05-03-2021, 01:58 PM
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Master Modeler
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Join Date: Jan 2009
Location: Fairbanks, Alaska
Posts: 6,507
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Quote:
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Originally Posted by ghrocketman
As long as the cans stay sealed, there should be no finite "shelf life" for R-12
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I agree--as gas with such large molecules should leak very little, if at all, especially from cans whose plastic button-valves have never been pressed (the XR 100 motors used these). The other type of totally-sealed can, with a screwed-down metal valve that cuts into the top of the can while being screwed into place (I believe the Coldpower Convertible motors--and perhaps also the Valkyrie series motors--used/use [or can use] these), can never leak, unless the installed valve leaks or the can rusted through, but the latter would never happen with normal storage, and:
The only example of leakage from such cans that I know of involved/involves the Canadian-made LOGIX (and also made by the Tandy Corporation) Aeronautical Lab Kit. They came/come (some unused ones are still around) a small can of helium (the can looked/looks like one of those used for aerosol shaving cream), for the balloons used in the section on aerostatic flight. The lab's manual itself warns to not leave the can unused for long after its plastic button-valve is first pressed, because the helium will steadily leak out once that is done. (The very small size of the helium atom makes this possible, which is why hydrogen- and helium-filled weather balloons, pleasure Charliere balloons [gas balloons, as opposed to Montgolfiere balloons--hot-air balloons--hydrogen is often used in Charliere balloons in Europe because it's much cheaper than helium; all components are electrically connected to prevent static sparks], and airships take off soon after inflation is complete, and require extensive use of envelope and valve sealing compounds on the fabric ones.) |