Spring Line Hum

[Ian Fritz]

Paul --

Well, you could probably make that sorta work. My concerns are that (1) the
extra mass will perturb the springs mechanical response, because it would
take a torque to move the foil and the spring is *very* soft in torsion. and
(2) the foil will add a lot of damping because it has to move air out of the
way. Again, since the spring operates in torsion its restoring force is very
small, so it wouldn't take much friction to produce unacceptable damping.

Not to discourage anyone from trying it, of course. Maybe there would be a
way to bounce a beam off the pickup-transducer arm.

  Ian


----- Original Message -----
From: "Paul Perry" <pfperry at melbpc.org.au>
To: <synth-diy at node12b53.a2000.nl>
Sent: Tuesday, July 18, 2000 4:56 AM
Subject: Re: Spring Line Hum


> At 09:25 PM 17/07/00 -0600, Ian Fritz wrote:
> >Once again I remind you all that springs operate in a torsional mode.
How,
> >exactly, would you make an optical pickup?
> >
> Why, with a shaped piece of metal foil attached at rightangles to the
> spring, so that as the spring rotates about its axis, it occludes
> more or less of the light in a beam perpendicular to it.
> The same way an optical footpedal works.
>
> paul perry Melbourne Australia
>
>