Hi Goeff,

Yes, that's a good idea.  There is no doubt that a flexible thin 
piece of metal makes a far better pivot than any two pieces in 
contact.  Virtually all commercial instruments use thin foil flexures 
in their pivots.

A flat foil strip might be better than a wire.
Assuming an operating stress of 50,000 psi, a wire would have to have 
a diameter of about 0.016" in order to support a 10 lb force.  A thin 
flexure of the same material  0.001" thick and 0.2" wide would 
support the same 10 lb, and all other things being equal I calculate 
that it would be about 191 times more "flexible" than the wire.

In a Lehman it's a little tricky to make a pivot that way, because 
you want the pivot force to always be pulling on the wire or foil, 
never pushing, but I have seen designs that could do that.

Regards,
Brett

At 11:50 AM 6/5/2010, you wrote:
>Is there some reason no one will use a short
>piece of wire to be the bearing in a Lehman Seismometer ?
>
>Like, it could be far better than any two seperate pieces
>of metal touching each other ?
>
>Thanks ahead of time
>geoff
>
>
>
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