[time-nuts] A different timenuts interest

Hal Murray hmurray at megapathdsl.net
Thu Jul 22 16:18:56 EDT 2010

time-nuts at kasperkp.dk said:
> As a kid, I did a self sustaining pendulum with no moving parts and no
> magnets:

> The bob was suspended by two parallel wires, lacquered together, and
> shorted at the bob end. As the bob passed over the center, a one-shot  sent
> a good-sized current pulse through the wire, heating it, making it  slightly
> longer, and then shrink again as it cooled at the outside of  the swing.

Neat.  Thanks.

> For a heavy pendulum, and thick wire, the time constant in the cooling
> phase will likely make this infeasible.

That sounds like a good excuse to build a bigger and more impressive 
pendulum.  You need a longer wire so it has a longer period and enough time 
to cool off.

Does anybody know how much piezo positioners cost, or where to get them 
cheap?  I'm not looking for a fancy gizmo that takes many tiny steps, just a 
something simple that will vary the height slightly.

Maybe build one from several piezo noisemakers.

Here is the fun part.  You can also use it as a sensor to measure the 

These are my opinions, not necessarily my employer's.  I hate spam.

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