I believe the Well Educated science peoples have resources the average
citizen does not so people like myself who live on
social security must use the cheapest materials
that will get the job done. I have found simple
piano wire very difficult to obtain it is like a
controlled substance just like absolute barometers
in millibars or whatever. I think here in the USA we
are fighting a paranoid national security peoples
to obtain some tools and materials of the sciences.
they want to watch and control who can have what.
Pleasure through the sciences is being watched much
more closely than is pleasure for the arts otherwise
the materials WE seek might be easier to obtain.
I must settle for what's in the local hardware stores.
Most all else is too expensive.
I like your wood and ceramic and mineral ideas.

----- Original Message ----- 
From: "JimT" 
To: 
Sent: Sunday, January 25, 2009 12:07 PM
Subject: Steel vs. other materials


> I'm a newbie and have never built seismometer.  I'm wondering why
> steel is used so much in seismometer construction when other materials
> have much less thermal expansion.  Spruce wood, for example, has about
> 1/7 the thermal expansion of steel.  Other materials expand even less,
> quartz, graphite, some glasses and ceramics, etc.  Some of the
> materials with low CTEs (Coefficient of Thermal Expansion) are
> expensive (invar, tungsten, polyimide, diamond), but others are
> affordable.  Spruce is inexpensive and widely available.  Here are a
> couple of sources of graphite rods and other shapes:
> http://www.waleapparatus.com/catalog.asp?prodid=548212&showprevnext=1
> http://www.graphitestore.com/items_list.asp/action/prod/prd_id/25/cat_id/22
> 
> Simax glass is cheap and has an extremely low CTE.  I wonder what kind
> of seismometer a good glassblower would make?
> 
> Jim Turner
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