Reading the GCR and comparing to the SRF there seem to be discrepancies. I'm wondering if it isn't being given a pass that a homebuilt DSR wouldn't receive. Am I reading the rules wrong?
Reading section 9.4.5 on page 117:
Cage may be of two designs, low front hoop (top of steering
wheel) or high front hoop (equal to rear hoop) but with no diagonal brace.
Virtually every picture I've seen the steering wheel is level with or proud of the bodywork, not even counting the bar underneath it.
G. Front Impact Attenuation
1. All formula cars registered or homologated with SCCA as of 1/1/1986 must have a front impact attenuation device meeting at least one of the following criteria:
a. An FIA-approved front impact attenuation structure.
b. A metallic structure, securely attached to the front bulkhead, with a minimum cross section of 200 sq cm (31 sq in.), 40 cm (15.75 in.) forward of the clutch and brake pedals (not depressed), constructed of a minimum of 18 gauge 6061-T4 or equivalent aluminum.
A non-metallic composite structure, securely attached to the front bulkhead or incorporated into the nose piece, with a minimum cross section of 200 sq cm (31 sq. in.), 40 cm (15.75 in.) forward of the clutch and brake pedals (not depressed), constructed of a minimum of 6 mm stabilized (e.g., honeycomb) material with inner and outer reinforcements of a minimum of 2 5-ounce laminate material (fiberglass, carbon, Kevlar, and so on).
6. Rear impact attenuation structures are strongly recommended for all formula cars, and may incorporate the materials and/or construction techniques listed above for front impact attenuation structures.
7. Pre-1986 formula cars and all Sports Racing cars are strongly urged to use front and rear impact attenuation structures, and may incorporate the materials and/or construction techniques for front impact attenuation structures listed above.
Note that this doesn't include side-impact protection. Both the Elan-based SCCA ESR/FE and the Elan NP01 (also a budget sports racer, although with a bigger budget!) have double bowed side bars. The Elan has barrier impact absorbing foam on the outside of the cage.
A. Main Hoop
The main hoop shall be constructed of tubing per 9.4.5.E.4. The minimum bend radius shall not be less than 3 times the tube diameter measured from the tube centerline. The main hoop shall not be less than 2 inches above the driver’s helmet, seated normally and restrained by seat belt/shoulder harness. A straight line drawn from the top of the main hoop to the top of the front hoop shall pass over the driver’s helmet. On Formula cars and single seat Sports Racing cars the vertical members of the main hoop shall not be less than 15 inches apart (inside dimension) at their attachment to the chassis. If the hoop does not go to the belly pan, proper gussets and tube triangulation shall be used under its attachment. On monocoque chassis, the main hoop shall be welded to mounting plates not less than .080” thick. It is important that these plates be attached to the chassis in such a way as to spread the loads over a wide area. There shall be a plate of equal thickness on the inside of the monocoque with solid rivets or bolts (5/16” minimum bolt diameter) through the non-ferrous metal and/or composite material.
B. Front Hoop
Low front hoops must be no lower than the top of the steering wheel. It is recommended the hoop extend to the belly pan. If not, it shall be attached to the chassis with gussets and triangulation in order to spread the loads. In automobiles of full height (top of the steering wheel) monocoque or composite construction, a steel cap plate, not less than .080” thick must be attached as a rub block.
Where to begin? Attached to the belly pan? Gussets and triangulation? Interestingly, the triangulation behind the driver seems to be designed to meet the requirement that the engine is prevented from entering the driver's compartment rather than support the roll bar.
There are two box sections of square tubing on either side of the driver's compartment. They undoubtedly add torsional rigidity. As for crash protection, they fold: