V8 vacuum pump?

[diyengineer]

Anyone have any pictures, links, stories, etc?

[Geof]

Your post is a bit cryptic. Do you mean converting a V8 engine into a hulking great vacuum pump. I have never dome that although I did convert a V2 air compressor into a vacuum pump. I think a V8 would make a great high volume moderate vacuum pump.

[diyengineer]

Yes, use a v8 engine as a vacuum pump. Or other DIY devices.

[Geof]

Do you have an engine and are you planning on doing the conversion. I am interested to find out if it would work as well as I suspect. I think it should be possible to get a bit better than 25 inches of mercury vacuum with a very large volume capacity.

[UUU]

You could use four of the cylinders to drive the beast and the other four as the pump.

[Geof]

And if you had natural gas available and ran it on that the cost would be minimal.

[diyengineer]

And if you had natural gas available and ran it on that the cost would be minimal.

I do have natural gas available as well as propane if thats a possibility. I would rather not pipe/plumb it into my house supply. I would probably go with a bottled route of some kind.

I don't have the V8 yet. I was trying to find someone who has gone this route before finding one. I could get just about any old V8 and hone the cylinders and re-ring it and should work well enough for a pump. How do i convert it to run on propane/natural gas? What other modifications do i need to do to it? Would adding a large 60gallon compressor tank help or do you think it would produce enough suction and flow it wouldn't even need a tank?

[UUU]

There are conversion kits to run gasoline engines on LPG. There's not too much to it, they mostly relate to the storage requirements. But running off gaseous fuel, I'm not so sure about, as the existing carburator or fuel injection system would not be suitable.

[packrat]

Piston style vacuum pumps are not very efficient. A piston make a good compressor but not a very good vacuum pump. Most vacuum pumps are vane or scroll type.

[Geof]

I am wondering why you are asking about converting a V8 when you do not have one already available. Do you just want a cheap, high volume medium vacuum, vacuum pump? As mentioned most vacuum pumps are vane type although scroll and lobe vacuum pumps exist. I believe the vane type can develop the best vacuum but they are not efficient because there is a lot of operating friction from the vanes so they turn a large amount of the elelctrical energy into heat whether or not they are pulling a vacuum. They are also notoriously sensitive to contaminants such as dust. Lobe pumps are more efficient in that they do not have the same operating friction so they don't turn as much eletricity into heat. They are also more tolerant of dust but they cannot develop a vacuum much better than 27"Hg.

However, if your definition of efficiency is the best vacuum available per dollar I think it is very difficult to beat converting a clapped out compressor into a vacuum pump simply by re-routing the inlet and outlet piping. I did this and got a vacuum pump that can move about 10cfm and develop 25"Hg and all it cost was a few dollars for copper pipe fittings and a couple of hours work.

[diyengineer]

I am asking because my large gantry cnc table originally came with a vacuum table top. It still has it but i do not use it because i don't have a beast of a vacuum pump. The table is 15 long and about 7' usable wide. The entire table is plummed for vacuum. A compressor may get you somewhere on a smaller table or fixture but i need something huge. It has 6 electric valves so im guessing it has 6 controllable zones? I don't have a v8 laying around, but i could easily acquire one and convert it. A v8 5.7L liter running on liquid propane, that has water cooled jackets, oil lubricated, and 4 cylinders dedicated to vacuum operation sounds fairly effective for a diy type pump. All the vane and rotary pumps are $$$$$$$. Even if they are junk, too small, or garbage.

That would give me roughly 175 cubic inches of air volume (4 cylinders) and 3-4 times higher revolutions per minute then any compressor could go (assuming it could run decent on half the cylinders). You could put the whole setup on a small cart and small tank.

Just exploring what options i have.

How could i methodically go about checking to see what kind of CFM requirements would be needed? count the number of valves and diameter? Also count the number of holes in the table top?

I am wondering why you are asking about converting a V8 when you do not have one already available. Do you just want a cheap, high volume medium vacuum, vacuum pump? As mentioned most vacuum pumps are vane type although scroll and lobe vacuum pumps exist. I believe the vane type can develop the best vacuum but they are not efficient because there is a lot of operating friction from the vanes so they turn a large amount of the elelctrical energy into heat whether or not they are pulling a vacuum. They are also notoriously sensitive to contaminants such as dust. Lobe pumps are more efficient in that they do not have the same operating friction so they don't turn as much eletricity into heat. They are also more tolerant of dust but they cannot develop a vacuum much better than 27"Hg.

However, if your definition of efficiency is the best vacuum available per dollar I think it is very difficult to beat converting a clapped out compressor into a vacuum pump simply by re-routing the inlet and outlet piping. I did this and got a vacuum pump that can move about 10cfm and develop 25"Hg and all it cost was a few dollars for copper pipe fittings and a couple of hours work.

[diyengineer]

Propane Conversion: How to Make LPG Cars

Here is an article on it. Seems like its easy to do with a carb motor.