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Modular seat mount - strenght/safety vs. weight

Discussion in 'The Garage' started by BadDog, Aug 28, 2003.

  1. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    I have a strength of materials/safety margin question on my back seat project.

    I need to build a modular rear seat mount that will hold a pair of cheap Summit polly seats with 5 points. This thing will be completely self contained and bolt into the cage only when I need to carry 4 rather than 2 (wife and daughter, or friends of me or my son). These seats will not be occupied on the “we’re probably going to go over” stuff, but need to be safe in the “oh [I love Jeeps], I didn’t think that would happen” case. The roll cage is no problem, but the seats have to stay low so there is not much leg drop.

    Sorry for the sad pic, and an isso view would help, but this should work without having to do CAD…

    It will be attached with wrap around clam shell clamps at 4 points on the end of the red bars (see pic). These will suspend the seats between 2 parallel bars about 42” wide. The seats almost touch in the center, closer than the pic indicates.

    The goldish side bars are angled down sharply to allow entry from the sides.

    The horizontal shoulder bar will mount the 5 point shoulder harness.

    The brown center bar is the main brace for the shoulder bar and provides a good handle for the occupants.

    [​IMG]

    Here is the question:

    What is the minimal reasonable material to build this thing out of? I’ve got round stock in 1” x 0.120” and 1.75” x 0.120” as well as square stock in 1.5 x 0.188 on hand. I am usually accused of dramatically overbuilding things, so my first impression is to use the rollbar material, 1.75 round. I *think* it will be ok, but sort of border line, to build the whole thing out of 1” round. But I don’t know. This is something that I want to keep as light as safety allows (without exotic materials) because I expect it will be added/removed frequently. It takes the place of a toolbox that will normally mount in that space (more gear for longer/tougher trips than when the rear seat is occupied). Smaller tool/part boxes remain even with the seats.

    So, what do you say?
     
  2. marv_springer

    marv_springer 1/2 ton status

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    Russ,

    I already made something just like that... It's out of 1" sq tube, I think .093 wall or something.... I still got it in the shed... Would give it to ya if you like. I used it for years, but replaced it w/ a Suburban 3rd seat so I could fit 3 in the back....

    Marv
     
  3. Twiz

    Twiz 1/2 ton status

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    [ QUOTE ]
    This thing will be completely self contained and bolt into the cage only when I need to carry 4 rather than 2 (wife and daughter, or friends (or Twizz /forums/images/graemlins/grin.gif)). These seats will not be occupied on the “we’re probably going to go over” stuff, but need to be safe in the “oh [I love Jeeps], I didn’t think that would happen” case

    [/ QUOTE ]

    I like it.
    Figure a 200 lbs dude can be easily be suspened by a piece if 3/16" sheet steel. Keeping the ocupants ocupied in a slow, easy flop, should be no-problem.
    Seat belt mounting location/strength, rather than seat mounting - would be more important. (I understand it is a "modual" assembly). Makeing it in "sub-sections". The "main-frame", suporting the rear most seat mount and seat belt mounting locations. Then triangulateing to the rest of the "modual" assembly. The main-frame being of the up-most importance.
    I realy like the cross-bar/grab handle idea. It worked quite well in BB02. Gave everyone something to hold on to. Located close to center and comfortable.



    Seems to me, you've got it nailed.

    Colorado K5 Jeprody:
    Your answer (or post) has to be in the form of a question. /forums/images/graemlins/wink.gif
     
  4. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Yeah, I was thinking of you when I designed that! /forums/images/graemlins/thumb.gif

    My thought of the moment is to make the cross pieces out of 1.75 x 0.120. Not that much heavier than the 1", but much stronger so no swagging even with some weight. Then the rest should be good with 1" x 0.120" round. Marv's got a very similar setup that was in his K5, but with the drive to his place (almost 45 minutes each way) and the work of adapting, I will probably just build it to suit. Best part is he was able to give me some real world info/experience on how it worked and held up based on material used. I may even build it this week end. My front seats (PRPs) just came in, so I've also go my front seats to mount.

    One thing about it, it won't look quite so getto this trip... new paint, floors, seats and harnesses, front clip and skins, and 4 new shifters should up the blink ratio. And now *I'VE GOT THE GEARING TO WHIP BREAKOVER WITHOUT THE WINCH!" ( or at least give it a heck of a shot!) I hope you can make it again...
     

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