Hollow front bumper as an Air Tank

harper7

harper7

Senior Member
I started a new thread on the front bumper instead of off topic chatter on SOcal's build thread.....anywho..... The actual front bumper under the plastic cover is a hollow Aluminum extrusion made of very strong high quality aluminum. I'm guessing 7075T6 or 6061-T6 with a center support and rounded walls on the inside.It was super tough and I had a hard time drilling thru it so I have no doubt it will hold air pressure.

Read about the idea of welding air tanks inside aftermarket bumpers and figured that it should work for our oem one too. I figure ours would hold 2-3 gallons of air,maybe more as it's pretty big really. We would need to weld the ends closed make some seal able covers for the bolt access holes and tap a couple holes for air.Now if you got in a bad wreck it would probably blow out the access plates first as they would be the weak point. Also read an idea of using the hollow sliders like bud's and shrockworks but don't think they would hold that much air.

Who thinks it would work?
 
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No reason that I can see that it wouldn't. In my old ratted out Nissan I used the frame rails as air tanks for the airride. It takes a good welder, but it can be done.

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I thought I had some photos of the inlets, but I cannot find them. I haven't had that truck in a few years. Huge POS, but a lot of engineering went into the suspension. Glad its gone :beer:
 
yeah, I think it would work well, and is a great idea, but ultimately would have to ask myself if the cost of fab & weld be worth it over tucking a tank somewhere under the truck? Great space saver though.

being a pressure vessel, i would want to seal the bolt access holes from the inside, but being low pressure, its probably unnecessary. It would probably be easiest to have the "tank" ports fabricated into the end caps, that way you wouldn't have to drill the crash bar any more than necessary and possibly weaken the crash bar itself with all the extra holes. (I'm assuming the bar was engineered to enable it to transfer forces in a specific manner, I wouldn't want to screw that up.)

A relief valve would probably take care of any over-pressurization (or compression from a wreck).
 
What's the wall thickness and the overall area ? Even a 10 psi pressure can cause a lot of stress in a rectangular pressure vessel. I'd break each section into flat plates, calculate the load caused by your desired pressure on the plates and then calculate the stress caused by the load using a clamped edge equation for a flat plate.
 
Interesting Interesting. Going to follow your work on this one Gary. If or when I get an air compressor I might try to put the tank in the front bumper.
 
Baja Runner said:
What's the wall thickness and the overall area ? Even a 10 psi pressure can cause a lot of stress in a rectangular pressure vessel. I'd break each section into flat plates, calculate the load caused by your desired pressure on the plates and then calculate the stress caused by the load using a clamped edge equation for a flat plate.
Click to expand...
I would personally make a box that hides behind the bumper versus using the bumper itself. Depending on how much pressure you intend on having in the tank, I would probably run a 3/16" wall or so. I do not know what the bumpers are built with, but I would not put air pressure behind something thinner.
 
Here is what I posted in response on my build thread.

The problem with the front aluminum bumper is just sealing it up. It wouldnt be that big of a deal to weld a plate on the ends to seal those or even seal up the access holes milled in the front. Those acess holes were only used by Toyota to put the splined studs in the back side of the aluminum bumper to attach to the frame, no bolts in there. The only pain would be sealing the studs up... if they were bolts you could use a sealing washer and be done... a little silicone might do the trick.

The aluminum front bumper is aluminum box extrusion with a stiffening web halfway through, running end to end. The front is .250" thick, the top and web are a bit thinner, maybe .1875" or so. To calculate the burst pressure if the bumper were to be made into a air tank I am guessing we would have to know the series and temper of aluminum. Its not welded so it could be pretty much anything, 2000 series, 6000 series... It is definately in T6 condition, like Harper said, the stuff is pretty tough to drill through. Hopefully its a weldable alloy. If I were doing it, I would weld it up, add the 1/4" pipe bungs and pressure test it up to 250psi or so. The little Viair compressors only run to like 140-150 psi or so.


Any fabricator with a TIG torch and some .25" aluminum plate could plug the holes in about 10 minutes. Only a few little 1.25" holes in the front and the end caps. Add some nice threaded bungs and your barbed hose fittings and your in business. :guitar3:
 
Why not just replace the aluminum tube with a steel 4" x 2" tubing or tubing, angle the ends so it's shaped just like stock. Drill holes through the tubing and sleeve them (mounting location). It would make for a stronger bumper and tank. I did this with my jeeps. I am sure it can even be done simpler then that.

Just to lazy now adays.
 
Last edited:
harper7 said:
I started a new thread on the front bumper instead of off topic chatter on SOcal's build thread.....anywho..... The actual front bumper under the plastic cover is a hollow Aluminum extrusion made of very strong high quality aluminum. I'm guessing 7075T6 or 6061-T6 with a center support and rounded walls on the inside.It was super tough and I had a hard time drilling thru it so I have no doubt it will hold air pressure.

Read about the idea of welding air tanks inside aftermarket bumpers and figured that it should work for our oem one too. I figure ours would hold 2-3 gallons of air,maybe more as it's pretty big really. We would need to weld the ends closed make some seal able covers for the bolt access holes and tap a couple holes for air.Now if you got in a bad wreck it would probably blow out the access plates first as they would be the weak point. Also read an idea of using the hollow sliders like bud's and shrockworks but don't think they would hold that much air.

Who thinks it would work?
Click to expand...

I absolutely think you could weld up your bumper reinforcement and turn it into an air tank. I measured a little and SWAG'd a little and came up with 2.96-3.0 gallon capacity at atmospheric pressure of 14.7 psig. I have no idea what pressure you could charge the tank at safely. I do not know the material yield strength of the reinforcement so there is no way of calculating the strength. I also know the shape of the member does not lend itself to storing higher pressures. I would think you will deform at least and rupture at worst long before you got to a usable pressure (100-130 psi) of your stored air. Low pressures of a few psi I would think would not be a problem. I have witnessed first hand what even a few psi will do to 1/2 inch steel plate and it is predictable. It wants to turn a rectangle into a cylinder every time.
 
Just for example, I designed a pressure box that is 27x17x2 " to hold 10 psi ... the box needed to be made of .25" steel. A 10psi pressure creates a load of 4590 lb on a 27x17" plate...its a lot !! It still makes my head spin.
 
Baja Runner said:
Just for example, I designed a pressure box that is 27x17x2 " to hold 10 psi ... the box needed to be made of .25" steel. A 10psi pressure creates a load of 4590 lb on a 27x17" plate...its a lot !! It still makes my head spin.
Click to expand...

Umm...I'm no engineer, but I'd say that box is slightly overkilled. Think of a cheap air compressor tank. Rated for 150psi, 21" x 45" or 26 Gallons. It's made of like 1/8 plate. Agreed, air does not compress well and generates tons of pressure. Was there some formula you used to arrive at 1/4" plate?
 
Socco said:
Umm...I'm no engineer, but I'd say that box is slightly overkilled. Think of a cheap air compressor tank. Rated for 150psi, 21" x 45" or 26 Gallons. It's made of like 1/8 plate. Agreed, air does not compress well and generates tons of pressure. Was there some formula you used to arrive at 1/4" plate?
Click to expand...
It isn't at all. Try grabbing a paper lunch sack and blowing it up. It is rectangle, but what does it do? Turns to a cylinder. The same thing will happen with a thin walled air tank that is a rectangle.
 
Baja Runner said:
Just for example, I designed a pressure box that is 27x17x2 " to hold 10 psi ... the box needed to be made of .25" steel. A 10psi pressure creates a load of 4590 lb on a 27x17" plate...its a lot !! It still makes my head spin.
Click to expand...

brockeverly said:
It isn't at all. Try grabbing a paper lunch sack and blowing it up. It is rectangle, but what does it do? Turns to a cylinder. The same thing will happen with a thin walled air tank that is a rectangle.
Click to expand...

Yeah, I agree that pressurizing a cube will cause the walls to deflect. I suppose I'm just in shock that that 10psi needs 1/4" plate. I'm used to dealing with high pressures. I see 3/8" copper tube with .035" wall holding back 600 psi all day long.

But there in lies my brain fart last night, you were concerned with deflection. Not rupture. :cheers:
 
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