Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Need thoughts on cage tie-in, please...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by txbartman, May 6, 2003.

  1. txbartman

    txbartman 1/2 ton status

    Joined:
    Jun 1, 2001
    Posts:
    1,975
    Likes Received:
    0
    Location:
    Plano, TX
    Okay, big project this summer is the full cage. Me and a couple of friends with K5/Jimmys plan to build all ours together. We will tack them and have a seasoned professional complete the welds for safety.

    Now for my questions... I have 3 different theories for how to tie the cage in to the rig's structure, all with their pros and cons.

    1. Build a cage that goes through the floor and attaches directly to the frame. PRO: strong and secure. CON: if the body were to break loose and the cage is still attached to the frame, there could be problems. Also introduces spots for leakage and rust where the cage passes through the body. As teh frame flexes (or tries to), will stress be applied to the cage welds weakening them over time?

    2. Build a cage that attaches directly to the body, with no tie-in to the frame. PRO: The cage and the body become a secured capsule. In the event of a rollover where the body comes loose (I have a 3" BL), the capsule or cockpit with myself and my passengers is safe. CON: Would I really be safer if the cockpit/capsule were allowed to separate from the chassis? In the event that the body does nt break loose from the chassis, will the cage puncture straight through it on a rollover and basically break loose of the body?

    3. Attach the cage as mentioned in #2 to the body, but then tie it in to the frame via some sort of sandwich plate beneath the cage-body mounts. PRO: Will prevent the cage from penetrating the body. Secures the body to the chassis more securely. Helps keep everything together. CON: What about frame flex? As with #1, won't this apply significant stress to the cage welds possibly weakening them over time? Or add stress to the frame since it won't be able to flex as well? With the body attached securely to the frame now, will ride be compromised as I am essentially bypassing the rubber body mounts? Could I add "body moutn rubber" in the "tie-in/body/cage sandwich" without compromising the strength and security of the cage?

    I know its a lot, but this isn't an area I want to compromise or do twice. What are your thoughts?
     
  2. Michael

    Michael 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,576
    Likes Received:
    0
    Location:
    Sherman, Texas
    I think one of the main effects to look for in a full cage is to reduce frame flex to a minimum. Idealy you want your suspension to do all the moving and have it "hung" from a very stable platform. It really depends on your needs. Is this an extreme trail rig, a weekend trail blaster, or a daily driver.
    I would not enjoy all the bad effects, noise and vibration, of tying a cage to the frame on a DD, but would not have a problem with doing so on a trail only rig. If I were tying one to the frame I wouldn't use any "flexible" mounts at all. Try to make the hole frame cage a non-flexing unit. I don't think "the body seperating from the frame" is a big issue with trial rigs. On mine I welded the frame to the body and had my seat mounts made into the cage providing the "capsule" you mentioned.I'm sure you'll get many more opinions as the day goes on.
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    [ QUOTE ]
    Okay, big project this summer is the full cage. Me and a couple of friends with K5/Jimmys plan to build all ours together. We will tack them and have a seasoned professional complete the welds for safety.

    Now for my questions... I have 3 different theories for how to tie the cage in to the rig's structure, all with their pros and cons.

    1. Build a cage that goes through the floor and attaches directly to the frame. PRO: strong and secure. CON: if the body were to break loose and the cage is still attached to the frame, there could be problems. Also introduces spots for leakage and rust where the cage passes through the body. As teh frame flexes (or tries to), will stress be applied to the cage welds weakening them over time?

    2. Build a cage that attaches directly to the body, with no tie-in to the frame. PRO: The cage and the body become a secured capsule. In the event of a rollover where the body comes loose (I have a 3" BL), the capsule or cockpit with myself and my passengers is safe. CON: Would I really be safer if the cockpit/capsule were allowed to separate from the chassis? In the event that the body does nt break loose from the chassis, will the cage puncture straight through it on a rollover and basically break loose of the body?

    3. Attach the cage as mentioned in #2 to the body, but then tie it in to the frame via some sort of sandwich plate beneath the cage-body mounts. PRO: Will prevent the cage from penetrating the body. Secures the body to the chassis more securely. Helps keep everything together. CON: What about frame flex? As with #1, won't this apply significant stress to the cage welds possibly weakening them over time? Or add stress to the frame since it won't be able to flex as well? With the body attached securely to the frame now, will ride be compromised as I am essentially bypassing the rubber body mounts? Could I add "body moutn rubber" in the "tie-in/body/cage sandwich" without compromising the strength and security of the cage?

    I know its a lot, but this isn't an area I want to compromise or do twice. What are your thoughts?

    [/ QUOTE ]

    I went through all this when I built mine. The problem is the frame is 28 inches wide and the points where the cage attach are about 54 inches in the rear and about 60 in the front. It's a rear towugh one to go to the frame in the rear without having the legs taking up cargo room and passenger space.

    Looking at the average roll your likly to have with most off roading is usualy a low speed "Flop" on to the side or a slow roll. Were not like a race car that is going to have high speed impact unless you go off the side of the mountain and then all bets are off anyway. If the roll is violent enough that the frame has enough force to rip free....let it. The truck is a write off at this point if it's ripping out the mounts. That also means the "safety cell" I'm in just lost 2,000 lb worth of weight that would make impacts worse.

    With this in mind I decided to skip the to the frame part. I was however very carefull where I placed the legs of the cage. All my legs are over or right next to heavy body suports. The Front legs are straddle the front cab suport, the middle straddle the middle cab suport and the rears are as close as I could get to the tail pan. Now my tail pan was shot and I replaced it with a peice of C-Channel. I have 10 times the strength back there as the stock roll pan. There is enough room on the rear where you could install a side to side 2x2 bar under the floor and bolt through the floor to the rear legs of the cage, It would have to pucs that 2x2 through the frame and that basicly what would have to happen on my truck. My truck also has no rear seat foot wells and I plan to add a cross bar under the floor at that location as well. It might be possible to do that on a 78 up as well if you locate the Hoop behind the front seats back to just infront of the fenders. The problem is gettin one of these bars in. You would have to lift the body off the frame a few inches to get them in.

    The gain...the frame is still free to do it's thing. The body is more ridged.
    One thing to make sure up is that your backing plate and your foot for the legs are not the same size. one needs to be a couple inches bigger then the other. If they are the same size they can act like a shear and punt through the floor. Making the top plate beigger is usualy better. I also cut some fill plates to put down in the ribs to keep the floor from smashing flat.
     
  4. DukeBoy88

    DukeBoy88 1/2 ton status

    Joined:
    Oct 16, 2002
    Posts:
    315
    Likes Received:
    0
    Location:
    Jonestown Pa
    Brian,
    I had the same questions as I'm about to start fabricating a cage with my friends as well. My floors and some cab supports are shot on my truck so I planned to replace them at the same time. I planned on fabricating my own body supports with the cage attachment points in mind. I don't have it all worked out yet but I planned on making my own rockers out of a long triangular shaped tube with a reinforcement on the bottom edge for a rockslider (possibly a piece of tubing) the cab supports would tie into the rocker and the cage into that. If I made this beefy enough I think I should be ok. I'm not sure how I'm going to tie the seat mounts in yet. I'd be curious to what you come up with. good luck.
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

    Joined:
    Sep 1, 2001
    Posts:
    8,972
    Likes Received:
    0
    Location:
    Peoria, AZ
    This is the way it was explained to me. I was looking to get a full cage attached to the frame. I was talking to DesertDueler about this. His dad builds NHRA certified cages, and this is what he told me.

    #1. You sit on the seat in your truck that is attached to the body.
    #2. Your seatbelt system is also attached to the body of the truck
    #3. Therefore you are attached to the body of the truck and not the frame.

    So he condones building cages that are attached to the body. This way if the body tries to seperate from the frame you go with the cage.
     
  6. Greg72

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

    Joined:
    Mar 5, 2001
    Posts:
    15,684
    Likes Received:
    1,392
    Location:
    642 Days to BB2018
    [ QUOTE ]

    One thing to make sure up is that your backing plate and your foot for the legs are not the same size. one needs to be a couple inches bigger then the other. If they are the same size they can act like a shear and punt through the floor. Making the top plate beigger is usualy better. I also cut some fill plates to put down in the ribs to keep the floor from smashing flat.

    [/ QUOTE ]

    Grimmy,

    You're not the first one to post this comment, but I'm always confused when I read it....???

    How will two plates that are the same size create any MORE or LESS shearing force, than plates of dissimilar size?? If you think about it, only ONE plate in that "sandwich" is applying force during a rollover event. If the truck is rolling onto it's roof (for example), the only plate applying force is the one mounted to the inside of the cab. The "underside" plate is doing nothing to add shearing forces, or to take any away. In fact I would argue that if the sheetmetal is going to "shear", the hole will be the size of the "top" plate regardless of the size of the bottom plate (bigger OR smaller).

    I would agree that the SIZE of the plate will determine how effectively the force is distributed, and I also agree that putting "shims" under the plate to account for the convoluted floor is a good idea, but I am not seeing the logic about the plates being more likely to "shear through" just because they are the same size..... ???? /forums/images/graemlins/shocked.gif
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

    Joined:
    Feb 24, 2001
    Posts:
    7,777
    Likes Received:
    11
    Location:
    Phoenix, AZ
    The difference is that the 2 same sized plates work back and forth on the same area, effectively work hardening the area leading to metal fatigue and more likely failure when shock loaded...
     
  8. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

    Joined:
    May 19, 2001
    Posts:
    45,032
    Likes Received:
    369
    Location:
    Vancouver, WA, USA
    its just my unprofessional opinion, but for most 4x4 uses a well-designed and well-built cage that is attached to the body is sufficient. I like the idea of using the cage+body as a safety "capsul" during more extreme rollovers. My cage is gonna be body-mounted only, but I plan on tying it into in lots of places... I dunno..maybe 10-12 points and with lots of gusseting at the joints/corners. Ought to be plenty strong enough for 99.999% of rolls that I might experience. The body on my rig, especially the floorboards, has very little (if any) rust.... if your rig is rust-tastic, that might be a consideration as well...

    j
     
  9. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

    Joined:
    Jul 18, 2001
    Posts:
    5,693
    Likes Received:
    0
    Location:
    CA
    I wanted to make a plate the same size as the top plate my cage is welded to, and bolt that plate underneath the floor sandwiching it... then weld a tube from that plate to a location on the frame where it can be attached with a bushing, like i saw a cage article online do...
    /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif
     
  10. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

    Joined:
    May 19, 2001
    Posts:
    45,032
    Likes Received:
    369
    Location:
    Vancouver, WA, USA
    not sure if using a plate that is the exact same size is the best idea... Im not a structural engineer or anything, but it seems like it'd be easier to shear the body if the plates were the same size...

    j
     
  11. Greg72

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

    Joined:
    Mar 5, 2001
    Posts:
    15,684
    Likes Received:
    1,392
    Location:
    642 Days to BB2018
    [ QUOTE ]
    The difference is that the 2 same sized plates work back and forth on the same area, effectively work hardening the area leading to metal fatigue and more likely failure when shock loaded...

    [/ QUOTE ]

    Russ,

    OK, I suppose I can accept that...

    I'm still somewhat dubious that the work-hardening will happen "precisely" at the edges of the plates though, especially if they have been beveled and smoothed.


    I know these types of discussions can become a "how good is good enough" arguement, but everytime I think of that Potato Salad Hill rollover video clip (the one where the Blazer's top shatters into a million pieces and the two Darwin Award candidates are miraculously unhurt) I know that rollcages are GOOD!!! /forums/images/graemlins/cool.gif Even a "basic" cage would have made that rollover much safer.
     
  12. TxK5Blazer

    TxK5Blazer 1/2 ton status

    Joined:
    Aug 13, 2000
    Posts:
    593
    Likes Received:
    0
    Location:
    Floresville, Tx
    Guys thanks for all the good information I just need someone to build one for me in texas....Jason
     
  13. BlaznRebel

    BlaznRebel 1/2 ton status

    Joined:
    Sep 1, 2002
    Posts:
    115
    Likes Received:
    0
    Location:
    Louisiana,Baton Rouge
    NHRA seems to think that all you need is a 6"x6" plate welded to the floor of your car. This should sustain a really fast roll over and still keep the driver safe. I tink .....
     
  14. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

    Joined:
    May 19, 2001
    Posts:
    45,032
    Likes Received:
    369
    Location:
    Vancouver, WA, USA
    one option you might consider is to just get a S&W or Smitty cage and install it as a starting point... then take it to a pro to add whatever crossmembers and supports you want/need and to gusset the living hell out of it. /forums/images/graemlins/grin.gif I know when i got a cost estimate for a full custom cage from Sky the cost was pretty high... mainly because of all the trial/error involved with fitting the cage to your rig. If you already have a S&W/smitty as a foundation, that extra labor is removed from the equation and the cost should be lower. Just an idea...

    j
     
  15. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

    Joined:
    Feb 17, 2000
    Posts:
    7,385
    Likes Received:
    0
    Location:
    Atlanta
    You kind of neet to look at it as the long run. The body flexes and it will still flex even with the cage. Over time the metal will start to fatigue in high stress areas. In this case the cage is more ridged then the body so the fatigue point will be the first point where the metal can bend once it is out from under the foot of the cage. Well if the foot and backing plate are the same size then it can easily flex at the same point both dirrections. If they are different sizes you actually have two points where there will be flex so you have cut the maount of movement at one point by half and doubled the length of time before it fails.

    Greg: I'm serously thinking about a bender once I get this Supra Sold. What Dies do you find most usefull? I was thinking the 1.75 and a 1.25.
    What brand are you using? You seen the deal that Rockbuggy has going?
     
  16. GORRILLA

    GORRILLA 1/2 ton status

    Joined:
    May 3, 2003
    Posts:
    315
    Likes Received:
    0
    Location:
    TX panhandle, out at the river.
    HERE'S A COUPLE OF IDEA'S THAT MIGHT HELP.
    FOR REFERENCE GET A COPY OF GREENLEE'S CONDUIT BENDING HANDBOOK. ANOTHER ONE WOULD BE AN ULGY'S HAND BOOK IT MIGHT GIVE YOU SOME INSIGHT ON HOW TO MAKE SOME OF THE HARDER BENDS. ALSO GET A COPY OF "HERB ADAMS, CHASSIS ENGINEEERING". I ALSO USE A LITTLE KNOWN TOOL CALLED A "NO DOG", IT CLIPS TO THE END OF YOUR TUBING AND CAN KEEP YOU LEVEL IF YOU HAVE A LEVEL BENDER THAT IS SECURE. THIS CAN BE MADE OR BOUGHT AT A ELECTRICAL TOOL AND SUPPLY STORE. I BEND ALOT OF CONDUIT, A ROUND HOLE WITH METAL WRAPPED AROUD IT. SAME AS TUBING.
    THE RADIUS'S OF THE BENDS MAYBE DIFFERENT BUT THE PRINCIPLES ARE STILL THE SAME.
    JUST MY $02.
    GORRILLA /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  17. GORRILLA

    GORRILLA 1/2 ton status

    Joined:
    May 3, 2003
    Posts:
    315
    Likes Received:
    0
    Location:
    TX panhandle, out at the river.
    I FORGOT ONE OTHER. IF YOU WANT TO DO ANY LARGER RADIOUS BENDS, THE FORMULA IS RADIOUS YOU WANT TIMES 1.57,THIS IS YOUR DEVELOPED LENGTH, MAKE SURE THAT THE PIECE OF TUBING YOU START WITH IS AT LEAST THIS LONG. DIVIDED BY THE NUMBER OF BENDS YOU WANT TO MAKE,THIS DIVISION IS THE DISTANCE BETWEEN BENDS. EX#1; 30 BENDS = 3 DEGRESS TO PER BEND TO MAKE A 90 DEGREE BEND.
    EX#2 YOU WANT A 28" RADIUS, TAKE 28 x 1.57= 44"
    44 DIVIDED BY 30 = 1.46 BETWEEN BENDS.
    IF YOU WANT GREATER THAN A 90 DEGREE JUST KEEP ON BENDING ON THOSE MEASUREMENTS TILL YOU GET TO THE DEGREE YOU WANT.
    MAYBE THIS IS COMMON KNOWLEDGE BUT I THOUGHT I WOULD THROW IT OUT THEIR. I ALSO SAY TIE IT TO THE FRAME!!
    GORRILLA /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  18. Greg72

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

    Joined:
    Mar 5, 2001
    Posts:
    15,684
    Likes Received:
    1,392
    Location:
    642 Days to BB2018
    Grimmy,

    I have 3 dies....the 2",1.5" and 1"

    I use the 2" for almost everything.....1.5" for seat cradles and some gusseting, and the 1" for a small amount of things (grab handles, etc)

    I could live without the 1" (if I had to) but the other two are quite useful to me.

    I went with the Pro-Tools M105 bender and I also ponied up the extra $$$ to get the 240-degree dies...I haven't had too many reasons to bend a true 180 degree bend, but having those dies will make them more cleanly...
     
  19. DukeBoy88

    DukeBoy88 1/2 ton status

    Joined:
    Oct 16, 2002
    Posts:
    315
    Likes Received:
    0
    Location:
    Jonestown Pa
    Greg do you have a link for who carries the Pro-tools M105 bender. I tried searching for it online, no luck. thanks
     

Share This Page