Keep in mind that the three bars for the
>pentagonal configuration are not all the same length.   With slightly more
>mirror deformation, you get the convenience of a right triangle on the back
>of your mirror cell-- this makes adjustment MUCH easier.
>
> > Each bar is attached to the cell and loaded with springs. The cell is
> > constructed of 1" steel square tubing, made in a 'Y' design (like the
> > original Discovery cell)
>
>That sucks.   Why do you need springs?    Why not use silicone pads?   They
>are easy to assemble in a stress-free condition.  And why use steel, when
>silicone adheres so well to varnished plywood?   If you go with the Y
>design and the pentagonal cell, keep in mind that your Y will not be
>symmetric.   After a star party in Lodi, California, where we were dewed
>out, I decided that steel is not a good material for telescope making.
>
> > Will this create too much distortion in the mirror?
> > Should I go with 1/4" aluminium triangles in a 9 point system?
>
>I do not like the 9 point system because the triangles are very long and
>narrow.   1/4" triangles are gross overkill.    Don't worry about
>distortion on your mirror; if the levers of your flotation are free to
>move, the flotation will isolate warp of the mirror cell back from the
>mirror (because three points of contact can't transmit warp).    The best
>flexible joints are silicone pads, and they work between the load spreaders
>as well as between the glass and the support points.
>
> > Is it too late and I am just being paranoid???
>
>It is definitely too late.   I already had to call  an atheist organization
>in Hoe-Town. (Center for Inquiry).    The phone number had "666" in it.
>(They are putting on a "magic" show Friday, and will be debunking
>fraudulent psychics.)
>
>. . . Richard
>
>


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