Tech Committee Bulletins on Cage Construction

Tech Committee Bulletins on Cage Construction

Postby Mopar 151w2 » Tue Feb 24, 2015 12:21 am

These "Recommendations" were deleted from the rules by vote of the 2015 Rules Meeting, and the consensus was reached to post them in a locked thread here. This post is a start on that:
. Recommendations for collision protection
1. Bend radii at least 3x tubing diameter, and continuous main hoop(s)
2. Mechanical tubing, as specified above is recommended for all collision protection and energy absorbing structures.
3. Tubing larger than specification, and /or additional diagonals & supports, are recommended.
4. 4 door bars are recommended, as are additional vertical supports, “intrusion” plating, and reinforcements of “X” joins, (i.e. “FIA”, “taco” gussets) in the door bar area, 2 continuous bars, and reinforcement to rocker or framerail, lateral reinforcement of rollcage mountings, framerails, or rockers (i.e. cross-members), and engagement of seat mountings in this reinforcement.
5. Windshield post support is recommended, as is a diagonal member in the roof, a vertical bar in the center of the windshield area, an anti-intrusion bar in the driver’s “window”, as well as 45 deg. sections in front frame rails and down tubes.
6. Cage installation should include significant structural enhancements and tie-in (i.e.
seam welding, gusseting, “fish” & floor plating, subframe connection, seat mount reinforcement, sill bars) to the cockpit area.
7. Cages should be tied in at as many points as possible (our rules specifically exempt safety equipment from class restrictions, but, other sanctions may specifically restrict this)
8. Entrants are urged to research specifications relevant to their particular car, and to it’s eligibility for other series, and to build to or above the highest specification available.
Mopar 151w2
 
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Re: Tech Committie Bullitens on Cage Construction

Postby Mopar 151w2 » Tue Feb 24, 2015 12:34 am

This is the draft guideline for evaluation of cages not meeting the full specification of the 2015 Rules. It was the consensus of the meeting that publishing this as a part of the rules would give the impression that marginal cages would fully meet the rules, which was not the intent of the draft proposal. They are presented here only as a reference, to show what the acceptance criteria for existing cages are likely to be based on. Please contact a member of the Tech Committie previous to an event if your rollcage falls into this category.
. Within our tubing specifications, ASTM a500 Type A, A513 Type 1, Schedule 40 pipe, and tubing with Carbon <.12% (ref. Rb <60) (i.e. 1010, “A36”) are considered marginal, and acceptable principally for existing cars. Prior good practice has been to increase wall or diameter ~20% when using these. Low grade material – butt-welded tubing, “schedule 10” aka “railing” pipe, 1005 hydraulic tube, (1008)exhaust pipe, and similar – is not allowed as rollcage members.
Mopar 151w2
 
Posts: 341
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Re: Tech Committee Bulletins on Cage Construction

Postby Mopar 151w2 » Thu Feb 26, 2015 11:18 pm

Some more detailed explanations of construction rules: re: socketed, gusseting, 2x weld
.Essentially, it means holesawing one side of the framrail or closed section of unibody, so that the cage leg "sockets" into it. makes it much stronger in a side impact, and allows an effective, multi-pass weld with MIG.
As you can see in the picture, the gusset adds more weld engagement than is possible by only welding the circumfrence of the tubing, and spreads load over considerably more tubing than the single perimeter weld.

It was my intent, with all of these items, for the rollcage tube to engage at least as much chassis material, in cross-sectional area, as is in the tube. Example: area of material in cross-section of 1.75 x .093 tube = .484 sq.in. Matching this area in .040 flat floor = 12.1" linear of weld = 3.86" diameter IF all welds are perfect and complete, so the old standby 6" Square footplate represents a reasonable margin of f*&^up
Example of joining 2 tubes in less than ideal conditions (weld 2x tube diameter, per the rules) Circumfrence of 1.75" = 5.50" x2 = 11" linear inches of weld! A 90 deg. gusset, 2.75 " in/side, will get you there. In the case of an internal sleeve gusset (tube splice) of the same size tube, the circumferential weld = 5.50". A plug or rosette weld in a 5/8" hole = 1.57" of linear weld. 6 rosettes, 3 equally spaced on each side of the joint, = 11.8" of linear weld
Mopar 151w2
 
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Re: Tech Committee Bulletins on Cage Construction

Postby Mopar 151w2 » Wed Jan 24, 2018 4:23 pm

I'd like to add some simple criteria for visual inspection of welds, and basic workmanship, to avoid nausea in the tech line if nothing else. Suggestions for a FEW example photos, or better-than-my illustrations, are welcome. Suggestions from our Webmaster on a location for the "supplementals" are eagerly sought, as well. :ugeek:
Mopar 151w2
 
Posts: 341
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