Bumper Air Tanks?

[anvil]

I'm just starting to build my rear bumper. Is there any reason not to seal it and use it for an air tank? There has to be some down side I haven't thought of. Would puncturing the bumper in an accident be dangerous? Will moisture buildup in the bumper? If you have a bumper air tank, do you use it and do you like it?

 

[CJJ92yj]

There's a reason pressure vessels need to be certified. Could be extremely dangerous in an accident. Say you have it filled to 100 PSI and someone in a little Metro rear-ends you as you are driving to the trail. And suppose that weld you thought was plenty strong in fact was not. Bye Bye Metro. Could have otherwise been a little fender bender.

I always assume the worse in these cases though because I work in a shop that builds pressure vessels. Ever seen a rectangular pressure vessel? Nope. If you have to do it, I would make it out of Seamless tubing at the very minimum. Then I would have all the welded joints 100% radiographed to ensure it's strength. Probably cheaper to just buy a small tank and mount it somewhere.

my $.02

Chad

 

[DevinB]

On the flip side, IMuneducatedO, 100psi in a tank isn't going to do crap if ruptured. You can hold 50 psi in a tire with your finger. The worst that's going to happen is when you're in a wreck and the bumper is ruptured, the air will escape through whatever hole in a couple seconds. You're not going to have a massive explosion or anything. If you're really worried and have a few bucks to spare, pick up a used air tank, fill that sucker up, and take it out and shoot it. Nothing special is going to happen.

:disclaimer: I could be totally wrong. I've been known to spout off absolute crap. Feel free to rip me a new one if I'm wrong.

 

[waynehartwig]

Worst case, leave the compressor off when you don't need it. Then the tank won't have any air in it anyway.

 

[bretto]

I concur with Devin. There is nothing going to happen if it ruptures. 100 PSI will be gone in an instant. Now if you had a Co tank strapped as a front bumper, I'd be worried. They certify those tanks cuz they hold in excess of 2k PSI.

 

[anvil]

Devin B, I always appreciate a good practical test. I've shot propane bottles before and they are higher than 100 psi. They twirled on the ground for a minute, but nothing catastrophic.

CJJ92yj, What do you mean "bye bye Metro?" I don't think it will blow a vehicle into small nonrecognizable pieces. If an entire weld blew open it seems like it would vent quickly with little destructive force. Maybe I'm wrong. Thanks for the input.

The bumper is 2x6 .188 wall. I know it's not the ideal shape for a pressure vessel, but I think it will hold 125 PSI okay. A pop safety valve should ensure the pressure doesn't go any higher. I'm very comfortable with the welding. Now that I live near DATC I've thought about getting certified. Maybe that should be a new thread.

 

[CJJ92yj]

I overexaggerated the "byb bye Metro" part obviously. Hopefully it would vent as quickly as you say it will. If it happens faster, I'll be glad to not be too close. Real world experience in this matter tends to lead people that because most of the time things don't go as badly as they could, they probably never will. I'll err on the side of caution though.

The first Boiler and Pressure Vessel Code (1914 edition) was published in 1915; it consisted of a 114-page book, measuring 5 x 8 inches. Today there are 28 books, including a dozen dedicated to the construction and inservice inspection of nuclear power plant components, and two Code Case Books. The 1998 edition of the Boiler and Pressure Vessel Code contains more than 14,000 pages, each of which measures 8 1/2 by 11 inches; it occupies 12 feet of shelf space.

Must be a reason that book is 12 feet deep.

Hopefully I don't rain on your parade, so to speak. It's just what I've been taught.

 

[great scott]

I ran one for about 2 years on the front of my blazer. It did'nt hold very much air, especial when used to fill up my 39.5 x 18" boggers. It did help some and I did like it (better then nothing). Eventually when trying to push over/through a huge bolder it did split when the bumper kinked. The air just spit out, nothing crazy.

 

[Rusted]

Just a little math even though I don't have all the details. But a 2x6x55 bumper will hold less than 3 gallons of volume. Maybe before you bother find one of those 3 gallon port a tanks and see how far it goes in your big tires. So don't count on the bumper being a very big tank, you will need an onboard air or something else to keep feeding into the bumper and the bumper may be more of a pain than anything else.

 

[1993yj]

My brother has a setup on the front of his Ramcharger that he actually tapped fittings into the two tubes on his brush guard. It doesnt do much to hold air, but helps to buid up some pressure for when he does use his on-board compressor in conjunction to air up his tires. He just has to male quick release couplers on each end of the tubes, that way when he wants to air up, he runs an air hose from his compressor to one tube, then to the next one, and then to his tires. When he is done airing up, he unhooks the hoses and the air releases. There is no air stored in there while he is not using his compressor, so no worries about explosions, which I seriously doubt would ever happen anyways.

And volume is also a big thing like rusted said. There is no way that your bumper could hold enough air to air up all of your tires. You will definately need an on-board compressor for that to be posible. I assume that is why you want the tank at least, to air up after a trail?

I think that having a bumper which held air in there already would be even more beneficial. If his motor wont run for whatever reason, then no air, period. If you do something to your motor, but have some air in your tank/bumper, then you may still be alright.

As for the 12 feet of space that book takes up, give me a break. We are on completely different terms here of Boiler and Pressure Vessel Codes here when it comes to 100psi of air in a bumper vs. the fact that I dont want the propane tank in the front of my trailer to explode and blow up my family

 

[anvil]

I currently have a CO2 tank, but I plan on running a york in the furture. I won't be relying on the tank to completely refill my tires after wheeling. I figured if I'm already building a bumper I might as well make it double as an air tank.

Thanks great scott for the crash test info.

 

[Rusted]

Also concider a way to either dry the air, or a way to drain the water out of your bumper. Can you coat or paint the inside with something?? Think of all the rust that a bumper would accumulate from the inside out.

 

[cheapzuk]

I concur with Devin. There is nothing going to happen if it ruptures. 100 PSI will be gone in an instant. Now if you had a Co tank strapped as a front bumper, I'd be worried. They certify those tanks cuz they hold in excess of 2k PSI.

co2 tanks are only at 600-900 psi depending on the temp. the reason for this is because at that pressure the co2 changes to liquid. if you were to put an oxygen tank on there you would be looking at 2000 psi. just some usless info if anybody cared.