ironizer Posted January 30, 2008 Posted January 30, 2008 Are there any piston/cylinder designs that do not use/need oil or other lubricants to operate? I'm not thinking of internal combustion engines, more like gas compressors, say up to 20 BAR at 2000RPM... that kind of deal; no model plane plastic engines or anything like that.
ironizer Posted January 31, 2008 Author Posted January 31, 2008 No, that is not what I asked. I need to know if there are any designs/examples of piston-cylinder arrangements where the lack of oil/lubricants is not extremely detrimental to their operational cycle. I vaguely remember reading something about SCUBA diving compressors, there is some design (with ceramic piston rings or something ?!?) that operate without oil because the air needs to be clean and have the proper gases in it (I think they add helium so the divers don't get nitrogen poisoned while under sea pressure).
iNow Posted January 31, 2008 Posted January 31, 2008 Perhaps if your metal (or whatever material you used) were made to be somehow extremely uber smooth on both the touching surfaces. Alternatively, what about something like Teflon? Also.. be patient, and keep "bumping" your thread. Sometimes it's just a matter of asking your question at the right time when the right set of eyes will see it.
DrDNA Posted January 31, 2008 Posted January 31, 2008 yeah. I thought about teflon, but it machines terribly. PEEK has similar properties but machines MUCH better. looks like a job for google
gcol Posted January 31, 2008 Posted January 31, 2008 Diaphragm pump. No moving piston. I have one, but it works at relatively low pressure. Perhaps that is its design limitation.
John Cuthber Posted January 31, 2008 Posted January 31, 2008 There are pistons that are always sealed and don't rely on oil as the seal but they have relatively high friction. Imagine getting a length of rubber tubing and putting a piece of wire through it. Tie the wire to the end of the tube and pull it back. This turns part of the tube inside out, inside the other part. Then pull the same end back through- this turns it the right way out again, but still inside the rest of the tube. At this point you have 3 layers of tube inside one another. If you connect a piston to the innermost tube and use the outermost as a cylinder you get a rolling tube seal. The friction's hellish but it's always sealed. If I can find a picture I'l let you know.
YT2095 Posted January 31, 2008 Posted January 31, 2008 does it have to be a Piston? I`m only wondering since you mention a Compressor. and one of the Best types is a Bit like the above in the way that it uses a "hose", but it also has 2 or 3 roller bearings mounted to a rotating motor driven housing, that puts pressure on the semi-circular arranged hose, the bearing crimp the hose and trap Gas or liquid in it, and the rotating action forces that gas/liquid to move in on direction only. it`s the same system used in Life-support machines, they`re very quiet too!
gcol Posted January 31, 2008 Posted January 31, 2008 The type just mentioned is called a peristaltic pump. Some pump manufacturers make both peristaltic and diaphragm types.
ironizer Posted January 31, 2008 Author Posted January 31, 2008 does it have to be a Piston? I`m only wondering since you mention a Compressor. and one of the Best types is a Bit like the above in the way that it uses a "hose", but it also has 2 or 3 roller bearings mounted to a rotating motor driven housing, that puts pressure on the semi-circular arranged hose, the bearing crimp the hose and trap Gas or liquid in it, and the rotating action forces that gas/liquid to move in on direction only. it`s the same system used in Life-support machines, they`re very quiet too! This sounds cool... do you know what this compressor is called, or do you have a link to anything with a diagram or picture? I was also thinking of a diaphragm compressor, but the diaphragm is probably not very reliable because it must stretched back and forth the whole time while in use.
gcol Posted February 1, 2008 Posted February 1, 2008 It is called a PERISTALTIC pump. Google images gives many variations.
ironizer Posted February 1, 2008 Author Posted February 1, 2008 It is called a PERISTALTIC pump. Google images gives many variations. Wikipedia has a great page on it. Yeah, it's quite a cool design. I can see how it would be good for medical uses. The rotary one looks pretty solid, a roller on the end of the vanes would make it smooth.
DrDNA Posted February 2, 2008 Posted February 2, 2008 Doh. I've been using peristaltic pumps for 20 years and I didn't realize that was what was being described here.
ironizer Posted February 2, 2008 Author Posted February 2, 2008 Those pumps look like they function best at moving thick liquids rather than gases. It's kind of like the mechanism used in the esophagus of animals. I wonder if it was inspired by it.
iNow Posted February 2, 2008 Posted February 2, 2008 Can you give more context surrounding the intended application?
ironizer Posted February 2, 2008 Author Posted February 2, 2008 Yes, but it's a longer story. I'll start a new thread about that. Thanks.
Spazmodica Posted February 14, 2008 Posted February 14, 2008 Have you considered a scroll compressor design? Google images has many good pics. They are used in AC systems with refrigerant. They are high speed and fairly high pressure.
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