Does the SRF Chassis Meet Current GCR Standards?

Technical and Repair Discussions

Still Learning to Type
Still Learning to Type
Posts: 40
Joined: Sun Feb 05, 2017 9:05 pm
PostPosted: Mon Feb 20, 2017 3:10 am
There are many factors that make SRF very attractive: competition, CSRs, the general nature of the cars. Safety is a major concern for me, and I'm guessing for most SRF drivers.

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:

crash damage.jpg
crash damage.jpg (64.71 KiB) Viewed 8210 times

Needs a Life!!!
Needs a Life!!!
Posts: 200
Joined: Sat Nov 24, 2012 7:38 pm
PostPosted: Mon Feb 20, 2017 7:36 pm
I built FST from scratch. So I looked a the rules a lot in this area. One thing in the rules is you can deviate from the measurement specs, but requires the frame be certified by an engineer. I have assumed this is what allows some FF to approved even though the main hoops are outside of rules.

Main hoop - I think this meets the intent. If it does not meet the letter, and I am not sure it doesn't, then maybe there was engineering somewhere along the way.

Front hoop - I agree they are lower than top of steering wheel. When homologating my FST frame that was not questioned or check to my memory. Four inch above helmet and broomstick test were.

Front impact - While I think it is lacking, I do not think it is worse than others. I remember what was accepted as meeting the rules when I built the frame. I think the radiator and aluminum is stronger than the attenuation box I had.

Side bars - It would clearly be better if they did not break, and instead only bent. But the fact that they fold on impact is a good thing

Forum Hermit
Forum Hermit
Posts: 102
Joined: Mon Dec 12, 2011 1:10 pm
Location: Huntsville, AL
PostPosted: Thu Mar 02, 2017 6:28 pm
9.4.5.E.5 - One continuous length of tubing shall be used for the main hoop member with smooth continuous bends and no evidence of crimping or wall failure.

The SRF with the mandated tallman add-on roll cage mod has violated this since it's very early days (was it year 2 or 3 of the SRF when the tallman kit came out?).

The British seem to be fond of putting a little extra hoop on their cages for helmet clearance with tall drivers. Back when I had a Lotus 7 clone I was told "he!! no" for using something similar to solve my 6'4" clearance problems. Yet my SCCA built (& approved) racecar has just a fancier version of that.
Bruce Funderburg
SEDiv SRF #4

Needs a Life!!!
Needs a Life!!!
Posts: 200
Joined: Sat Nov 24, 2012 7:38 pm
PostPosted: Thu Mar 02, 2017 8:49 pm
BFun wrote:9.4.5.E.5 - One continuous length of tubing shall be used for the main hoop member with smooth continuous bends and no evidence of crimping or wall failure.

The SRF with the mandated tallman add-on roll cage mod has violated this since it's very early days (was it year 2 or 3 of the SRF when the tallman kit came out?).

The British seem to be fond of putting a little extra hoop on their cages for helmet clearance with tall drivers. Back when I had a Lotus 7 clone I was told "he!! no" for using something similar to solve my 6'4" clearance problems. Yet my SCCA built (& approved) racecar has just a fancier version of that.


9.4.5.F - Any roll hoop design which does not comply with the specifications
in 9.4.5, will only be considered if it is accompanied by engineering
specifications signed by a registered engineer stating that the
design meets the stress loading requirements below. No alternate
roll hoop will be considered unless it contains a main hoop having
a minimum tubing size of 1.375” x .080” wall thickness. The roll
bar must be capable of withstanding the following stress loading
applied simultaneously to the top of the roll bar: 1.5 (X) laterally,
5.5 (X) longitudinally in both the fore and aft directions, and 7.5 (X)
vertically, where (X) = the minimum weight of the car.

I am assuming the tall man hoop was approved under 9.4.5.F

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