Making a box with a sheetmetal brake

Im not the brightest of men, and this os making me feel dumber than i am

How do i make a three sided box with a sheetmetal brake? I have 20 gauge steel, an old sheetmetal brake, and no clue. 

This will replace the rusted out tub in the trunk of my race car and house the fuel cell. 

What's a 3 sided box?  I thought they had 6...

You mean a "U" shape?  Or a top with 2 sides?

 Do you have a finger brake (box and pan brake)? You remove the fingers for clearance for the 3rd and 4th sides.

Or a "sheet metal brake" with a solid leaf?

The first one is what you need. The second will allow you to bend two of the sides and then you have to get creative for the 3rd

...the answer is usually make the corners a bit more than 90* (about 120*) and finish the bend by hand. 
 

Or a finger brake. 

Ok, should have said 5 sided box. Gour walls and a floor.

Its a standard brake,  not a finger brake. 

Local hvac guys want $200 to make it....

In reply to Dusterbd13-michael :

No can do with a solid leaf brake. 

Not exactly sure why they are so ubiquitous since they can't perform the most basic metal brake tasks.

In reply to Trent :

I disagree. 

In reply to Dusterbd13-michael :

Welded edges or riveted?

I built two cars using nothing but a section of I-beam and square tubes to bend all the panels to square corners, and various round things to curve everything else.

In reply to SV reX :

Oh, It can be done. bending the two parallel outside lengths and then clamping stock between those to hammer it to shape. Or making it in multiple pieces to weld it up.

It just isn't as easy, fast or convenient as a finger brake.

In reply to Dusterbd13-michael :

How deep are the sides of this box?

One of the features of my brake might be able to be implemented on a cheap brake one didn't care about.

I splashed out on a magnetic brake 6 years ago and I still love it. One of the leaves is notched for "common box sizes"

You could cut similar slots in a solid leaf to gain the clearance you need. Problem here is the leaf needs to be the strongest part of the machine. A mag brake holds differently so this works awesome on this machine. I would imagine a solid leaf would need a lot of reinforcing after something like this was done to it.

By the time you get to folds 3 and 6, you will be running into the brake.  You will have to leave them a bit open (120* or so), and finish by hand.

Right, but the presumption is that this is being done in an urban garage as part of a hobby, so there's not the space, money, or rush requiring a true leaf brake. I get that the OP wasn't asking how to do it, but what to use, and I'm just saying that there are many ways. Me personally, I was in no hurry and absolutely don't have the space for such a tool.

"Rusted out tub... battery box"

Im assuming perfection is not the goal. 

Tabs like this will give you flanges to rivet or weld to the floor, but you will definitely have to fold them by hand with a pair of seamers:

I forgot the last fold (the lid)..

I'd fold that first, then flatten it out again (leaving a crease).

After making the other bends, re-bend that by hand (close the lid) and rivet the tabs together.

Edit: Other option would be to make the lid as an entirely separate piece, with tabs to rivet on all 4 sides. 

Box is 25 long, 17 wide, 9 1/8 deep. Fuel cell sits inside it, has a 1x1 square steel cage around it. This is just the can that nascar had that was heavily mangled and rusted out.

So, paul: thank you!! I really need yo study or obtain an explanation of the sequence of bends in your template. But that makes sense, and i can almost see the process in my head. It will be welded, but sparingly due to galvanized metal. 

Trent: i have a standard brake. It was given to me, and i assume it was shop made sometime when gas welding was still common. It lives in the flower bed cause its too damn heavy to move again. Its beefy, but. It most definitely would not accept the cuts in it and still function. 

Kb: exactly. Trying NOT to buy more stuff to make this. But still needing to with the tools i have, which is a standard metal brake, a welder, galvanized flat 18 gauge steel, flanging pliers and a welder. 

Thanks everyone!!

This way might be easier:

Again, you'll be hitting the brake with the last 2 folds. 

Do you really need to make the box out of one piece of steel? Sure its cool to do the origami exercise but I would bend up the perimeter from one length and then make the bottom a separate piece. Or do the perimeter in two pieces and a separate bottom.

Or, to make it really simple, cut steel the dimension of your walls and bottom and make a bunch of L's with an inch on each leg and use them as corners.

edit: SV reX beat me by a minute

Alright, so i drug my metal out and measured what i had, modified pauls blueprints for material on hand. 

I have two pieces of 70x22 sheetmetal. 

Plan for five sided box is:

Two pieces for sides. One piece will have one inch flanges to weld to the other side to make corners. 

Bottom will have one inch flanges all the way around. 

Use leftover steel as filler panels and upper register to attach box to existing floor. 

I am not an engineer, and high school drafting class was a lot of dead brain cells ago. So please go easy on me....

I used to make chimney caps and the like on a 26' brake at work. Paul's got it, but the last two sides aren't hard to bring in as long as the bend has been initiated in the right place. We'd do a 10 degree X corner to corner on the top to give it a little strength, and maybe help it drain (not really pertinent here).

Thanks everyone  

Can someone smarter than me look at my craptastic blueprint and give me feedback? Like, do i need to account for bend radius, etc? 

In reply to Dusterbd13-michael :

That should work. 
 

With 20 ga, you won't lose anything significant to bend radius. 

In reply to SV reX :

Fantastic. Thank you sir!