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Frames Wont Last Forever...

Discussion in 'The Garage' started by 1985K20, Feb 15, 2005.

  1. 1985K20

    1985K20 1/2 ton status

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    While i was taking my gas tank off my truck today, i seen that my frame is awfully skinny right at the big cross member at top of rear end, it's also cracked.

    Since i really love my truck, i aint gonna get rid of it,and i aint gonna get a brand new 40 000 bucks gmc 2500HD, i'd like some advices on what would be the easiest to fix that:D
     
  2. RustBuket

    RustBuket 1/2 ton status

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    If you are a good welder, you can drill a hole at the end crack so it doesn't keep cracking and then grind a v-notch into the crack and fill it up with weld. If you aren't an experienced get someone who is.
     
  3. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    Full cage tied to frame is what I am doing. that will extend the life of the frame a bit.
     
  4. sled_dog

    sled_dog 1 ton status

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    eh, if your cage is too stiff it will stiffen your frame too much and could cause frame cracking rather than preventing.
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    All tying a cage to the frame is going to do on these trucks is fatigue the cage to hell and destroy the frame at the attachment points.
     
  6. miniwally

    miniwally 1/2 ton status Premium Member

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    It all depends on how much of a cage you are talking about. A well thought out and attached FULL cage strengthens the frame.

    A simple roll cage that is only in the drivers area will create some stress issues and create more cracking over time.

    Get the crack ground out and welded up then if you think it needs it add some plating around the area and call it good. You are however correct in sayin that frames are not meant to last forever.
     
  7. 1985K20

    1985K20 1/2 ton status

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    Yeah i'll probably go with the grind/weld and ad plates idea, the quicker it's gonna be fixed; better it's gonna be for me. Someday i'll have a building to work on it!!:)

    Thanks y'all for your posts

    1985K20
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I agree on all points and cautions with tying the cage to the frame. Brandon is dead on with the "full cage" comment, but to carry it one step further, the cage needs to be tied in at the suspension mounting points in order for it to "strengthen" the frame rather than kill it. If the suspension can work the frame against the 3 dimensionally stable cage (a space frame in effect) then it will fatigue the frame over time. Of course, if the cage is not properly constructed you can fatigue the cage as well, which might fail at an inopportune time. Lots more to doing this stuff "right" than most think…
     
  9. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    The cage will be tied to the frame at 6 points with spring bushing/bracket ends plus frame tied sliders. I will make the suspension do its job thus decreasing 'work' stress on the frame and body. It will be stronger and last longer. Plus the cage is not an option for safety reasons.
     
  10. rcamacho

    rcamacho 1/2 ton status

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    On a related note, anyone out there make replacement HD frames for the K5's like are available from several mfg's for jeeps? Perhaps wishful thinking on my part....:frown1:
     
  11. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Curious, but what does this mean?
    Tying to the frame (with or without bushings) may eliminate some of the obvious flexing, but if you don't lock down the suspension mounting points, you are just making a minor but visible problem into a more serious but less visible one, localized fatique. I fail to understand why everyone gets so bent over the frame flex itself. Legthwise flex is not harmful, that is what it was designed to do. Really, the only down side is damage to the body due to it's lack of ability to flex *with* the frame.

    I'm also not sure what this means.
     
  12. rubbinz raczn

    rubbinz raczn 1/2 ton status

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    baddog by tied into suspension mounting points i assume you mean on frame above spring hangers? i pmed PJTPW (ryan) awhile back about his input concerning his truggy. his is tied into frame at lots of places, 20 plus IIRC. he mentioned he thought he had eliminated most of the frame flex so suspension did most of the flexing. he also hasn't had any big cracking issues. given very little frame flex what would be the first to start cracking if anything would?
     
  13. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    I agree - the frame flex from these trucks allows them to work better. But the flex is starting to damage parts of the truck (my doors are starting to push out as 1 example). I do worry about the frame failing in some way that I can't prepare for or prevent.

    If the metal is not bending and twisting it will be less likely to fail (work hardening/fatigue).

    Yes, more stress will be applied to all attachment points (frame and suspension). I'll deal with those as they happen. As you make one part stronger you uncover another weak area or problem....

    The cage is going in for the primary purpose of safety for the occupants during rollover. (cage is not an option statement) You had a question about that - do you agree with that?


    Do you think a non-cage frame will last longer? I'll get back to you in a year :D
     
  14. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    rubbinz:
    Ideally, the tie in would be directly at the suspension mounting points so that no stress transferred along the frame and almost all of it ran linearly along straight spans from node to node. But things are rarely ideal (re. my rear suspension post in CoG). But as long as it's relatively close, or tied in on both sides of the suspension mounts, or otherwise in some way limiting the leverage of the suspension against the part fixed by the cage, it should be fine for any reasonable time span. Problems really start to mount with the "typical" family style cages in K5s and the like where the cage is well made and rigid while also tied to the frame at the bottom of the foot well. Already a high stress area (where the frame turns up), the leverage of the suspension bending against that point without allowing the flex to "travel" will multiply the fatigue at the bend. Will it fail right away, certainly not. Just as an example, what may have otherwise lasted many years and 100k miles of moderate wheeling and daily use may now last only 2-3 years or 20k, or more, or less…

    2dogs:
    Ok, I get it now about the cage. Yes, I agree that you do not want to take a chance on damaging the cage by trying to co-opt it for another purpose (like stopping flex). However, properly designed and triangulated structure utilizing "nodes" and straight spans can handle those loads just fine without damage. But more aesthetically pleasing designs are often much less rigid in general and weaker when called on. However, people will still make those compromises…

    Your also right about the flexing, to an extend. Problem is, people see the end-to-end flexing in the stock ladder frames and say "Oh my! Gotta do something about that!" And they tie in the cage, or scab on some plate or partial boxing, and they see "reduced flex", and think they have succeeded. What they don't realize is that small movements are still taking place and are localized to a very narrow area, with the net effect being reduced time to failure at that point.
     
  15. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    I think I started getting into an unbalanced frame condition when I added the bumpers with super beefy attachments and frame boxing at the ends. I know the frame was tweaking harder over shorter sections. Each time we add stuff like bumpers or rock sliders we are doing this.

    I will be concerned about the front spring mounts for the rear leafs - they will be on the largest section of unmodified frame. Next weakest point is the frame behind the steering box and brace. I notice outward flex when you turn the wheel even under the lightest of loads.

    Also keep in mind that my K5 will rarely have 1 wheel off the ground for extended periods (less torque that the suspension can't handle). The excursion wheeling I do keeps the suspension working in it's sweet spot almost 100% of the time. The cage in this case makes me feel like I will complete my journey with less damage to the truck and occupants than before - thats my goal anyway. And I will look into spanning the frame where I can to help the next week spot ;)
     
  16. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    The frame flex around the steering box is a somewhat different animal. It's an example exactly what we are trying to avoid and does need to be dealt with before serious damage occurs. The rigid cast box with 4 mount points fixes a portion of the frame rigid, right behind the front spring mount. The box then torques the frame rail while steering while working against the suspension mount over a very short span. Of course, that leads to the well known "weakness" of Chevy frames where the break in that area. This is exactly the same kind of thing that *most* naïve frame to cage tie-ins will result in, to greater or lesser degrees. It's just reversed.

    And your goal is a perfectly valid one. I don’t mean to come across too "hard line" on this topic (though that is how it seems I guess). I only keep jumping into these discussions with my warnings because too many people seem to have this "go with the herd" mentality and will boldly state with no hesitation that "a cage is worthless if not tied to the frame" and "gotta stop that evil flex!" Neither approach/goal is particularly awful if understood and evaluated while being aware of and trying to deal with the side-effects. The problems come in when that last part, "being aware of and trying to deal with the side-effects", gets left out. Or they *assume* that because so-n-so has been running it for 2 years with no disasters that it's ok and will not be a problem. By that same logic, there is nothing wrong with the GM frame and steering box design since it usually lasted the 20+ year life of the truck without breaking, but that doesn't stop those same people from almost invariably cursing GM for the "crappy" design. I hope my evangelizing on the subject at least makes people think for themselves on the matter so they can make an informed decision...

    Well, that should cover this topic for me for another month or so... :D
     
  17. 2Dogs

    2Dogs 1/2 ton status Premium Member

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    :D:thumb:

    I am hoping to cure the weakness behind the box and the wander under hard braking someday.....

    Have you ever been in a C/K5 with a full boxed frame? Does it track better in the rough and hard braking conditions?
     
  18. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Can't say as I have.

    But I wouldn't fool with boxing the stock frame if that's what your thinking. Talk to Brook, it's a freaking lot of work. I think I would follow Greg's (Greg72) approach and build one out of rectangular steel first...
     
  19. sled_dog

    sled_dog 1 ton status

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    no one makes a replacement frame. At least not like pre made, could find a shop to custom make you one.
     
  20. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    There was a right up in *i think* 4 wheel and off-road for a company that makes replacement tube frames for vehicles and they mentioned that they were planning on making them for full size trucks as well in the future...though who knows, we here that all the time and nothing comes of it :crazy:

    A replacement frame for these trucks would be awesome, the stock frames are the real weak link if you wanna build a hardcore rig that will last.
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