[sdiy] About that spherical impulse generator...

[harrybissell]

Hi Glen (et al)

Whatever point you fix it at will become a node... so you can influence the
vibrational
mode you prefer by the mounting. Look where they mount commercial benders for
some
ideas on mounting... usually they clamp the edges... or they use a ring of
silicone RTV
in a circle maybe 10-20% inside the diameter of the disk.

Suspended over a hole would be OK... probably you could just make a circle of
RTV
at the edge and let the thickness of the silicone suspend the disk above the
spherical
surface...

H^) harry

Glen wrote:

> At 11:10 PM 1/9/04 , harrybissell wrote:
>
> >You have to consider the vibtatory modes of the discs... they are usually
> >mounted at a nodal point and flex like a drumhead. Bind them at the edges
> >and you might be right back to the beaming problem
>
> I would have thought that the disc movement was more piston-like and less
> like a flexing drumhead, since the piezo crystal is expanding across the
> whole surface of the disc, and not expanding from the primarily the center,
> like a drumhead.
>
> So, what is the best way to mount a disc for this purpose? Should I put a
> drop of epoxy in the center, and mount it over a solid, flat surface?
> Should I use a sheet of glue across the complete rear side of the disc, and
> mount that on a solid, flat surface? Should I suspend the disc over a hole,
> nearly as big as the disc itself, and glue the outer edge of the disc, as
> if mounting a speaker by its rim?
>
> I suspect that mounting it like a speaker might produce the most volume,
> but mounting it with a sheet of glue to a hard, dense, flat surface would
> possibly provide the best transient response.
>
> >Have you just considered explosives ???   ;^P
>
> That's actually been tried, but the frequency response of a typical
> explosion isn't flat enough. It's just too boomy.   ;)
>
> later,
> Glen Berry