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Picture of Venturi Vacuum
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I wanted to use my air compressor as a vacuum pump. For more info on how that works, see the wiki article on the Venturi Effect.  I made it at TechShop.  I took a piece of aluminum measuring 1.25x1.25x3".  I only went 3" because the longest 0.75" end mill I had only cut to 2" depth.  Keep in mind, a longer exhaust section would give a stronger vacuum.

In order to use the standard 0.25"NPT shop air fittings, use a 7/16" drill bit.  Drill one hole on the end to a depth of 0.6".  Drill the other end to a depth of 2" using the 0.75" end mill. Be sure to use plenty of lube & back out regularly to clear chips. Go back to the end where you drilled the 1st hole & drill a 0.2" hole in the center of the 1st.  Drill all the way through to the hole made by the 0.75" end mill.  

Now, on the top surface, start at the end of the 0.75" hole & measure back 1.78".  This is the center point for your next hole.  Drill this one with the 7/16" bit.  Stop once you clear the wall of the 0.75" hole. do not drill into the other side of that wall.

Next step is to tap the holes.  Put the block into a vice & tighten securely.  Take your 1/4NTP tap & carefully start cutting into the hole.  It's best to use lube & back out regularly to clear out chips.  Do the same on the other hole.  Now your ready to install the quick disconnect fittings.  Make sure to use teflon tape.  

Once you reach this point you can test the rig.  Hook the horizontal QD fitting to your shop air.  when you apply sufficient air pressure, it will generate a vacuum in the vertical fitting.  You can test the performance of this setup by connecting a vacuum gauge to the vertical fitting.  
 
gwbisho2 months ago

The described vacuum pump might get 5 hg. OK for some things. Too low for AC work. However, shows a good example of how to quickly make one. The author should have stated it's efficiency and max vacuum. This one will require a huge amount of air input. I just made one out of pvc pipe and fittings that provides a partial vacuum up to 24.5 hg (vacuum is 29.92 hg). This one can run on a small compressor at 80 psi.

diydonut3 months ago

Perfect! Just what we needed for draining the car AC

Huzefaz3 months ago

hey

just want to confirm if the drawing that i have attached is appropriate or not.

Early reply will be appreciated.

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steven_r_pace5 months ago

tapering increases efficiency. Of course you can buy them for about $20. To make an efficient one would cost a lot more in time.

Of course it is never going to be an efficient vacuum, but they are used in situations where maintenance issues make other sources of vacuum inefficient.

rimar20002 years ago
I think the air intake of your compressor is a lot more efficient than a venturi.

I'm going to be building one of these for work- the air intake on the compressor sounds like it might work for moving only air, but I'll be using this to create a vacuum on a container with a hose for pumping liquid. I work with flammable materials and as such, sucking gas or jet fuel into the compressor will end many things, the least of which will be my job.. I think using this and all metal fittings will let me ground the whole setup and make an explosion proof vacuum. Any thoughts?

I think the opposite, the intake on the compressor is trying to move a lot of CFM at low pressure, whereas this venturi, I think more appropriately its called an eductor pump, uses the pressure differential to move a small CFM but at a "higher" (low since its vacuum) pressure.
But the venturi needs a very high air speed to reach low pressures, and spend a lot of air in the process.
The compressor intake can work as a high volume vaccum pump, and the lowest pressure depends on the motor power and piston diameter.
I build one venturi pump, and it isn't energy eficient. The only two advantages that i found in this type pf pump is that has only a few parts and it's very small.
The one published here probaly won't reach a very low pressure ( probably 0,9 to 0,8 ATM, or 80 to 90% of the atmosfere pressure).
The best initiative is to do the test. We could discuss the issue for years without agreement. I think if the compreesor is piston-cylinder driven, the vacuum should be high at the intake.
" a longer exhaust section would give a stronger vacuum."

If you need more vacuumed than is archived by your 2" cut you could extend it with some pipe of the right ID. A bit more work on the mill and you could have several different length pipes that screw into the exhaust port and are calibrated for different strength vacuum :)
blkhawk2 years ago
This could be the beginning of a homemade carburetor.
Hey this has been something I've been looking for- getting suction by using pressure.

What where your numbers for pressure put in and suction received?