Help building AC pumps

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So I'm trying my hand at engineering, and I thought "maybe an air conditioner would be a good place to start, that doesn't sound too hard". Stupid idea. Of course it's too hard. But I'm gonna try anyways. So what do you guys think about this as a pump? I want to find a very clean cut, circular metal tube. inside the tube i want to wedge a circular rubber block of undecided depth. Then i want to screw through the rubber block, have a large (almost the size of the tube itself) washer tightened down on each side of the block, and the screw itself will be attached at the other end to the mechanism I have set up to push up and down. Is this realistic? Or am i going to see technical difficulties from such a set up?
 
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  • #2
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You've just designed a reciprocating piston water pump, no more or less leaky than what you'll find on a windmill or the old hand pumps you see in the movies.
 
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Fair Enough. But should I be concerned about what type of rubber, how thick the metal needs to be, etc.?
 
  • #4
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what type of rubber
You probably want to check O-ring manufacturer's handbooks/catalogues for rubber compounds, materials compatibilities, service conditions and other details. If you're planning on using the various fluorinated/chlorinated refrigerants, DON'T. Sealing refrigerant loops containing such materials is not something to approach in "shade tree mechanic" fashion.
 
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Thanks for the heads up. Can you recommend any refrigerant?

I'll google up some handbooks tomorrow and post my findings here
 
  • #6
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With the exception of water, in swamp coolers, they're all nasty, or have the potential to become nasty. You might browse HVAC manuals/handbooks to get an idea of methods used to "evade" the necessity of mechanical seals in pumps/compressors.
 
  • #7
Danger
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Check with local authorities, too. Some refrigerants are illegal to handle without a license.
 
  • #8
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So I'm trying my hand at engineering, and I thought "maybe an air conditioner would be a good place to start, that doesn't sound too hard". Stupid idea. Of course it's too hard. But I'm gonna try anyways. So what do you guys think about this as a pump? I want to find a very clean cut, circular metal tube. inside the tube i want to wedge a circular rubber block of undecided depth. Then i want to screw through the rubber block, have a large (almost the size of the tube itself) washer tightened down on each side of the block, and the screw itself will be attached at the other end to the mechanism I have set up to push up and down. Is this realistic? Or am i going to see technical difficulties from such a set up?
I don't know your age or experience level but you can be sure that you will l find yourself going through a lot of trial and error. Do a lot of reading before doing anything. Refrigerant 134 a is available at any automotive parts store, but using it without the knowledge of what size of a hole a high pressure equipment failure can put in your head is not a good idea.

Don't buy a cheap can of "refrigerant substitute" because most of them contain propane. Hopefully most of those have been pulled from the market by now.

Rather than trying to re invent the A/C system starting with the compressor (there are other components) why don't you just buy an old automotive compressor at a salvage yard. If it doesn't work out you can always make an air compressor out of it.

You might even want to first try your idea to see if it can compress air.
 
  • #9
russ_watters
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Can you recommend any refrigerant?

I'll google up some handbooks tomorrow and post my findings here
Please do. The primary purpose here is for you to learn, so you should be doing the bulk of your own research. This is not a trivial project you are undertaking and isn't one with a high probability of success (how can you design a compressor if you don't know what you are compressing and by how much?), but at the very least we can ensure that you learn something.
 
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For the sake of my health, I've decided to forego the a.c. project and build a hydraulic Jack instead. My assumption is I want a generally noncompressible fluid (like water) in my hydraulic pump. I figure this will also be a good way to gauge how sealed my pumps are, although I imagine water is much more viscous than coolant. Do you guys have any suggestions on where I can find metal tubing with no weld line on the inside? As of right now I'm thinking I'll need to make the pump out of copper tubing (since it has no weld line inside) immersed in a cement mold
 
  • #11
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Please do. The primary purpose here is for you to learn, so you should be doing the bulk of your own research. This is not a trivial project you are undertaking and isn't one with a high probability of success (how can you design a compressor if you don't know what you are compressing and by how much?), but at the very least we can ensure that you learn something.
I'm not at the point where I could make solve the systems of equations regarding those values, but I figured so long as I had a compressor and a decompressor with intake and outtake fans (and an oil system) I should see somewhat positive results, although I wasn't expecting it to be a spectacular a.c unit.

At the end of the day learning is all I'm really hoping to accomplish
 
  • #12
Baluncore
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At the end of the day learning is all I'm really hoping to accomplish
The best way to learn about how things should work is to fix things that don't. If you cannot fix a broken thing, then how can you possibly expect to design and manufacture a working prototype.

Today's technology has evolved in a stepwise fashion. You should not expect to leap from inexperience to competent designer, without first studying the the reason why other designers products are failing.
 
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  • #13
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Hey, young HVAC tech here. In my state, it is illegal for you to handle the good stuff without a licence from the EPA. With that said, you are able to get R134a from auto parts stores, so I don't know what kind of exceptions there are.

Compressors are usually either reciprocating or scroll. If I were you, I would skip trying to build a compressor and just try to build a unit with an existing compressor. The problem is that there aren't really all that many parts. You have your compressors and heat exchangers. That's about it. Everything else is about dictating when and how they turn on.
 

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