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Last Post 17 Mar 2014 04:28 PM by  mr_han_solo
Crossbar for Mounting of Harness
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mr_han_solo
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12 Mar 2014 02:36 PM
    Hello,

    I am building a XP class 240z (Chevy 350 engine swap essentially), and have a question about a harness bar. Since I am not planning on doing any club racing, I am wanting to hold off on building a full cage, as I feel I can spend that money elsewhere currently. However, I am wanting to fabricate a crossbar to mount my harness to. The 240z, has these holes in the sides (behind the rear seats), where the factory roll bar would have been installed on racing chassis.


    Here is some pictures of someone else who has fabricated the bar I am wanting:


    I was wondering what the correct plate and tubing size is. The gentleman who built that bar used 3/16th plate for the ends and the tubing was 1.375 inches, .062 wall, 1.25ID. Just wanting to make sure I get everything to make the crossbar correct.

    Also, my harness is a V mount with a bolt on end. Would it be legal to drill through the center of the tube and mount it that way, or should I weld a mounting point to the tube (3/16th plate) and mount the harness to that?

     


    Thanks,

    Han
    mtuhro
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    Posts:76


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    12 Mar 2014 08:34 PM

    Make sure that bar is not too low for for the shoulder harness.  If it is too low, it can compress the spine.

    If you are set on using the bolt mounts, best to use two weld on tabs, to put the mount in double shear.

     

    mr_han_solo
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    13 Mar 2014 11:42 AM

    Alright,

     Does the plate and tubing size sound okay? If so, would the 3/16th" plate suffice for the tabs? Also, i'm assuming it wil lhave to be grade 5 bolts to bolt thing baby in correct?

    mtuhro
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    16 Mar 2014 10:04 AM

    3/16" for the tabs that mount harness to the bar sounds like plenty.  Especially, if you are putting the harness into double sheer (two tabs, sandwiching the harness mount).  You can use the thickness of the connection on the harness side to guide your decision on the bar side tabs.  No, point in going much thicker than what the harness manufacturer uses.  Go to Jeg's or Summit, they have some nice prefabbed tabs for this application.

    I would be concerned that the bar will be too low for proper mounting of the shoulder harness.  It needs to be about shoulder height.  Usually the harness manufacturer provides specific instructions on this.

    As far as the other dimensions you are looking for feedback on, I don't dare venture an opinion.  Other than, I haven't seen much 1-3/8 diameter bars used in roll cage construction.

    mr_han_solo
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    17 Mar 2014 04:28 PM

    I went and measured from the mounting holes. Depending on how I weld the tube and mounting tabs, the harness will mount anywhere between 4" and 6" below the rear seat openings. Did some reading and from everything I read, anything 6" or below the seat holes is what's recommended.

     I know Appendix C (Solo Roll Bar Standards) of the Solo rule book state that a car weighing over 1500 lbs should have 1.500x0.120 tubing size as a medium. However, this really isn't a roll bar, it's a harness mount.

     That said, I will probably end up going with the 1.500x0.120 tubing just to make sure everything passes and I dont have to go back and do it all over again. 

     

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