PSN-L Email List Message
Subject: Re: copper weight
From: John Popelish jpopelish@........
Date: Mon, 27 Jun 2005 20:21:09 -0400
> has anyone tried copper instead of lead for the weight on a Lehman? The
> idea being that it could also be used for magnetic damping.
Either can be used for magnetic damping. Lead's advantage is its
density at 1.27 times copper's. It is also easier to cast into a
compact lump that is the right shape to be attached to a pendulum.
The higher conductivity of copper (13 times that of lead) increases
its damping effect for a given magnetic field strength, but lead is no
insulator. A good compromise is to use a block of lead (for mass)
attached to a thin sheet of copper or aluminum (1.6 times higher
resistivity than copper). The thinness of the sheet allows you to get
a pair of magnets closer together on opposite sides of it, increasing
the magnetic field strength.
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