Fuel cell in a wagon

I'm going to mount my fuel cell under the floor in a sheet metal box to protect it with an aluminum door to cover it and for access. I will be cutting out the rear floor and will have to build a tubing frame work to attach and support it. Can I use 1x1 tubing to make the framework or do I need to go bigger and what gauge tubing should I use?

I used 3/4" tubing for the framework around my fuel cell. Its .062 wall thickness. 1x1 will work just fine.

If we're just talking about supporting a fuel cell's weight from the bottom, IMO it can depend on the size of the cell. In the past on smaller 3 to 5 gallon fuel cells (that were either front mounted, or 100% above the trunk floor) I have used either 1/2" x .065" steel tube, or 1" x 1/8" aluminum strip, or 1" x .083 or .065" (forget which) steel strip to support the bottoms. And once used 1" x 1" square tubing to support the bottom of a bigger 12 gallon cell. The 1"x 1" tubing was probably overkill for the 12 gallon cell's weight, 3/4" x 3/4" would have probably been OK.

If we're talking about protecting the fuel cell the rule book says if it's outside the body and/or frame structure you need a guard made of at least 1 1/4" od x .058 cm/.118" ms wall tube. And if any part of the cell is outside the body lines or trunk floor it needs a box around that part to protect it.

If we're talking about protecting the fuel cell the rule book says if it's outside the body and/or frame structure you need a guard made of at least 1 1/4" od x .058 cm/.118" ms wall tube. And if any part of the cell is outside the body lines or trunk floor it needs a box around that part to protect it.

Ok, do I have to use round tubing or can I use square instead and what size and thickness would I need? I'd prefer to use square because I have it on hand and it will make attaching the new floor and the safety box easier to mount. Or am I better off mounting it above the floor and building a fire wall around it? I'd rather mount it where the spare tire well is and keep the floor flat if I can.

Man that's hard to say what to do one way or the other, 1-1/2" square tube would be technically as big/bigger than 1-1/2 OD round tubing. But that's a lot of extra weight added if you use it to build a framework surrounding the entire cell to hang sheet aluminum off of. I have never wanted to (or need to) put a fuel cell 100% under the rear frame/trunk floor "out in the breeze" since that would usually kill way too much wheelie bar room under a lot of cars. It would also make the fuel cell a lot harder to hide from view outside the body lines when viewed from the side/behind the car, especially a big cell.

What if you raised the cell up some so it's somewhere around 1/2 way in/out of the trunk so it's technically "surrounded" (protected) on 3 sides by the right & left main frame rails, and the rear most crossmember. Then build a raised flat rear floor/bulkhead/deck surface to separate the fuel cell/vents/lines from the rest of the driver compartment. That way you could make the actual cell mounts out of much smaller tubing or strip material. And then just build a simple aluminum box (without a big steel supporting frame) to shield whatever amount of the cell sits below the floor.