Air supply

For constant flow when air brushing the addition of an air tank has been suggested. What size is satisfactory? I see 5 gal tanks for under $20 at
Harbor Frt.. Guess a pressure reg. & water trap would also be necessary. What experiences have you had? My pump is a small Badger type.
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I've been using a tank that I had made way back when and it is a piece of 5" tubing with caps on both ends that is about 7" long or so. Probably about a quart of cap. This tank has been quite good for me. A 5 gallon tank will provide air for quite a while after the pump goes off and will be more than satisfactory for this use.
-- Why do penguins walk so far to get to their nesting grounds?
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Bob May wrote:

I assume you mean a steel tank? Made properly that is certainly adequate.
As per MANY previous threads, let me remind everyone ...
DO **NOT** use PVC plastic for the tank or plumbing ... it is not rated for, nor is it safe to use, with compressed air! Such use is illegal in many areas.
I am well aware that many get away with using PVC air plumbing ... for a time. The literature is full of reports of the consequences, however, and they are NOT 'pretty'. Common PVC is rated for COLD water only ... VERY different than compressed air! When used with compressed air, PVC can and will explode unpredictably and catastrophically, sometimes at quite low pressures (only 15 psi). Sharp shards of the broken PVC can be scattered at high velocity. Severe injury is possible.
There ARE industrial plastics that are rated for compressed air use, but you won't find them at the average home supply house.
Dan Mitchell ===========
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At 30psi, aluminum or even PVC works fine. At 100psi, I'd either use a thick aluminum or steel tank. I'd even put a modified cap on a plastic soda bottle as they are designed to handle that kind of pressure. I'll note that even that little 1 quart or so tank takes a few moments to empty with the airbrush so there is plenty of filtering.
-- Why do penguins walk so far to get to their nesting grounds?
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Bob May wrote:

I disagree that PVC is safe, even at 15 psi. I've personally seen the nasty mess that results from a PVC vacuum chamber imploding, and that's only 15 psi. Such failure hospitalized a friend of mine, who now has permanent injury as a result. The total energy stored in the vacuum tank was much less than that stored in even a small compressed air tank (at the usual pressures).
The biggest problem is that the PVC fails catastrophically, without warning, and throws sharp shards all over the place. Metal can also fail, but tends to leak, bend, split, or collapse instead of fragmenting violently.
PVC is *NOT* rated for, nor safe for, compressed air use, period.
Yes, a soda bottle would indeed be safer ... and they're *NOT* made of PVC. I still would not recommend one for the use being discussed, however. They too can do nasty things, but fail at much higher pressures (as in bottle rockets).
Dan Mitchell ===========
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Dear folks:
How about an old car or truck tire? A donut spare should be able to hold enough air for a little airbrush.
I used to have a cheapo spray gun that ran off a tire. It seemed functional enough.
Cordially yours, Gerard P.
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On 12 Aug 2005 13:56:25, snipped-for-privacy@gannon.edu wrote

Hey, stupid. Greg Proctor already mentioned that. Read the whole thread next time, okay? Gosh.
Cordially yours, Gerard P.
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snipped-for-privacy@gannon.edu wrote:

I use one.

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On 12 Aug 2005 12:23:58 -0700, snipped-for-privacy@gannon.edu wrote:

The wonderful thing about your suggestion is that so many model railroaders have spare tires.
--
Steve

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He, he, he. I might have a spare tire, but there is no valve. Besides, since I am a cop, it is a donut tire.
wrote:

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On Sat, 13 Aug 2005 15:05:59 -0400, Frank Rosenbaum wrote:

Test tube baby? Or did you lose it? No biggee, a great man like Churchill was also a former navel person.
--
Steve

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No, not a test tube, I have an innie.

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agpete wrote:

Any size tank will act to smooth out the airflow - the larger it is the closer you get to a smooth flow. Five gal should be more than enough. I use an old car wheel/tyre with no valve and a cobbled up "T" junction

If you're using a pump intended for basic airbrushing then the pressure should be about right. A water trap is an excellent idea to stop the occassional "spit" that can spoil a pait job. My cheap and dirty answer is to use an extra long piece of 1/4" plastic tubing and loop it half a dozen times over a nail on the wall between tank and brush. Any moisture tends to collect at the bottoms of the loops and if any is visible I take it down and blow it out.

Adding the extra volume between pump and brush is definitely an improvement in spray quality. I have both a little Badger type pump and a full size commercial compressor/tank. Being able to alter the pressure is more versatile but occassionally I use the little pump for quick and simple jobs.
Regards, Greg.P.
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agpete wrote:

For an even air flow only a very small tank is needed ... perhaps one quart in capacity. Even a pint sized tank will help. Certainly a 5 gal. tank would be more than adequate for this purpose. I suppose the bigger the better, depending on available space.
The larger tank can assist with other properties, however. *IF* your compressor has a pressure switch to turn itself on/off, then the larger tank will mean it will run less often. The bigger tank may also serve to better catch moisture, as moisture tends to collect in the tank (which is much better than having it pass along the air hose to your airbrush!) Periodically, the tank will need to have any water deposited in it drained off to minimize internal rusting (inevitable with a steel tank).
Use a proper compressed air tank that is rated adequately for the pressure you intend to apply. Any 'garage' style tank will be more than adequate (usually rated to 100 psi or so.) Most airbrushing is done at 10 - 30 psi, and many small compressors can't reach much above 30 psi. There's no harm in going to higher pressure in the storage tank, as long as the compressor and all fittings are adequately rated. The regulator will step-down the pressure to the desired level.
A regulator and filter/moisture trap is also a necessity IMHO. Some get by without them, but you just won't get your best results that way.
A lot depends on your local conditions ... humidity, temperature, and dust in the air. The higher the humidity the more you need the moisture trap(s). Many use more than one ... one between the compressor and tank, and another between the tank and the airbrush.
The full assembly, in order, would be:
Compressor - hose - possible moisture trap - storage tank - mandatory moisture trap/filter - regulator - hose - airbrush.
You'll probably want a hose between the compressor and the tank/trap/regulator assembly. This just minimizes vibration (from the compressor) and noise issues. The tank/trap/regulator assembly are normally hard-plumbed together, though hoses could be used.
Small moisture traps are available that fit in the air hose near the airbrush. That's fine for a secondary trap, but if you use only one, get a larger one to put on the tank output. Drain it as needed (usually you can see the water/moisture inside the bowl)
Dan Mitchell ===========
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