I wonder if electrolysis would come into play using aluminum that may contact steel supports or other dissimilar metal pieces causing unwanted corrosion?
CK5
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'72 K5 - Greg's @MightAsWellK5 Build
- Thread starter Greg72
- Start date
This is the build description. I will improve this later. (GB)
Buy 2 mats, and run a rib down the center of the tank, with holes allowing fuel to go between both sides.
I have seen guys do the flange and drill holes in the tank. Then weld through the holes to attach the baffle to that side of the tank.
That tank you built is awesome. That's alot of welding lol.
I much prefer a tank to be a rectangular. Much easier to bend that way and less overall welding
@Greg72 I would do whatever I could to minimize weld joints. I've only buil a couple tanks in my life, we did everything possible to minimize welding.
Though both were out of 16 gauge stainless
Yea I prefer them as well, but I had to use all the space I could and I still only got 11.5 gallon tank with 10 being useable. Car got 30mpg on highway so it wasn't terrible. And it was chopped and channeled 13" total with a roof height of 43" so you wanted to get out anyways haha.
If you can keep it a rectangle, you can break the sides up, then your bottom joints are breaks. Much easier and stronger.
All my tanks I used a high density 1/4" rubber between any where steel and aluminum touched. That car had 9k miles when I sold it, never had even a sign of wear.
If you can keep it a rectangle, you can break the sides up, then your bottom joints are breaks. Much easier and stronger.
All my tanks I used a high density 1/4" rubber between any where steel and aluminum touched. That car had 9k miles when I sold it, never had even a sign of wear.
Is you rear axle going to tuck up above your frame rail ? What about your tires ?
I am going to presume that both those answers will be no. That being said you are going to have __X__for a departure angle anyway. Why not fill some of that space with the tank. If at full compression you axle is say 10 inches from the bottom of the frame and you tires are 42's or so you are going to have alot of dead space after the axle that nothing is ever going to hit.
I dont think you would have any issues getting hung up on things.
I am going to presume that both those answers will be no. That being said you are going to have __X__for a departure angle anyway. Why not fill some of that space with the tank. If at full compression you axle is say 10 inches from the bottom of the frame and you tires are 42's or so you are going to have alot of dead space after the axle that nothing is ever going to hit.
I dont think you would have any issues getting hung up on things.
bp71k5
3/4 ton status
2016.04.21 - UPDATE: GAS TANK: ALUMINUM OR STAINLESS???
Before the new bedfloor goes in, I really want to get a gas tank designed. The entire process will be SOOO much easier working with a nice open area and not having to do it all from underneath.
Here's the rear area I'm working with....
The stock tank was only 20 gallons which was a laughable amount of fuel for a truck that only got ~7MPG. Even if I can improve that to 10MPG on the highway with a carefully tuned EFI system, I still want to be carrying a much larger fuel payload... realistically, no less than 30 gallons is acceptable.
A few goals for the project:
- NO low-hanging tanks behind the rear axle. This is a classic spot to get hung-up on rocks, and it kills the departure angle. Ideally I want the tank flush with the underside of the framerails so that I can put a nice flat skidplate across that area and never worry about getting "turtled" on a rock, or damaging a tank and losing all my fuel on the trail somewhere!
- As much capacity as I can get... 30 Gallon minimum
- Must not encroach up into the bedfloor. No bedmounted fuel cells..
- Build it myself so I can get a LOT of practice with my TIG welder.
So this is where I get stuck. What material do I use?The common materials are stainless or aluminum. But what thicknesses are considered appropriate for a fuel tank application? I am sure that aluminum needs to be a lot thicker to give equivalent strength to stainless, and I'm not sure what grade of aluminum or stainless is most appropriate. I also need to figure out how to properly baffle the interior of the tank.... this will serve the obvious purpose of keeping fuel near the pickup (I am planning to use one of those new Holley Hydramats, BTW) but will also add some needed strength to the large spans of metal that this tank will have so they don't sag or balloon when filled with 200+ Lbs of fuel.
My first attempts to find usable space yield the following design: (in yellow)
Yeah....that's a monster of a tank! It's about 8" deep at the very back of the frame (to keep it flush with the lower framerail) then transitions to about 4" deep as it passes over the axle (for clearance) to the other cross-sill. The width is 28" at the very back, but it needs to taper inward to follow the lateral "notch" in the framerails to about 23"... I haven't decided if I want to flare it back outward to gain more capacity, or just leave it at 23" all the way to the cross-sill near the front seat area. Overall length of the tank (using all the space between those two cross-sills) is 61"... If I build it this way I end up with 36 Gallons. (8464 cu in)
That 61" length is why I'm so concerned about "sagging" of the tank. That's a LOOOOONG unsupported span of metal with a lot of weight pressing down on it from fuel... so I want to be sure that I've got good interior bracing from the baffles to keep it stiff.
What sort of clearance seems reasonable for a fuel tank vs. surrounding framerails? I figure that the frame won't really twist much given that it's fully-boxed with a stupid-amount of cagework holding it in place...so I'm thinking maybe 1/2" of space all the way around is adequate.
-G
The stock tank has about 1/2" of clearance between the frame rails so i'd guess it's fine. That's a long looking tank though. I guess overly long isn't a big deal if you have enough of a sump area to keep enough fuel near the pickup. I've seen systems with multiple pickups I think as well. Maybe im thinking of that blanket though.
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I understood most of what you were saying, but this comment about T-joints vs flanges lost me....
The top of the axle tubes are within 1" of the underside of the framerails at full compression. If I keep the tank flush to the underside of the framerails in that forward section (toward the front seats) then there's no chance of interference with suspension links, driveshaft, etc.
I'd have to experiment with the depth of the tank in the very back of the truck (behind the axle) to see what I'm really gaining (in gallons) for each extra inch that I allow the tank to hang down. My thought process is that I'd rather make the tank super-long use up the all that dead space between the framerails / cross-sills FIRST... Then if I still can't get the capacity I want, keep extending the rearmost portion of the tank below the framerails.
Brian, I noticed that Holley offers a mounting kit for the HydraMat that is basically 4 super-strong magnets with threaded bolts that allow you to lay the mat where you want it and stick it magnetically in place. I wouldn't be able to use aluminum (obviously) for that one, but they make adhesive-based options too. The idea is that you can keep the mat exactly where you want if in the tank.... So I could buy a decent sized one and anchor it in that deep part of the tank and I should be pretty well covered for any off-camber or steep hill scenario I'd ever encounter.
-G
OK..... a little more data:
Here's a crude sketch of the two "sections" of the tank design....a conventional rectangular shape that is closest to the rear bumper, and a second thinner and longer section that continues all the way over the axle and ends just before the front seat area...
In my first attempt, I maximized the available space that I could get while keeping everything flush with the underside of the framerails.... This morning I played around with Excel (big surprise!) to see where I could squeeze and manipulate the dimensions and how much could be gained by going into areas with the tank that I don't really want to go...
What becomes clear is that the real opportunity to increase fuel capacity comes from the rearmost part of the tank. If I allow it to hang down by even 1"... I can pick up another 2.5 Gallons of capacity!!! That's huge...
So I guess at this point, I really need to think seriously about how much I'm willing to let that tank come down in the very back of the truck. I might be able to make peace with dropping it a couple of inches for the extra capacity.... and by reworking the thin part of the tank, I might be able to accommodate getting the exhaust through that area and let it exit out the back corners instead of dumping in front of the rear tires (which is the current plan that I actually don't like)
-G
Here's a crude sketch of the two "sections" of the tank design....a conventional rectangular shape that is closest to the rear bumper, and a second thinner and longer section that continues all the way over the axle and ends just before the front seat area...
In my first attempt, I maximized the available space that I could get while keeping everything flush with the underside of the framerails.... This morning I played around with Excel (big surprise!) to see where I could squeeze and manipulate the dimensions and how much could be gained by going into areas with the tank that I don't really want to go...
What becomes clear is that the real opportunity to increase fuel capacity comes from the rearmost part of the tank. If I allow it to hang down by even 1"... I can pick up another 2.5 Gallons of capacity!!! That's huge...
So I guess at this point, I really need to think seriously about how much I'm willing to let that tank come down in the very back of the truck. I might be able to make peace with dropping it a couple of inches for the extra capacity.... and by reworking the thin part of the tank, I might be able to accommodate getting the exhaust through that area and let it exit out the back corners instead of dumping in front of the rear tires (which is the current plan that I actually don't like)
-G
If you're going to armor the tank, just keep it somewhat within your departure angle.
Yep. I probably need to temporarily hang the bedsides back on the truck next time its out in the driveway so that I can see the profile of the truck standing back 20 feet to get a better feel for it. I think in the meantime, I might pick up a sheet of 1/8" Masonite board from Home Depot and start cutting out the shapes that I think I'll need for the tank and drop it in place in the frame. I can do some flex testing to make sure there are no interferences and see how the whole thing will look from the sides and back.
It seems like a silly thing, but I want to make sure that I don't drop the rear of the tank down so far that it hides the pumpkin from view. It's really fun to watch people trip-out on the axles and the offset that they have from the wheel centerline..... especially from the back. I don't want to lose that "conversation starter" in the finished product.
-G
I don't think you'll have an issue with covering the pumpkin from the rear. But I totally get the fact you want people to see it 
T joint is is a T one single vertical ( baffle) peice butting up to one single horizontal peice (tank)
The flange would be putting a 90° bend on top of the vertical ( baffle) peice so the you gave a horizontal section in your baffles. It basically becomes a lap joint . this would also allow you to drill holes in the exterior portion of the tank. The flanges correspond with the holes and you have a very easy way to weld the top bottom and sides of the baffles.
I can't believe I'm about to say this.......but Keith is right.
I would use that area behind the axle and even drop the tank down below the frame rail. Not far but like you said a couple inches makes a huge difference.
Then build a skidplate.
I think your 30 ish gallon goal is a good one too. I love that I have a big tank in Horton. Relative to others guys I know running 20 gallon fuel cells.
Although a couple of times my arrogance over mah huge gas tank has made me run out or nearly run out. Oh I got enough it's a 32 gallon tank lol
The flange would be putting a 90° bend on top of the vertical ( baffle) peice so the you gave a horizontal section in your baffles. It basically becomes a lap joint . this would also allow you to drill holes in the exterior portion of the tank. The flanges correspond with the holes and you have a very easy way to weld the top bottom and sides of the baffles.
I can't believe I'm about to say this.......but Keith is right.
I would use that area behind the axle and even drop the tank down below the frame rail. Not far but like you said a couple inches makes a huge difference.
Then build a skidplate.
I think your 30 ish gallon goal is a good one too. I love that I have a big tank in Horton. Relative to others guys I know running 20 gallon fuel cells.
Although a couple of times my arrogance over mah huge gas tank has made me run out or nearly run out. Oh I got enough it's a 32 gallon tank lol
As someone with a running/driving first gen (cough cough), you won't have trouble starting conversations. Plus, if you're busy chatting up the locals, you won't be driving it...
and here i love my dual 18's and wanted to go dual 30's ... lol.. but then the extra weight but hey its a fullsize...
I'm gonna try to get a 100 gallon tank in my crew cab somewhere somehow.
I really don't think you will hit the tank too often Greg. Even dropping it a couple inches.
Though as far as trail rides go unless your in the boonies. Like 2 or three days without fuel type areas ( Alaska, Siberia, The Kalahari desert, etc) you don't "need" much more than 20 gallons.
Just something to keep in mind.
Also 10 mpg, ya think? all that strange parasitic stuff in those portals big tires etc.
Will be interesting to see
I really don't think you will hit the tank too often Greg. Even dropping it a couple inches.
Though as far as trail rides go unless your in the boonies. Like 2 or three days without fuel type areas ( Alaska, Siberia, The Kalahari desert, etc) you don't "need" much more than 20 gallons.
Just something to keep in mind.
Also 10 mpg, ya think? all that strange parasitic stuff in those portals big tires etc.
Will be interesting to see
I was thinking this too. And it's not like you're in a jeep with no other storage options. If you are going to be on a long run, you have plenty of options to store 10+ gallons in fuel cans. If getting to 30+ gallons keeps you from putting the exhaust where you want it, I would say the exhaust is a higher priority. You can't change that based on what trails you're running. You can easily up your fuel capacity.
*edit* Oh, and on dragging the tank, I have a stock tank and I've never hit it. I know your truck will be way more capable than mine, so presumably you'll get into hairier situations, but I've smacked my rear bumper on the ground plenty of times and not hit the tank. I'm guessing with your longer wheelbase and bigger tires than mine that you could get decently low on it and still never hit it.
plus, it'll be armored.
I don't think you'll have an issue with covering the pumpkin from the rear. But I totally get the fact you want people to see it
Yeah.... I guess I keep forgetting that most of the time the truck is "laid out" with the struts fully collapsed so that it's at a more reasonable working height. That makes it seem like the axles are getting buried underneath the body / frame / low-hanging fuel tank.
In reality, the axle should be pretty easy to see. This is a rear facing shot taken at ACTUAL RIDE HEIGHT:
-G
old picture, looks like a blazer and not a skeleton.
I think he just puts those 5 gallon buckets under there to show off.
Maybe paint em a brighter color Greg.
Jerk.
Maybe paint em a brighter color Greg.
Jerk.
Ok I'm done throwing a fit LOL.
Greg I think that I would bring the tank further back. Taper it up at the end like the factory tank. I really think it could hang down 3 or 4 " and you would have zero issues
Greg I think that I would bring the tank further back. Taper it up at the end like the factory tank. I really think it could hang down 3 or 4 " and you would have zero issues
