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Is it tough enough?

Discussion in 'Center Of Gravity' started by DPI, Nov 7, 2003.

  1. DPI

    DPI 1/2 ton status

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    Will an '89 K5 frame withstand the punishment and weight a set of rockies can dish out?

    My new project is taking a frame up 89 K5 and turning it into a offroad only beast using the 2.5 ton top loaders, 4 link with coils and a minimum of 44's.
    Will boxing the stock frame and applying some triangulation be enough for the abuse? I am planning to narrow the front and rear, possibly skinning everything or just going tube. Two possible alternatives to the stock frame are: possibly a M1008 frame or build a tube frame. I want to have this going sometime in the reasonable future, so I am leary on doing the tube frame...

    Another question - Would it be a bad idea to bolt the body directly to the frame without the body bushings? My reasoning is to make the frame as rigid as possible and tie in the tubed front, rear, and cage directly into the frame.

    btw, I hope my questions warrant this section! I am wanting to get started on this ASAP and I am having a hard time keeping myself from complete sheet metal removal. /forums/images/graemlins/rotfl.gif /forums/images/graemlins/eek.gif BUT, I wanted the opinion of the pros before I started...
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    For the body to frame issue. I wouldn't recommend bolting the body directly to the frame unless your frame is rigid as hell and won't flex. If the frame flexes then the body will have to flex. Eventually instead of the body flexing you will fatigue the sheetmetal of the body enough that you will tear threw the body mounts. So unless you run a super rigid frame or like repairing body mounts then I would run the rubber or poly mounts. Another thing to think about is if you put the body onto a rock on the trail the frame will try and pull away from it and also try and tear the sheet. That is where the pucks help because they let the body flex.

    If you use a stock body you should also probably reinforce the body mounts anyway because it sounds like you are looking to have a project that is going to be used hard.

    For the stock frame of the 89, it might work, but I would be looking into boxing it out totally and reinforcing the crap out of it. You can break stock frames pretty easy with stuff that is little larger then stock. I would look for a M1008 frame and shorten it to the length desired or look at tube. Russ (you know the green guy of the forum /forums/images/graemlins/grin.gif) and should be able to put some input in on the M1008 frame.

    Harley
     
  3. DPI

    DPI 1/2 ton status

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    The frame flex was my main concern with attaching the body directly to the frame. My reasoning for doing this was to have a rigid body/cage tied directly into the frame.

    My other thought was to tube the front and rear and use the existing body mounts (stregthened of course) as attachement points. Would it be advisable to use body bushings to attach the new "tube body" and cage? This way the whole "body" would move together.

    The M1008 might be an option if I can get it. I have a buddy that has one, but he has told someone they could have it. That was a year or two ago. He is going to ask if the guy wants it, if he doesn't IT'S MINE!~

    Otherwise it will be the modified K5 frame or tube...

    If I had the choice, I would go with the M1008 frame.
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Hmmm, these are not easy questions...

    Will the frame handle Rockwells? In general, I would say a qualified yes. As long as the link mounts are built to distribute the load and not cause localized stress I think it would be ok. Lots of separation and not mounting the uppers and lowers to the same cross member/area would be a good idea too.

    Boxing the frame? If you box the frame, my opinion is that it is an all or nothing proposition. I believe you should either go all the way, front to rear, or let it flex. You could also build a boxed section connecting the mount areas for the front and rear links. But you have to be very careful about making part of the frame rigid when the rest still flexes as it was designed to do. For a partial box, you would definitely want to fish mouth the added plate so you don’t have a rigid section butting right into a flexy “C” section, that leads to fatigue cracks near the intersection.

    M1008 frame? No different than any K30 just for the record. Definitely stronger and better than a K5 in that respect. The problem is the shape of the frame can make it a pain to do things like floor boards. Ask me how I know… Also putting on a K5 tub without some funky mount work would not be easy.

    Tube frame? *DING*, *DING*,*DING*, /forums/images/graemlins/thumb.gif we have a winner! LOL! This is where I would go. Stronger and lighter, plus you can build it to deal with the problems inherent in the top loader axle design. This is something that is in my long term radar after I recover from my current fab burn-out. Maybe next year, or the next... Depends on how I feel about the latest round of mods after I have some seat time...

    As for being in this section… Hmmm… /forums/images/graemlins/thinking.gif I think the frame boxing tech makes it worthy. Approaches to mounting Rocks is certainly not basic or main stream. And it is certainly an offroad capability enhancement (depending on goals off course). But it is sorta borderline, I think it would be better to open by talking about more specifics than you started with, but we will get there. I’m still trying to figure out exactly where the line is myself. It will become clear to all of us over time.
     
  5. Greg72

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

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    Hee Hee Hee.....


    Boy I can relate to this one.


    I have a similar desire to REALLY stiffen up the stock ladder frame design and put as much of the twisting as I can into the suspension (which is where it belongs IMHO!) My motivations are slightly different from yours (I just want my sheetmetal to hang nicely forever and not "sproing" and ruin itself when I'm twisted up.

    But to your topic of how to attack the frame issue:

    I was afraid to start with a clean sheet of paper and build a new frame from scratch (...and I'm still afraid! /forums/images/graemlins/grin.gif) So I started by building "add-on" bracing (2x2" box tubing) to create a sort of sub-frame around the ladder frame to strengthen it structurally. There's almost NOTHING you can do to prevent twisting when you are working in the single "plane" that the frame sits in. It needs triangulation in a vertical dimension to help prevent the twist.

    The Herb Adams book "Chassis Engineering" has some great diagrams of how race teams have dealt with torsional issues. You can use triangulation, as well as shear panels to really make HUGE improvements.... unfortunately, like most things in life. The most effective bars for triangulation are also the ones that go in "inconvenient" places (Like straight up the middle of the windshield, or between the front seats at about chest height!)

    Anyway, the short version is that you should really check out that book for ideas....I took his advice and built some balsa wood models (in 1/8th scale) of my frame so that I could experiment with new designs.

    Since you need to get some "vertical" bracing to make everything stiff, you need to tie the frame to the rollcage somehow....but you really DON'T want to tie the body to the frame. So the body needs to "float" within the frame/cage structure somehow.


    Anyway, I'll shut up now and let someone else talk for a while! /forums/images/graemlins/rolleyes.gif
     
  6. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Forgot a few things:

    [ QUOTE ]
    am having a hard time keeping myself from complete sheet metal removal.

    [/ QUOTE ]
    TELL ME ABOUT IT BROTHER! The sum total of my remaining sheet metal is about 70% of the hood and the fire wall...

    Mounting the body to the frame, I only have one thing to say, don't... You'll rip the body appart in short order for the reasons Harley states.

    [ QUOTE ]
    My other thought was to tube the front and rear and use the existing body mounts (stregthened of course) as attachement points. Would it be advisable to use body bushings to attach the new "tube body" and cage? This way the whole "body" would move together

    [/ QUOTE ]

    This is what I did, and I highly recommend it if you plan to use a stock frame (which is built to flex). Mine is this way, and my son’s is in progress for the same thing on a smaller scale. I like to build the body and cage as a strong structural unit. The term “capsule” has been used to describe this approach. Then mount that using the stock rubber pucks on the sock mounts (reinforced ideally, I have a cracked one now). This lets the frame flex as it should, while giving you all the benefits of a “frame mounted cage” (i.e. no punch through or rip off problems in a catastrophic roll). I am absolutely AGAINST frame mounted cages in the traditional sense when combined with a “C” channel ladder frame. I stand by this even with poly spring bushings and the like as isolators. In hard use like you seem to have in store, these fixed points cause rigid areas that the frame flexes against leading to fatigue failures. Of course, I’m in the minority on this and I have expressed my views on this here as well as on PBB several times. I’ve yet to hear a convincing argument against my assertions and design, but it seems everyone is SO conditioned that the only “right way” to mount a cage is to the frame, they just don’t want to listen. You can search and you should fine a much more in-depth discussion if you care. BTW, this comment applies only to frames built to flex, there are other considerations and options dealing with tube and fully boxed frames.
     
  7. marv_springer

    marv_springer 1/2 ton status

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    [ QUOTE ]
    There's almost NOTHING you can do to prevent twisting when you are working in the single "plane" that the frame sits in. It needs triangulation in a vertical dimension to help prevent the twist.

    [/ QUOTE ]

    I completely agree w/ Greg on this one. Within practical limits, you can box the frame all you want and it will still flex. Only way to get past it is to make a structure that has some vertical height and reinforcement. ....So, like BadDog said, setup the body/frame to allow for some flex, or build a tube frame (enclosed structure from front to back) in an effort to eliminate the frame flex.

    Stiffening up the back half, then the nose, and not tying them all together will just cause concentrated flexing in the area between. The broken up body on my old Green Thing is a perfect example of this.....

    Look at this recent example of Rob's Blazer at BB03. [​IMG]
    His rig has a decent cage mounted in the back to the floor, and to the rock sliders (which are in turn mounted to the frame, rigid) around the front seat area. But the nose of the body really has no tube in it, till you get up to the front bumper/winch mount.

    The whole thing is enduring some good twist here, and if you look closely you can see that the lines on the rear roll bar stay pretty straight up to the windshield frame. But then look at the hood, stinger, and winch mount and you can really start to see some flex. He needs to tube the rest in... or his body will soon be in the same shape as my old Green piece. /forums/images/graemlins/tongue.gif

    Marv
     
  8. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    [ QUOTE ]
    just want my sheetmetal to hang nicely forever and not "sproing" and ruin itself when I'm twisted up.


    [/ QUOTE ]
    Honestly, IMO, this is the only valid argument for actively stiffening the frame other than actually fine tuning the suspension. It’s hard to really fine tune a suspension (like competitors need to do) when the frame is adding variables to the mix. For the rest of us, the tuning is not a sufficient reason in itself to take on a project of that magnitude. The only concern I have for frame twist is body damage, and that is a distinct concern. Otherwise, I say let it twist like it was engineered to do. But then, you and I have discussed this a few times haven’t we… /forums/images/graemlins/laugh.gif LOL…

    [ QUOTE ]
    I took his advice and built some balsa wood models

    [/ QUOTE ]
    I use “mechanics wire” or bailing wire for mine with hot glue “welds”. It’s great for cage design testing too. You can really see which directions it wants to move, easily make changes, and see what the effects are. Seems more similar to how tube reacts with real radiused bends and such…
     
  9. DPI

    DPI 1/2 ton status

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    [ QUOTE ]
    Tube frame? *DING*, *DING*,*DING*, we have a winner! LOL! This is where I would go. Stronger and lighter, plus you can build it to deal with the problems inherent in the top loader axle design. This is something that is in my long term radar after I recover from my current fab burn-out. Maybe next year, or the next... Depends on how I feel about the latest round of mods after I have some seat time...

    [/ QUOTE ]
    This is what I was afraid of. I want to be trying to tear this up ASAP. And like Greg72, I am "afraid" to start from scratch. With that amount of work and as ANAL as I am, it would take me forever and a couple days.

    At this point, I am going to yank the frame either way. I can either use it to copy or add strategic bracing and/or to setup the four link.

    I like the capsule idea.

    TO BE CONTINUED! I have a meeting in 30 seconds!!!
     
  10. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Your willing to attempt boxing the frame and linking but not a tube frame? It doesn't have to be a monkey bar buggy. You could use 2 x 3 x 3/16 square and pretty much duplicate the stock frame with some added clearance for the axles along with and engine shifted back (to clear the front Rocky AND give better balance). Personally, I would MUCH rather do that than try to box and reinforce the frame the *right* way. Plus you can get cross members where you need them, no (or at least reduced) problems putting links where you need them, and MUCH stronger and lighter than what you will get otherwise. Win, win, win...

    Another sweet thing that makes it more interesting to me is you don't have to tear up what you have now to get a good start. Just like Gregs project, you can get a long ways before you take apart you current truck. If I did it, I think I would get some stripped axle housings (or mock up something to simulate the Rockwell and support the chassis for work/testing/moving), a stripped engine block and trans case, etc. Get it all started and play with it for a while, no rush, still drive and wheel you current rig. When you get close, just strip out the drive train and swap the body or whatever… you get the idea…
     
  11. Greg72

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

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    Marv,

    Give me a dolla, and I'll "triangulate" your cholla!




    Disclaimer: This is in no way intended as a solicitation of fabrication services....this is, in fact, intended to be funny....
     
  12. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    You better watch out! I got my *good* eye on you, and I'm just itching to use that ban button... /forums/images/graemlins/tongue.gif /forums/images/graemlins/rotfl.gif

    BTW, don't quite your day job to be a comedian... /forums/images/graemlins/rotfl.gif
     
  13. DPI

    DPI 1/2 ton status

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    The good thing is, the '89 will be my beater! And I have the 1-Ton 90K5 when I get the urge to wheel while in the process of the '89 build up.

    You know, I keep forgetting about a rectangle tube frame. That would be a lot "easier" to build than the round tube. And it would make "copying" the factory frame a LOT easier. /forums/images/graemlins/thinking.gif

    Anyway you guys have given me a ton of new stuff to think about and no personal BS - This new forum kicks butt! /forums/images/graemlins/thumb.gif
     
  14. Kyle89K5

    Kyle89K5 1/2 ton status

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    You knew the answer to this just didn't want to go there huh. After seeing the way the frame flexed on mine without a front bumper, I'd be hard pressed to try rockwells without something. Personally, I think the choice is simple, and you've got a decent go-by right here in town...

    [​IMG]
    [​IMG]
    [​IMG]

    You could always see about picking up a scrap frame to use as a go by, then do a side by side switch to your new "custom" frame. I think rectangular tubing would be the ticket.
     
  15. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    if u got ca$h (and i assume u do since boggers, coilovers etc are bank)...

    [​IMG]

    /forums/images/graemlins/thumb.gif

    j
     
  16. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    But where is the fun in buying a buggy? I thought we were all about "Built, not Bought"? /forums/images/graemlins/wink.gif
     
  17. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

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    i didnt build my k5 frame... whats the diff? lol!! /forums/images/graemlins/grin.gif

    i do want to make my own tube buggy someday though... thinking toy drivetrain. 2k pound single seater. full hydro steer. 38" iroks (if they ever make em!)... be so fun. /forums/images/graemlins/thumb.gif

    j
     
  18. sled_dog

    sled_dog 1 ton status

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    Only thing I get ick about when it comes to the idea of tube frame is the whole motor mounting and drivetrain mounting. I guess its not really that hard but it just seems to me like it coule be.
     
  19. Greg72

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

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    [ QUOTE ]
    Only thing I get ick about when it comes to the idea of tube frame is the whole motor mounting and drivetrain mounting. I guess its not really that hard but it just seems to me like it coule be.

    [/ QUOTE ]


    To me, the scariest part is creating the body mount points on a "from scratch" frame buildup. I don't know how the later K5's are, but it seems like every pair of body mounts on my K5 are on a slightly different plane than the rest!!!

    The reality is that once I build my whole "subframe" idea within the factory frame, it will be OBVIOUS at that point how I can build a "from scratch" frame to accomplish the same thing....... who knows, at that point maybe I WILL!!!!

    /forums/images/graemlins/thinking.gif
     

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