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solid mounted body/ cage to the frame post?

Discussion in 'Center Of Gravity' started by Thumper, Jul 8, 2004.

  1. Thumper

    Thumper 1/2 ton status

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    I tried searching... cant find it:
    There was a post with some real in depth talk about the pros and cons of mounting the body hard to the frame, and building a cage off the frame, you know... the frame stress issues, the body stresses etc. Does anyone remember this one?
    If not... I have a question:

    I am going to be swapping an S-15 extended cab onto my K5 frame soon. I have measured and remeasured and it looks like it will fit ok. (we will see /forums/images/graemlins/smile.gif)
    Is there anything wrong with solid mounting the body mounts to the frame and cage as well? I know what Russ will say... as long as the cage makes a strong 'insert proper name here' framework for the suspension so it wont flex the frame, but is there any real need for rubber mounts?
    Also, if I rubber mount the body, the cage will be bolted to the body, not the frame... I think I know where the post is discussing this.

    Mike
     
  2. Mudzer

    Mudzer 1/2 ton status Author

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    You will probably find that the mounts where the cage meet the body will crack out no matter what type of plate you use on the flooring. I would suggest using bushings.

    I bought a set of spring hanger brackets and the fab bushing kits to match from ORD and they will be perfect. /forums/images/graemlins/thumb.gif
     
  3. jac6695

    jac6695 1/2 ton status

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    Unless you plan on a lot of street driving, I would do the solid mount. I think I am going to redo my mounts and cage and do solid mounting. My body mounts on the S10 Blazer body it self are collapsing due to the body not flexing from the cage bolted to it and the frame having too much flex. Not much need for rubber mounts for a mostly trail truck.
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hard question to answer clearly.

    Using the cage as a "space frame" (uses triangulation in a 3D frame to convert bending forces in to compressive/tensile forces) will stop most, but not all of the "frame" movement. For this purpose the cage/body needs to be attached solidly at the suspension mounting points so that the suspension loads are not carried by the flat(er) OEM frame. Otherwise, the OEM frame will flex against the more rigid cage and fatigue.

    Mounting the body rigid is a whole different thing. Most cabs are fairly rigid, in part due to the multiple layers of sheet metal acting as sheer planes. If you try to mount it rigid, just as Neil said, the localized mounting point is going to get worked by ANY deflection at all and will likely fail sooner than later. Even with the cage stabilizing the frame, there will be some flex, it's just a matter of how much. And there are other issues as well. Best to mount the cab with bushings. But then the only way to combine the two effectively would be to exo the smaller S-10 cab. Running the cage through holes has it's own problems.

    And finally, mounting the cage to the body is fine as long as the isolation remains flexible enough. IMO, this is the best way to do things if your not going "all the way" with the space frame approach I mentioned first. And this works in a similar way such that you need to support the body mounting points with the cage to take most of the load of the sheet metal. Basically run the cage legs close to the mounts and the brace them in on top of the mounts. This takes most of the stress of the ladder frame flex off the body so it does not start to fatigue and rip out spot welds, while also providing a sort of safety capsule for catastrophic rolls. Going further, you can do like I did which is to replace the formed sheet metal braces under the floor with square tube, tie the cage into that sub-frame structure, incorporating rock sliders as well, and you truly do have a full capsule around you, with the body effectively bolted solid inside the cage. The cage then is what sets on the bushings, and the bushings get to deal with the different rates of flex as they were designed to do. I prefer the doughnut style bushings from the 80s for this purpose and I use them in all mount locations.
     
  5. ntsqd

    ntsqd 1/2 ton status

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    Digging up an older thread here:

    What my friend Sherman and I have worked out is to mount the cage to the body as if it were going to be the truss structure Russ talks aboot. Then off the far side doubler plates (you were planning on doubler plates, right?) make mounts to the frame. His specific plan is to use urethane shackle bushings at the join to the frame. The stock body mounts will only be used long enough to set the body in the right place, and then removed. This way you get some flexibility so you don't work the frame as hard and the body moves with the cage (no squeaks).

    If you are anal-retentive then you should spigot on one side of each sandwich and put a receiver tube on the other side so that you do not load the bolts in any direction except tension. F911's or Holo-Krome SHCS' & washers with prevailing torque lock nuts would be a good choice for those sandwich bolts.
     
  6. Chris Demartini

    Chris Demartini 1/2 ton status

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    <font color="blue">I hard-mounted the Smittybilt cage on my Blazer last year. I just made plates under the floor that bolted to the top plates, then ran square tube to the frame. Then I tied the windsheild frame to it too since the tub was so flimsy. Stiffened and quieted it up substaintially, frame twist was almost eliminated. I just got done solid-mounting the 8-pt cage in my Jeep the other day. I highly recomend it /forums/images/graemlins/waytogo.gif
     

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