[ATM] If it's in a supremely stiff cell, that does not twist,why would a thin mirror sag?

[artbianconi at blast.net (artbianconi@blast.net)]

I agree with you whole-heartedly.

When I got my first job after school, the chief engineer turned down my 
requests to be in the Design Group, insisting instead that I spend 3 to 4 
years in the Manufacturing Group. 

"Until you know how things are made, you can't possibly design things that can 
be manufactured at a price that can be marketed".

It would take another 25 years before I appreciated that wisdom. And the wedge 
that was always driven into the heart of any design was the need to compromise 
what we wanted by the reality fo what we could do. 

ATM's are a curious lot.

They'll argue over technical annamolies from the perspective of a perfect 
world, that does not exist, except in their own mind and then build telescopes 
that use cardboard.

I'm comfortabe with the materials and with the application.

When it's built, I'll have some of the most intense, knitpickers put it to the 
test. It will either work, or it will not. I have little attachment to the 
outcome.

Besides, I will probably be somewhere else, playing with an entirely different 
discipline!

Regards

Art





Quoting "Good, Donald" <dgood@aha.org>:

> I don't think there is any resistance to your logic.  The lack of agreement
> occurs in the details when you try to define what is a "properly designed
> supplemental support" and "suitable materials".  Add to that cost, weight
> (portability), and ease of construction, then not only should you not
> expect
> agreement, but there are many useful solutions to pick from, depending on
> design goals.  
> 
> Also, ATM'ers have a tendency to lapse into discussions of ideal situations
> (I know I do) and have to draw themselves back to reality from time to
> time.
> But the desire to build that perfect machine is always a strong temptation.
> 
> Don
> 
> 
> -----Original Message-----
> From: artbianconi@blast.net [mailto:artbianconi@blast.net]
> Sent: Friday, February 13, 2004 8:28 AM
> To: atm@atmlist.net
> Subject: [ATM] If it's in a supremely stiff cell, that does not twist,
> why would a thin mirror sag?
> 
> 
> Maybe I am dense.
> 
> Maybe I am stupid.
> 
> No matter how I try I cannot fathom why a thin mirror would not maintain
> its
> 
> parabolic surface if held by a uniformly planar cell made of of carbon
> fiber.
> 
> If it be true that the sagging issue begins with using a thin mirror,
> instead of a 
> thick one and goes away to a major degree when the mirror is made thick 
> again, then any properly designed supplimental support made from suitable 
> materials, should restore the correct geometry and prevent the distortion.
> 
> There seems to be a great deal of resistance to this logic.
> 
> I don't understand.
> 
> Art Bianconi
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 




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