SCCA Solo Roll Bar on a $2011 car

In building my $2011 challenger, I'm trying to figure out if it's possible to make it useful for any competition besides the GRM $201X. I think SCCA Solo is my best bet. If it was to race SCCA, it would go straight to A Modified. I'm trying to figure out what is REQUIRED to compete in AM, not just suggested. Suggestions are nice, but requirements are what matters. From what I can tell, here are REQUIREMENTS that a closed top Solo car would require (condensed from SCCA solo rules):

3.3.2 Roll Bars A roll bar meeting the requirements of Appendix C or a roll cage meeting the requirements of Section 9.4 of the Club Racing General Competition Rules (GCR) is required in all A Modified (AM). The roll bar or roll cage height may also be reduced in the same manner for cars in the Prepared category with a full original equipment windshield assembly and a standard (as defined herein) hardtop which has been bolted securely in place. APPENDIX C - SOLO ROLL BAR STANDARDS A. BASIC DESIGN CONSIDERATIONS 2. In a closed car, it must be as close as possible to the interior top of the car. 3. The roll bar must be designed to withstand compression forces resulting from the weight of the car coming down on the roll structure, and to take fore-and-aft loads resulting from the car skidding along the ground on the roll structure. 4. The two vertical members forming the sides of the hoop shall not be less than fifteen inches apart (inside dimension). B. MATERIAL 1. The roll bar hoop and all braces must be of seamless ERW or DOM mild steel tubing (SAE 1010, 1020, 1025) or equivalent, or alloy steel tubing (SAE 4130). 2. The size of tubing to be used shall be determined on the basis of the weight and speed potential of the car. The following minimum sizes are required and are based upon the weight of the car without the driver. a) Over 1500 lbs – min 1.500” o.d. x 0.120” wall or 1.750” o.d. x 0.095” wall b) Over 1000 lbs – min 1.250” o.d. x 0.090” wall c) Under 1000 lbs – min 1.000” o.d. x 0.060” wall 3. Each mounting plate shall be at least 0.080” thick if welded and 3/16” (0.188”) thick if bolted. A minimum of 3 bolts per plate is required for bolted mounting plates. 4. All bolts and nuts shall be SAE Grade 5 or better and 5/16” minimum diameter. C. FABRICATION 1. One continuous length of tubing must be used for the hoop member with smooth continuous bends and no evidence of crimping or wall failure. D. BRACING 2. All roll bars must be braced in a manner to prevent movement in a fore-and-aft direction with the brace attached within the top one third of the roll hoop, and at an angle of at least thirty degrees from vertical. E. MOUNTING PLATES 1. Roll bars and braces must be attached to the frame of the car wherever possible. 2. In the case of cars with unitized or frameless construction, mounting plates may be used to secure the roll bar structure to the floor of the car. The important consideration is that the load be distributed over as large an area as possible. A backup plate of equal size and thickness must be used on the opposite side of the panel with the plates through-bolted together.

I'm trying to interpret this to have the most absolutely simple roll bar possible. For example, if I have a 2000 pound car, I could have a hoop that is 1.5 x .120" and two 1.25" tubes that attach 3" down from the top of the hoop, then go rearward at 30°. Another example: with a 1400 pound car, I could have a hoop that is 1.25 x .090" and two 1" tubes that attach 6" down from the top of the hoop, then go forward at 60°. These tubes all terminate at the bottom of the car with .080" plates.

Am I reading this right? I can't stand how complicated and wordy this stuff gets, SCCA rulebooks drive me bonkers. Thanks to any help. If somebody has a clear picture/example of a bare minimum roll bar, that would be helpful too. I've had a hard time wading through the internet BS to find some reliable info.

Bryce

I'm not seeing the allowance for the 1.25" braces to the rear.

Section B.1 says the roll bar hoop and all braces must be ERW or DOM, then B.2 gives minimum sizes according to the weight of the car.

Looks to me like it ALL needs to be 1.5 x .120".

Not that this helps Bryce, but the Oregon PCA offers two Non-Porsche classes with just 1 rule each, NP-S (Street Tire, 140+ TW0 and NP-R (Slicks, r-Comps, etc). There's even a Season-long points championship with trophies at the end just like SCCA. Plus you'd only have to go to Packwood once instead of 6 times.

I just want to know what you are building that puts you in A-Mod.

SVreX wrote: I'm not seeing the allowance for the 1.25" braces to the rear. Section B.1 says the roll bar hoop and all braces must be ERW or DOM, then B.2 gives minimum sizes according to the weight of the car. Looks to me like it ALL needs to be 1.5 x .120".

One of the things I omitted, as it is recommended but not required:

D. BRACING 1. It is recommended that braces be of the same size tubing as used for the roll bar itself.

From what I read, the only thing required is that it resists fore/aft loads from the car skidding along the ground on the roll structure. If there are means to prevent this, whether it's additional tubes or whatever, then the requirements are met. I read it that all tube must be DOM, and that the roll bar must be X size/thickness based on weight, but that braces are only recommended to be the same. That's one of the things I'm not clear on.

Bryce

T.J. wrote: I just want to know what you are building that puts you in A-Mod.

SCCA doesn't like people changing powertrain configurations for a given chassis. On the opposite end of the spectrum, I love putting powertrains where they don't belong.

Bryce

the only thing i am not sure of in your interpretation is that it all rests on .080 plates. mostly because i dont know i you are welding or bolting to the car.

itsarebuild wrote: the only thing i am not sure of in your interpretation is that it all rests on .080 plates. mostly because i dont know i you are welding or bolting to the car.

For the example, I was assuming welded. Good catch.

Nashco wrote:

SVreX wrote: I'm not seeing the allowance for the 1.25" braces to the rear. Section B.1 says the roll bar hoop and all braces must be ERW or DOM, then B.2 gives minimum sizes according to the weight of the car. Looks to me like it ALL needs to be 1.5 x .120".

One of the things I omitted, as it is recommended but not required:

D. BRACING 1. It is recommended that braces be of the same size tubing as used for the roll bar itself.

From what I read, the only thing required is that it resists fore/aft loads from the car skidding along the ground on the roll structure. If there are means to prevent this, whether it's additional tubes or whatever, then the requirements are met. I read it that all tube must be DOM, and that the roll bar must be X size/thickness based on weight, but that braces are only recommended to be the same. That's one of the things I'm not clear on. Bryce

Got it.

What else did you omit? Are there requirements for # of bends, total degree of bends in hoop, etc? (I am learning too).

In reply to Nashco:

Bryce,

They don't like a lot of things. My Mini would be classed in SM because it doesn't have the stock camshaft. I figured that was silly, so I bought a set of Hoosier F500 slicks for it and ran it in G Prepared instead. Thought about taking off the bumpers, window glass, back seat, etc. to get a tiny bit closer to what is allowed by the prepared rules, but didn't ever do it since I enjoy driving it on the street.

Agree that the rulebook is not too fun to read.

Nashco wrote:

T.J. wrote: I just want to know what you are building that puts you in A-Mod.

SCCA doesn't like people changing powertrain configurations for a given chassis. On the opposite end of the spectrum, I love putting powertrains where they don't belong. Bryce

Does DM or EM work?

The rules are a mess, which is why I posted the condensed version above with JUST requirements. What I posted above was from the Solo rule book, which doesn't say jack about construction (bend radius, etc.) from what I can tell.

http://www.scca.org/documents/2011%20Tech/2011%20SCCA%20Solo%20Rules.pdf

The Club Racing rule book has more detailed info, but it is technically all about cages, not roll bars.

http://cms.scca.com/documents/2011%20Tech/2011%20GCR-printed%20version.pdf

From what I can tell, max bends in the hoop is 4, bend radius is three times the diameter, and no greater than 180 degrees of total bend in the hoop. That's the critical stuff.

Bryce

DILYSI Dave wrote: Does DM or EM work?

Nope. DM/EM rules state:

D. Drivetrain 2. Engine and/or drivetrain changes are permitted within the following limitations: a. Original front-engine design must remain a front-engine design, i.e., no part of the engine block or cylinder head may extend rearward of the midpoint of the wheelbase. b. Original rear- or mid-engine designs may be interchanged with each other, but no part of the engine block or cylinder head may extend forward of the midpoint of the wheelbase.

SCCA sends the car straight to hell...err...A Mod!

Bryce

X Prepared? I've seen some crazy swaps in that class, though granted never a drive-wheel swap...

Javelin wrote: X Prepared? I've seen some crazy swaps in that class, though granted never a drive-wheel swap...

Hmm...interesting thought. If you keep a transverse car transverse, but change it from FWD to RWD, that does seem like it would be XP legal. It says engine orientation (transverse vs longitudinal) must remain the same but doesn't say anything about drive wheels changing.

An XP car wouldn't need a roll bar at all, would it?

Bryce

Exactly

Not to mention XP is very healthy in our region (Britain's STi-powered 914, Josh's LS1-powered RX-7, and the ex-PRE Miata).

Anybody else have any input? I was hoping somebody who has actually been down this road could chime in. Sounds like I might be best asking on the SCCA forums or just sending an email to the head tech equivalent at SCCA. I wonder how that will go...

Bryce