[sdiy] oscillating a plate

[Czech Martin]

Well, depends on what you want.
Of course the plate should oscillate -very little-
if you blow it with a speaker.
However, since the mass and stiffness is considerable,
you can not expect it to bend much if you hit it with air
particles, right?

A better way would be to use magnetic force to drive the plate.
I.e. you need a roll of enameled copper wire and a 
magnet iron core, rod or the like. Wind your own magnet.

Is it a steel plate?

Problem: the magnetic force will have the same direction
for both possible current directions then. I.e. basically
full wave rectification. To get rid of that you should
have a permanent magnet on the plate. Perhaps one
of the old speaker.

Anyway, if the mass of the plate / magnet is too high,
the first mode of oscillation is perhaps at very low frequency.
Also the magnet inductance will cause grief.

You can test the modes with a rubber hammer (soft!).


m.c.

-----Original Message-----
From: cris at music-service.nl [mailto:cris at music-service.nl]
Sent: Dienstag, 1. April 2003 09:04
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] oscillating a plate


Hi all,
i don't think this is the best forum for this question, but i have to try...
i have a 1,52m long metal plate and i want to bring this plate in 
selfoscillation with sound, this sounds crasy but some people do 
things like that....
I hang this plate vertically and i put a frequency of 60 Hz in the front 
nothing happened. I think you need 1/4 of the wavelengt in frequency 
to make this plate to oscillate, but nothing happened, only my ears 
and my speakers are almost damaged.....
If somebody knows something about this, just some links or 
something like that, please please help me, because i get more and 
more frustrate with this problem....
thanks in advance
cris