soundboard press

[Ron Nossaman]

>My vacuum pump draws 24 inches when run continuously.  Total clamping
>pressure is a function of area as well.  For a sound board of 20 sq feet,
>the clamping pressure would be approximately 69,000 pounds from top AND from
>bottom.   Believe me, with vacuum, you can bend sheet steel.  This kind of
>force would require a pretty LARGE conventional press.
>
>Frank Weston

24 inches of mercury, I presume? With 30"@14.7 psi, 24" would be 11.76psi,
no? Times 144 would be 1693.44psf, times 20 would be 33,868lb. That's not
the point though. You may have an enormous load on the panel as a whole,
but you will not get a high psi clamping pressure on each rib unless you
have a rather wide caul to concentrate the atmospheric load along the rib.
Granted, you might get double or triple atmosphere, depending on how thick
and tightly stretched your plastic was, and how rigid the frame in which
it's mounted, but then you're back to building and storing a big expensive
tool. You're also still limited to lower clamping pressures than the
pneumatic or mechanical clamp (which may not really be a problem), unless
you make wide enough cauls for each rib, and it will likely be more of a
problem to ensure that the ribs are positioned accurately when the pressure
is applied (which likely will be a problem). I'm aware of what vacuum can
do, but to get high pressures, you always have to compound a wide
atmospheric pressure area to a small working surface. 

Build one and try it out. It might work great.


Ron N