Fuel Tank construction

[brighty]

OK, I've tried the search thing every which way and can't get any results... damned if I can ever get that to work for me

Just trying to find some info on building my own fuel tanks for my truck, not sure if someone on here has done a step by step on how to build one yet.(links would be great )

Will be building to hold diesel, going into a GQ. My idea is to run a larger main tank to fill in the void areas where the standard one sits, & then have that gravity fed into an auxilury tank on the passenger side(instead of the drivers side) so I don't constantly have the fat bastard in the drivers seat and the 80kg or so of fuel on the same side too. Due to the cab being chopped I can take advantage of the extra room for more tank space too.

I would ideally like to run two aux tanks either side of the rear tail shaft, but can't come up with a way to plumb the exhaust out the back. This way I could use the space from the original tank for the spare tyre instead... leaving more tray space. If anyone can give me a great idea on how to do this would be great too.(I have a V8 and the exhaust currently crosses over just behind the rear transfer output flange)

Things I need to know are....
1: What material?? (I was thinking 3mm steel top & sides with 4mm bottom for strength)
2: Baffles?? How to construct??
3: How much clearence do you give between the tank and chassis for flex??
4: What type of paint do you coat the inside with to protect against rusting without peeling off/effecting the diesel?? (I know you dont have to but would prefer to)

Will prob think of some other things later but that should get me started on things to buy for me to have a go over the chrissy break.

Cheers

[Ruffy]

Hey Brighty,
3 and 4 mm plate is way heavy for a fuel tank.. That's gunna weigh heaps. I have one constructed of 2mm plate and it's heavy enough.
Baffles are simple. Just put a piece of plate, like a wall, across the tank. Depending how big the tank is would depend on how many. Make the bottom edge like the top of a castle, to let fuel through, with square holes about 10mmx10mm every 40mm or so, and make the wall about 40mm shy at the top.
Dan

[brighty]

Hey Brighty,
3 and 4 mm plate is way heavy for a fuel tank.. That's gunna weigh heaps. I have one constructed of 2mm plate and it's heavy enough.
Baffles are simple. Just put a piece of plate, like a wall, across the tank. Depending how big the tank is would depend on how many. Make the bottom edge like the top of a castle, to let fuel through, with square holes about 10mmx10mm every 40mm or so, and make the wall about 40mm shy at the top.
Dan

Only reason I was going 4mm on the botton was cause it'll prob cop a fair bit of abuse in the bush and in comps... I seen a mate do a tank for his comp truck and has dented a 3mm tank pretty good.

[sootygu]

A little bit here.

http://carl.outerlimits4x4.com/ftopic156696.php

[ozy1]

i have been thinkin about this a bit latley as well, i want to carry some more fuel, planning on a cape trip in a year or so time, and im tryin to find 2 tanks that can sit either side of the tail shaft infron of the rear diff, to reduce some of the weight right at the back of the truck, i will then sort the exhaust prob out while im there,


thinking something like sportage diesel tanks might be the go, they seem to be rectangle and hold something like 60l, so 2 in a GQ would take you up too about 215L's,

[brighty]

i have been thinkin about this a bit latley as well, i want to carry some more fuel, planning on a cape trip in a year or so time, and im tryin to find 2 tanks that can sit either side of the tail shaft infron of the rear diff, to reduce some of the weight right at the back of the truck, i will then sort the exhaust prob out while im there,


thinking something like sportage diesel tanks might be the go, they seem to be rectangle and hold something like 60l, so 2 in a GQ would take you up too about 215L's,

Shaun,

Your tray is at a similar height to mine but I've not jumped under your truck to actually have a look at how it all sits in relation to your cab and chassis.

I'm thinking I want to make mine in an L shape so that the forward point of the tank sits under the cab and as it gets behind the cab then goes up towards the under side of the tray. (sorta like ___| shape.)

If you were going to run twin aux tanks either side of the tail shaft, how would you transfer fuel from one to the other... or would you just have them run separately on an in cab switch to flick over?? Have you thought about what you would also do with the exhaust yet or nut that out later once the tanks were in???

Would be good to throw a few idea around so more ppl can use this for ideas.

[-Scott-]

Things I need to know are....
1: What material?? (I was thinking 3mm steel top & sides with 4mm bottom for strength)
2: Baffles?? How to construct??
3: How much clearence do you give between the tank and chassis for flex??
4: What type of paint do you coat the inside with to protect against rusting without peeling off/effecting the diesel?? (I know you dont have to but would prefer to)

I looked into designing my own a few years back, and this is what I concluded:

1: 2mm sides & top, 4mm bottom.
2: Similar to ruffy's description. Think about how you'll keep fuel around your pickup when you're on big slopes.
3: Was advised to allow 10mm clearance all round, and only 3 point mounting - to prevent the tank being ripped apart as the chassis flexes.
4: I'm pretty sure mine is built with gal - no paint inside?

[hiluxmad]

4mm bottom not a bad idea.
feed aux to main on sypon system two fillers one gauge or split fillers 100series style
run mufflers under cab with heat sheilds and run pipes over tank or between them with 2nd muffler after tank if reqd(are stacks out of the question?) i got a 65 lt mq shorty tank under my lux bolted to underside of the tray on frame doesnt even touch the chassis.
have you thought of modding truck tanks? on / in tray?
we had a modded beer keg in back of one rig worked great and its a pressure vessel essentialy to begin with!!!!!
if its diesel prob wont matter if its gal too much oil content to rust

[TWISTY]

Few pics of the tank we made a tank for my 40 on the link below....I believe it was all 1.5mm thick. Goes inside the the cab but, so no chance of dinting it like yours, but will give you some ideas of the baffles and how it was constucted.

http://www.outerlimits4x4.com/ftopic92609-0-asc-240.php

[jcclures]

Brighty if you want to look on my build up I have a few photos of the tanks I made, you can see how I had the baffles folded, getting baffles made this way allows the tank to expand and contract and not pull the weld causing leaks in the future. I had a local sheet metal shop fold all the bits to my design.

http://www.4wdmonthly.com.au/forum/show ... hp?t=17736

On the next page after this one shows the tanks finished and fitted, although upside down as well as the new filler pipe I made.

[Slunnie]

If you're worried about fuel pickup, you can run a swirl pot.

[Freakazoid]

I did tanks either side of the tail shaft. They hang from the round tube ebhind the transfer and at the back from a hanger I welded onto the upper links mounting point.

I made mine out of 4.5mm alu and have a 3mm Domex plate on the underbelly. Alu is lighter and the welds are way bigger. Hopefully no cracking welds as with my previous steel tanks.

Have CAD files etc. if interested. Here is link to build

http://www.nissan4x4.co.za/forum/forum_ ... p?TID=2688
[/img]

[Loanrangie]

If you're worried about fuel pickup, you can run a swirl pot.

Or do what they do in efi tanks, you weld in a small round or square baffle that the pickup sits in and has holes so it can fill with fuel but not drain out on slopes.

[hammey]

when my mate built mine he welded in a 2lt drop tank on the bottom and we put the pickup in there.

i think he used 2mm zinkalum.

[ozy1]

brighty,

I was more talking about my wagon, which is why i liked he idea of 2 smaller tanks either side of the tail shaft, to use fuel i would run a 6 way valve so i can run out the main tank, or the aux 1, the aux 2 tank would have a transfer pump which would pump into one of the other tanks, this would give me the ability if there was a failure somewhere along the lines i would always have one tank, and only have to swap a couple of fuel lines to get me out of trouble,

now your idea with the __| shaped tank is a good idea, and i havnt been under your truck either, but i know my ute, the tank would have to come up just behind the upper control arm cross member, which would mean you might have to narrow the top of the tank to clear the upper control arm,

depending on your cab you might be able to run a GU ute aux tank as these are designed similar to what your looking for,

Shawn


EDIT, GU ute tank

[AFeral]

The holes in the baffles do not need to be that big run only a 20mm hole at the top and bottom of each baffle . Never had a drama fueling a V8 ls1

[ozdave]

Just a side point. Last time I checked, Diesel and Zinc don't play well with each other. Don't use zincanneal or zincallume for diesel fuel tank construction.

[awill4x4]

If you decide to build a fuel tank (or a tank that holds any fluid really) stop and think of the forces involved with the movement of that fluid throughout the tank. Try to think of the fluid as approx 1 kilo per 1 litre (I know the specific gravity of fuel is less but it's a pretty good guide) and imagine what that weight does to tanks as it shifts on cornering, braking and acceleration.
Internal baffling is extremely important in controlling this movement of fuel and should be adequate for what you want to achieve.
Baffles should have folded edges to increase strength, a flat sheet baffle will eventually tear from the tank body and fail with a possible tank shell rupture as well.
I've got a few pics below of a tank and surge tank from a couple of different projects we are building at the moment, both are Aluminium but the same basics apply. I build my tanks with the idea in my mind that I want them to be as strong as possible so I know that a tank failure isn't a likely scenario.
There's a lot of cheap alloy tanks available from some of the larger wholesale sellers like that don't baffle their tanks and rely on foam filling to control movement. The problem is there's not enough foam filling in them to control it. These tanks WILL FAIL, not may fail, WILL FAIL. I've seen how they are fabricated and been asked to fix too many (I refuse to touch them).
You'll notice on my tank I also fold the end/side plates, again this is for strength, the folded edge strengthens the welded seam markedly and it allows me get a weld very much like a lap weld. The end plates aren't tacked along the folded edge inside the tank yet but they will be, just like the centre baffle.
There is also another pair of baffles going in where the tank changes depth at 90 degrees to the centre baffle, they will also be full height baffles.
The holes in the baffle to allow the fuel to equalise are comparatively small, you don't need large holes for this, just remember to put holes up the top also or when you fill your tank you may have a large air pocket that won't allow you to fill your tank.
A tall narrow tank is better at controlling fuel movement than a flat broad one like this one. Unfortunately this is the only design option we have for this one, but it's also going to have a large sump in it as well to take two fuel pumps that will also be baffled in some way.
Regards Andrew.

[-Scott-]

Andrew - please stop posting pics of your work. You're teasing - the more I see, the more I want to see.

If you insist on posting pics, please post pics of crap - I can happily ignore that.

[Moph]

Andrew - please stop posting pics of your work. You're teasing - the more I see, the more I want to see.

If you insist on posting pics, please post pics of crap - I can happily ignore that.

LOL well put - I second that!

Some very, very nice welds there

[brighty]

So I think I'm gunna go with a 3mm/4mm bottom and 2mm sides and top.

Internal baffles will be put in but design is yet to be worked out. I think I will start worrying about that once I got the tank half built and can have a play with things on the inside with no top fitted.

Mounting points would be on the crossmember just behind the transfer output flange and on the rear upper link mounts crossmamber too. Prob be 2 mounting points F&R of each tank with some sort of rubber between mountings points to allow for flex(Is this a good idea or not???)

Would powder coating the inside and out of the tank be sufficent protection from rusting??? More concerned about the internal as I don't want it to affect the diesel if the paint starts coming away/mixing with the diesel. If not, what do the manufacturers like Long Ranger etc use to paint their tanks with???

Still need to work out the exhaust piping and where it'll go, but shouldn't be too much of a drama... hopefully

Ok, so I've had a bit of a play on the PC and come up with this sort of design... it's not definite yet as I want to mock up one first and see how it fits first... hopefully it'll work for both sides of the tail shaft.. more than likely I'll be plumbing these together, but may look at running individually.

[-Scott-]

Mounting points would be on the crossmember just behind the transfer output flange and on the rear upper link mounts crossmamber too. Prob be 2 mounting points F&R of each tank with some sort of rubber between mountings points to allow for flex(Is this a good idea or not???)

I wouldn't do it this way - you have four mounting points on your tank, and I doubt rubber between the mounting points will be able to compensate for all the flex you may get.

Use three mounting points. I would put two on one cross-member, well separated, and a third on the other cross-member. As the chassis twists, the tank will move with one cross-member, and "twist" around the third mounting point.

[awill4x4]

Regardless of how you mount the tank make sure that the mounting points on the tank are strong and I highly recommend welding a flat plate (compensator) to the outside shell of the tank slightly larger than your mounts and then welding your mounts to that plate. In the event of a mount tearing it will tear away from the compensator plate and not rip a hole in your tank shell at the same time.
Regards Andrew.

[bogged]

Regardless of how you mount the tank make sure that the mounting points on the tank are strong and I highly recommend welding a flat plate (compensator) to the outside shell of the tank slightly larger than your mounts and then welding your mounts to that plate. In the event of a mount tearing it will tear away from the compensator plate and not rip a hole in your tank shell at the same time.
Regards Andrew.

You think of everything....

[brighty]

Mounting points would be on the crossmember just behind the transfer output flange and on the rear upper link mounts crossmamber too. Prob be 2 mounting points F&R of each tank with some sort of rubber between mountings points to allow for flex(Is this a good idea or not???)

I wouldn't do it this way - you have four mounting points on your tank, and I doubt rubber between the mounting points will be able to compensate for all the flex you may get.

Use three mounting points. I would put two on one cross-member, well separated, and a third on the other cross-member. As the chassis twists, the tank will move with one cross-member, and "twist" around the third mounting point.

Only reason I was considering 2 either end was that if you look at the OE tanks that they come with, they don't mount the way you state. I can fully understand you're reasons, and I'm not saying that you're wrong, just thought 1 mounting point might not be enough at one end, that's all.

[-Scott-]

Only reason I was considering 2 either end was that if you look at the OE tanks that they come with, they don't mount the way you state. I can fully understand you're reasons, and I'm not saying that you're wrong, just thought 1 mounting point might not be enough at one end, that's all.

Fair enough. From the factory, mine was mounted like I described, and the aftermarket tank uses the same mounting points.