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

["Jerry" <wa4guu@verizon.net>]

	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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