werner at openmoko.org
Fri Jul 23 12:57:07 EDT 2010
James Xakh Lynch wrote:
> You sure we couldn't use a different metal? One that isn't so toxic? I'm not
> sure if I'm okay with having the nanonote associated with large quantities
> of lead...
With my current estimates for shape and placement I need something
with a density of about 10 g/cm3 or more. This list is handy for
Bismuth would be a good choice. The ~17 g we need would cost only
about USD 0.3. A "Ben Silver Edition" or, better, a "Gold Edition"
would work, too. Molybdenum and particularly tungsten would be
more economical choices, but they're both difficult to shape.
Copper and nicket may already be too light.
Since tungsten has a density of 19.25 g/cm3, the center of the
counterweight could be closer to the front, reducing the mass
needed to perhaps as little as 10 g. At today's market price of
USD 30/kg, that would cost only 0.3 USD, as much as bismuth.
So if future NanoNotes need a counterweight, bismuth and tungsten
may be an affordable choices for large quantities.
That is, if all this works as calculated. We'll see.
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