Spring Line Hum

[Ian Fritz]

Paul --

Ah right, the foil could be parallel to the coil windings. I was picturing
it the other way, with a long reflected path to get some leverage.

You scheme could be made to work differentially: Use two detectors, with the
intensity on one decreasing as the intensity on the other one increases.
This could reduce the need for critical alignment.

  Ian


----- Original Message -----
From: "Paul Perry" <pfperry at melbpc.org.au>
>
> I cant see this. The foil is not moving ANY air at all, it is rotating.
> Consider a disc rotating like a wheel on an axis. If thin, it rotates with
> practically no movement of air.
> Now consider the disc with a slot in it (to pass a variable amount of
light).
> This, too, does not displace air appreciably. True, there will be some
> miniscule drag, but losses would I believe be less than in a magnetic
pickup
> situation.
>