Fuel Tank Safety

[Gonzo]

This is my first SAE car we are building and I am concerned about fuel tank safety. It appears that everyone runs welded aluminium tanks, which I assume are filled with foam. Is this true or are some people running bladders in their tanks?

We did see some teams struggling with fuel tanks that kept cracking and leaking at FSAE-A last year and I would like to avoid this issue on our car.

Geoff Spear
University of Auckland

[imajerk]

Welding aluminium is often done incorrectly... especially with TIG. I would try and use generous folds to shape the tank to keep welding down. Ideally someone with DLI qualifications should weld. Whether TIG or MIG is used, copper (or preferable brass backing) should be used for: clamping, temperature control and to stop hideous deformations around the weld area. I would use MIG as you are able to blast parent material away (in the form of lots of splatter) and deposit completely new material leaving 100% penetration (not to mention the time savings). Something I've noticed is that starting from an existing weld is often done poorly and big holes are left under the surface of the weld... same with the end of the weld (pull the TIG piece back over the weld quickly to stop a dip forming). Also, you have to use the right gas or the weld can have surface pits/cracks... and pits and cracks can form if inadequate angles are used for material deposit. Now, inspect the welds and don't be shy to grind back bulbus welds with a flap disc. You also have to make sure the weld is not convex and grind the toe of the weld until it is reasonably flush with the parent metal (I don't care what you engineering lecturer tells you contrary to this!). After all that the weld should be treated with the appropriate acid.

[Alan]

We use an aluminum tank with foam and have never had an issue with leaks. My advice on TIG welding aluminum:

1. Use the right material. We use 3003 which is very bendable and weldable.

2. Clean the material thoroughly at the weld joints. Wipe the area with acetone and wire brush all the oxide off.

3. When doing the outside corners, use a gas lens and increase your gas flow to roughly 20 cfh (cubic feet per hour, not sure what that is in metric). On corner welds I found it much easier to overlap the material slightly (inside edge of one face touching the outside edge of the other) and not use filler rod.

4. Use lots of tack welds.

Assuming you have somebody with some TIG experience, I don't think leaks should be an issue.

Kettering University FSAE Alum(00 - 03)