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Modified compressor.
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davelectronic:
Not sure if this is the right category, I've wanted to convert two fridge compressors for air brush use for a while. The problem I have come up against has been start stop cycles and the start relay and PTC not liking it, and tripping out the compressor. So I've since found a couple of compressors that will play ball...
So I wanted to attempt to add an oil glass level to show oil level, and an oil filler port. I have a few ideas how to do this, but want to avoid getting metal swarf inside the units. And as the hematically sealed casing isn't that thick, find a way to mount these two service ports, either adding some kind of boss etc.

What I thought was silver solder with a torch, as it's got good tensile strength. But then remembered opening one of these compressors some years ago and realised the casing inside is not under positive pressure, but more a vacuum, or even nutural pressure state. And the original pipes as a refrigeration compressor are just normal solder joints. So debating if to soft solder, or even epoxy, although I'm not sure on longevity using epoxy. I know the slower curing epoxy Araldite is incredibly strong on a suitable surface, and any minor gap filling. And on a final, I'm not familiar with the clearances between the outer casing and the stator and windings, I could use another compressor as a sacrificial. Removing  the top of it to establish clearance for two service ports (same model compressor) but at £ 40 a pop that's wasteful, and expensive. I was debating on drilling the casing as not toget any fine swarf inside the compressor, not easy to avoid when drilling regardless of how carefully it's done. And perhaps a Puch type tool maybe. The idea around all this is to create a silent airbrush compressor like the Bambi models available on the market, although the very expensive.

Any refrigeration engineers out there have any thoughts on this task ? Sorry if this is the wrong section to post this question in, but it's not an electrical problem, so thought this section was the most appropriate to post this to. Thank for reading, any thoughts appreciated.
BradC:
Pressurize the shell with compressed air as you drill through and the swarf will just fly out. Best to remove the oil first though :)
I'd use silver solder, but that's because I have the gear in the garage, but yeah the shell is at suction pressure rather than discharge.
nctnico:
Why would the oil get out? I'd just leave them as is. Any soldering on the shell likely turns any internal coating or oil residue into debris. If too much oil is coming out then the compressors likely aren't useful for air-brush anyway due to the oil getting in the paint. You'll want a filter on the intakes as well. In my experience the in and output pipes are solderable using leaded solder. Just make sure to include an overpressure vent valve though near the compressors in case the output hose gets clogged.

Still, how much does a real airbruch compressor cost (from Ebay or Aliexpress)? By the time you are done with the modifications you might have spend more than a new or 2nd hand airbrush compressor costs.
amyk:

--- Quote from: davelectronic on March 24, 2021, 11:07:12 am ---But then remembered opening one of these compressors some years ago and realised the casing inside is not under positive pressure, but more a vacuum, or even nutural pressure state.
--- End quote ---
It depends on the model. Some are "high side dome" (compressor discharges into the housing) and some "low side dome" (compressor sucks from the housing).

Likewise with where the stator and windings are. Reciprocating ones will usually have a separate spring-mounted internal unit, while rotary ones usually have the stator pressed into the housing.
davelectronic:
Thank you for your replies, I don't think oil will end up going through to the airbrush, as I'm using a trap to catch any water or oil residue. The compressor inside is mounted on springs, just a slight wobble and I can feel the enersure. For price and buying one, my Son and myself will be having a go at airbrushing, I have all the gear already. The compressor I purchased is border line on noise, ok daytime early evening, but to noisy after say 8:pm. We live in a block of flats, I have people above and below me, so I don't want to upset anyone, I know youg families putting out there kids to bed early evening. And a compressor do keep us both running simultaneously is upwards of £500 and a perfect retail compressor for both of us would be upwards of £900. It is costing a little to do the DIY option, but I'm using the air receiver and pressure control gear from the compressor I already have. That compressor is an oil less type compressor. The actual compressor can supply the air volume easily, but at just over 70db it's just to loud. Below is the compressor I have, but not yet modified. I wanted a bit bigger air receiver, that one is 24 litres it's ok for now.
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