Large Cap fuel tank design

[Jesus_man]

In order to not take over Justin's thread, I thought I'd start a new one. When I had my 23 gal tank out a few months ago, I took all the measurements for it. It's been beat up pretty bad, but I think I have them all pretty close. Here's what I believe I am working with, but I can't be completely certain as there are no markings on mine.



But, I've always wanted to move my rear axle back a total of 3" or so. It's been pushed back 1" on the spring perches already. I don't like the idea of losing a bunch of capacity in the name of clearance, so I've come up with a design that might only cost a gallon or two, but it only works with a 2" body lift.

Basically all I did was deepen the reliefs that were used to avoid contact with the front cross member and move that surface down to 7" (see white lines). This pushed the fuel pickup line down accordingly, but kept the overall height at 13". The shelf created by that L-shape would interfere with the rear pumpkin when you move the axle back more than 1". So I measured the pumpkin width to be about 10" (Ford 9") and cut the horizontal leg of the L-shape off for that 10" width (see red line - should be hidden). That would allow for 2" more clearance there. If you wanted to be sure of a clearance, that same 10" cut, could be angled towards the rear of the tank (See blue line - also hidden).

This would require the countersinking of the sending unit assembly.

One thing I'd like to discuss is some sort of enclosure around the fuel pickup that would keep the pickup in fuel on steep hill climbs in the hopes of not starving the engine. Something that has small holes to allow fuel to seep in and drain out slowly.

Also, mounting systems...mine is j-hooks and a strap right now.

[Gunnibronco]

I like the Aero brackets a lot, very sturdy. I know the WH design is well liked, but I haven't actually worked on one. I welded mine on years ago, expecting to possibly do a 2" b/l, so I fitted 2" pieces of tubing in as spacers. I didn't end up with the b/l, so they are still there.

I'd really consider moving the tank back to the rear of the frame rails. It was pretty easy really. The only thing I haven't figured out is how the fill tube will work out with the axle so far back. It feels a bit exposed to the rear tire/rocks. If you don't move the tank back (or the filler neck) the fill line will most likely interfere with the tire. You can see the progression of where my fuel neck started, then moved when I went to the Silverback flares, now where it is with the tank & axle pushed back. I don't have a good pic with the tire location & filler tube.

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[Digger]

I have my Sherman tank modeled up in CAD, which is close to yours.

The only thing I wanted to change was the access hole and maybe build a tank that is held up with a skid plate. Also stainless would be nice.

It would be cool to design a tank that was modular, so you could swap components and go from carb'd to EFI or diesel setups. I also thought it would useful to have the mounting system designed so it was easy to drop on the trail or roadside to service internal components.

[Jesus_man]

The body work is the major reason I have not moved my axle back. I don't have the confidence I can do it right and I've hacked the rest up bad enough already.

Who uses unistrut for a mounting system? Run the rails vertically and you could adjust them if you added/removed a body lift. Our basement has unistrut installed into the foundation walls and there are several 30" deep shelves hanging off them so I think that would hold up a 20 gallon tank easily.

As to the filler, a friend of mine frenched one into his steel bed (Jeep MJ with custom flat bed). You lift the cover and the filler neck comes up with it. You could do that in the bed, but it might take some extra time to fill. Would solve a lot of problems tho.

[Gunnibronco]

The body work is the major reason I have not moved my axle back. I don't have the confidence I can do it right and I've hacked the rest up bad enough already.

Who uses unistrut for a mounting system? Run the rails vertically and you could adjust them if you added/removed a body lift. Our basement has unistrut installed into the foundation walls and there are several 30" deep shelves hanging off them so I think that would hold up a 20 gallon tank easily.

As to the filler, a friend of mine frenched one into his steel bed (Jeep MJ with custom flat bed). You lift the cover and the filler neck comes up with it. You could do that in the bed, but it might take some extra time to fill. Would solve a lot of problems tho.

I took the hard route, sectioning & extending the wheel well. I'd do what Justin did and use a new wheel well to cut up and add length.

I think WH uses the unistrut as a hanger.

Rerouting the filler neck to the bed might be a good idea. At this point, a much easier route might be to just put a fuel cell in the bed. I kind of wish I had done that.

[Digger]

I've looked at the effort involved in stretching the wheelbase via various methods and came to the conclusion that it was easiest and best to cut the whole thing in half and stretch it between the door and rear wheel opening.

[Gunnibronco]

I've looked at the effort involved in stretching the wheelbase via various methods and came to the conclusion that it was easiest and best to cut the whole thing in half and stretch it between the door and rear wheel opening.

Including cutting & extending the frame?

That would eliminate the need to relocate suspension & gas tank, and maintain the space for the fuel filler neck. Still a ton of work. I guess if it were easy, everyone would do it.

[Digger]

I've looked at the effort involved in stretching the wheelbase via various methods and came to the conclusion that it was easiest and best to cut the whole thing in half and stretch it between the door and rear wheel opening.

Including cutting & extending the frame?

That would eliminate the need to relocate suspension & gas tank, and maintain the space for the fuel filler neck. Still a ton of work. I guess if it were easy, everyone would do it.

Yes. Hardest part would be the sheet metal work and re-painting the tub. But compared to relocating all the brackets, custom fuel tank, filler issues, etc it would likely be easier, especially with complexity of the multilink suspension in the back already. The front is similar. Too much surgery to gain a few inches. If I split the thing in half, I could have 6", 12" or 18" extra inches of wheelbase for the same effort and gain the interior space at the same time. But that's my 2 cents.

[Kinder]

All this talk of frame extending reminded me that I have 2 sections of frame prepped for doing it. So the question is who’s name am I putting on them? [emoji38]

[Gunnibronco]

Yes. Hardest part would be the sheet metal work and re-painting the tub. But compared to relocating all the brackets, custom fuel tank, filler issues, etc it would likely be easier, especially with complexity of the multilink suspension in the back already. The front is similar. Too much surgery to gain a few inches. If I split the thing in half, I could have 6", 12" or 18" extra inches of wheelbase for the same effort and gain the interior space at the same time. But that's my 2 cents.

I agree, you are correct. Tons of work squeezing out a few inches or fractions of an inch. The only thing you don't get is increased approach/departure angle.

All this talk of frame extending reminded me that I have 2 sections of frame prepped for doing it. So the question is who’s name am I putting on them? [emoji38]

Not me, I've spent too much time relocating suspension, brackets, steering, fuel tank & filler neck, brakes, etc. Just need to find the motivation to tie it all up.

[Jesus_man]

I would love to stretch it 4-6", but as Chad said, I would like to improve my departure angle a bit. I guess 37's would help, but I wonder where I am going to rub when I do that??