Okay... so I'm almost done with my home-made vacuum press. I was
surprised at how easy it was to make, actually.

Anyway, I've got my home-made bag, the pump, and pressure switch all
hooked up. As a test, I put my bathroom scale in the bag and turned on
the pump. The pump was starting to top out at 250 lbs on the scale
(and 100 sq. in. on the scale comes to a paltry 2.5 lbs/sq.in.), which
isn't fantastic... but, over the 2'x4' surface that I'm planning to
veneer, it's probably more clamping pressure than I could get with my
clamps.

Anyway, I'm going to start checking the bag for leaks and sealing the
vacuum connections better and then I hope to get up closer to 7-10
lbs/sq.in. We'll see.

My *problem* is this: I've got a pressure-actuated switch hooked up to
the system, with the notion that I can get the thing to pump down to a
certain vacuum and then shut off the pump... and then turn the pump
back on when a certain amount of air leaks back in.

In theory, it's great. In practice, it doesn't work so well. When I
start getting down to the target vacuum, each stroke of the vacuum
pump creates a momentary vacuum surge which triggers the vacuum
switch... which cuts the power to the pump for a moment, and the surge
subsides, and the vacuum switch turns back on, etc. What this sounds
like is like an engine running out of gas. The pump starts slowing
down... starts "running rough" (even though it's electrical) and just
keeps running slower and slower and never does get to the point where
it shuts off completely.

My plan, at this point, is to build a little electronic circuit which
will keep the pump going for a minute or so past the point where the
vacuum sensor first triggers, so that I'll get well past the trigger
point of the vacuum sensor. Then, the motor can shut off completely
and it won't turn back on until the vacuum drops to the point that the
sensor turns back on again.

Now, before I go and build this circuit, has anyone else made their
own vacuum press? If so, how did they get around this problem? Did you
just skip the vacuum switch and let the pump run constantly all night?
What does the real VacuPress do?

- Joe