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Portable air tank for home shop jobs

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  • #31
    Originally posted by darryl View Post
    How much 'air' can you get from CO2?
    The off road racing and Jeep guys have been doing this for a long time. They get the liquid CO2 cylinders that are normally used in fast food. soft drinks etc. with special regulators. Not real cheap. However, one bottle can easily air up a Jeep on 38" tires after a day of trail riding. They usually let the tire pressure down to 7 or 8 PSI for the actual jeeping -- gives better traction when the tire can "wrap around" obstacles. The more hardcore jeepers do not rely on the bead to keep the tire sealed -- instead they use sheet metal screws to hold the bead onto the rim, or else they use split rims (widow makers) with inner tubes.
    Last edited by nickel-city-fab; 07-28-2020, 03:08 PM.

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    • #32
      Lot of good ideas, will check out the small compressors. Used small Aircans when they were cheap. Office supply houses don’t seem to have them any more. Don’t have much of anything in stock. So far this week detail cleaned two rifles one 125 years old & real dirty. Little air after carb cleaner makes it easy.

      Might not need to drain the big compressors tank (big to me may not be big to someone else) But it’s over 20 years old & no rust problems. Home shop it may sit idle weeks. Humid here and salt air too.

      Boats

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      • #33
        Comes to mind that an ingenious home shop made device can boost air pressure far past its normal pressures. Use air to operate a cylinder, which in turn operates a smaller cylinder. The pressure step up ratio is the ratio of the piston diameters. You don't necessarily need a second pump. I suppose it would be quite wasteful of energy, using one adiabatic process to drive another, but it would work. The rest of the hardware is paintball equipment- high pressure tank, suitable regulator, suitable hoses and fittings. Off road guys use this as well.

        I read quite a good explanation of why a high pressure tank can deliver a lower pressure longer than a larger tank at normal pressure. Basically you get to use a lot more of the air that's in the higher pressure tank before the pressure drops below the set level. It's easy to see- imagine a regular tank at say 102 psi. You are set for 100 psi on the regulator. You only get to use about 2% of the air before you have to accept a lower and dropping pressure. A tank at 1000 psi would let you use about 90% of the air before you started dropping below your set level of 100 psi. The small tank could be 1/5 the size of the larger, yet deliver twice the air.

        1000 psi is childs play when you consider that high pressure normally means 3000 to 4500 psi. The implication is clear.

        One thing bouncing around in the grey matter is this issue of oxygen. The 20% oxygen is concentrated as well as the nitrogen in the air, and at some pressure and temperature it starts to be capable of bad effects on combustible things, like seals and lubricants. Does anybody know the scoop on this?
        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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        • #34
          If you are looking for a small portable and quiet compressor, I bought this one on clearance at Menards a while back:
          https://www.menards.com/main/tools/a...23-c-12910.htm

          harbor freight carries similar ones under the 'Fortress' brand.

          It is very quiet, can barely hear it run and seems to hold pressure very well. I worked for years in construction, and HATE loud compressors, so bought this one for the smaller jobs that I don't need the big compressor for.

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          • #35
            Originally posted by nickel-city-fab View Post
            The more hardcore jeepers do not rely on the bead to keep the tire sealed -- instead they use sheet metal screws to hold the bead onto the rim, or else they use split rims (widow makers) with inner tubes.
            Screws are old school (-:, auto racing has been using bead locks for the last 40+ years. However bead locks on the inside of the rim can often run afoul of brake calipers and suspension components.

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            • #36
              IkeHarris had the tip. Portable battery powered tire inflator . Bought a Ryobi, power drill size. Extra nozzles for basket -foot balls & pool toys etc. Just enough air, no tanks and uses same battery as other tools

              Thanks

              Boats

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              • #37
                Originally posted by boats View Post
                Wonder If one of the small portable emergency air tanks would hold air for couple weeks, enough to use for small jobs. Low pressure blowing.
                Boats
                I have had this one for years and never an issue. It holds air forever. Last used it prolly 8mos ago and its still at 120psi. JR

                Click image for larger version

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                My old yahoo group. Bridgeport Mill Group

                https://groups.yahoo.com/neo/groups/...port_mill/info

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                • #38
                  Originally posted by Bented View Post

                  Screws are old school (-:, auto racing has been using bead locks for the last 40+ years. However bead locks on the inside of the rim can often run afoul of brake calipers and suspension components.
                  Yep bead locks (thanks for jogging my memory...) my jeep isn't quite radical enough to need any such thing -- yet.

                  BTW last I heard (4 yrs ago) TWF had actual mil-surp H1 humvee rims/tires with the run-flats in them. $750 for a set of 4 with the goodyears still on them and inspectable.

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                  • #39
                    One thing bouncing around in the grey matter is this issue of oxygen. The 20% oxygen is concentrated as well as the nitrogen in the air, and at some pressure and temperature it starts to be capable of bad effects on combustible things, like seals and lubricants. Does anybody know the scoop on this?
                    I was involved with paintball for a while and with the phasing over from CO2 to HP air came a lot of issues with folks lubricating the quick connect nipples in a misguided attempt to make it easier to use the fittings. What would happen is that the oil or grease during the "slam fills" that were all too possible in some bad setups would cause the oil to diesel ignite. There were apparently a couple of bad accidents early on until word got out to avoid oil on those fittings.

                    It would seem like it would be super easy to avoid the issue by simply putting a restrictor in the line to avoid the super fast filling that the PB community refers to as "slam filling". But I ran into a couple of fields where they let the players fill their own tanks and they didn't use any restrictors of that sort. No idea why. I'd be working the valve on my own fill to ease the air in and some kid would walk up, plug in and just flick the valve lever open fully. The tank filled with a very audible bump sound that make me think I'd just avoided the "Big One". Crazy....
                    Last edited by BCRider; 07-30-2020, 12:00 PM.
                    Chilliwack BC, Canada

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                    • #40
                      Originally posted by boats View Post
                      .....Might not need to drain the big compressors tank (big to me may not be big to someone else) But it’s over 20 years old & no rust problems. Home shop it may sit idle weeks. Humid here and salt air too.

                      Boats
                      Boats, keep in mind that the moisture only condenses out as the warm air cools in the tank. So there's nothing saying that you should or cannot vent out any condensate at the end of each session. But if your system will hold air it won't get any further condensation and standing water in the tank over the next few days. And that way you'll have the air you want for the odd use by the machines.

                      Chilliwack BC, Canada

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                      • #41
                        The portable tanks may not fill a trruck tire.. but will put enough in that you may be able to drive to an air source.

                        when rapping or just wanting to clear small amount of chips , I have blow tubes.. a few Ti thinwall tubes about 3/8 dia 7 inches long. I just blow a quick burst of air through it by mouth.. problem solved.l

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                        • #42
                          Originally posted by darryl View Post
                          Comes to mind that an ingenious home shop made device can boost air pressure far past its normal pressures. Use air to operate a cylinder, which in turn operates a smaller cylinder. The pressure step up ratio is the ratio of the piston diameters. You don't necessarily need a second pump. I suppose it would be quite wasteful of energy, using one adiabatic process to drive another, but it would work. . .
                          Such devices have been around nearly 100 years now. They're called 'strut pumps' and are used to service landing gear struts in the aviation world.

                          Southwest Utah

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                          • #43
                            Interesting- just read up a bit on strut pumps. I liked where you get to hook up a nitrogen tank to use as the 'air' source- and you get to use more of the nitrogen at a higher pressure, even if the nitrogen tank pressure is too low to be useful. Same idea basically of getting to use more of the air in a tank if the pressure is higher to begin with before hitting the regulator.

                            I'm sure this had gone off topic since the OP was asking for a simpler solution to portable air needs. My apologies for continuing to go on about the high pressure air systems- though it certainly is one solution.
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #44
                              I used the rotary compressor from a window A/C unit. Quiet and quick but no reservoir. After each shot you'll have to wait a few seconds for pressure to build up.

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                              • #45
                                Hmm- I wonder how the window AC unit pumps would compare to a refrigerator compressor in terms of pressure and volume, etc. I've had one of the little buggers apart and the pump in it was a single piston- perhaps a full size window unit would have a bigger pump. I can imagine though that it would be somewhat comparable to a fridge pump in pressures and volume capability, considering that it's probably using a common working gas. At any rate, something like that is designed to work continuously, which might make it a better choice for a small air system where it doesn't matter if it takes an hour to build up tank pressure.

                                My first air system used a fridge compressor. I know I could smell the oil in the air, but it wasn't a big deal. At the time I didn't consider what would happen with the moisture in the air, but I suppose it's just a matter of having a drain valve like most compressors do. I also used mine for vacuum, though I did come to realize the limitations there. You can run it for hours, but you'll only get down to perhaps 13 lbs or so- which at the time I thought was pretty good.
                                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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