[time-nuts] Thermal time constant

[Bruce Griffiths]

There's at least one known case where someone attempted to grind a 
beryllium mirror substrate using conventional methods without proper 
control of dust resulting in his death.

Bruce

Neville Michie wrote:
> Just in case anyone finds a beryllium brick somewhere and tries to use 
> it:
> Beryllium is very very poisonous.
> cheers,
> Neville Michie
>
> On 11/03/2010, at 10:08 AM, Bruce Griffiths wrote:
>
>> phil at pseng.org.uk wrote:
>>> Looking at the specific heat of metals:
>>> http://www.engineeringtoolbox.com/specific-heat-metals-d_152.html
>>> Wouldn't Beryllium be better instead of aluminium?
>>> I could foresee a few problems though eg machining holes at home, 
>>> never mind where to get a block from.
>>>
>>> Phil
>>>
>> Actually in this application minimising the volume of the metal block 
>> rather than its weight is probably better so one should use specific 
>> heat*density as a figure of merit.
>>
>> METAL            Specific heat*density (W/J/cubic cm)
>> Aluminium         2.46
>>
>> Beryllium            3.29
>>
>> Copper               3.49
>>
>> Silver                  2.41
>>
>> Iron                    3.87
>>
>> Thus copper and iron are better choices than Beryllium they also 
>> poses fewer machining diffculties
>>
>> Bruce
>>
>>
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