My thoughts on building a gas tank

Discussion in 'Painting, Welding, Bending and Gas Tanks' started by Sgt. Howard, Jun 5, 2014.

  1. Sgt. Howard

    Sgt. Howard Member

    Seems simple enough, right? I mean, seriously- if you can fold a cardboard box and have ANY welding skills, you SHOULD be able to do this... one might think.
    I have been doing up two saddle tanks of the 1912 HD variety to drop on a Worksman cruiser for some time now.... Simple, squared (more or less) boxes with a filler cap and a out spout, one for either side, about 2.3 gallons between them.
    I bought a sheet metal brake. I bought a wire feed welder that can also do MIG. I bought a specialty sheet metal tool for small bending.

    What could go wrong?

    Well, after the first three attempts at a decent pattern, I began to realize that corners can change dimensions of the finished product more than you might think- a slight radius will increase a linear dimension by not pushing more material into a perfect edge. Standard High School geometry will require adjustments to work... SEVERAL adjustments. So, I finally got the pattern where I wanted it- I cut out the right tank and proceeded to bend it in my brake. Two of the end pieces got a corner crimped because they were across the line ... well, unless you are doing a truly SQUARED box, that can happen. Hammer the crimps out on the anvil with a chasing hammer. Looks good (enough).
    Now, to weld- I have never operated a wire feed welder before- I was told they are simple to learn.
    Well, yes and no- a gas tank in NOT a good first project. They are actually a bit demanding, as I will describe- I was told to use the MIG operation as that give a less porous weld.... I was too impatient. Plus, I didn't have the right wire or gas. Oh well, I will figure it out I tell myself.
    First weld looked like chickens took turns pooping out the seam. I ground it down, and re-welded. Now it looks like they had the runs. I ground it down and re-welded. Now it just looks disgusting- and further grinding shows where the metal around the weld is paper thin... so I go (next day) to build up that area.
    I have an automatic helmet- it goes dark with the first spark. I set up and hit the first spark. My retinas scream and run for the Canadian border... little Andrew had found my helmet and played with the dials. I was blind for a few hours. Got most of the sides beefed up and smooth- then somebody suggests I lay down some brazing. Sounds simple enough- sorta like using brass for solder, right? Never done it before but I am told it is simple to learn (you would think that I should recognize that phrase as a red flag by now, right?). So I get the necessary stuff and light my pony torch- after five minutes, I am again blind. James 'borrowed' my gas glasses and replaced them with ordinary sunglasses. My retinas did not leave my body, but both fovias are still upset with me.
    Well... there have been six runs of braze on both tanks. They still leak. Minor pinhole leaks, but leaks non the less. I will purchase gas tank sealant and cheat- at least it is not like before where I could comfortably BREATH through the tanks...

  2. Buell916

    Buell916 New Member

    Good story.
    You could write for a magazine.
  3. AssembleThis

    AssembleThis Member

    Learning To Mig Weld

    Hi Sgt. Howard!

    Recommend you go to You Tube. Enter Welding in search, there are many videos with excellent information. I've worked professionally as a welder, auto body mechanic and other trades and I still go to those videos. Every time I watch one I learn something new or something I forgot. I also have a channel with the same name, you can check out a few of my project videos. Unfortunately I'm still learning to use the Nikon digital camera so they are not great lolol. But I love to learn so I'll keep trying till they get better.

    Practice as much as you can on scrap metal. As your skills improve decrease the gauge of the metal. Start with say 1/4 inch thick plate. When you can weld paper thin steel your there. But continue to practice.


  4. butre

    butre Well-Known Member

    My welds are decent enough but any time I absolutely 100% need them to be airtight, I put a bit of jb weld over them to seal any gaps.
  5. Sgt. Howard

    Sgt. Howard Member

    Finally going after it again- had to get through some RL drama before I could worry about motorbikes. I have been informed of virtually every error I had made in this adventure (too many to list) and have been properly schooled by no less than the archives of the Davidson boys! As such, I have built my first last! No, that is not a typo... pre-WWII gas tanks were built on what is called a 'last', which will determine the size and shape of the tank... well, the pieces are shaped on the last, then removed and brazed. We will see how properly I screw that up...
    Herman Klutz likes this.
  6. Herman Klutz

    Herman Klutz Member

    That is how my former neighbor and I built a tank for a 3 wheel bicycle based buggy, we took a piece of 2x6, and doubled so it was 3" wide and 5.5" high. Then cut it to shape to fit in between his 2 cross bars, leaving a little space. Next we cut sheet metal to fit the sides, with over lapping tabs on the top and bottom. The cut the sheet metal to fit the top and bottom. We sheet metal screwed it together on one side, ten did the other side and tack welded that side. Removed the screws on the other side and tacked it together. He knew a radiator shop owner and had them finish welding it. No leaks, even under pressure.
  7. Sgt. Howard

    Sgt. Howard Member

    My first attempt at brazing- looks lousy, but apparently it is sealed tight gas tank 1.jpg
  8. Frankenstein

    Frankenstein Well-Known Member

    What are you using to braze and the metal you are working upon?
  9. Sgt. Howard

    Sgt. Howard Member

    22 gauge steel, flux-covered rod and a pony gas rig- what you see there is my first so many inches.

    Also- that has not been cleaned up at all
  10. Frankenstein

    Frankenstein Well-Known Member

    Not bad, looks like almost 2 maybe more gallons! How big us it actually seems like a lot of gas for a motorized bike (though I'll admit I installed a 2 gallon tank for a time, maybe even 2.5 can't remember?)
  11. butre

    butre Well-Known Member

    nothing a flap disk can't fix
  12. Sgt. Howard

    Sgt. Howard Member

    If my calculations are correct, it will be about 1.5 gallons... but remember, this is the LEFT tank... the RIGHT one hasn't even been started...
  13. Frankenstein

    Frankenstein Well-Known Member

    Nice, I've been thinking about using 2 or 3 oxygen, Mapp, or propane tanks as a gas tank, I figure I could braze some small steel tube to the sides and connect them with some sort of tube to act as connections. Paint may even be done over though I think I could dig the industrious look of the original tanks, hard to decide...

    I've tried the brazing thing it's a unique pain, I've actually seen better success in simply soldering steel pieces together, my metal ammo box I used as a battery and electronics case has an out channel on the side that's just a copper pipe soldered to the steel with silver bearing pipe solder..

    I seem to burn holes with brazing on even the simplest things, though maybe it's because I'm always trying on thin metal crap...
  14. butre

    butre Well-Known Member

    the trick to brazing is not having an oxidizing flame. it's something that comes with experience and no amount of reading the instruction pamphlet will get you there.