Here's how I had to have the tank guy build the filler neck on mine because of how tight it was to the frame
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)
2016.04.25 - UPDATE!!! - 38 GALLONS IN A WOODEN BOX...!!!
Spent a bit of time working with old cardboard boxes to get a general sense of space and dimensions, but over the weekend I decided to just pick up some 1/4" MDF at the local Home Depot and make things a little more precise so that I could really understand what sort of fitment issues I should expect building my "fuel coffin"
The basic layout is a pretty conventional rectangular box at the very back of the truck which is 12" deep and holds 25 gallons.
The next section is only 5" tall, which allows it to travel over the rear axle and driveshaft (at full compression) and measures 41" long and 14" wide... this is good for another 12 gallons or so. It was kept narrow to allow for the routing of a 3" exhaust tube on either side of the tank (with 1" of clearance on both sides). I think there is a way to transition the exhaust from an "outboard" style to "inboard" by snaking it over the framerails just above the large upper link hangers that are bolted to the frame near the rear seat "step up" area.
The view from out back.... It seems to hang down pretty low, but I think this is somewhat deceiving since there is no bumper installed.
From the side.... (sorry about the busy backgrounds, it makes things a little hard to see). This is probably fine from a "departure angle" perspective, but when I temporarily hung the bedside I don't like the way it sticks-out in an clumsy way from underneath visually.... the rear quarterpanels have a gentle 5.5* slope on the underside of the panels as from the bumper to the rear tire area. I think I'd like to replicate that same slope on this tank so that I don't have a goofy sharp corner poking out from underneath when viewed from a distance....
There is one potentially HUGE benefit to building a tank that runs the full length of the two cross-sills. If I were to mount the tank to the forward cross sill with a hinge-type mounting system, the entire tank could then be lowered (at the bumper side) VERY easily and controllably with a floor jack. If I ever needed to get access to the top plate, hoses, or electrical connector for the fuel sender... it would be quite easy to do!
I'm still not sure that I'm willing to go with an in-tank fuel pump yet (unless maybe I could run TWO of them in there for redundancy) but knowing that I have a pretty simple way to gain access could change my mind!!
So that's about it so far. Any thoughts on the tank material? I know that aluminum is popular... but it's also a bit harder to weld cleanly, and is more susceptible to rock damage. Stainless is stronger and I could use a thinner sheet than the aluminum stuff... but I've never priced either one to know what sort of price premium is involved.
-G
Spent a bit of time working with old cardboard boxes to get a general sense of space and dimensions, but over the weekend I decided to just pick up some 1/4" MDF at the local Home Depot and make things a little more precise so that I could really understand what sort of fitment issues I should expect building my "fuel coffin"
The basic layout is a pretty conventional rectangular box at the very back of the truck which is 12" deep and holds 25 gallons.
The next section is only 5" tall, which allows it to travel over the rear axle and driveshaft (at full compression) and measures 41" long and 14" wide... this is good for another 12 gallons or so. It was kept narrow to allow for the routing of a 3" exhaust tube on either side of the tank (with 1" of clearance on both sides). I think there is a way to transition the exhaust from an "outboard" style to "inboard" by snaking it over the framerails just above the large upper link hangers that are bolted to the frame near the rear seat "step up" area.
The view from out back.... It seems to hang down pretty low, but I think this is somewhat deceiving since there is no bumper installed.
From the side.... (sorry about the busy backgrounds, it makes things a little hard to see). This is probably fine from a "departure angle" perspective, but when I temporarily hung the bedside I don't like the way it sticks-out in an clumsy way from underneath visually.... the rear quarterpanels have a gentle 5.5* slope on the underside of the panels as from the bumper to the rear tire area. I think I'd like to replicate that same slope on this tank so that I don't have a goofy sharp corner poking out from underneath when viewed from a distance....
There is one potentially HUGE benefit to building a tank that runs the full length of the two cross-sills. If I were to mount the tank to the forward cross sill with a hinge-type mounting system, the entire tank could then be lowered (at the bumper side) VERY easily and controllably with a floor jack. If I ever needed to get access to the top plate, hoses, or electrical connector for the fuel sender... it would be quite easy to do!
I'm still not sure that I'm willing to go with an in-tank fuel pump yet (unless maybe I could run TWO of them in there for redundancy) but knowing that I have a pretty simple way to gain access could change my mind!!
So that's about it so far. Any thoughts on the tank material? I know that aluminum is popular... but it's also a bit harder to weld cleanly, and is more susceptible to rock damage. Stainless is stronger and I could use a thinner sheet than the aluminum stuff... but I've never priced either one to know what sort of price premium is involved.
-G
Oh, I like the idea of hinging the tank for access to the top. That is genius!
As far as tank material goes, I don't know what would be best, but I don't think MDF is going to hold up very long...
As far as tank material goes, I don't know what would be best, but I don't think MDF is going to hold up very long...
Did you leave room for the filler neck someplace?
Isn't your exhaust going outside the frame? If so, you should fill up the width at the front, that heat won't make it past the frame.
Isn't your exhaust going outside the frame? If so, you should fill up the width at the front, that heat won't make it past the frame.
Filler neck is going to be tight, but I'm going to try to land it in the rear upper left corner so I can use the stock factory filler hardware. The hose itself will probably end up being custom.
There's a small amount of space between the "step up" vertical panel and my 2"x3" cross sill (maybe about an 8" gap) where I think I can transition the exhaust from that torsion box area (outside the framerails) back over the frame to the inside area.....then run it along the inside of the framerails before kicking it back out just before the BIG part of the tank steals all the remaining space. My hope is that with a fully thermal-coated exhaust and 1" of air space all around the exhaust in that area... I shouldn't be boiling my fuel, or cooking the powdercoat off the framerails.
I'm also seriously considering hanging my batteries in those rear corners (just behind the rearmost cross-sill, on either side of the gas tank) as a way to get more of the weight well-past the rear axle. I think I can build small cubbyholes on either side to hold them securely....
I still need to find room somewhere for a high-quality air compressor (or two!)... hopefully something that flows enough CFM that I don't need to mount a big air tank underneath. I'm definitely running out of room!!!!
-G
I don't know if it is just the grade of aluminum, but the one Brett put in the buggy has had the welds crack multiple times and he has had to bring it to a shop to have it re welded. The thing is vented well, and has rubber isolators at all points in contact with the buggy and mounts.
Like I said it may just be crappy material on a crappy Summit fuel cell, but he just had it welded up for a 3rd time, and its put a bad taste in my mouth. Just thought I would share.
He said he is just going to build one out of steel next time. You can use thin steel so its not like the weight will change much.
Like I said it may just be crappy material on a crappy Summit fuel cell, but he just had it welded up for a 3rd time, and its put a bad taste in my mouth. Just thought I would share.
He said he is just going to build one out of steel next time. You can use thin steel so its not like the weight will change much.
Most of the racing cells are steel with a bag inside right? If it was me Id be more inclined to go stainless.
That's kind of what I was thinking too..... this tank is stupid-long, so with a soft metal like aluminum it just seems like I'm begging for trouble.
-G
Plus the fact that when its that long the torsional stress probably wont be doing any favors to the aluminum.. You have plans for baffles etc?
My plan is .......MANY!!!
Probably a couple of longitudinal "spines" that follow the bottom profile of the tank to help support it where it transitions from 12" deep to only 5" deep (that transition won't be a sharp 90* like it's built, I'm going to do a 45* instead)... then maybe some kind of interlocking cross baffles every 12" or so to prevent fuel sloshing. It's definitely going to be tricky and I want to use Eric's idea of flanging all the baffles for extra strength. I think when the time comes I will probably lay out the whole thing in a nice heavyweight card stock to plan the cuts, flanges and pan-brake locations. I've got a local metal shop that has huge brakes, so if I can diagram what I need I'm sure they can bend it up pretty easily for me.
-G
That looks perfect Greg. Looks good from the back. Sits perfect with the pumpkin!
I'm pretty pleased with it, and I think it's a good compromise between fuel capacity and ground clearance.
Once I put that 5.5* taper on the bottom edge of it I think it will look a little less "bulky and blocky" underneath. I will probably also make the entire tank about 1/2" shallower (From the top side of the tank, for a bit of extra clearance to the bedfloor), and as I make other "tweaks" to accommodate a larger diameter driveshaft, exhaust (maybe) and so on. I'm sure that I'll probably lose a couple of gallons in the process, but since I'm at 38 currently it's not a big deal to me. I was really hoping for 35 gallons as my ideal value... and was willing to go as low as 30 gallons if I just couldn't make everything work.
Ultimately, if I'm willing to trade gallons for clearance..... this design will cost me about 2 gallons / inch of additional ground clearance in the deepest part of the tank. I may still pull the whole thing up another inch (maybe) depending on how it looks to me once the rear quarterpanels are re-hung on the new bedfloor and I can really study it from a few different angles.
At this point, I just want to block-out the space that the tank will need, so that I can plan my exhaust routing.... battery installation and maybe ViaAir compressors and/or air tanks.... space is getting hard to find for sure!!!
-G
bp71k5
3/4 ton status
It looks like you could gain another gallon by making an angled transition from the shallow portion of the tank to the deepest part in the rear. That might offset some capacity reduction in other areas.
Brian,
Yeah, it's hard to see in the photos I posted, but I did that already (5" down, 5" back....~ 7.00" diagonal) and picked up 0.75 gallons of extra capacity (that was part of my 38 gallon total)... I think the diagonal would help prevent cracking at the transition point as well.... something about a hard-90 in that spot that just seems like it's begging for trouble.
-G
I assume the pickup is going in the deeper portion, and for that reason why not keep the 90*?
It would keep gas down in the bottom if you are going down a hill or obstacle. If you put an angle on it the gas can move forward...
It would keep gas down in the bottom if you are going down a hill or obstacle. If you put an angle on it the gas can move forward...
I assume the pickup is going in the deeper portion, and for that reason why not keep the 90*?
It would keep gas down in the bottom if you are going down a hill or obstacle. If you put an angle on it the gas can move forward...
Are you "baffled" by my designs???
I haven't done much research on what good baffles look like, but it makes sense that all you really need are tall solid interior walls with a small set of holes at the very bottom to allow fuel to SLOWLY move between the various sections of the tank. Even at WOT, it's not going to take much flow through those baffled holes to keep up with fuel demand... and with one of those HydraMats in there, if the fuel lands ANYWHERE in that lower tank section....it's going to get sucked into the mat and rock-n-roll out the fuel lines to the motor.
-G
I thought the point of the hydra mat was to eliminate the need for a lot of baffling and sump setups etc.
That's probably true for a classic rectangular fuel tank design.
In this case, I've got massive long spans of metal that are going to need some kind of bracing no matter what.... so, I drill a few holes in the bottom of those braces and voila! now they're called "baffles"...
I could probably get a few cans of Flex-Seal (it's like a handyman in a can!) and make this box watertight.... then fill it with a couple of gallons of water, to experiment with different baffles and tilt the tank at all sorts of crazy angles to see how it behaves.... sounds kind of fun, actually.
-G
Would be cool to see how different designs work baffle wise
I think your going to find that you want a bladder in that tank, if I was you I would be talking to someone like fuel safe or ATL and see what you can do with them. I think that you can build the tank shape and have a bladder custom made to your shape. My belief is you have a really awkward shape and will fight cracks with any material, but especially AL.
Might as well
Might as well
