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Old 12-19-2007, 10:52 AM
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DIY air compressor

Does anybody here think it would be possible to build you own air compressor. What I was thinking of, a person could use a 500 gallon propane tank. Then find a washing machine or dryer motor, buy a pump and build one monster air compressor. Does anybody think something like this is possible, it is just a thought.

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Old 12-19-2007, 11:03 AM
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Quote:
Originally Posted by onebadmerc
Does anybody here think it would be possible to build you own air compressor. What I was thinking of, a person could use a 500 gallon propane tank. Then find a washing machine or dryer motor, buy a pump and build one monster air compressor. Does anybody think something like this is possible, it is just a thought.
Absolutely, you can build one. But to build a "monster" compressor, you'll need way more power than a washing machine motor.

My dad built me a small compressor using;

welded schedule 40 steel 12" diameter pipe and ANSI end caps,
an old Quincy hvac control air compressor - about 5 cfm I'd estimate
3 HP electric motor. He was a union welder, so......

It works great for filling tires and small air tools, but that's about it. It weighs about 500 pounds though! Even though he put wheels on it, it's stationary!! He put a lifting lug on it too....to make it portable!

I keep it for sentimental reasons more than anything else.

Antny
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Old 12-19-2007, 11:18 AM
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monster air compressor

It is possible to build a monster air compressor, I am actually in the process of building one out of a 350 chevy V-8. I will post pictures and the process when it is finished, but it will be about as monsterous as they come. It will put out over 200cfm at 120 psi. If you are interested in something that big, or maybe something a little milder, I would definitely help you out with the design, if you are interested.

-David
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Old 12-19-2007, 12:20 PM
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Sure, but what you are proposing isn't going to be a monster but rather a tire pumper. Expert welding is a must. Only use a new tank. Old tanks are suspect at best. If you have never seen a tank rupture it is not a pretty sight.
The one I am building is not a monster either, but will do 37 cfm at 120psi at the compressor outlet. Power is a 12 hp gas motor geared down 4-1 for about 48 hp before friction lossses. I could have bought a complete one new for a couple hundred more, but do like building stuff. Lousy pic but you get the idea.
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Old 12-19-2007, 02:29 PM
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"Power is a 12 hp gas motor geared down 4-1 for about 48 hp before friction lossses."

Nope. 12 hp is 12 hp. The torque will quadruple but the RPM will fall to 1/4 of the original RPM. Same hp as you start with assuming zero friction loss.
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Old 12-19-2007, 02:55 PM
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That 500 gallon tank would be waaaaaaay too big! With the amount of power you are talking about (1/2-3/4 HP) and a pump matched to the power output it would take hours to fill that tank to pressure but believe it or not only minutes to drain it using something like a DA sander or sandblaster. Monster? it sure would be but not in the sense you are thinking. Also before pressurizing a used tank that big (or any used tank for that matter) it must be tested to be safe and one that size could level a good sized area if it ruptured. An LP tank in good shape would safely hold the pressure but if it has been taken out of service it is probably because it has already failed. If you are serious about building your own compressor then it certainly can be done but you need to do some major re-thinking and concentrate on the size of the pump and the power source but with a MUCH smaller tank. Remember a big tank does not make a big compressor and no matter how big the tank is it will not make up for a lack of CFM.


Boss, is that 350 going to be a self powered unit using half the cylinders to compress and the other half for power? I have dealt with that type of compressor for years, based on Buick engines of even smaller displacement, and you are right in that they WILL make some serious air!
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Old 12-19-2007, 04:04 PM
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Ok - I've always been a little curious about the 1/2 compressor 1/2 engine deal. How do you do this? I'm thinking on the pump cylinders you'd remove the rocker arm from the exhaust valve and then put a one way poppet type valve in the sparkplug port? Is that all their is to it or more complex? How do you balance out the firing order? Last - how do you regulate the tank? Just keep the engine running and have a poppet valve at 120psi that self re-sets when pressure drops below or what? Kinda interested in this as a V8 or I6 idea.
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Old 12-19-2007, 04:59 PM
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So if the washing machine or dryer motor is too small then would a 6 hp Honda vertical engine with a much smaller tank be more efficient? Would building a air compressor be cost effective or is it going to cost more if you have to buy a new tank, pump and motor? Right now I have a 5hp DevilBiss air compressor I bought about 11 year, it works fine but I need more power. I will either need to buy a bigger one or build one, or could I get another 5hp compressor and piggy back two compressors together?????
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Old 12-19-2007, 05:28 PM
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A bit different than what you're talking about here , but I had a 84 mazda b2000 pickup with a built in air compressor. The guy I bought it from had modified it as follows :
He ran the smog pump output to a tank mounted under the bed and had the air hose connectors inside the gas tank door! It was a really neat setup to say the least. as long as the engine was running , it would work like a charm . with a tank full ( engine off ) you could fill 4 tires on a car , no problem. I'd guesstimate the tank was about 35 gallons or so. While I only used it a few times , it came in really handy when I needed it.

Last edited by 79C10; 12-19-2007 at 05:29 PM. Reason: I forgot to type "hose"
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Old 12-19-2007, 09:13 PM
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Koolaid, Those Buick engines had a special head designed just for that purpose along with a cam that changed the firing order so they were not really a simple conversion. The things ran a governer coupled to a throttle kick-down that idled the engine when the tank was full along with an unloader that took the load off when the engine was at idle mode. As I said they made some serious air but they used some VERY $eriou$ fuel too! They are a good set-up for a service truck or for other mobile use that needs a lot of CFM but would not be practical for a garage or shop due to the noise and enormous operating costs.


Badmerc, A 6 HP gas engine would not be enough power to operate a pump big enough to do much more than about 10-12 CFM and it can be quite complicated getting it set-up to operate right. In order to get any real efficiency you need that idle kick-down and unloader to take the load off the engine and to keep the pump from compressing more air when the tank is full. I have seen several set-ups that simply dumped the excess air when the tank reaches pressure but that is very wasteful of fuel which at todays cost makes these things terribly expensive to operate anyway, and that does not even address the problem of excess wear from running the engine under a load all the time.
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Old 12-20-2007, 06:15 PM
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I was thinking about getting a 13 HP Harbor freight engine and running 1 of the Harbor freight twin cylinder pumps into 2 100 gallon LP tanks that we have around... bought the house on forclosure and the gas company we got would not take them, so we used up the gas they had in them and well.. the garage needs a compressor
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Old 12-20-2007, 08:09 PM
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2 100 gal or 100 lb tanks? 200 gal, if it is 100 gal tanks, would still be way to big and about 60-80 gal is all you would really want with a 12 to 20 CFM compressor and with less than 12 CFM you would want a 60 gal or less. If you are talking about the standard upright tanks commonly used with residential LP service they are probably 100 lb with about 35 to 40 gal capacity each.
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Old 12-20-2007, 10:03 PM
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Ok What about VW engines? I know that CP Rail at one time used these as air compressors I think that they were 4 cylinders 2 for air and 2 for running and to top it all off they are air cooled so no messy antifreeze. And probably lighter than a V8. Its a though because I was told that they would put out serious air also.

Kinda on a different note. Has any one else ever seen the spark plug air compressor? My Grandfather had one and you would pull a plug and put this hose in and fill tires with it. Cool idea i think.

Edit: Did a quick little looking around and found Dunn-Right conversions. And they are saying 58 CFM at 100 psi. Might be a touch on the large side but if you need air that would do it.

Dunn-right Site
John

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Old 12-20-2007, 10:43 PM
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Quote:
Originally Posted by BossChevy62
It is possible to build a monster air compressor, I am actually in the process of building one out of a 350 chevy V-8. I will post pictures and the process when it is finished, but it will be about as monsterous as they come. It will put out over 200cfm at 120 psi. If you are interested in something that big, or maybe something a little milder, I would definitely help you out with the design, if you are interested.

-David

that would be cool, look up v8 chainsaw on youtube. I work as a mechanic, and we use to have a grimmer schmitt compressor at work, which was a ford 302, one side of the engine was an engine and the other four cylinders was the compressor. 125 cfm no air tank. the air side had a head with a series of one way valves which would be opened or closed as air was being used, kinda hard to explain, it was hard to understand till I had to fix it, I always swore it would have worked better if they used a chevy. but it actaully worked pretty good. I bet it still works for the guy we sold it to.
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Old 12-21-2007, 05:30 AM
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Originally Posted by mike's hotrods
that would be cool, look up v8 chainsaw on youtube. I work as a mechanic, and we use to have a grimmer schmitt compressor at work, which was a ford 302, one side of the engine was an engine and the other four cylinders was the compressor. 125 cfm no air tank. the air side had a head with a series of one way valves which would be opened or closed as air was being used, kinda hard to explain, it was hard to understand till I had to fix it, I always swore it would have worked better if they used a chevy. but it actaully worked pretty good. I bet it still works for the guy we sold it to.

That's the same as the one I mentioned except it is based on a Ford instead of a Buick engine. There is nothing unusual about these things and they were (still are on some jobs) common for service truck use at the mines, one place I know has 4 of the dang things. The VW conversion was used quite a bit years ago but I think they are kind of scarce these days although they would be more practical than the big V6 or V8 conversions unless someone has a need for a couple hundred CFM, such as a large sandblaster or jackhammer. Trust me these things are not for shop use and are good only for an industrial application because of noise and operating costs. I worked with (and listened to ) the things for years and it is almost unbelievable how much fuel they can use so unless you have a serious need for that much air they are simply not worth the horrendous operating cost.
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