(Really ideally, you'll get it for $2 at the Blue Hanger.) Failing that, be gentle with your cheap little pump. Ideally, you'd like a pump with a heavy finned aluminum cylinder, a cooling fan, and a powerful motor, rated for continuous long runs. If you don't know if it's rated for more than 15 minutes, only run it for 5 or 10 minutes at a time, giving it 5 minutes to cool down before restarting it. ) Err on the side of not running your pump for too long at a stretch. (Better inflators can run for up to an hour.
Really dirt cheap inflators may only run for a few minutes before overheating. NOTES(added in light of comments below): If you use a really, really cheap tire inflator, such as the $10 "mini air compressor" from Harbor Freight, don't expect too much. (About 17 inches of mercury or 8 pounds per square inch.) That's still several times harder than a vacuum cleaner can suck, and good for vacuum-bagging things like RC model airplane wings, but only a little more than half the ideal vacuum.) The upside is that they're quieter and run cooler, and will likely last longer. They're quieter, but don't pull as hard a vacuum. I've done very similar conversions of "nebulizer" air compressors (for medical equipment) from thrift stores. power isn't available.) Thanks to Doug Walsh and his book "Do It Yourself Vacuum Forming for the Hobbyist" for the basic idea. (Or sometimes off of a 12-volt deep cycle, trolling motor-type battery, for vacuum forming in locations where A.C. I run it off my 6-amp car battery charger.
Since this is a 12-volt device that draws almost 4 amps, it requires a fairly hefty (DC) power supply. Weld steel-filled epoxy All of these things are available at home improvement stores. In addition to the pump, I used: a few feet of 1/4" inside diameter braided PVC tubing a nylon fitting with a hose barb for 1/4" I.D. Converting it to a vacuum pump required a few dollars worth of parts & glue. I got my little air compressor for $2 at a Goodwill Blue Hanger store (a.k.a. (About 25 "inches of mercury" out of a possible 29.9, or 12.3 pounds per square inch-or 1768 pounds per square foot.) It is strong enough to achieve professional-quality results for many processes that require vacuum. The vacuum created is several times stronger than any vacuum cleaner can produce, and most of the way to a perfect vacuum. This makes a vacuum pump suitable for vacuum bagging laminates and composites (like fiberglass), or for evacuating a tank for a small vacuum former. In this instructable, I'll show how to convert a 12-volt "tire inflator"-type air compressor into a vacuum pump. Many air compressors make good vacuum pumps if you can find the air intake, enclose it, and attach an appropriate hose or fitting. A vacuum pump is just an air pump, like a compressor, where you use the input side for suction, rather than using the output side for blowing.
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