RE: [ATM] Use of bearings in (static) mirror cells

[Dale Eason <atmpob@yahoo.com>]

Take a look at my web page and look at my mirror cell.
http://home.comcast.net/~doeason/16inchscope.html
You really can't see how I hinged the two supports
that provide colimation, but they are flex hinges. 
Two piceses of brass shim stock crossed in an X when
viewed edge on.  Don Clement should be proud.  Also
follow the link on my page to Nils Olaf Carlin's
description of his mirror cell.  Mine is derived from
his.  He does not use flex hinges but at least you can
see where my hinges might be.

If anyone is interested let me know and I will try to
get better pictures.  The hinge design was taken from
plans I found on the net for a seismograph pendulum.

Dale Eason

--- Jerry <wa4guu@verizon.net> wrote:
> 	There is the stiction fiction faction and the
> stiction friction
> revision faction. This thread has been on a slippery
> slope and has slid out
> of control.
>  
> 	To this non-enginier it seems that Don Clement is
> right on with the
> flex bearings. Then you can forget having slipping
> and sliding at the
> contact points with the glass and bearings in the
> supports. Fix those points
> on the glass and let the flex adjust for
> differential expansion of glass and
> support. Let the flex handle what should be almost
> microscopic movements of
> the mirror laterally in the cell.
> 
> 	I don't know much about Alcoa numbers and fluid
> dynamics is what
> happens when I drink beer, but I don't think it
> takes an enginier to have an
> idea of what stiction is at least to the point of
> how it affects mirror cell
> design. There is a threshold of force that must be
> reached to break whatever
> bond there is at the interface of objects in contact
> that resists relative
> motion along the interface. When that force is
> reached there is a slippage.
> If there is a force but it has not reached the
> threshold there may be
> deformation. In a telescope the deformed body may be
> the optic.
> 
> 	I have noticed Don's zeal urging consideration of
> the compliant
> hinges and/or flex bearings for various telescope
> parts. This discussion has
> been helpful for me to understand his zeal. I'd bet
> his would be a very good
> mirror cell. I'm surprised there is so much
> resistance to his suggestions.
> But then I am not an enginier.
> 
> 	Even though somewhat argumentative this has been a
> good thread for
> me. I've learned a bit. In the beginning I couldn't
> even spell enginier.
> 
> Jerry .....Slip sliding away.
> 
> 
> 
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> 

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