I guess I still dont under stand the rule. How do I measure minor major ratio? Google is good. Ok i get it now. I think Im .93 so should be fine. Im going to bend a 90 degree with my 4.5" die and see what it is.



Edited 1 time(s). Last edit at 12/02/2011 06:34PM by Reamer.

Ratio just means you divide the minor by the major. So if you measure min diameter at 1.2" and max a 1.8", at a given cross-section, the ratio is 1.2/1.8 or 0.667

Yeah I feel like an ass. Had to go back to 5th grade math class. probably 2nd grade. Thanks for the reply!

Bump..

Just want a quick sanity check before excitement of a tool sale takes over...

http://www.pirate4x4.com/forum/showthread.php?t=1049456


A 1.75 die with a 6" CLR should be safe for .095 right? At least one guy in the thread uses a pro-tools die this size...

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This isn't floor mat anarchy

The .9 ovalized ratio came from FIA rules.

As for door bar designs. I'll make one statement about the upper and lower shallow U's connected at the center; it solves the 'broken tube as a spear' issue, but presents a whole new issue. The center joint needs to be SUPER STRONG for this design. If you hit hard anywhere close to the central joint, as the tubes bend in, they will also want to rotate, as the points of support are not inline with the tube centerlines. This rotation will tend to want to 'roll' the tubes relative to each other, swing the upper one upwards and in, and the lower one downwards and in, and this will put a tremendous amount of tearing stress on the center joint. It should be plated with .120" steel plate on the INSIDE, along the full length of where the tubes meet, preferrably with the plate wrapped a bit over and under the top and bottom of the 2 tubes. In this way, the plate has to tear apart before the tubes can tear apart. The flimsy 1mm clamshell gussets have little or no chance in this case. The center area in the double-shallow U design should be like 5-6" long so there is ample length for a stong joint.

Since studying this design more, I have been favoring the simple sill bar and sloped single door bar. The X designs really don't add anything specail for side impact except extra tubing and more support points that can spread the load, but it presents some real issues in keeping the center joint together. The rationale that I think really brought the X side bar design into being is so that the forward upper part of the X can meet the A-pillar at the same place where the forward strut brace, if used, also meets the A pillar. It carries the load coming through the strut brace and takes it back to the floor area at the base of the main hoop. So that is not a safety thing. It also can carry frontal impact loads better to the whole back half of the car, and so that part can be a safety benefit.

Mark, Mark, Mark....
I agree.

The double V door bars needs the bigger heavy gusset on the inside. The outside could be plated in slightly thinner stuff as it is mostly for looks.

I like to use a sill bar and drop the top bar down in V fashion but forward of center so it doesn't hinder ingress/egress. I've also been able to do this and allow manual window cranks to remain intact. Or the 2 door bar as you described with the top one raked downward.

I also think any X bar door should have a 3rd straight sill bar, especially these newer ones with the humungous X that really doesn't provide much strength.