I think they've relaxed the wording in here. I think it used to say welds shall be unaltered. I worked at nuke plants and they ground down the welds smooth after every pass. These organizations tend to be run by anal retentive geeks that don't really know what they're doing.
APPENDIX C - SOLO ROLL BAR STANDARDS
A. BASIC DESIGN CONSIDERATIONS
1. The basic purpose of the roll bar is to protect the driver in case the
vehicle rolls over. This purpose should not be forgotten.
2. The top of the roll bar shall not be below the top of the driver’s helmet
when the driver is in normal driving position, and shall not be more
than six inches behind the driver. It is strongly suggested that the roll
bar extend at least three inches above the driver’s helmet. In case
of two driver cars, both drivers must be within the roll bar height requirement,
however only one driver must be within six inches of the
roll bar. In a closed car or an open car with a removable OE hardtop
which is equipped with a roll bar/cage, 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). It is desirable that
the roll bar extend the full width of the cockpit to provide maximum
bearing area in all soil conditions during rollovers. The roll bar vertical
members on formula cars and other single seat cars with a center
driver position must be not less than fifteen inches apart, inside
dimension, at their attachment points to the uppermost main chassis
member.
5. An inspection hole of at least 3/16 inch diameter must be drilled in
a non-critical area of a roll bar member to facilitate verification of
wall thickness. This should be at least three inches from any weld
or bend.
6. It is recommended that steel gusset plates be used at all welds. Gussets
should be at least two inches long on each leg and 3/16 inches
thick.
7. It is recommended that roll bars be coated only with a light coat of
paint. If, however, a roll bar should be chrome-plated, it is recommended
that the structure be normalized.
8. Post or tripod types of roll bars are not acceptable.
B. MATERIAL
After 9-22-85, aluminum is not an acceptable alternate material. Cars
using aluminum roll bars or roll cages must file proof with the SD that
the structure was approved prior to 9-22-85 as provided in this section.
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
238 — 2011 SCCA NATIONAL SOLO RULES
tubing (SAE 4130). It is strongly recommended that roll bars not be
constructed of ERW due to quality and strength concerns.
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
Dimensions are nominal. 0.005” variation in wall thickness is allowed.
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.
2. All welding must be of the highest possible quality with full penetration
and will be subjected to very critical inspection. Arc welding, particularly
heliarc, should be used wherever possible.
D. BRACING
1. It is recommended that braces be of the same size tubing as used
for the roll bar itself.
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 onethird
of the roll hoop, and at an angle of at least thirty degrees from
vertical. It is strongly recommended that two such braces be used,
parallel to the sides of the car, and placed at the outer extremities of
the roll bar hoop. Such braces should extend to the rear whenever
possible.
3. It is suggested that roll bars include a transverse brace from the
bottom of the hoop on one side to the top of the hoop on the other
side.
E. MOUNTING PLATES
1. Roll bars and braces must be attached to the frame of the car wherever
possible. Mounting plates may be used for this purpose where
desired.
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
APPENDIX C - ROLL BAR STANDARDS — 239
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.
F. REMOVABLE ROLL BARS
Removable roll bars and braces must be very carefully designed and
constructed to be at least as strong as a permanent installation. If one
tube fits inside another tube to facilitate removal, the removable portion
must bottom on the permanent mounting, and at least two bolts must be
used to secure each such joint. The telescope section must be at least
eight inches in length.
G. INSTALLATION ON CARS OF SPACE FRAME AND FRAMELESS DESIGN
It is important that roll bar structures be attached to cars in such a way
as to spread the loads over a wide area. It is not sufficient to simply attach
the roll bar to a single tube or junction of tubes. The roll bar must
be designed in such a way as to be an extension of the frame itself, not
simply an attachment to the frame. Considerable care must be used
to add as necessary to the frame structure itself in such a way as to
properly distribute the loads. It is not true that a roll bar can only be as
strong as any single tube in the frame.
H. ROLL CAGES
It is recommended but not mandatory that all cars utilize a roll cage as
defined in the applicable section of the GCR.
I. ROLL BAR PADDING
Braces and portions of the main hoop subject to contact by the driver’s
or passenger’s helmet, as seated normally and restrained by seat belt
and harness, must be padded with a non-resilient material such as
Ethafoam (R) or Ensolite (R) or other similar material with a minimum
thickness of one-half inch.
