air tank bumper

admin

I'm have some 3"x5" rectangular tube I'm planning on using for making a rear bumper on my 4x4.  It's somewhat common to use bumpers as storage tanks with onboard air to actuate lockers, and I'll be running a pressure switch that cuts off at 110 PSI.Will my MIG welds for this be porous enough that they leak air, and is there anything I can do to prevent it?  I have an OA torch that I could use to re-melt the welds, but I don't know if that would do any good.  Obviously my experience level is pretty low with this, so any advice would be helpful.- James B
Reply:It is possible to make this leak tight with MIG.
Reply:a pressure tank out of square or rectangular tube is not a good idea pipe would be okChuckASME Pressure Vessel welder
Reply:An air storage tank is a potential bomb. Round is the ONLY way to go,  using square or rectangular is BEGGING for trouble. I personal don't think a bumper that is there to protect you in case on an accident should be used for high pressure air storage. I would prefer to see an air compressor hooked up to the motor, this would also give you unlimited air, not just the capacity of your "tank" Also, as you admit, "Obviously my experience level is pretty low with this, so any advice would be helpful." NO ONE, but a certified welder should be building pressure vessels! Yes, you might luck out, but what if you don't?  Picture yourself, a buddy, or a little kid, next to the end cap with over 100 psi blasting it into them....Just my  opinion, not from a book, just from the road.Howes Welding Inc.www.howesweldinginc.com
Reply:Originally Posted by tessdadAn air storage tank is a potential bomb. Round is the ONLY way to go,  using square or rectangular is BEGGING for trouble. I personal don't think a bumper that is there to protect you in case on an accident should be used for high pressure air storage. I would prefer to see an air compressor hooked up to the motor, this would also give you unlimited air, not just the capacity of your "tank" Also, as you admit, "Obviously my experience level is pretty low with this, so any advice would be helpful." NO ONE, but a certified welder should be building pressure vessels! Yes, you might luck out, but what if you don't?  Picture yourself, a buddy, or a little kid, next to the end cap with over 100 psi blasting it into them....
Reply:Interesting reading guys, never even heard of that before this post. Neat idea!If you don't have the time to do it right, then you definitely don't have the time to do it over.
Reply:We routinely use square and rectangular tubing on Folding machines in Industrial laundries for the frame members.These machines use lots of compressed to actuate air cylinders and blasts of air for folding and such. So given the proper wall thickness you can certainly build a safe air storage reservoir.My concern here is your welding profeciency..... It can, as stated above be a very dangerous thing to weld improperly... Please be very carefull ... As Dirty Harry once said "A man has to know his limitations".I know of a guy who was standing next to an air compressor when the copper pipe on the end blew off due to bad soldering. When he came back from the hospital he had quite a few stitches.Washman
Reply:i'd use a real air tank from harbor freight or northern tool and find a nice place to mount it..i would not ever use a homemade bumper for compressed air..even if I was to make it..its downright dangerous... ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I'd do it. Should be fine... But, If I were you I would TIG weld it.
Reply:I think what alot of the statements are saying is why take a risk, there are alot of proficient and tech savy welders out there but in todays world if something went wrong and you built the tank you are liable! So take zaps advice buy a tank and install it and if the tank ever fails the tank builder is liable.
Reply:I had a Ford F-350 years ago that had a factory made 4x4 sq tube rear air tank bumper that held 175 #. Can't remember the company but it had a pressure vessel plate on it. I made up a manifold with a gauge and a quick connect to inflate tires on junk cars. I could do 4 tires completely flat so the car would roll onto my trailer. Just my .02 ...BobBob WrightSalem, Ohio  Birthplace of the Silver & Deming Drillhttp://groups.yahoo.com/group/southbend10k/http://groups.yahoo.com/group/sawking/1999 Miller MM185 w/ Miller 185 Spoolmate spoolgun
Reply:Originally Posted by alanakerI'd do it. Should be fine... But, If I were you I would TIG weld it.
Reply:Originally Posted by zapsteri'd use a real air tank from harbor freight or northern tool and find a nice place to mount it..i would not ever use a homemade bumper for compressed air..even if I was to make it..its downright dangerous... ...zap!
Reply:Originally Posted by Dipper Welder64I think what alot of the statements are saying is why take a risk, there are alot of proficient and tech savy welders out there but in todays world if something went wrong and you built the tank you are liable! So take zaps advice buy a tank and install it and if the tank ever fails the tank builder is liable.
Reply:I gotta go with Rojo on this one--- Not that much pressure and not that much volume to be that worried about. Keep it in perspective. It aint rocket science. Its a bumper with a little bit of pressure in it. Do it. Do it right. Be happy. I did.
Reply:I'm comfortable that with wall thickness 3/16"" or better there should be good safety margin for a tank under 200 psi in the approx. bumper size mentioned. Your bumper tank will be way higher quality the thin cheapie air tanks from Harbor /Northern.  Build it! If you painted your bumper tank black and left it out in the sun, the pressure could rise considerably higher inside. Probably a reasonable idea to add a 250 psi pressure relief valve somewhere facing away from where people are likely to ever be.  www.mcmaster.com has several suitable pressure relief valves like p/n 48435K72 which cost $5.05 plus shipping and thread into an extra 1/4" NPT fitting you weld onto your tank. I love McMaster-Carr. They have almost everything...
Reply:Originally Posted by RojodiabloThat application is a no brainer for the intended use. I agree, if it were nitrogen or CO2, I would say no, but it is just a holding tank for the compressor.
Reply:Originally Posted by ClanweldLoving this post, even though I have no intention of making one up. Question: why air but not nitrogen/co2? I know I'm showing my gaps here, but it's among friends anyway. Thanks!
Reply:This has been an entertaining thread, for several reasons.To put some perspective on things, it doen't matter WHAT gas is compressed (within limits such as it doesn't decompose explosively at high pressures like acetylene, etc). The energy stored is solely a function of pressure and volume. For perspective, the gas in a 40 gal tank charged to 100PSIG has (roughly) the same energy as 1 stick of straight dynamite. In improperly made tank can, for example, a) be brittle, and therefore b) crack and throw shrapnel under even light impact. Not what I would use for a bumper.
Reply:A real world comparison - Tire repairmen routinely hold a 10 gallon tank charged with 150psi air in their hands. To seat a tire bead, they dump the contents in a one second rush of air, by opening a 2” gate valve. Now you wouldnt want to be in the air blast, but the bumper failing is not going to flip the truck over or anything. 3 x 5 x 72 = about 4.5 gallons.  Not much volume and no explosive generation of pressure, almost as soon as the bumper would  start to fail, it would be empty, probably no chance of a projectile. As a compromise, maybe tuck a pipe inside of a rectangular tube?
Reply:there is nothing wrong with one of these..there is no way you are putting 10 gallons of air in a bumper.. and it has legs and "mounting points" already  ...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Your right zapster.231 cubic inches in a gallon. Proposed bumper with id of  3 x 5 x 72  = 1080 cubic inches = 4.6 gallons.  ½  the volume potential of the 10 gallon hand held tank or tire air cannon.Hardly enough to blow "stainless dude"... off the barbeque!Last edited by denrep; 12-03-2006 at 01:08 PM.
Reply:I really don't care if he builds an air tank out of the bumper or not, but, knowing you need an inlet, outlet, tubing to and from, and should have a petcock for drainage----------------I wouldn't want all that crap on my so-called bumper. Especially if it's supposed to be a hard core 4 wheeler. I'd have it all ripped to crap in a week or less. I'd rather have a nice little reservoir discretely hidden up in a cubby hole somewhere. Nice neat little package that nobody knows is there and gives fail safe operation. That's the challenge.
Reply:sandy is right! You can get one off an old truck, complete  with fittings, drain valve, check valve and mounting brackets. Now, how about an auxiliary liquor supply in that front bumper?Last edited by denrep; 12-03-2006 at 01:22 PM.
Reply:[QUOTE=enlpck] For perspective, the gas in a 40 gal tank charged to 100PSIG has (roughly) the same energy as 1 stick of straight dynamite. Care to share where this came from?That ready made Northern air tank would be easy and convenient...Wow ya know I had a friend back in the 80"s that built such a bumper and it worked well but like some of the post's say there are other ways to get the same results! And Rojodiablo get real you can buy tanks thru mc master car that have nothing on there except for the stamped piece of steel which say's it meets DOT standards now show me were  it will be on his bumper.
Reply:http://www.grainger.com/Grainger/wwg...h&L1=Air+Tanks
Reply:[QUOTE=alanaker] Originally Posted by enlpckFor perspective, the gas in a 40 gal tank charged to 100PSIG has (roughly) the same energy as 1 stick of straight dynamite. Care to share where this came from?That ready made Northern air tank would be easy and convenient...
Reply:This is all good info.  I actually have an air-tank fitting kit that has a draincock, pressure relief valve, and connections.  This is going to be run with an onboard air compressor and controlled by a pressure switch relay.  Here is some reasoning on using the bumper for air:  after I mount the compressor and an extra winch battery under the hood there isn't room for my 10 gal tank, putting an import air tank in the passenger compartment seems more dangerous from an explosion and rollover perspective, this will only be pressurized on the trail not the highway, and I will treat the endcaps with caution.  The company that makes my front bumper uses the same material as I am going to use for the rear, and sells them as air tanks.  They just paint the insides first, which didn't get done with my bumper since it wasn't sold as an air reservoir.  I plan to primer and paint the inside of this one, and generally just enjoy doing things like this myself.  Plus I suspect the failure mode for this bumper would be a crack that causes the pressure to be released and not a simultaneous seperation of all four sides of the complete end cap. So back to my original question:  is there any merit to going over my MIG welds with a torch or would this just make it more brittle?- James B
Reply:No benefit other tham asthetics to tigging over the mig welds, as long as you are not welding the tank shut.
Reply:[QUOTE=Rojodiablo]No benefit other tham asthetics to tigging over the mig welds, as long as you are not welding the tank shut.[/QUOTE? ... .....  What am I missing?Washman
Reply:[QUOTE=Washman] Originally Posted by RojodiabloNo benefit other tham asthetics to tigging over the mig welds, as long as you are not welding the tank shut.[/QUOTE? ... .....  What am I missing?Washman
Reply:[QUOTE=Washman] Originally Posted by RojodiabloNo benefit other tham asthetics to tigging over the mig welds, as long as you are not welding the tank shut.[/QUOTE? ... .....  What am I missing?Washman
Reply:Then, BLOWOUT!! It takes a lot of extra work to get a tig to shut a weld on a tube. But if there is a bung fitting, or vent hole, tig is great.
Reply:[QUOTE=enlpck] Originally Posted by alanakerThe energy stored in 40 gal of air at 10ATM (approx 150PSI) is about 0.4MJ, or the equivelant of burning about 15 cm^3 of gasoline, half a shot glass full, or, equivelantly, or about one  stick of straight dynamite. Calculated the stored energy using standard equations from thermodynamics (I can reproduce if you really want.....) and looked the other data up (gasoline and dynamite) in a standard chemical reference.My original statement should have said "150PSIG" not 100, by the way. At 100PSIG, it is equivelant to  approximately 1/2 a stick of dynamite.I bring this up principly in response to several prior statements that were incomplete or incorrect. ANY compressed gas, air included, even at low pressures, represents substantial energy per unit volume and needs to be treated with care. Pressure vessels present a substantial risk if made improperly or abused, and can (and do) let go without warning, especially if abused (like a bumper may be). There is a reason that the many states call any pressure about 15PSI high pressure, and REQUIRE licensure and/or permitting for people to do work to even fairly small pressure retaining equipment.
Reply:[QUOTE=Washman] Originally Posted by RojodiabloNo benefit other tham asthetics to tigging over the mig welds, as long as you are not welding the tank shut.[/QUOTE? ... .....  What am I missing?Washman
Reply:Originally Posted by elvergonNot want to mess with you bro, Energy is the same but the amount of energy it has ain´t a real comparison on how "destructive something is". The real factor here is how fast the energy is released and other stuff...People would tie hollow tubes filled with pressure in the demolitions...hell less expensive...
Reply:I guess everyone has their own opinions on this subject.  Personally, I'm confident in my ability to build such a bumper and have done so in the past.  My .02DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:Bottom line appears to be that you can indeed build a bumper out of rectangular tubing and mig weld it and the final product will hold air.  Other than that, I haven't seen anything in here that factually states that doing so is hazardous.  In fact, this is done quiet often and very seldom, actually, never, have I heard of anyone being seriously injured or killed by an exploding bumper.  My own guess would be that using a welder is potentially far more dangerous than the proposed bumper would be.  Carry on with the beating of the dead horse.
Reply:Please post pics whenever ya get done DewayneDixieland WeldingMM350PLincoln 100Some torchesOther misc. tools
Reply:Perhaps Clint Eastwood/Dirty Harry had it right when he said "A man has to know his limits" .If you are comfortable with your welding/fabrication skills and understand the potential there, it can easily be done safely. My .02.
Reply:Just a suggestion. Instead of going to all the work to make a big heavy bumper for the back end of the truck there is another solution that might even workout better for you.Back a few years ago when I and a few of my friends were racing hot and heavy, each of us installed our own compressors on each of our pickups or tow vehicles.Here's how it works:First get a AC compressor from a like model engine, with the mounting bracket and install it on your engine. On the suction side of the compressor install a filter. On the discharge side run a pressure line to a tank, or if you want more air, mount one tank on each side under the pickup bed with a line tee'd into each tank. On the outlet side of one of the tanks run a air hose up from under the bed into the bed to a hanger so that you can coil up the hose, so it will always be out of the way. On the outlet side of the other tank mount a safety relief valve. Since both tanks fill together only one relief valve is needed. Hook up a toggle switch from the electric clutch, on the compressor, to the dashboard and a pressure gauge so you can see how much air is in the tanks. Whenever the air is used or is low, just start the engine and flip the toggle switch and the compressor kicks in and pumps up the tanks. This way you always have a air supply wherever you go and when not in use, the compressor is not wasting any horsepower and gas. The air tanks are not hard to find and with the right one or ones they do fit under the pickup bed nice and neatly and are out of the way. I have done this with quite a few of my pickups and so have some of my friends and it's worked quite well. Just a thought.
Reply:Thanks for the tip about using an AC compressor.  I looked into a York compressor, but from what I read it looked like quite a bit of bracketing and a very tight squeeze.  Those do make enough air to run some pneumatic tools, which would be nice, but I just opted for a Viair onboard compressor I found on Craigslist.If this was in my truck, I would just bolt my 10 gal tank in front of the wheelwell in the bed and be done with it.  But this is going in my Jeep Wrangler and I need to leave the back seat installed for hauling the younguns.  There are only a few square feet of storage, and I just can't get a tank in there.I've only been hobby welding for five years or so, so my skills aren't on par with a professional.  But I have tried to get as educated as I can about good practice, and understand the limits of what I can do.  In general, I try to make critical structural assemblies where the welds serve more to hold things in place than to take the bulk of a load as part of the structure.  This isn't my first bumper, and hopefully I can learn from what I didn't like about the last one.  Plus, I am going to cut up some test welds with the same material I am using for this project, to get the welder dialed in.Hopefully this weekend I can get this project going.  I need to make a winch mounting plate first, then am going to start on this.  I'll try to post some pix when I get done.- James B
Reply:Hey diluded000, Here’s the deal - Describe the tube specifications. I’ll look for a  similar  tube. We’ll build one and pressure test it.Maybe with hydro test method, maybe pneumatic.Test will be documented.Now if it’s legal, can we start collecting wagers? Bets could be based on how close the bumper gets to the moon!Proceeds would be used to help finance the test model or pay damage claims!
Reply:Originally Posted by denrepHey diluded000, Here’s the deal - Describe the tube specifications. I’ll look for a  similar  tube. We’ll build one and pressure test it.Maybe with hydro test method, maybe pneumatic.Test will be documented.Now if it’s legal, can we start collecting wagers? Bets could be based on how close the bumper gets to the moon!Proceeds would be used to help finance the test model or pay damage claims!
Reply:Originally Posted by RojodiabloIf I recall Diluded's spec's, he said it was going to be 1/4" wall. That=.250.....X100,000= 25,000PSI is my guess at burst strength. Actually, my guess is more in the range of .250X1,000,000=250,000 PSI. But to test that one this weekend is not a good idea...Nasa is already planning on launching their own object into space!!!!@ I seriously bet the bumper would hold 25K if it is .250 wall. And I have $100 to give to Zapster to hold if someone wants to bet against it. My question, how do you get 25,000 PSI out of a compressor to test this?? Or, to do it, do you have to switch to hydro for that kind of pressure??? And of course, I will have to agree on the bumper design and more importantly, the fittings used for this 'test'..... Me and Ben Franklin say it will hold. PERIOD.
Reply:Rojodiablo,I’ve reconsidered. Taking your bet would be the same as stealing your money! I say the house allow you a chance to reconsider and retract. Or else… it’s post time!
Reply:Originally Posted by denrepRojodiablo,I’ve reconsidered. Taking your bet would be the same as stealing your money! I say the house allow you a chance to reconsider and retract. Or else… it’s post time!
Reply:Originally Posted by RojodiabloSo maybe some kind of graded bet??? If say the bumper blew at 2500PSI I'd be on the hook for $100, and then it would graduate downward as the pressure rose? Say like $75 for5K psi $50 for 10K psi, and $25 for 15K psi. And I assume you would be on the hook for $10 starting at 2500, and going up in graduations until it blows. And that is what I am looking for....when will this thing BLOW. Not deform a bit. We can note that, but I am talking holding pressure until it dies. And honestly, the money is just to pay admission to see the show!!! I don't really care if it pops at 200psi. It will be fun just to see it go off.
Reply:Originally Posted by denrepI’m game! Maybe a stop and side bet at every 100 psi? Say,10 times the dice roll, if it takes another 100 lbs?