Mini compressor *56k WARNING*

[skmetal7]

Since there is a lot of interest in my lathe/mill thread about my homebuilt compressor, i decided to start a thread on it.

Yes it does work(yay!), but im not quite done with it yet. i still have to figure out how fast my new motor that i won on ebay will spin the compressor.

it is made from a solid piece of 6061 aluminum round(duh) stock, the pistons are 3/4" nylon, the belt cover is made of plexi and SS shim stock (0.01" from enco) all SS screws, and fitting from clippard.com, poweraire.com

ill post some pics of the internals but for now ill just repost the ones that i posted in the other thread

*note* this is not the motor that i will be using, too wimpy

[diarmaid]

Thats really really cool. Looking forward to seeing the pics of the internals. Can you control the output pressure and cfm?

[Mcgyver]

interested to see how works (the innards), looks good though. your threw me a bit on the cfm part, iirc its the cfm at a given pressure that has meaning, ie 63 cfm @ 100lbs, man you're on to something, 63 cfm @ 0, its a fan

Based on the expectation of a 1hp compressor putting out say 2/3 cfm @ 100lbs, to keep it chugging at 900 rpm at 100lbs or so is going take some serious hp?

[Geof]

Your 62 cfm seems a bit extreme. Compressors are rated as X cfm, with this volume being measured at atmospheric pressure, and Y psi which is the pressure at which the compressed air is delivered. A compressor rated at 110 psi and 30 cfm takes in the 30 cubic feet of air at atmospheric and compresses it to 100 psi; after the compression of course the air no longer occupies 30 cubic feet. A screw compressor with this rating needs a 7-1/2hp motor and a piston compressor with this rating would need something like 10 hp.

[skmetal7]

oh ok, i didnt know how cfm is calculated, i just took how much air it pumps out in one min.

ok here it is guys. the first few were a 'proof of concept' design to see if it would work




'exploded' view



pistons dangling from SS ball joints/home made SS ball cups

the only thing i didnt make was the angled part on the shaft(the shaft is even hardened), that is what gave me the idea in the first place. it is from an ooooold impact wrench that didnt work.


one piston needs to have a solid connecting rod and the other two need to be able to move, i found that out on the proof of concept (these things just dont come out on paper)


piston block


small video
http://media.putfile.com/mini_compressor-034
Click here to watch mini_compressor-036

[lerman]

If you run this at high pressure, it will generate a lot of heat. I would be surprised if the nylon can take the heat. But it's a really neat design.

Ken

[aggie_67]

Isn't this the same principle as a standard automoble rotary Air Conditioning compressor with less pistons? Not knocking the concept, it works very well. Auto AC by itself is not feasible for air use as the pistons require a lot of oil, hence your plastic ones.Thought you could save yourself a lot of machine work by using an auto ac compressor then replacing the pistons with your plastic ones?

[Burn]

I would use a belt drive if you can, it will quiet it down a bit. If you can't, try to tighten the chain up a bit...You'll get quite a bit of noise/vibration off the chain drive.

[Geof]

The principle is similar to what is called a swash plate pump. These are often used in hydraulic systems, particularly hydrostatic transmissions.

Ken's comment regarding heat is probably correct. Neither nylon nor acrylic can handle much heat.

[skmetal7]

that is where i also got the idea from, an auto ac compressor. i didnt want to use one because these are too big and i didnt want to buy a big motor to run it. the chain drive is just fine, doesnt produce a lot of noise, since its inside of a chainguard, with 3/8" plexiglass on either side. i could have made it out of aluminum but i didnt have any laying around. ill mill slots so i can adjust the motor and tenison on the chain.

the pistons are made of nylon, but i dont expect this to run at 100PSI, just enough to move some actuators, i guess i could have made them out of CI but i dont have any and i thought it would be overkill. i know acrylic melts very easily but nylon has a melting point of 410 - 432 °F and an operation temp of 104 - 338 °F (from matweb), i dont think it'll get that hot the way ill be running it.

keep in mind that this is a MINI compressor its probably not going to compress air up to 100 PSI, maybe 30-40 PSI. i was wondering what i could use as an air tank, an exhausted propane torch tank, a paintball gun tank. right now im using a 2 liter soda bottle

the basic workings of an A/C compressor


thanks for the feedback!!!!

[pminmo]

Interesting, is the "wobble" assembly just a cam mechanism?

[skmetal7]

it basically a piece of round stock drilled on an angle, a bearing preses on to that, then the outer ring with the ball joints presses onto the bearing