[ATM] Re: Second Thoughts on Mirror Support

[greg.emery at mohawkcollege.ca (Greg Emery)]

As was discussed previously ( I believe it was this thread) use of a 
carpet under a mirror or tool during grinding is a slightly different 
animal.  The tool and mirror are rotated relative to one another as well 
as to the carpet throughout the grinding process.  IF the carpet was a 
problem, it should average out over the course of the hundreds or 
thousands of strokes in the process.

ttfn
greg

B. Bainbridge wrote:

>Many people grind large thin mirrors on a piece of carpet.
>Is this use of carpet adequate?
>
>
>On Wed, 11 Feb 2004, Emery Greg wrote:
>
>  
>
>>Hi Geoff:
>>
>>Didn't Dobson originally design his mount to be easy to use as well as to be able to be constructed from common materials by a typical person?
>>
>>If this is true, the carpet support support is a common material which doesn't require specialized tools or knowledge.  I believe ( on thin ice here) that Dobson's design also had full thickness mirrors which allowed for greater latitude in mirror support/cell design.
>>
>>ttfn
>>greg
>>
>>----- Original Message -----
>>From: gjnelson@absamail.co.za
>>Date: Wednesday, February 11, 2004 7:05 am
>>Subject: Re: [ATM] Re: Second Thoughts on Mirror Support
>>
>>    
>>
>>>>The original John Dobson style scopes use carpet, not wiffle
>>>>        
>>>>
>>>trees
>>>to
>>>      
>>>
>>>>support the mirror.  Thus it does appear to work to some (as yet
>>>>unquantified) degree.  Think of  it as a 10000 point variable force
>>>>cell.
>>>>        
>>>>
>>>This is a compliant support. Where you have the most force you
>>>have
>>>the most give thereby increasing the area of support and reducing
>>>the
>>>point forces. This would give you instead of three points of
>>>contact
>>>three areas of contact that would essentially merge not each other
>>>seamlessly dependent on how flat the support of the carpet is.
>>>
>>>I guess it could be modelled in PLOP but setting it up or even an
>>>approximation of it would be quite a challenge.
>>>
>>>Now what would happen if you RTV'd the mirror to the carpet? No
>>>sling
>>>would be required and you will still have a large support area.
>>>
>>>Geoff
>>>
>>>
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>>>
>>>      
>>>
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>>    
>>