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Opinions please, Skid plate metal thickness

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ZZ4x4, May 15, 2002.

  1. ZZ4x4

    ZZ4x4 1/2 ton status

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    Can anyone recommend what thickness steel to use in fabricating a transfer case skid plate, and fuel tank skid plate? I have been busy building the full roll cage, sliders, and bumpers from .134 wall mild steel DOM, and the truck is getting HEAVY. I am considering 1/4 inch steel plate for underside protection but I usually overdo it. Would something thinner (lighter) be strong enough? Maybe 3/16? Hoping for real world experience in bashing rocks. Thx, JT
     
  2. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Too much left unsaid. How big a gap is it expected to span without support? How much support? Even with that info it would be hard to say for sure. 1/4" factory plates that span about 10" from member to member under the case get bent. 3/16 would bend more/easier. But, a bent skid that doesn’t start contacting the thing it protects is still ok, within reason that is. Then again, a skid that is just to keep rocks from getting hung on a cross member would have less issues associated with bending since it won't hit/damage anything if it does. If there is an aluminum 208 less than 1/2" behind it and it spans 10-12", then I wouldn't be happy even with 1/4".

    Lots of things to consider and it will all boil down to a personal decision based on what YOU want and what you are using it for.
     
  3. ZZ4x4

    ZZ4x4 1/2 ton status

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    Yep, I get the point. I am building two .134 x 2" tubing hoops on the belly. One spans the frame by the front spring shackles and one behind the xfer case. The rock sliders will tie into these. The steel plate would connect the two hoops. Its a large span, but the transfer case and cross member are not wimpy behind the plate. There would also be some tension on the plate by being welded on each end to the hoops . The fuel tank plate will just be a box made of the steel to surround the stock sized poly tank. This tank can take some squishing without rupturing. I guess 3/16 is out of the question. thanks, JT
     
  4. SkulzNBonz

    SkulzNBonz 1/2 ton status

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    I would hazard to say that 1/8" would be plenty thick for the fuel tank, since it shouldn't see near the abuse or weight that the transfer case area would. I am currently designing a skid for the transfer case/crossmember, and I have 1/4" plate for that.

    John
     
  5. Mudzer

    Mudzer 1/2 ton status Author

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    Steve Frisbie has skidplating in 3/16", my diff covers are 3/16" and I slide off rocks all the time. I am planning to skid plate the whole bottom of the frame under my Dual Case kit similar to Watson's setup. I was planning to use 3/16" for weight savings. Every pound counts.

    3/16" plate is roughly 7.660 pounds per square foot. Lets say you had a 3'x3' square skid plate - the weight would be 69 pounds. Using 1/4" plate at 10.21 pounds per square foot would yield you a 92 pound skidplate using the same dimensions. The difference is 23 pounds. Thats quite a bit! (roughly 25 percent difference). Thats like having a 25 pound bag of dog food thrown on top of your skidplate when you are lifting it into place. /forums/images/icons/laugh.gif Let me know if my fuzzy math makes sense.

    If I had my choice between lifting a 69 or 92 pound (or 69 pound with dog food) skidplate into place when working on the rig - you know what my choice would be! The lighter the better.
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    The stock skid on my 73's case is 1/4" but the tank skid is 10ga or 1/8" (about the same thickness). If you're doing just a small plate for the case I would use 1/4", but if you're doing a belly pan I would go thick spots over the vitals and somthing thinner-like 3/16" or 1/8"- for the filler. For the tank I would go w/ 3/16" but would use 1/4" for the mounting tabs.
     
  7. ZZ4x4

    ZZ4x4 1/2 ton status

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    Thanks for the info. I am definitely trying to save weight. All this added armor is noticeable when accelerating. And cutting/ machining thinner metal is much more fun /forums/images/icons/smile.gif I think the solution will be to use the 3/16, but double it up in certain small areas where it needs to be really strong. Thanks again.
    JT
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd use 3/16" and instead of doubling it up in places I'd brace above it strategically with a bit more tubing. I'd consider using AR plate too (Abrasive Resistant) It's less prone to galling than regular A-36 Mild plate.

    I also recall a type of steel we used for gravel boxes. The thickness we used was 1/8" but the stuff was extremely strong and if we wanted any of it formed it had to be sent out because our brake press couldn't bend it at all. I'm pretty sure it was called SB-50 but I have no idea if that was a trade name or a spec like A-36 is. I may try and find out more info from my former boss...it would be killer as a skid plate and pretty light too.

    Rene
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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  10. ZZ4x4

    ZZ4x4 1/2 ton status

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    Thanks Rene, I'll ask my steel shop about this and the abrasive resistant stuff. See ya. JT
     
  11. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    The span is the problem. You could use a thinner material and put some 1inch tall ribs running between the suports on it that would make it stronger than just a flat plate of thicker material. That would letyou use a 3/16 plate and save some weight. As for the gas tank...1/8 of the factory is pitifuly thin. I made a skid out of 3/16. I have a reciever hitch on the rear and the way it's made I was able to turn the cross bar upside down so that nothing hung down. I made the skid attach to that cross bar so when I do drag the rear I have the class III hitch taking the weight. It leaves it nice and smooth under the truck so I can slide right off stuff and not catch the rear bumper. Even as braced as it is I came down on it HARD about 8 inches from the rear and bent it and the mounting bracket. It saved the tank from getting damaged like it was supose too. Factory skid would have caved and the tank would have been bent badly.
    Few pictures where you can see it in my sites, link in sig.
     
  12. ZZ4x4

    ZZ4x4 1/2 ton status

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    Gimmy, cool pics. I was planning on something similar for the gas tank skid with the hitch bar being the main structural support for the rear. Good idea to turn the bar over so there is nothing hanging below. For the belly skid, I don't really have the ability to bend creases in 3/16 so I will be using flat sections with reinforcement behind. Thanks for the input. JT
     

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