Re: ATM 'Frozen' liquid mirrors

["Ken Carter" <kencar@worldnet.att.net>]

Bob,
  My tests on flats have showed a nice flat surface that you can see
yourself in with out difficulty. No ripples.  This is still a work in
process, but it is working better than I expected to this point.  The tests
so far have been fairly thin, I will be going thicker in the next phase.
Ken...

I don't mind being wrong, so long as I can learn.
Visit my home Page: http://kencar.simplenet.com



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> From: Robert  C. Pfaff <PFAFF2@delphi.com>
> To: atm@shore.net
> Subject: Re: ATM 'Frozen' liquid mirrors
> Date: Friday, February 21, 1997 10:42 PM
> 
> >Hello Peter,
> >It may be, that the rotor in your motor is unbalenced.  Balenced
electrical
> >motors are an unnecessary expense, in potters wheels.  If you balence
it,
> >retrofit with silicon nitride bearings, true and align the pulleys, you
> >should be better off.  Otherwise, I need a potters wheel  <smile>
> >
> >-Andy
> >
> >
> ><snip>
> >
> >I rewired the speed controller in
> >>the foot paddle and replaced the variable resistor with a fixed
> >>one to keep the speed constant.  Still had problems
> >>with vibrations despite putting everything in a sandbox as my
> >>laser holography friends suggested.  I am not sure whether the
> >>problem is due to inadequate damping from the ground or a worn
> >>bearing in the motor drive. Probably both. 
> >
> ><snip>
> >
> 
> As this seems to be a thread that will not die I have some questions.
> People on this thread seem to think that if a vibration free table
> can be made then a precison optical surface can be had.
> 
> The people making those large spin cast mirror have ripples on the glass
> not because of bearing vibration but because the surface of the glass
> cools uneven and surface tension. Now it would seem to me if epoxy
> is free from these problems a person could  just pour some epoxy
> in a dish and have a nice optical flat. Mercury makes great flats.
> Now you could can use a congrete substrate if you wish. If this worked
then
> I would think that there is some merit in doing this project. 
> 
> This is not a flame but just how an old dog looks at things.
> 
> Bob Pfaff
> 
> 
> 
>