Building your own fuel tank....

[tinkerer]

Hello! I've got a ? for all of you about building a fuel tank. I would like to know your opinions on what I am planning on doing. As some of you already know, I am building a backup gen set with a Yanmar 2TNV70. I plan on building a square frame 44 inches long and 24 inches wide from 3" I beam. I was thinking about incorporating a fuel tank into the frame on the end the generator head is located. I planned on using 1/8" plate/sheet and covering the bottom and another sheet covering the top. According to what I calculated and how I am designing it, the tank should hold about 7.6 gallons which will be perfect for what I will be doing with it. I'm not to worried about not being able to weld it "fuel tight", but am more worried about the welds breaking from vibration over time. What do you guys think? Should I go for it or go another route? 

Thanks!
Ben

[squarebob]

When we were building/rebuilding motorcycles we would coat the inside of the tanks with "KREEM" or "RED KOTE". Forms a skin in the tank and resists vibration very well. If it can stand the vibes from a rigid mount Harley engine, it should hold up to the Yanmar.

http://www.kreem.com/fueltankliner.html


http://damonq.com/TechSheets/Red-Kote.pdf

Bob

[tinkerer]

Bob, thanks for the links and info. I never thought about using a sealer of any kind. I had to laugh when you said if it will hold up to a Harley engine, it should hold up for the Yanmar. I love those old harleys. There's nothing quite as classy as them. We don't live that far away from Sturgis, SD. I've been through Sturgis a time or two when the Sturgis Rally was on. It was quite a sight. I've never seen more motorcycles in my life.

Thanks!

[mobile_bob]

something to consider

that is the large flat plate section of the top and bottom, they will likely flex or "oil can" if they are not domed or have
rib rolled into them to provide stiffness.

anything you can do to provide that domeing of the plates will greatly increase the vibration resistance and reduce cracking

motor cycle tanks don't crack because they are dome  or bubble shaped as opposed to being simple flat sided boxes.

another way to accomplish the dome, would be to weld in a large nut (maybe a 3/4") in the center of the upper panel, then after you weld
the tank all up, screw a long piece of allthread down through the nut and against the bottom panel, torque the crap out of it until you notice the bottom warp down and the top warp up a bit. then cut off the allthread and plug weld it off, leaving the allthread in the tank.  all it would take is maybe a quarter inch of bulge top and bottom to accomplish the dome needed to keep the panels from vibrating and cracking.

then take it to a radiator shop, which generally also repair and seal fuel tanks,and let them clean it out and use the sealer.

fwiw
bob g

[tinkerer]

Bob, thanks for heads up. I too was wondering about "oilcanning" causing problems. I noticed that all of our portable fuel tanks, that we use, have an "X" creased in the middle of each panel. It looks like they just put it in a sheet metal brake and bent it from corner to corner a little bit. I was thinking about having the local welding shop use their shear to cut my sheet metal to size. I could maybe see if they would let me use their brake also. Your bolt idea sounds like a good ideal also. Its simple and should work.
Ben

[fabricator]

More tanks than you can shake a stick at  http://www.usplastic.com/catalog/default.aspx?catid=838&parentcatid=-1