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Old March 29th, 2012, 22:02
frijolee frijolee is offline
NAXJA Forum User
Join Date: Oct 2010
Location: Tustin, CA
Posts: 377
Re: Joel's multipurpose XJ build (rocks/boulevard)

Thought Iíd give this one away with the flexing shot above but seems like no one picked up on itÖ

Gas Tank Skid:

Having done a few fast car projects Iím not used to the concept that weight doesnít matter. Between that and the fact that a car fire usually ruins your day (even if you get it put out), I wanted to build a gas tank skid so Iíd have one less thing to worry about under the vehicle when I bang it on something. Plus the bottom side of this jeep was just about as clean as the top and Iíd like to keep it presentable (the boulevard part of the build, right?)

I read that there was an OEM skid but it was only 1/8Ē steel and still weighed 30+ lbs. Thereís also the problem that most of the OEM skids seem to have rusted their way to dust by now. You can buy an aftermarket skid (usually made from the 3/16Ē steel that the custom fab folks seems to love) but you put about 70 lbs under the back of your vehicle and that seemed a little nuts to me just for some gas tank protection.

Instead I did a little bit of math and figured out I could make this out of 1/4Ē aluminum plate and itíd still have greater bending stiffness than the steel. I did go with 5052 aluminum rather than 6061 because itíll take an impact better. Since Iím welding it (but didnít plan to heat treat) Iíd lose a lot of the properties of the stronger alloy anyways.

Didnít take any pictures of the cardboard mock-up but it looked exactly like what I built (only made of cardboard and tape). Didnít both mocking up the gussets.

Note I added 7/8Ē drainage holes in all four low corners in case I go wading as Iíd rather carry back memories of a pretty stream, rather than the stream itself.

The rear bumper had a few supports built in that ran along the rear unibody rails so I replicated those into my skids. Getting the fit correct was a little challenging but Iím happy with the end result. Itís well gusseted and 100% welded inside and out.

Oh and it weighs one lb more than the stock skid while being a hell of a lot stronger (less than stock if you include the supports I removed). Looks gangster from the back too.

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