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question about frame boxing where frame is not square?

Discussion in 'The Garage' started by cybrfire, Sep 27, 2003.

  1. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    I'm boxing my frame in front of the factory front leaf shackle area. The frame lips are not straight with each other top to bottom and the frame curves here also. Anybody box this area and how did you do it? Do you have any pics?
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Why not just weld a plate into the frame? Is there a reason to completely box it?
     
  3. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    by boxing it I can weld in a new tube for the shackle. The boxing will strengthen the frame and allow for the tube to be supported on the inboard side of the frame.
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    First off, I'm not a fan of boxing GM frames, especially partially boxing, but that's something I've said many times before.

    But, dealing with odd shapes like that is not such a big deal. Put it on the anvil, use heat and a vice, grind/cut it to fit, weld in a small pice cut to make it square, or even grind the frame a bit to make it easier (your going to box it anyway).
     
  5. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    Why are you not a fan? Just curious what your thoughts are.
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    [​IMG]

    This is what I was referring to. This guy from Chuck's Chevy Truck pages used 3/16" plate. I would have used something along the lines of 3/8"-1/2" or so. I think 3/16 was a total waste of time but it will strengthen it some.

    He ran it the entire length of the frame.
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Well, in the past I posted some long explanations. Try search for "frame boxing" about a year ago...

    But to summarize.

    The GM frame (and other light trucks with ladder frames) was *designed* to flex from end to end at specific rates. When you lock part of it down, the rest flexes against the stiff part and you get metal fatigue followed by failure beside the rigid area. Sometimes it takes a year or two, but it happens. I saw this repeatedly when I ran a frame machine years ago in an area with lots of small logging companies. They used K20/K30s and such with modified (cut down or extended depending) frames. Many times these were done by a "friend that can weld". Almost invariably they scabbed on big "reinforcement plates" or "boxed" the spliced area. 6 months later it looks like a sway back nag and they drag it in to me. Several times I cut out the botched sections and did a backed “but weld” with a non-straight cut to put them back together with grafted in frame sections to replace the junk. Often, with a new customer, I would hear "Why that aint gonna hold, just look how that big heavy piece broke!" /forums/images/graemlins/rolleyes.gif Yeah, right beside the big rigid scab... Then after my repair holds up long after they have broken others, they came back for more of my wimpy work. I never once got one back that broke anywhere near my repair.

    If your set on boxing, then you need to do it all to do it right. If your going to box part, then you should definitely fish mouth the plate so that at least it doesn't keep the fatigue too localized. I have never understood why people are so dead set on eliminating the frame flex. The only bad comes when it gets so bad it starts damaging the body or drive train, and there are better fixes for that than making the frame rigid...
     
  8. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I think frame flex is horrible. Hopefully one day my fabrication skills can get good enough that I can eliminate it completely. I've never seen a semi's frame flex, or a duece and half frame flexing so bad that the cab went one way and the rest of the body the other, etc.

    I do agree with you though, if you strengthen one area, one of the weaker areas will surely crack. You've got to do it right and do it all.

    There is a reason that 1 ton trucks have thicker frames and more crossmembers. Having had the body off my truck and had it down to the bare frame, I definitely understand how flimsy and crappy our stock frames are.

    One day, I'm either going to make my own frame from some really thick C channel or strengthen a stock frame so much that you could drop my truck off a cliff without having the frame tweak.

    Ever seen a truck pulling and hopping and the way the frame flexes every which direction? I think that's so stupid I can't even put it into words.

    There would be NOTHING wrong with a completely rigid frame, and one day I'm going to attempt to do it. I'm just going to make sure I do it right so I don't end up like your customers did.
     
  9. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    I appreciate your insight however I am set on boxing. Thanks anyway. I have boxed small areas already. I do fishmouth the plates. This is a simple pic of what I have envisioned.

    [​IMG]

    endview of frame area to be boxed. I hope this will show what I am trying to acheive. Pic is kinda small.
     
  10. Triaged

    Triaged 1/2 ton status

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    I have seen shackles put in non-boxed frames. You just have to either use the factofr cast piece or weld the tube in at either the top or bottom of the frame....Make sure you fishmouth that box piece well. I also don't see a reason to use thicker than 1/8" (about what the stock frame is).
     
  11. jjlaughner

    jjlaughner 3/4 ton status

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    I'm not sure if this helps or even if its what your talking about. If you talking about where the frame curves and you need to measure to match curve, Use a piece of card board and a rubber mallet. Mark the cardboard at the bottom to keep it aligned and then use the rubber mallat to stamp the cardboard into the frame making sure you line you drew stays in the same position. Then cut just inside the marks made my by the frame on the cardboard, then transfer those lines over to the steel your using.

    You will have it crack later on because of what was said above about the frame flexing, but I dont care the look of the inside of the frame where the shackle mounts either. /forums/images/graemlins/smirk.gif

    Good luck and take pics before and after
     
  12. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    I totally understand what everyone is saying about a frame flexing and the cracking. I've been thinking about some alternatives but for now this seems the best way to go. I don't believe frames flex much after a roll cage is installed and tied to the frame. Besides I would rather the suspension do the flexing. I guess I will just peice it in and see where I end up.
     

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