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Mad Max

Mad Max

Imagineer
Joined
May 19, 2020
Member Number
325
Messages
359
so I have this idea for an air tank...but I'm not sure it's a 'good' idea - might be, might not be, and I'm surfin' for inputs.

Real estate in my truck bed is at a premium, and I am trying to use 'available space', in my case a rectangular area between the front bed wall and the tool box, and I'm in the middle of fabricating a 'rectangular' air tank to fit in that space. It'll have the usual 120-150 psi of air pressure, and it's either I continue with this tank, or...if the feedback indicates otherwise I'll go get a simple long round tank and be done with it...at the cost of losing precious bed space...and 'under the frame' is pretty packed too. If I can put this tank where I want I'll be delighted, but if it's a bad idea I'll do what I have to do with a standard round unit.

This tank is made entirely from 1/8" diamond plate steel, and it is roughly 39" x 7" x 3" - heavily seam welded. It'll have three bungs - one for fill, drain, and use. I drilled three holes through the middle along the long sides and welded in steel dowels to prevent ballooning. The mounting bolts are seam welded from the inside.

I've shown this to a local professional fabricator and retired desert racer who I trust a lot and he gave the idea a thumbs-up - didn't have a problem with the idea or design. I've also seen and read several reviews that have the common thread of 'it could be a bomb' and I am not indifferent to that intel - however - I also know that 'different' ways of doing something do not equal a 'wrong' way just because its different.

So - Good idea? Bad idea? I understand the PSI 'math', but I don't really know if this is a good idea or a bad idea.

lgD8uGr.jpg


93ONTJQ.jpg


lnCwU9m.jpg


36qJKbE.jpg


- Sam
 
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Mad Max said:
so I have this idea for an air tank...but I'm not sure it's a 'good' idea - might be, might not be, and I'm surfin' for inputs.

Real estate in my truck bed is at a premium, and I am trying to use 'available space', in my case a rectangular area between the front bed wall and the tool box, and I'm in the middle of fabricating a 'rectangular' air tank to fit in that space. It'll have the usual 120-150 psi of air pressure, and it's either I continue with this tank, or...if the feedback indicates otherwise I'll go get a simple long round tank and be done with it...at the cost of losing precious bed space...and 'under the frame' is pretty packed too. If I can put this tank where I want I'll be delighted, but if it's a bad idea I'll do what I have to do with a standard round unit.

This tank is made entirely from 1/8" diamond plate steel, and it is roughly 39" x 7" x 3" - heavily seam welded. It'll have three bungs - one for fill, drain, and use. I drilled three holes through the middle along the long sides and welded in steel dowels to prevent ballooning. The mounting bolts are seam welded from the inside.

I've shown this to a local professional fabricator and retired desert racer who I trust a lot and he gave the idea a thumbs-up - didn't have a problem with the idea or design.

So - Good idea? Bad idea? I understand the PSI 'math', but I don't really know if this is a good idea or a bad idea.

lgD8uGr.jpg


93ONTJQ.jpg


lnCwU9m.jpg


36qJKbE.jpg


- Sam
Click to expand...
IMO Bad idea.
To be marginal it is going to need "tie bars" on a pretty close grid through out the flat side.
That tank is going to want to be round more than rectangle.
 
I've got the tie bars already in it...just not shown in the pics
 
On one of my rigs 20 yrs ago , I made the rear bumper into an air tank for my OBA setup. It was rectangular tube and just the ends capped and welded. So a little different than sheet metal seem welded.

Can't remember off the top of my head but I'm willing to bet I went with a wall thickness of 3/16" for the tube. Worked great. Rig was a wheeler. If you can come up with a design close to what you have , but using box tube and less seem to be welded....I'd try that route.
 
Maybe build a simple hydro test rig (grease gun for pump?) to take it up to 2X your max working pressure and see if it deforms.

Instinct tells me that the support rods should be every 6" or so but you could probably go town to 5/16 or 1/4 diameter rod.

Also, I have had a pressure switch fail on my OBA setup. The pressure got so high that the gauges swept all the way over to back side of the pin and I thought it completely lost pressure. My cylinder tank held up to probably 3-400 psi.

Also that step in at the top is going to be trying to become a step out. In sheet metal that adds strength I don't think that is the case in a pressure vessel.
 
I have posted up here before the calculations needed to build a square pressure vessel. I'll try to find it again.
 
...I'm not gonna go through the math - I don't need this that bad, but here's pics anyway - on the back side the through pins are right in the middle

VvBGluX.jpg


QOj7tli.jpg
 
You did a good job on it. :beer:
If you are hell bent hook it up to a pressure washer and bump it up to 200 psi or so and see how she looks.
The constant flexing will kill the weld seams and the pass through rods.

If you go back to the MORR thread where they boxed the frame with much thicker material and used pass through rods and it still swelled and impressive amount IMO.
I know I have taken for granted how much force is in a air tank at "only" 100 psi.
I'd make sure if that failed it wouldn't maim or wound me/mine.
 
Mad Max said:
...I'm not gonna go through the math - I don't need this that bad, but here's pics anyway - on the back side the through pins are right in the middle

VvBGluX.jpg


QOj7tli.jpg
Click to expand...
Stupid square air tanks are no good. Toss it out and build a round one. Maybe if it was 3/8 wall thickness it would be fine but 1/8 that bitch is gonna blow up like a pillow.
 
don't get me wrong - I don't want to maim or wound anyone, which is why I asked y'all for yer inputs. Not all of my Mad ideas pan out and this one appears to be in the no bueno category, and as much as I want to use this tank I surely don't 'have' to - I'll probably just play it safe and grab a decent 5 or 7-gallon unit.

Thanks all
 
...I'm mostly just pissed I wasted a bunch of good diamond plate...but again I've wasted way more spendy things. Trying to think of what I could possibly use it for instead but nothing legit comes to mind. Can't use it for fluids because the inside isn't clean nor painted - meh - no big dealieo.

Thanks all for yer inputs 👍
 
Mad Max said:
...I'm mostly just pissed I wasted a bunch of good diamond plate...but again I've wasted way more spendy things. Trying to think of what I could possibly use it for instead but nothing legit comes to mind. Can't use it for fluids because the inside isn't clean nor painted - meh - no big dealieo.

Thanks all for yer inputs 👍
Click to expand...
Just keep it around until you have a need for the diamond plate. Torch it, cut off wheel, plasma....whatever. I've built plenty of things that just don't get used and then I pirate that shit for when I need a little material for whatever it might be. But saves me a trip to the steel yard, and then makes me feel like less of a ding dong for building something that I didn't use. Metal karma
 
Air tanks might be one of the most over rated things in offroad. It does absolutely nothing for airing up tires and maybe very little for air lockers.

I'm betting no one is running air tools anymore, so really there is almost no purpose at all in a wheeler.
 
Add like 20x the number of pins you have (like make a grid 2.5" on center or so) hammer form and weld on some additional reinforcement around the ends and run that bitch.

Throw a couple of bungs in and toss in some over pressure valves. Worst case it fatigues and vents out a weld after a couple years.

Also, rubber and strap mount it like a fuel tank since it's gonna flex a little. You don't wanna have it tear near the mounting tabs.
 
Meh, it's fine.
I've been running square air bumpers on tons of rigs, it's been done for years, but todays reddit engineers freak out.
The worst part is chasing all the pin hole leaks out of the seams.
 
...I'm really tempted to just 'try it' - weld on a bung, put it in the back of the shop, and pressurize is just to see what happens. If it handles the pressure maybe I'll run it. Honestly my biggest reservation is internal corrosion weakening the welds and the tank failing and then having to do a typical round tank anyway. I can pour in some sealant/paint etc and coat the insides - hell I dunno. I just like the cool nature of filling the space back there but I'm kinda over thinking about it...
 
YotaAtieToo said:
so really there is almost no purpose at all in a wheeler.
Click to expand...
What if you need to run a train horn:flipoff2::lmao:

I have a two gallon tank on my setup, I think it gives an initial boost to filling tires but have not done any tests with or without. I have a York so I probably don't need it at all but running the ARBs off of the regulated tank air gives me some pressure storage if something goes wrong I guess.
 
Mad Max said:
...I'm really tempted to just 'try it' - weld on a bung, put it in the back of the shop, and pressurize is just to see what happens. If it handles the pressure maybe I'll run it. Honestly my biggest reservation is internal corrosion weakening the welds and the tank failing and then having to do a typical round tank anyway. I can pour in some sealant/paint etc and coat the insides - hell I dunno. I just like the cool nature of filling the space back there but I'm kinda over thinking about it...
Click to expand...
Leak test it. Use acid to prep it for paint, wash it out. Then slosh some paint around in there and call it good.
 
...yah I might - got nothing really to lose. And no ARBs here - we're fans of auto-lockers (Grizzlys in our machines), but for sure I want some decent reserve air capacity because of air tools and having plenty of air to air up tires for road use, plus I will for sure have an air horn ;)
 
MigGunslinger said:
What if you need to run a train horn:flipoff2::lmao:

I have a two gallon tank on my setup, I think it gives an initial boost to filling tires but have not done any tests with or without. I have a York so I probably don't need it at all but running the ARBs off of the regulated tank air gives me some pressure storage if something goes wrong I guess.
Click to expand...

Ok, that's a good point, engine driven compressor and arbs, I can see a tank bring helpful.

I still stand by them being mostly useless for everything else :flipoff2:
 
Mad Max said:
...yah I might - got nothing really to lose. And no ARBs here - we're fans of auto-lockers (Grizzlys in our machines), but for sure I want some decent reserve air capacity because of air tools and having plenty of air to air up tires for road use, plus I will for sure have an air horn ;)
Click to expand...

It does nothing for airing up tires but give you a 2 second head start.

You actually bring air tools on the trail? :flipoff2:
 
Mad Max said:
...yah I might - got nothing really to lose. And no ARBs here - we're fans of auto-lockers (Grizzlys in our machines), but for sure I want some decent reserve air capacity because of air tools and having plenty of air to air up tires for road use, plus I will for sure have an air horn ;)
Click to expand...
Before you get too excited pump it up to 150 and see what happens.:flipoff2:
 
...keep in mind - this truck is not a competition rock buggy - this is an overland build, so yes I bring air tools and use air for things other than refilling tires...which is why I'm not looking at 7 gallon tanks - if I'm going with a typical tank and it's gonna take up some space I might as well get one with decent capacity. I picked up a twin-screw compressor (ARB knock off) so I'll have good refill rate so I don't 'need' a big tank...prolly go with a 5 gallon unit
 
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