Electron, you do good professional looking work! Keep it up!
XAXXAT- The refrigerator “pumps” do a respectable job bit they have a few drawbacks. They can run quite hot when not pumping cool refrigerant gas, the cool refrigerant helps to cool the motor. Worse, they are oil lubricated, if they are “older” and had been designed and used with R-12 or R-22( now “banned” and taxed out of common use ) the oil is just a good mineral oil sort of like thin motor oil but the pump will blow more or less oil and oil mist out the exhaust air, messy, smelly and a possible health hazard, and the health & safety inspectors at work made us put oil mist trap/mufflers on all of our oil lubricated vacuum pumps, very expensive! The newer refrig. pumps, designed for R-134 “NEW FREON” use exotic synthetic non-oil lubricants, which form strange and innappropriate sludges when exposed to moisture, which will be significant in our application, supposedly not too good for the pump internal works. I haven’t looked into their health problems. The Gast and other similar oil-less pumps would be much better, even though they are somewhat noisier, than the sealed, oil-lubricated types. I found an unusual vacuum pump which is completely silent and it also “cycles” the pressure. It was designed for hospital suction use and it works by warming the air in a “semi-closed” chamber so the pressure rises and then flows out through a one-way “exhaust” valve, a timing circuit then turns the heater off and as the remaining air in the chamber contracts sucking in more air through the “inlet” one-way valve. The cycle keeps repeating silently and the maximum vacuum is limited by the expansion-contraction of the air based on the time and heat. It only generates about 120 mmHG = ~4.7 in. Hg, for the less science minded, which is a very nice, safe vacuum. I will try to post the information and some pictures soon, but I’m taking a week’s vacation very soon and it may be a week or so. I haven’t had time to plot the vacuum vs. time but plan to as well as look into adjusting the cycling to give different vacuum cycling profiles. One of my long term goals, with this pump is to achieve a very low amount of vacuum, cycling up and down and try it for extended times, like overnight. Yeah, Yeah I know, the advice is not to do any PE while sleeping, but at the very modest vacuum, perhaps only ~1 or 2 in. Hg, with a cylinder and seal which don’t pinch or reduce circulation may well be safer than commonly thought. Don’t try this at home! I can’t tell anyone to try this, but my few trial runs have gone very well, with no apparent ill effects but a very nice plump circumference with little to no donut. I still have the opinion that long periods of light to moderate PE may in some cases be as good or better than the heavy forces most of apply for much shorter times. We probably will still argue or differ on the light or heavy, long or short times, but I think each have some merit, and we are still “inventing” this as we go along.
