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

["john sherman" <atm@mail.johnspics.com>]

Don,

>> The ball joint with a teflon cup is a pretty low stiction joint. 
>
>Flexures have zero stiction. 

How can that be possible? Please explain, as I want to build a perpetual-motion machine!

>The movement of a flexure is intermolecular 
>within the solid.

And those molecules usually want to stay in the place they are, not be forced into a new place. That friction causes a resistance to beginning a motion. Even a wet noodle resists being pushed around. 

>Stiction is where there is higher friction when 
>moving from a static state than when changing 
>velocity of a moving state.

Stiction is the resistance to the start of motion. I just got this from a quick Google search for definitions. None gave the definition you do. Maybe they are all wrong? Where did you get your def?


Arjan,

>The moment caused by the mirror weight hanging from 
>the cell, when pointing at lower altitudes, probably 
>causes more deformation than bearing stiction would do. 

Agreed. Have you ever heard of the Jello test?
http://astro.umsystem.edu/atm/ARCHIVES/NOV03/msg00197.html

Bye,

John







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