[time-nuts] Thunderbolt mounting

bownes bownes at gmail.com
Sat Jul 14 01:36:09 UTC 2012


As someone pointed out, it is dependent on where you are, as well as a number of other factors. 

I've got a nice chunk of concrete tied to bedrock about 10' below the surface with a thermal variation that is below the threshold of the thermometer i have there.

  Since I need to put something else on the concrete block (seismograph) I thought it might be interesting to toss a frequency std on it a well. 

Yet another project...:)



On Jul 13, 2012, at 20:25, Neville Michie <namichie at gmail.com> wrote:

> 
> You have to go deep into the ground to get stability.
> At 15 metres deep there is a lovely pure sine wave of about 0.3C P-P.
> I measured it on the roof of a cave, its period one year.
> My design for the bolt is to put it in a 1/4 inch thick aluminium box which 
> is held at a constant temperature by a fan. Switching control is good enough as the 
> thermal diffusivity of 1/4 inch aluminium will attenuate any spectral components shorter than 
> a minute. The aluminium box is so conductive that the box is isothermal, so once the bolt 
> has established its internal temperature gradients, nothing changes.
> cheers, 
> Neville Michie
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