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

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

Hello Arjan

Yep. I agree. I just can't support not using edge supports. I can see
counterbalancing but I'm not even sure that is not just a marginal "illusion
solution".

Personally I have never thought of gluing in lieu of lateral edge supports
as being reasonable except in small thick mirror maybe 6" or smaller. But
now I'm sure that is an even worse idea than I had previously thought. 

I think with edge support gluing would be plausible and maybe with the
stictionless flex-bearing very good. But if just for keeping the mirror from
falling out of the cell gluing a few tethers would work just as well and not
have to alter the mechanics of the cell.

This has been a good thought exercise for me. I think I have a good cell
design for a 16"X1" blank I have.

Arjan... The 6 point cell optimized by plop.....  I can't help but notice
that if this is the optimum it is quite interesting that the fulcrums for
the cantilevers are located virtually perfectly at 50% radius.


Jerry


   

-----Original Message-----
From: Arjan te Marvelde 
Jerry,

Of course you can compensate the torque with counterweights, but does
anybody actually do this? Side support is probably easier to build, and
requires less space/weight.

AtM

----- Original Message ----- 
From: "Jerry" <wa4guu@verizon.net>
To: "'Arjan te Marvelde'" <arjan.te.marvelde@hetnet.nl>; <atm@atmlist.net>
Sent: Saturday, 23 April, 2005 4:52
Subject: RE: [ATM] Use of bearings in (static) mirror cells


Hello Arjan,


Referring to http://home.hetnet.nl/~artm/atm/articles/deformation.html

This raises several questions in my mind. I will ask the first as the others
dependent on my understanding of the answer.


Why assume that the cantilever as viewed in the vertical position (as in
Fig. 1B) is asymmetric in mass to the left and right of the fulcrum? Can't
we balance that so that it imparts no force to the glass that is a result of
its attitude from vertical all the way to horizontal?
Instead of shaping it like  ]  shape it like  I  .
If Balanced I do not see how it imparts any deformation to the mirror as a
result of tilt and the fulcrum being some distance from the glass.


Jerry



-----Original Message-----
From: Arjan te Marvelde

Hello Jerry,


These numbers can be compared with an analysis of deformation of a mirror
glued to its cell: http://home.hetnet.nl/~artm/atm/articles/deformation.html
As you will see, the force couple caused by glueing the mirror to the cell
is way more than this 3.6 gr caused by stiction:
120gr when pointing at horizon,
60gr when pointing at 60deg elevation,
0gr when pointing at zenith.






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