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Gremlin Roll Cage, Seat, Harness

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WesternRed View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Topic: Gremlin Roll Cage, Seat, Harness
    Posted: Aug/10/2019 at 5:40pm
Ok, so I'm looking to put a cage in my Gremlin and looking for any tips on the subject. Being in Australia, an off the shelf cage is not an option so a local fabrication shop will be engaged. For my purposes of running down to 10.0, I will need a main hoop, back stays, door bar and taxi bar. Seems pretty straight forward, however some questions.

How far back to people run the back stays, I believe straight is preferred and I have no requirement for the rear seat. Would you run them right down to the back of the car and pick up the chassis rail there?

Only need one door bar, but would two be better, to add say some stiffness to the car. Just run them to the floor pan with reinforcing plate or do the need to pick up on the rockers? Does anybody add a Mopar style torque box to the front to tie the rocker into the front frame rail and maybe add a bit of strength to the front door bar attachment.

How are people mounting their race seats? Kirkey, RCI, Jaz or something else? Aluminium or Poly? Don't actually need a proper race seat at my level, but the factory seating position is terrible for me.

Will let the fabricator determine what is best, but would like to go armed with a few ideas and suggestions.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Aug/10/2019 at 11:16pm
If your going to run leaf springs I would run the rear bars over the top of the rear spring hangers. Per NHRA rule book you would use a 6" x 6" x .125" plate in any area you weld the tube to. You can also drill an angled hole in the plate and extend the bar into the frame rail, but probably not needed. If you don't have a NHRA rule book send me a PM with your email address and I can send you a copy. Main hoop is great, but you also want to run a horizontal bar behind the seat in between the main hoop uprights. Those are where you shoulder belts attach to after you weld a tab on. Use 1-5/8" .134" to be NHRA compliant or you can use .083 Chromemoly. With stock rockers a lower bar that runs parallel with the rocker is not required. I would build it so you can survive if a fast car runs into you, so what's actually required for your time is not what I would honestly be looking at. After you get it all in your car is going to slow down do to the added weight, but safety in my back is above all else, so put the pipe to it. I would also plate both door jams and install a dash bar without question. The NHRA book has a lot of illustrations of cages and is what you should brush up on prior to your appointment with the fabricator.

Tom


Edited by PROSTOCKTOM - Aug/11/2019 at 12:53am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Aug/11/2019 at 12:46am
Thanks for the suggestions, we run to Australian National Drag Racing Association (ANDRA) specs down here in Aussie land, this is their current roll cage specification:


The horizontal bar behind the seat is what we call a taxi bar. I think by the time I gut the interior and get rid of the two factory front seats, Ambassador center console (Aussie Hornets ran them from the factory) and carpets, I might be close to weight neutral. Race seat should be a fair bit lighter than factory.

If I do a full 6 point cage, I can run down to 8.0, but there is so much other stuff required in addition to lots more horsepower that I doubt I would ever go there. I don't need any cage to run down to 11.0, currently 11.7, but do need a harness and as you say, safety is definitely a consideration. I can always add the front half of the cage later if budget permits.

Have some rust issues to deal with first before I do anything:



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Post Options Post Options   Thanks (0) Thanks(0)   Quote PROSTOCKTOM Quote  Post ReplyReply Direct Link To This Post Posted: Aug/12/2019 at 1:13pm
Your tubing thickness specs are what NHRA used to be about 15 years ago. In the states the new spec is .134" on mild steel. I don't even see a dash dash listed on your sheet, but in my opinion every car needs one.

Tom
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Aug/12/2019 at 5:13pm
I would think most drag cages over here are chrome moly, the cost of labor is high, so a little more material cost isn't a big issue. I think our road race CAMS spec cages use heavier steel tube rather than chrome moly, ANDRA accepts a CAMS cage, but not the other way around although with a basic CMS cage, I wouldn't need the forward door bar. The dash bar does make sense to me, especially if you were doing a full 6 point cage. The ANDRA spec seems to be for low level cages and above that they tend to follow NHRA, which would make sense since a lot of high end cars get imported from America.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nastynash Quote  Post ReplyReply Direct Link To This Post Posted: Aug/12/2019 at 11:26pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Aug/13/2019 at 12:25am
Shipping one of them to Australia would be fairly expensive and would still need to be welded up by a suitably qualified person, so might as well get them to cut and bend the tubes as well. 
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