Aquarium Air Pump -> Vacuum

I needed a vacuum pump for making some FRP parts, so I modded an aquarium air pump for that.

Christoph

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Description

Aquarium air pumps are usually membrane pumps, cheap, and easy to modifiy to generate a (weak-ish) vacuum. I tried it and it worked right away.

Details

Membrane pumps basically consist of a membrane, something to agitate it, and a pair of one-way valves. Turning the valves around also flips the direction of air flowing through the pump, turning a normal air pump into a vacuum pump.

What can we expect from such a thing? Aquariums are usually less than a meter high, so a pump made for pumping air down to the bottom of such a thing should be able to provide a suitable pressure difference (about 10000 Pa, or 0.1 bar) just to get an idea about the magnitude.

Turning it into a vacuum pump shouldn't change that significantly. Compared to a professional ("real") vacuum pump that doesn't sound like a lot (they go down to almost 1 bar pressure difference), but it's enough to be very useful.

It turns out that the only thing to do was to rotate one part by 180 degrees.

Components

1 × Membrane air pump for aquariums
1 × Screw driver
1 × Sharp knife

Project Logs

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Size doesn't matter
Christoph • 01/26/2015 at 13:06 • 0 comments

It doesn't really matter how large the part you want to make is. Here's a 10" long, 14" diameter, carbon fibre - plywood - epoxy resin shell, curing in a vacuum:
(The steel part is just a positive mold)

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Build Instructions

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1

Step 1

Check if the pump is plugged in. Is it? Unplug it.
2

Step 2

Open it and see if you can locate the membrane(s) (mine has two):
If not, see if you can still give it back and try another one.
3

Step 3

The membranes (centered in the image) are attached to small retainers, which sit in a piece of silicon tube (left). At the other end they have a magnet, next to a coil (the fat white thing to the right). In my pump, the whole left part (everything but the coil) was attached to the case with one screw. You can see that screw above, between the magnets.
Loosen the screw and take the membrane block out of the case: