pressure question

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So, I want to make a train horn for my jeep, run off a 20# CO2 cylinder.Simple, no electronics.I'm thinking a 2-3cf expansion chamber between the horns and the cylinder.Ball valve to activate the horn, a regulator to pressurize the expansion chamber (125 psi?)How dangerous would it be to weld the chamber myself?I have pipe at work I can use (6" x1/4 wall)
Reply:If my math is right, it's only about  1 1/4 TONS for ever linear inch of pipe on the side wall plus about 3 1/2 TONS for the two end caps.You tell me if you think something like this is dangerous. To me it sounds like a pipe bomb..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I wouldn't even have known where to find the math. Haha.Looks like I'll be finding a pre-made tank
Reply:Math is easy. Circumference of a circle. 2 x 3.14 ( Pi) X R ( 3" in this case).  That gives you a surface area of 18.84 square inches for ever linear inch of pipe roughly. End caps are R squared x 3.14 ( Pi) or about 28.26 square inches ( times 2 to cover both ends)Then you take your areas and multiply it by the pressure you are going to be at, 125 pounds per square inch.Worst place will be the two flat ends. They will want to bow naturally  from the pressure and the connection between the plate and side walls is exactly where your welds are going to be. Most concentration of stress at the point most likely to have a failure. All it's going to take is one minor flaw to start a failure and that thing will unzipper in a hurry..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:'' Worst place will be the two flat ends ''. Flat plate would definitely be a bomb waiting to explode and is not rated for pressure. IF you do make use schedule 40 weld caps.
Reply:I think I'll find a fire extinguisher to sacrifice.
Reply:What grade of pipe is that 6 inch?  If it's over x65 it will hold over 2000psi all day long. PVC will hold 150 psi in 2 inch. 1/4 wall pipe is plentry .188 will hold 1000 psi. Just make sure it's good grade pipe and caps.  Pm me if you have questions. Lots of guys here shouldn't do that type of welding and flat end caps are a big time disaster waiting to happen
Reply:You don't want to make a pressure vessel out of PVC. If it ever ruptures the plastic pieces will function as a grenade. Being non-metallic, the doctors will have great difficulty finding and removing all of the pieces from your body. Use a properly designed and built metal pressure vessel that is rated for more pressure than you will ever put in it by a factor of 2 or more.CharleyMiller MM252Miller Bobcat 225NTMiller DialArc HF / DIY Cooler2 Victor O/A TorchsetsMilwaukee 8" Metal SawMilwaukee Dry Cut "Chop" Saw 5 Ton Wallace Gantry Various Grinders, Benders, etc.
Reply:Tons of shops run shop air through PVC. Not that it is the best option for everyday use. I wasn't saying to build it out of PVC just stating what PVC can hold to compare how little pressure that. 6 inch would have in it.Shoot we weld daily on big diameter gas lines with 600 to 900 psi in them. 6 inch with 150 psi isn't anything. Hardly any volume in it.   If the op wants an easy fix go to harbor freight and get an air tank that is close to the size he wants.Last edited by specopswelder; 11-02-2014 at 06:38 PM.
Reply:Originally Posted by specopswelderTons of shops run shop air through PVC. Not that it is the best option for everyday use. I wasn't saying to build it out of PVC just stating what PVC can hold to compare how little pressure that. 6 inch would have in it.Shoot we weld daily on big diameter gas lines with 600 to 900 psi in them. 6 inch with 150 psi isn't anything. Hardly any volume in it.   If the op wants an easy fix go to harbor freight and get an air tank that is close to the size he wants.
Reply:Why bother !! just get a small air tank off a truck or little compressor and install it with a 12,Volt compressor . It's not like your going to be blowing it all the time running down the road.
Reply:Originally Posted by BD1As for PVC , the manufacture states that it is not to be used for air piping. http://www.usplastic.com/knowledgeba...contentkey=787OSHA does too, https://www.osha.gov/dts/hib/hib_data/hib19880520.html     http://www.lni.wa.gov/safety/hazardalerts/902.asp
Reply:Go ahead and use the 6 inch pipe but buy some proper butt weld caps.  Once you see the price on 6 inch butt weld caps I think you'll realize the economy of buying a pre-fabbed tank.  6" butt weld caps are $45 each on McMaster.com
Reply:Originally Posted by specopswelderStraight of Harvel plastics web page. Might not be recommend for air lines but sure as hell will hold the psi in question. Now pressure is givin in water without shock.
Reply:Why would you go through all the trouble to use Co2 and weld all this. By the time your done you may as well of just bought an onboard compressor like a Vair. Then you have onboard air and unlimited horn use.A grover 1510 stutter tone horn is a nice alternative to a train horn if your into that kinda thing...www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:I have the CO2 cyl.  And running an OBA setup for basically a toy, is too expensive.
Reply:So is filling CO2...What kind of train horn are you looking to run here? Those things use a very large amount of air. Whats the point of a horn that you press for 2 seconds and you are out of CO2?www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:20# of co2=2 seconds? The point is to accompany my weak factory horn,  to bring attention to colossally bone-headed moves by inept drivers.The expansion chamber is only there to prevent freezing of the horn during extended use and will be constantly filled from the main CO2 cylinder via a regulator.
Reply:Years ago I met a trucker who had a tug boat horn under his cabover KW ,He installed a second brake pedal to the left of the clutch ,he was using the air brake pedal as a valve for the horn .He had a large air tank like they use on air start trucks .  He said two blasts from the horn and he was out of air .It really freaked me out when I went to move his truck and there was an extra pedal.
Reply:Depending on the horn you are using, yes 20oz could be gone in 2 seconds.A real train horn uses A LOT of air. A 20oz paintball cylinder is very very tiny.Guy I know has a 5 trumpet train horn in his pickup. It needs a garden hose size line to feed it and it dumps a few gallons of air in about 5 seconds. If you are using a little toy of an air horn then I'm sure ul be fine but eventually you will spend as much in Co2 as it would of cost to have a handy on board air setup.There's a reason these things use air 99% of the time and not co2. By the time you do all this other stuff like an expansion chamber, high pressure supply lines and all you are going to be pretty in the hole on this project as is.Last edited by BrooklynBravest; 11-03-2014 at 12:39 PM.www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:I did not know if you knew this. In California, a train horn can be mounted on a car but not used. On a semi-truck, it is allowed if it is attached to the air brake system, powered by the air from the brake system, complies with FMVSS standards 121 and 106, and has the appropriate certifications. If you are found to have violated those terms, you can receive a MINIMUM $108 fine if there are no other violations or citations on your CDL.http://trainhorns.usLast edited by kiwi; 11-03-2014 at 04:27 PM.
Reply:Here is the whole kit.
Reply:20 pounds of CO2.... Not ounces.
Reply:So if you already have the 20 lbs of co2  ,save it for something important like quick cooling a 6 pack on a hot day and get the system shown above ?
Reply:In an earlier day the definition of the word safe was a relative thing. Is it pretty safe, safe enough, or reasonably safe? These days it is more of an absolute. Any mishap, somebodys gonna get sued! I've welded numerous tanks to use with 150 LBS of compressed air, typically, it's an adapt, or patch. I haven't had a mishap in 40 years. I've repurposed the same 120 gallon propane tank, (maybe 36" diameter) with modifications several times, once it took a journey down Otter Creek in flood water, came back battered, but useable. Is what you plan absolutely safe? No! Is it pretty safe? Maybe. How confident are you in your welding? How about your math? Could I build a tank? Yes. Can you? I don't know.  The circumference of a tank multiplied by the pressure gives the tensile strength needed, be conservative, figure 20,000 PSI tensile strength. A ten inch diameter tank holding 150 PSI needs to be 1/4" thick to hold with very conservative safety margins.The ends will control 12,000 Lbs each, hemispherical shapes are less prone to deformation. A weld 31" long will control 12,000 LBS pretty easily if sound. Let's consider corrosion. Over time the bottom will rust. Sound metal will get thinner. Should the vessel split, where will the blast go? Is it mounted securely enough to not become a projectile?At room temperature they claim CO2 requires 870 psi to turn it into a liquid. So I would have to imagine that the liquid could generate upwards of 800 psi at room temperature. I would do it with two smaller pipes myself. I would also funnel the ends if I could not round them. Nitrous oxide creates about 600 psi and not many common pneumatic products can handle that pressure without leaking. One time a lower pressure regulator I was using blew up in my face. That wakes you up.                       Sincerely,                            William McCormick
Reply:I still just don't see the benefit to using Co2. I realize you are trying to save money but you are now going to have this big 20lb co2 tank in your jeep at all times? Just seems silly man. As a fellow jeep enthusiast I am trying to steer you the right way on this. Its not really a custom welding project its something you should be buying ready to go for safety and operation sake.www.FirehouseFabricators.comZachLincoln 210mpLincoln SW200Hypertherm Powermax 45xp2x4 CNC Plasma Table.
Reply:I'm surprised that this has not been attached to this thread yet.
Reply:Harbor Freight (I know) sold some air horns with a rotary pump that was/is pretty loud, actually, a lot louder than the electrics, They are/were made in Italy. I installed them in my mercedes "but" with a relay so if I honked the horn (steering wheel horn) while applying the brakes, the trumpets honked. Some fool cut yah off, slam on the brakes & let em know.-c-