building a fuel cell / gas tank

[daniel_buck]

So I'm going to be relocating the fuel tank in my CJ, and I'd like to take that opportunity to weld up my own fuel cell. Any chance I can to get more welding experience

So anyway, from what I gather reading online, a tank made of mild steel needs to be sealed on the inside (or have a bladder, I guess). Since I don't know anything about welding aluminum (and I'm not setup for that either), I'm just going to stick with mig welding (argon/C02 gas) mild steel.

Eventually I think I'll make one that fits under the tub, once I get my suspension and everything else figured out, so that I know how much room I really have. But for now, I'd like to just make a simple one to strap down in the tub behind the seats.

A few questions:

* what gauge steel would be appropriate for an in-tub fuel cell?

* anything that I need to be aware of while welding? obviously the welds need to be air/liquid tight. Should I run a bead on either side of the main bead just for security? And maybe pressurize the tank for a few house to check it for a good seal?

* could I still use the mechanical fuel pump that's mounted to the motor?

* is it just as simple as putting a filler cap and vent on the top, and hooking up a line to the bottom of the tank (if mechanical pump is used) with a tip-over valve? Just those 3 main additions to an otherwise simple metal box?

[curtis]

I made a steel tank for one of my cars a long time ago. I was never happy with it because of rust and contaminants. I would have one built by a tank fabricator. I don't think it would cost that much and I would feel alot better about safety. My :2:

[aw12345]

I second what Curtis said find a place that makes fuel tanks and have them built you one.
When you make one, you are going to find leaks. You have no means of pressurizing it, nor do you have a water tank tp see where it leaks once you have some pressure in it. So your best bets are either a tank shop that can built you one or buy an aluminum cell that fits your needs

[inVERt'D]

I think it's great that you're getting into fabrication and challenging yourself, but these guys make good points. If you're an inexperienced weldor, that's really not a great project for you. You run a high risk of having pinhole or weeping leaks and weld defects that you likely won't discover until gasoline has been in it awhile. It could also catastrophically rupture as the result of a defective MIG weld. You don't want to be doing the Ricky Bobby dance for real.

If I were going to do it, I would use aluminum (probably 14-16 GA) or stainless (probably 18-20GA). I can run a nice, smooth MIG bead, but I would NOT MIG weld it. MIG welding's major issue is cold lap. I would use either TIG or Oxyfuel (e.g. oxy-acetylene), since I could produce a weld with less risk of unknown defects--especially cold lap.

BTW, in my magnificently humble opinion, MIG is probably the worst process to start out with. I would suggest oxy-acetylene. You can also use oxy-propane, but it's not as hot. Oxy-fuel is fairly inexpensive to get started with and will teach you to get good at the most fundamental skills in welding. 1) how to start and run the puddle, 2) how to melt two pieces of metal together, 3) how to add filler material 4) knowing the difference between 2 & 3. MIG just runs those first three things together so fast you can hardly tell what's going on. By the way, this isn't known very well, but Oxy-acetylene can be used to make excellent welds in just about anything. Some tout it as superior to TIG for aluminum--more ductile welds. But that's mostly from light airframe guys--what do they know (except they don't want to die)? Oxy-fuel is also a great prep for TIG. Plus you can cut thick metal, heat stuff, sear a steak--you name it.

[jonah]

I made one out of 16 ga. with a design that minimized seams at the bottom of the tank. It took me a few tries to get all the pinholes closed up so it wouldn't leak. The welds really have to be perfect. I was going to coat the inside, but I plan on redoing it in aluminum now because I want to make it bigger. All in all I don't think it was worth it except I wanted it to fit in a very specific place and I wanted to try it. You can see what I did here: http://www.myjeeprocks.com/forums/sh...g-says./page14

But, I would seriously consider a pre-made tank especially if it is just going in the tub. A lot of CJ guys use RCI's 2161A for about $250.

In fact I think I might order one!

[aw12345]

Just bought one of those for my new toy, off ebay 200 bucks including shipping. Once in a while Fleabay is the shit

[jonah]

Nice, I just went out and measured my tank area. I think I could drop it into my existing mount (with minor modification) and cut a bit of the floor out and it would only come a couple of inched into the bed. Can't wait to see the new one going!

[Toolman]

one way to pressure check a fuel tank is with a smoke machine, (evap tester). I use my smoke machine to find leaks in everything from, vacuum lines, gas tanks, air tanks, t-case, transmission, engine you name it, if fluid goes into it and finds a way out, so will the smoke. Never , never , never pressurize a tank with compressed air when it has gasoline in it. Use Nitrogen.

I'm interested to learn how to weld aluminum with a torch, just need to buy some filler rod.

[inVERt'D]

Good advice, Toolman.

Besides rod, you'll need a proper flux, a stainless steel brush, special goggles, of course, practice.

Here's are a couple of links you'll probably enjoy. This is something I've been wanting to get into myself for awhile now. Oxy-acetylene was the first process I learned back in high school metalshop, and I have loved it ever since. I had long heard of "old timers" using OA for aluminum, but only fairly recently begun to investigate it in earnest. Acetylene isn't cheap when you weld a lot, but there are other options. Plus the starting cost is a lot lower than a Miller Dynasty, and the results often better.

http://www.youtube.com/watch?v=aF1Srs_e1Aw

http://metalshapers.org/tips/white/a...ding/index.htm

[Ol Man]

Way back when I took welding at Adult Ed in Simi Valley, our instructor had us using Oxy/Acet for quite a while before allowing us into different types of electrical welding. He really wanted you to learn how to observe and control a puddle.

[daniel_buck]

Sounds like OA would be fun, I may have to try that some time :-)

Maybe I should pass up on the fuel tank, probably not a good idea for a beginning welder? and just think of something else to get some welding experience with, something else practical :-)

[inVERt'D]

how to observe and control a puddle.

That's where it's at, right there.

Sounds like OA would be fun, I may have to try that some time :-)

Maybe I should pass up on the fuel tank, probably not a good idea for a beginning welder? and just think of something else to get some welding experience with, something else practical :-)

OA can be a lot of fun. It isn't the best answer for everything by any means, but it is very versatile and very portable. I wouldn't want to use OA for welding 1/2" steel plates together. It can be done, but OA isn't hot enough to do it easily or economically. Stick in DCEN mode would probably be my first choice.

Don't get me wrong, MIG can be great. It is capable of making good, strong, attractive welds very quickly and economically. But it is also capable of fooling you. Stick is great too--I love welding on thick metal with 5/32" 7018.

Think up some projects according to what your MIG is well-suited for (which is why I asked what it is). In the meantime, you can get set up welding "coupons" of clean steel together. Weld 'em together, put em' in a vice, whack 'em with a sledge hammer, and see how they hold up. Cutting the cross-sections is instructional too, especially if you etch them with a mild acid so you can see exactly how your bead penetrated.

[daniel_buck]

my Mig is a Lincoln 180 Dual. I don't have 220 power at my house yet though, so I'm stuck running it on 110 for now. I'm going to see about having 220 run into the garage.

I've mostly been running it with solid wire (.025 i believe) and the typical Argon/CO2 mix, but I've tried it with .035 Flux core and no gas as well. I like that the flux core seems to penetrate more, but I don't really like cleaning up the flux coating, and I think I need more practice with the flux core, sometimes I get odd results.

I'm getting pretty confident with the Mig, on thinner gauge stuff, up to 1/8" maybe. But I still want more practice :-D That's why I was thinking a thin gauge gas tank might be a good project. I don't really have the resources to bend metal (if it's thicker than what I can bend by whacking at it with a hammer or pulling on it in a bench vice). I've got an angle grinder and a chop saw for cutting.

[inVERt'D]

That's a good little welder. 110V MIG is good for very thin sheet metal, like auto body stuff. The thinner the wire the better really. Try .023 if you haven't yet.

I've screwed around a little with 110V flux core, but not much, and not with great results. With 220 on the other hand, I've laid down some beads I was pretty happy with using .035 Innershield. For a wirefeed welder, the wirespeed determines the amperage used. The other knob on that thing controls the voltage. Turn the voltage all the way up and crank your wire speed up until your puddle buzzes (this doesn't work with 110). Remember to always switch your polarity when going back and forth between MIG and flux core: DCEN and DCEP, respectively. Could explain your sometimes "odd results." BTW, DCEP, aka "reverse polarity" is the reason that flux core penetrates a little better than MIG.

When you get the 220V going you'll probably never want to screw with 110 again. That machine will be able to weld 1/8" single pass with good penetration with 220V, but not 110V. If anyone tries to tell you that you can weld anything critical with 110V and preheat, poke them in the eye.

Preheating makes a big difference in MIG--especially in the first few inches. The sun can warm stuff up enough to make a difference.

Keep your stickout (distance from metal) short--about 1/4" to 3/8". Keep your ground close to your welding. Remember to disconnect your battery when welding on your Jeep. Don't ever have your ground on the opposite side of the vehicle from where you're welding.

[jonah]

Glad to see you have upgraded from the "PowerMig". Although I got a lot of great welds out of that machine, it was pretty fussy to use. The Lincoln will treat you well. Like David said, I too have had better luck with thin wire on 110. The flux core I stay away from, I always found it harder to get good results.

Get that 220 going and you will really be in business.

As for a sheet metal project idea, I would build a center console with built in cup holders. Basically the same type of structure as a gas tank with less chance of explosion!

My only welding tip is make the metal really clean and the joints tight and the welding is so much easier.