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cage in the making, questions.

Discussion in 'Center Of Gravity' started by Seventy4Blazer, Nov 8, 2003.

  1. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    if this is the wrong forum, im sorry. like the rest of us i am still learning what can and cant go here for sure

    the idea is a inner floor made of 2x4 3/16ths wall. 4 sections in the "bed" of the blazer. 3 more in the "Cab" of the blazer. all 7 going across the truck. then 4 more going from front to back. kind of like a grid. the bed section and cab section would be connected with mitered and fit 2x4 stock as well. the cage would be built on this. including the dash, seats, fuel cell, spare tire, tool box, spare parts. the inner roll cage would tie into the body at the body mounts with rubber bushings. the frame ties into the body with polly bushings. i have stiffened up the frame a bit with braces and what not. the rockers in the body are 4x6 .25 wall tube they will be tied into the roll cage with rubber as well.

    reasons for doing it this way are as follows
    i like the looks of my blazer. im not about to remove the body fully. some day, but not till its trashed.


    this way, once the body is trashed i can remove it and then install the cage on the frame with very few mods, or a new frame.

    i think it will firm up the body and frame to the point that i am happy with it.

    when the body is totaled, if i desire i can find another body and swap the cage in as it is all bolt in, for the most part(cage will be welded, but its a 74. unbolt the cage from the body, re install it in new....

    i dont see any drawbacks, but im sure there are some.
    let me know what you think. and im sorry if this is the wrong area.
    Grant
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    First problem I can see is weight, and that may be enough of a problem right there. Nearest I can figure between the floor 'grid' and your 4x6 rockers you've added 560 lbs of steel. /forums/images/graemlins/eek.gif

    2x4 x .188" wall tube is 7.5 lbs per lineal foot. 4x6x.250 wall is 18.4 lbs per lineal foot. For comparison 1.75" x 120 wall tubing is 2.06 lbs per foot /forums/images/graemlins/thumb.gif

    Unless you're planning on using the truck as ballast for something I think there are smarter ways of gaining strength.

    Rene
     
  3. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    forgot to mention, weight is notmuch of a concern in this. but you are right. that is a lot more than i though i was gonna end up adding. i think with the 450 i have removed already, and then the 350 i have added.... and a lot more to go, ill be sitting at "aboot" 6800 lbs., eh?

    this is good though. any more input from anybody else?
    i dont think weight will be that big of a deal as the majority of the weight will be down in the body. i can remove more and have been thinking big time of skinning the bed sides.
    grant
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Why not use .125" wall? Instant 33% reduction in weight and it would be plenty strong enough. /forums/images/graemlins/thinking.gif

    Rene
     
  5. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I also think it's over kill and over heavy. I really don't think you need that much support for the cage unless your planning a TV special where you drive it off into a canyon or something.

    IMO, all you really need is something to (1) transfer the a-pillar load onto the body mounts and (2) something to spread the b-pillar load across the frame. I like spanning the frame on the b-pillar/hoop simply because it is the main support for the cage which MUST NOT fail, and on many chassis the body mounts in that area are on the inside of the frame anyway.

    Just an example of how I’ve approached this…

    On the buggy, I have 2 x 2 x 1/4 wall dog legs coming off the front body mounts to my rock sliders (rockers) and the a-pillar mounts to those. These are that heavy only because they have to support the load with a very large lateral force vector. Unfortunately this is impossible to triangulate (to get the load properly in compression/tension) without a bar going through my lower legs. For the b-hoop/pillar, I have a 2 x 3 x 3/16 tube going all the way across. The ends support my rock sliders and the main hoop. The center sets on the factory inboard body mounts. Even if the factory frame mounts fail, it will just fall to the frame and can’t go further till the cross bar fails. The only other cross support is in the very rear. It is built from 120 wall tube since the rear tubes come down right on the rear body mounts (which I built and are much stronger than factory) and it doesn’t have to support a bending load. And I built this thing with *knowing* one day it will roll and may roll hard.

    On the K5. This truck is built to be safe in a roll, but not built to tackle what my truggy was intended for. Pretty much the same front support, but 3/16th wall. For the b-hoop, the factory floor sub structure was reinforced as part of mounting the sliders. The b-hoop tube will come down right on top of this. And rather than a complete transverse bar, I’m adding only a piece of 3/16 x 4 strap stock welded to the floor. Main point is to make sure the down tubes can’t punch through the floor. In a hard roll, that srap will bend, and the tub will be toast anyway, but it should be almost impossible for it to fail catastrophically.
     
  6. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    [ QUOTE ]
    Why not use .125" wall? Instant 33% reduction in weight and it would be plenty strong enough. /forums/images/graemlins/thinking.gif

    Rene

    [/ QUOTE ]
    because i like overkill. and in all honesty my mind can get set on things like that. but after thinking about it and having 2 others say it will be strong enough i guess that will be change one of many to come. thanks rene.
    Grant
     
  7. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    [ QUOTE ]
    I really don't think you need that much support for the cage unless your planning a TV special where you drive it off into a canyon or something.

    [/ QUOTE ]
    kind of... but not a canyon. get the truck done, test it out on the streets. work out those problems. drive it to FJ and wheel it. work out those problems. take it to the dunes and roll it at about 15-25MPH down a small dune.

    crazy, but i want to do it and will. /forums/images/graemlins/thumb.gif
    i think ill step a few of the sizes down a bit. but not many of them.
    thanks for the input guys. keep it comming.

    here is an idea i was wondering about on the 2x4 base of the cage. it is stronger if i notch the tubes out so they lay like lincon logs? then full "circle" weld them?!?
    would doing the work to make them all line up and be true and square worth the strength gains? thanks
    GRant
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I think you could get the same strength with at least 400 lbs less weight by building a more mainstream style of cage and using frame connectors.

    In my opinion the 2x4 sub floor is a very heavy 'redundancy'. You already have a floor...

    If the "A" pillar goes through the dash and straight down from the speaker holes they'll hit the floor on the sloped part ahead of the body mount. A fairly strong area all by itself...add a connector to the frame underneath and that's about as strong as it can be made without building a custom tube frame and grafting skins on.

    "B" pillar area can be done the same way

    I plan on connecting the "A" pillar and "B" pillar along the floor and making a 'bridge' for seat mounts.

    The "C" hoop at the rear will also be connected with a bar running between hoops like the "a" and "b" hoops and the rear seat will be attached to another bridge. The "C" hoop will also have frame connectors.

    Built this way I beleive it to be as more structurally strong than a box tube sub floor...plus it'll be hundreds of lbs lighter.

    Cages are a lot of work, I just think you should re-think your plan.

    Rene
     
  9. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    ....yeah,

    [lecture] Steel doesn't grow on trees ya know! [/lecture]
     
  10. Butch

    Butch 1/2 ton status

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    Why when thinking of how heavy this will be do I get a vision of that Dodge Hemi commercial when the guy is in the old dragster trying to go with the parachute out.

    I sure hope you plan on a big block to get that baby rolling.
     
  11. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    well, i agree with yall on some of it. well, most of it.
    think ill go back to the drawing board on it. thanks guys.
    Grant
     
  12. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    4.10 gears, 6.2L(in the works) 42 tsl's(in the works) and Sm465 with a dual t-case design(dual t-cases in the works as well)

    i shouldnt have a problem with street driving or with trail driving. like i said, weight is not a concern of mine. it should be. but im not worried about it till it becomes a problem. /forums/images/graemlins/grin.gif
    Grant
     

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