[time-nuts] Thermal time constant

Bob Camp lists at rtty.us
Wed Mar 10 23:51:58 UTC 2010


Hi

The same caution applies to the beryllium in beryllium oxide heat spreaders. You find them in old RF transistors and some RF tubes.

Bob

On Mar 10, 2010, at 6:45 PM, Bruce Griffiths wrote:

> 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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> 
> 
> 
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