What thickness are those dimple die roll cage gussets? You know, those ones that are on the door bar X or where the down tubes connect to the A pillar. Never used them before, but the current build is the perfect place to start. I have some left over 18 gauge I used to make a floor in a Hillman several years ago. Looks about right.
Are you talking about taco gussets? The only place I've seen a spec on them is in the FIA rules. 16ga I think, but you'd better check. There is also a minimum size spec'd there too.
Edit- Turns out NASA has made the FIA rules comprehensible. http://www.nasarallysport.com/rules-forms/2012-NASA-Rally-Sport-GRR-Appendix-B.pdf
Gussets are required to be made as follows:
U-shaped sheet metal (taco shell). Refer to figure 253-34 below. Minimum thickness is .040” (1 mm). Minimum length along the unwelded side of the gusset is 3 times the tubing diameter.
Round tubing. Minimum length of the longest dimensions is 3 times the tubing diameter. Minimum tubing diameter is 1” with minimum wall thickness of . 083”. Maximum diameter and wall thickness is per the materials in table of section 6.6.
One or 2 triangular plate steel gussets with combined thickness equal to the tubing which is being gusseted. Minimum length along the unwelded side of the triangular gusset is 3 times the tubing diameter. Any plate or u-shaped gusset that is welded into a jointlocation where it can block the view of the welds between the tubes being reinforced must have the corner cut back to enable visual inspection of the tube joint. This is illustrated in figure 253-34 and typically looks like a bite out of the corner of the gusset.
I was wrong. 18 ga is .478 in steel, so it will work fine.
I had not seen those particular rules... which would allow you to go lighter than I have -
16ga is always what I've used for "formed" gussets like across door Xs and the dimple die box A pillar stuff because once you buy a 4x8 sheet of the stuff you don't look for reasons to buy more sheet until it's gone ;). For anything in only 1 plane I either use a cut of the same tubing or 1/8" plate cut in triangles.
In the past I have either used more tubing to form triangled corners or used those pre made triangle gussets. I'm thinking about using a modified X design instead of Nascar bars for the drivers door bars. The kind where there are two bars that bend towards each other, then run parallel touching each other for 5 inches or so and then bend away from each other. Seen them done that way on several Porsche cars, and always thought that would make for an easy in and out on a street car. This build is a street/track TR8. For once I'm building a car the way I want and not what the rules book say it has to be. Goal is to be as fast and as safe as possible without breaking the bank. I want the cage to disappear into the body work as much as possible with as many points of contact as possible. I may just say screw it and gut the doors and run the bars out there.. cause its safer, lighter, faster. It just sucks climbing over door bars when you just run down the street to grab a gallon of milk. Plus to 99% of the world, you look like a tool, and the other 1% wants to talk your ear off about your car.
The last one I built, I used a bar along the door sill then a bowed X with a deeper center to make access less of a hassle w/o giving up anything in the way of strength or load transmission. If you look at how low/forward the center of the X is... very easy to drop my ass into it without too many contortions yet still good protection at the shoulder when seated.
I can't find any finished pics with the gussets done but here is what I mean - final fitting before welding.
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