I've been asked by a friend to build a fuel tank for his unimog project. I've never built a tank before, and since the search function is not working I thought I would ask you guys.

The tank needs to be around 700 litres.

I was thinking of building it out of 3mm aluminium?

What would you suggest for baffles?

 

Unimogs are nasty off road machines...

 

.100 aluminum which is basically 3mm is a good choice.

as for baffles, it all depends on the shape of the tank, but most likely a simple idea like used when sumping a oe fuel tank is what has worked for us.

 

Have you welded many liquid or gas tight vessles before?

Even with a reasonable ammount of baffles to control the fuel, I'm not sure that 3mm will be thick enough. The forces 185 gallons of fuel can impart on a tank are huge.

Baffles need to be structural in this case. consider breaking flat sheets in to Z shapes to add structure to the tank rather than a regular flat baffle like you might put in a small automotive tank. I would run them all the way to the bottom and weld as much as you can reach. Drill a few 20-30mm holes along the bottom of each baffle to let the last of the fuel reach the sump or pickup but still retain as much strength as possible.

 

depends how big of a tank were talking. we have made plenty of 10-20 gallon fuel cells out of .100 for anything from sandrails to hotrods. to be honest a few of the sandrail ones are .080 al due to not really seeing much street time.

 

700 liters is a lot u need to step up to 1/4 inch aluminum and maybe round shape.

Gil

 

its only 184 gallons, haha. yeah use .125 for that massive tank. sorry i thought i read 70 liters.

 

allot is going to depend on the shape. If its going to be a retangular tank ( more then likely)
the I would go with 3/16. It may sound overkill but the flexing that a 1/8 thick tank will do will cause cracking. A unimog is not a smooth riding vehicle even on good roads. I have done baffeled 250 gal water tanks and there a problem. These were done in 1/8 5052 aluminum. If it was a round tank the 1/8 wouldn't be a problem. You sure you have the right capacity. That is a big tank for that little vehicle. Its going to fill the whole bed. Don't bolt it. It has to be strapped in so it can expand and contract. Radiused corners are a must. Be honest I would build 2 or 3 seperate tanks to equal the capacity so if there was a problem you could at least pump from one to the other in a pinch. This method could also eliminate some of or all the need for baffling depending on the final shape.

 

I vote Round for a 700L tank. that's pretty damn big....

 

Thanks for the great input so far.

I have not had much experience with welding water tight vessells although i work with alot of people that are coded in doing it so i may even get one of them to weld it.

700 litres may not be correct. That is the number he quoted off the top of his head but we still need to measure up properly.

Great idea about the Z shaped baffles. I never really thought about how much force the tank may be under.

I'm gonna try and get a drawing together then i will post it up so you can let me know what you think.

 

If long trips are planned it's not really that giant...those things get as bad as 6-7mpg.

I like that idea of 2 or 3 seperate tanks. You could build a steel cradle that they would all sit in and have straps over the top to secure them. Maybe out of thick walled 1 1/2" tube and flatbar? If the cradle had a nice strong ring around the middle of the tanks, it could help support them and also protect from damage from any cargo shifting or rough loading.

Is this a flat bed one? I'm imagining the tank(s) right behind the cab.

 

Im not sure wether it was a flatbed version originally or not. He is turning it into a camper and going travelling in so will deffinately be doing long distances.

But you are right, its going behind the cab. And then the interior of the rear cab will be built around it.

 

yeah if you want a 184 gallons of fuel definately cut it in thirds or at least halves and make a few tanks.