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Custom Fabrication: TIG/MIG welding, jig-building, metal working, fiberglass, carbon fiber, and other custom fabrication projects.

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Old 12-29-2011, 02:44 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #1 (permalink)
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Fuel cell


I want some structural advice on this.



Yes the metal is rusty blah blah will be cleaned up.
Anyways, I cut out the wheel well hump, I did not cut out everything, just the hump impeding the way of making the metal flat.

Now, this is 16g steel. I am going to tack weld it in and use self tapping screws to fasten it down just to be extra sturdy.

My main concern, this tank is a 15 gal, when it is full it will weigh 129.9 pounds not including the cell.

Should I brace this from the bottom? My main reasoning against this is to sucessfully do it I will have to cut out almost all the trunk metal to brace across from the frame rails in the back, that being said, I do not know if it is worth it to risk a faulty weld causing my cell to drop, as opposed to having the remaining metal from the trunk hold it in if anything were to happen.

If the g-forces from an awd launch (probably 1.2) will cause too much flextural stress on the metal, it would break the welds, but still be safe in the back (just not properly mounted). I did not study fluid mechanics so I have no idea how much extra force a G would cause on 15 gallons of liquid moving laterally.
(Not even sure if it would be compressive stress, or tensile tress along with flextural)

I am going to bolt the brackets of the cell onto the 16gauge. Any advice?

Sorry for rambling.



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Old 12-29-2011, 04:47 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #2 (permalink)
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I would brace it just to give yoursekf some piece of mind as long as your metal is all clean and not rusted and you sand the paint off where you're going to weld the metal to. Id take some scrap to set your welder up. You want your welder to sound like bacon cooking a steady crackle or buzz. If you need some pointers pm me man ill help ya through it.


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Old 12-29-2011, 08:47 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #3 (permalink)
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Quote:
Originally Posted by Lofty View Post
flextural
Lol is that a word?

Personally, I'd just cut a patch for the hole, and weld that in. No need for that monster you have there. I'd just bolt it down to the floor when your done.

When I did my AWD swap I had to cut the whole spare tire well out and put a new floor in framerail to framerail. I used 16ga, and its stiff as hell. I'd have no major qualms mounting a fuel cell directly to is. I ended up smashing the hump on a 1gawd tank down flat and mounting it like normal.

I'd also check the NHRA rule book and see what they have to say about fuel cell mounting. They may have some insight on how to keep you safe incase of an accident.

by the way theres a GVR4 fuel tank for sale on chitowndsm.com the guy is on here username minizilo, I think. I know you already have a cell, but a oem tank would be easier.

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Old 12-29-2011, 08:56 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #4 (permalink)
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You didn't ask, but I think for that to be legal at the track, the cell needs to be enclosed in another "box" if you will. Paul (99_GSTRacer?) should be able to shed some more light as he's chimed in on this topic a few times before, but the cell needs to be protected.

If I were you, I would add some structural rigidity to the under side where the cell is located. I'm thinking take some bar stock and weld an "X" underneath the cell, welding it in place. That way, you'll eliminate the flex of the sheet metal when the tank is full and eliminate the flex during cornering as the fuel is sloshing around.

My $0.02. Good luck Lofty.

BTW, is that an autometer sending unit I see bolted to the cell? Let me know how you like it....I've yet to bolt up my Frontline Fabrications 2G cell and I'll be using an autometer fuel level gauge and sending unit once everything is bolted up.


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Old 12-29-2011, 09:25 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #5 (permalink)
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Are you just tack welding the new floor metal in (not sure I understand what's going on)? Why not just full weld it in? I wouldn't trust/use sheet metal screws for something like that, personally. Or tack it in and stand on it a bit. This should give you an idea how 130 lbs of weight would affect any sort of flex on it. If it flexes, then either brace it or remove the tack welds and replace it with some thicker steel.

Or send calan a PM and see if he could run some FEA analysis on the setup (if he can).



I think he should be ok to run the fuel cell like that, as long as there's a firewall completely sealing the cabin from the trunk. I think the Galants have a firewall that separates the trunk from the cabin, but not sure if it's of legal specs.

Quote:
Originally Posted by 2011 NHRA Rule Book - Stock Cars
GAS TANK
Must be correct year, make, and model for car used, with stock fuel inlet and outlet locations. Must be in stock location; fuel line and pickup may be resized. Fuel cell permitted; maximum capacity 16
gallons. If fuel cell is used, OEM gas tank must be removed, and a firewall of minimum .032-inch aluminum or .024-inch steel must be installed to totally seal driver compartment from fuel cell. Trunk floor may be modified to accommodate fuel-cell sump. Where OEM gas tank is in the trunk floor, area occupied by OEM tank may be replaced with material equal to or heavier than OEM floor. If OEM gas tank is used, it must remain unaltered.
http://www.bremertonraceway.com/2011...20Rulebook.pdf


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Old 12-29-2011, 10:55 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #6 (permalink)
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Yes this is perfectly legal. Gvr4 rear seats are a firewall.
Flextural is a word, wiki it.
I went this route because in the end it will look more clean. Im talking about tacking/stitching it AND using self tappers.

To my general knowlege you dont want to seem weld anything this big on the chassis. It will warp to hell. Thus people stitch weld their chassis as opposed to seam welding it


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Old 12-29-2011, 11:00 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #7 (permalink)
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Well, stitch + tack does sound like a better idea than just tacking as you initially mentioned. Understandable about stitch vs. full. Just not sure how much that trunk area actually flexes.


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Old 12-29-2011, 11:07 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #8 (permalink)
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You got it! Still torn about if the 16g will flex too much or not. Id assume it wouldnt. Just a lot of cutting if i make braces. But ill probably end up bracing it... ugh.
Still want some more input.


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Old 12-29-2011, 03:34 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #9 (permalink)
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Quote:
Originally Posted by Lofty View Post

To my general knowlege you dont want to seem weld anything this big on the chassis. It will warp to hell. Thus people stitch weld their chassis as opposed to seam welding it
That's wrong. If you warp your car to hell welding in a trunk patch your doing somthing very very wrong.

This is like the idiots that think you can glue floor pan patches in.

I can guarantee that you do not need braces. Jesus, I have a 200lb subwoofer box in mine. I also pulled enough hard launches to rip a rear end mount of the frame rail, and the trunk floor hasnn't been deformed.

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Old 12-29-2011, 03:53 PM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #10 (permalink)
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Not so much the chassis i guess but the patch panel. Cool good to know. Thanks bastard.


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Old 12-30-2011, 01:49 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #11 (permalink)
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Woops


Bracing has started. Moar work tommorrow.


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Old 12-30-2011, 08:15 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #12 (permalink)
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I would now use aluminum that you added a brace(s). The aluminum can be drilled and riveted to the body and it will look a lot cleaner/lighter. I would then measure the the width of the mounting holes for the cell and space the next brace to that distance. You can then bolt the cell to the brace.


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Old 12-31-2011, 01:10 AM Show Printable Version Show Printable Version   Email this Post to a Friend Email this Post      #13 (permalink)
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All done.

Thanks guys.





It will be automotive sealed and painted black for fre$hness.

I stood on it and jumped up and down, and bashed it with a hammer.

150lbs of fury.


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