Re: [ATM] Mirror cell ramblings re: thin plate glass3/4-inchx24-inch

["Bob May" <rmay@nethere.com>]

Perfectly logical and also fairly correct.  If somebody really
wants to go beserk with glass, they can get some single thickness
plate in a 24" diameter piece and slump that to whatever ROC they
want and polish it up.  Then they will need to make a many
multiple layer support for it so that the really light weight of
the glass will overcome the stiction of the joints and be
supported properly.  All this can be done but it would be a true
feat of silliness to do so unless you're going for the record of
lightness in a telescope.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: David Harbour <stainless_steel@suddenlink.net>
To: Bob May <rmay@nethere.com>; <atm@atmlist.net>
Sent: Wednesday, May 28, 2008 3:46 AM
Subject: Re: [ATM] Mirror cell ramblings re: thin plate
glass3/4-inchx24-inch


> Bob-
>
> It would seem logical, then, to reverse engineer this support
system from
> three hypothetical (intentionally placed, and correctly placed)
contact
> points, via rockers, pads, to 18 self-seeking floating points,
as per the
> old tradition, and then, why stop there? Couldn't a person add
to those
> points, with an ever increasing system of free
common-plane-finding
> additional rockers, and additional points of contact? You know-
like
> "Sometimes the way forward is the way back?"-
>
> R-101
> ----- Original Message -----
> From: "Bob May" <rmay@nethere.com>
> To: <atm@atmlist.net>
> Sent: Tuesday, May 27, 2008 8:29 PM
> Subject: Re: [ATM] Mirror cell ramblings re: thin plate
> glass3/4-inchx24-inch
>
>
> > Discrete support points are located at well known and stable
> > points of the surface.  They do poke the surface up a bit but
> > that is the reason why there is the error answer in the
program.
> > Put enough points in and you get a decently good surface.
> > With a continous support, you don't really know where the
actual
> > support really is.  You're dealing with nanoinches
(0.000000001")
> > and your machining efforts are only in the thenths of a
> > thhousandth of an inch (0.0001") which is a long distance
away.
> > As a result, you get by placing the glass on the aluminum
> > actually only 3 points that are rigid that are really holding
the
> > glass up.  Compare that against the seperate point support
with
> > compliant points that will all press approximately (within
the
> > abilities of the joints to equalize) the same amount on the
> > glass.  54 properly located points are a lot better than 3
random
> > points!
> > Now, why am I saying 3 random points?  This is because the
only
> > stable support on a surface is 3 points.  4 rigid points will
> > have 3 points on the ground and the 4th point up from there
> > somewhere.  One of the standard jokes I've seen on TV and
movies
> > is the guy trying to make a table not rock on a floor.  Next
> > thing you know, the table is 5" high and it still rocks!
> > Bob May
> >
> > rmay at nethere.com
> > http: slash /nav.to slash bobmay
> > http: slash /bobmay dot astronomy.net
> >
> > ----- Original Message -----
> > From: Ted Cohen <tcohen@blakeglobal.com>
> > To: <atm@atmlist.net>
> > Sent: Monday, May 26, 2008 7:19 PM
> > Subject: Re: [ATM] Mirror cell ramblings re: thin plate glass
> > 3/4-inchx24-inch
> >
> >
> >> I apologize if it seems that I don't appreciate the
excellent
> > advice on this
> >> list, since I really do appreciate the feedback I've
received.
> >>
> >> For those who feel strongly about using PLOP, I'd be
interested
> > to know from
> >> a design perspective, why discrete support points are
superior
> > to a
> >> continuous support system?
> >>
> >> _______________________________________________
> >> ATM mailing list http://www.atmlist.net/
> >>
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
>

_______________________________________________
ATM mailing list http://www.atmlist.net/