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Discussion Starter · #1 ·
I haven't seen a thread on cage construction principals yet. This could be valuable for all of us. I'd suggest keeping this thread focused on cage design and construction, and use other threads for other safety matters. Also IF someone has a list or description, and someone adds to it, it would be good if the original poster could edit their post to include the new idea if it fits. People interested can save the thing that way, as a cleaner thread.

Roll bar, simple cage, Exo cage, integrated chassis cages, they come in many varieties. Some are very effective and some are near useless, depending on the situation. Cages should be made with all aspects of the vehicle's use in mind. Making a cage for "slow rolls" on the trail is delusional for 2 reasons. You still have to drive it to the trail. A highway crash can be just as deadly as one on the trail. Even if it's a trail only rig, what happens if you take a tumble down a steep hill? You might roll many times before stopping.

First, cage mounting. Body mounted bars and cages are inherently weak, even if the rest of the fabrication is first rate. Sheet metal can be very strong structurally, but bolting on a plate to sheet metal is not a strong connection. Even if the bolted joint were strong, the body can separate from the frame in a violent high speed crash, leaving a very floppy floor of the cage to fold up.

Even if you plate both sides, you only increase the joint's strength marginally. Taking that plate and bracing it to a frame member is what is needed for a strong connection. But, that will transfer vibrations into the body, making it even noisier, and can, over time, punch out the body section due to vibration. What will prevent both is to either mount to the plate using something like a suspension rubber bushing, or mount the bottom plate with a thick rubber sheet (old tire tread?) between it and the body. If you weld the brace to the frame, either go completely through the frame, welding both sides, gusset it, or make it another bolted connection plate.

Adding to the standard roll bar is a common and effective way to complete a cage if done properly. Besides what has been discussed on frame attachments, gussets, braces and diagonal braces adding triangulation (space frame designs) are needed. Longer vertical runs of tubing need to have straight horizontal bars to prevent collapse of a cage hoop in the event of a side hit, T bone style. Enough headroom has to be allowed for, as you can get a concussion from beating your head on a cage just as easy as the ground. Padding of the cage (as well as helmets for any extreme wheeling) is needed to minimize head injury.

What keeps cages from pulling apart at the seams? Especially at the welded joints? Every race association requires gussets at every welded cage joint, to increase the linear inches in a welded joint. Short gusset type bars are also allowed in lieu of gussets. These add to the weld, but also provide better triangulation of the corners. Effectively the short bar acts as a second joint that will hold the bars together in the event of catastrophic failure of the primary weld joint.

It's late and I'm tired, so some one jump in here and talk about materials or whatever…


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1 - General Requirements
a. All vehicles, regardless of date of manufacture, must be fitted with a roll cage conforming to the following specifications:

b. The top of the roll bar shall be at least 5.08 cm (2") above the top of the competitors helmet or as close to the roof as possible. The top of the roll bar shall be no more than 25.4 cm (10") behind the competitor's helmet when the competitor is in the normal driving position.

c. It is highly recommended that any part of the roll cage structure which may be struck by the competitor's helmet in a serious impact be covered with a flameretardant energy absorbing material.

2 - Construction Materials
a. The main hoops and primary bracing should be constructed from round, mild steel, ERW or DOM type tubing. Chrome molly tubing such as 4130, may be used but is not recommended.

b. Aluminium and composite materials are prohibited construction materials for roll cage structures.

c. All cages must have a 0.476 cm (.1875") diameter inspection hole drilled in each main hoop.

d. Minimum tube size and wall thickness are as follows for vehicle weights including competitor:
Under 1500 lbs 3.49 cm X 0.24 cm (1.375" X .095")
Under 2500 lbs 3.81 cm X 0.24 cm (1.500" X .095") or 3.49 cm
X 0.30 cm (1.375" X .120")
Over 2500 lbs 3.81 cm X 0.30 cm (1.500" X .120") or 4.44 cm
X 0.24 cm (1.750" X .095")

3 - Fabrication
a. One continuous piece of tubing must be used for the main hoop. A similar piece shall be used for the other main hoop or hoops. The allowable cage configurations are:

A figure of each hoop configuration is provided to illustrate the acceptable basic configurations:

b. All bends must be smooth with no excessive evidence of crimping or any evidence of wall fracturing. All bars should start as close as possible to the floor of the vehicle and come as close as possible to the sides of the vehicle for maximum competitor protection. Construction guidelines for acceptable ovality and crimping will be:

Ovality: Maximum allowable ovality is 8% of the nominal pipe diameter. Ovality is measured as the variation between the maximum and the minimum dimension of the pipe in one location per figure 1.

Crimping: Crimping is measured per figure 2. The maximum allowable crimping is 3% of the nominal pipe dameter.

c. In the case of tube frame vehicles, the roll cage structure must be attached to the chassis with suitable webbing or gusseting to distribute loads over as wide an area as possible.

d. In the case of unit body vehicles, it is recommended procedure to attach the four ends of the main hoop tubes into L shaped plates at the junction of the floor and rocker panels rather than just to a plate on the floor. Additionally, it is highly recommended that all cages be tabbed into the basic body structure at least every 60.96 cm (24") or wherever possible.

4 - Bracing

a. In the case of the twin lateral hoop design, the front and rear hoops shall be joined by a piece of equal dimensioned tubing on each side.

b. Rear stays must attach to the rear hoop no lower than 20.32 cm (8") from the top of the hoop and at an angle no steeper than 35 degrees from vertical. These rear stays must be made from a straight piece of tubing and be attached to a suitably stiff or reinforced area. A diagonal brace must be fitted from near the top of the hoop to a position near the opposite corner of the hoop. This brace must be as straight as possible.

c. Side protection bars must be attached between the front and rear hoops on both sides of the vehicle. These bars should be attached to the front hoop no higher than 30.48 cm (12") off the floor and on the rear hoop and no higher than 60.96 cm (24") off the floor. The competitor's side must be fitted with at least two side protection bars which follow as closely as possible the outline of the door. NASCAR style multiple anti-intrusion bars are highly recommended.

d. A bar joining the two outer members of the front hoop near steering column level is required.

5 - Mounting Plates

a. The four lower hoop tubes must be connected to plates welded or bolted to the frame or floor of the vehicle.
b. On unit body vehicles, all plates shall be at least 129 square cm (20 square") in area. The minimum thickness of these plates shall be 0.20 cm (.080") in the case of weld on plates and .1875 for bolt on types. Bolt on types shall have a minimum of three 0.952 cm (.375") grade 5 bolts fastening each plate and must have a backup plate of equal size and thickness on the other side of the floor with the bolts passing through both plates and the floor.

c. Vehicles with frame type construction must use plates of at least 51.6 square cm (8 square") area and .1875 thickness regardless of whether they are bolted or welded.

6 - Welding

a. It is essential that all welding be of the highest possible quality. Slag welds, poor arc and gas welds are NOT acceptable. It is highly recommended that only certified people carry out arc welding on roll cages. TIG or MIG are the preferred welding processes. Cages with unacceptable welding will not be passed.

7 - Gusseting
a. It is important that loads be distributed over as wide an area as possible especially in the case of cages on space frame type vehicles. Gussets or tie-in tubes must be used at main tube junctions of the roll cage members. Gussets should also be used
when it is not possible to weld all around a tube because of body interference. Gusset thickness should be at least the same as the tubing wall thickness they are attached to. Each gusset shall extend in length for a minimum of one pipe diameter in both directions from the centre point of the gusset.

8 - Removable Type Cages

a. Removable roll cages may be fitted to vehicles only if their construction and design allow them to meet the strength requirements of the designs above.

b. Where tubes join, a double shear type mating tab may be used. Where such a tab is used, the tube joining this tab shall have a small piece of tubing welded perpendicular to its length for the bolt to pass through to prevent crushing of the main tube. Tabs shall be at least 3.49 cm (1.375") wide and 0.476 cm (.1875") thick and must be welded to one of the main tubes. When single bolts are used to fasten tubes, they must be of at least 1.11 cm (.4375") diameter and grade 8 material.

c. Sliding tube type junctions may also be used if they meet the following criteria:
i. Wall thickness of the joining tube shall be a minimum of 0.30 cm (.120").
ii. Length of this tube shall be a minimum of 7.62 cm (3") on either side of the splice.

d. Attachment shall be made using two bolts on each side of the splice 90 degrees to each other passing straight through the tubing. Grade 5 bolts of at least 9.52 cm (.375") diameter shall be used here. Splicing tubes may be slid either inside the main tubing or over the outside.

e. Alternate joint designs may be approved at the discretion of the scrutineer.

f. Basic design and fabrication of removable type cages must conform to the specifications for non-removable type cages.

9 - Alternate Designs

a. Alternate cage designs may be approved by the scrutineer provided the competitor can produce stress analysis data from a certified engineer stating that the roll over structure is capable of withstanding the following loads applied simultaneously to
that structure:
1.5 G lateral
5.5 G fore/aft
7.5 G vertical

b. Calculations shall assume the all up race weight of the vehicle with competitor.


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2,678 Posts
Pipe and tubing thanx to siverzuk
Product Definitions
Standard Pipe- is ordinarily used for low-pressure conveyance of air, gas, water, oil, or other fluids and for mechanical applications.

It is used primarily in
machinery, buildings, sprinkler systems, irrigation systems and water wells rather than in pipelines or utility distribution systems. It may carry fluids at elevated temperatures and pressures which are not subject to external heat applications. It is usually produced in standard diameters and wall thickness to ASTM (American Society for Testing and Materials) specifications.

Applications Include:
Ammonia or Ice Machine Pipe Nipple Pipe
Pipe for Plating or Enameling Bomb Casing
Pipe for Rigid Conduit Pressure Piping
Distributor’s Pipe Pump Pipe
Driven Well Pipe Drive Pipe
Standard Pipe Coupling Stock Dry Kiln Pipe
Turbine Pump Pipe Water Well Casing
Water & Gas Service Pipe Furniture Pipe
Dual Stenciled Pipe Sold as Standard Pipe English Gas and Steam Pipe
Water Well Reamed and Drifted Pipe
Applications Exclude:
Conduit Tubing- EMT Water Main Pipe
Pipe for Structural Uses

Oil Country Tubular Goods ( OCTG ) – are pipe used in wells in oil and gas industries consisting of casing, tubing and drill pipe.

A. Casting- is the structural retainer for the walls of oil and gas wells and covers sizes 4.5 to 20 inches O.D. inclusive.
B. Tubing- is used within the casing to convey the oil or gas to the surface (ground level) and ordinarily includes sizes 1.050 to 4.5 inches O.D. inclusive.
C. Drill Pipe- is the pipe used to drill the well by transmitting power to a rotary drilling tool from the surface to below ground level. Normally covers sizes 2 3/8 to 6 5/8 inches O.D. inclusive.
Oil Country Tubular Goods are produced to API (American Petroleum Institute)

Specifications. There are also OCTG Specifications in ISO 9000.
Applications Include:
OCTG Coupling Stock Drill Pipe
Casing Tubing
Line Pipe- is used for transportation of oil, gas, or water generally in a pipeline of utility distribution system. It is produced to API (American Petroleum Institute)
and AWWA (American Water works Association) Specifications.
Applications Include:
Line Pipe Coupling Stock API Line Pipe
Dual and Triple Stenciled Pipe AWWA - Mill Type Pipe

Mechanical Tubing- is welded or seamless tubing produced in a large number of shapes of varied chemical composition in sizes 3/16 inch to 10 ¾ inches O.D. inclusive of carbon or alloy material. It is not normally produced to meet specification other than that required to meet the end use. It is produced to meet O.D. and decimal or metric wall thickness.
Applications Include:
Aircraft Tubing Furniture Tubing
Airframe Tubing Mechanical Tubing
Tubes for Bearing Precision Pump Tubes
Applications Exclude:
Structural Pipe and Tubing ( having
normal diameters and wall thickness)
Conduit Tubing- EMT
Pressure Tubing- is used to convey fluids at elevated temperatures or pressures, or both, and is suitable to be subjected to heat applications. It is produced to exact O.D. and decimal or metric wall thickness in sizes ½ inch to 6 inches O.D. inclusive, usually to standard
specifications such as ASTM.
Applications Include:
Air Heater Tubes Boiler tubes
Oil-Still Tubes Header Tubes
Pressure Tubing and Pipe Coupling Stock Heat Exchanger and Condenser Tubes

Grade Definitions
Carbon Steel- All ferrous materials other than alloy and stainless which are usefully
malleable and which contains by weight 2 percent or less carbon. (In
effect, all steels other than complying with the definition of alloy or
Note: In all carbon steels small quantities of certain residual elements, such as
copper, nickel, molybdenum, chromium, etc., are all unavoidably retained from raw
Alloy Steel- Steels not complying with the definition of stainless steel and containing by
weight one or more of the following elements in the proportion shown:
0.3 percent or more of Aluminum
0.0008 percent or more of Boron
0.3 percent or more of Chromium
0.3 percent or more of Cobalt
0.4 percent or more of Copper
0.4 percent or more of Lead
1.65 percent or more of Manganese
0.08 percent or more of Molybdenum
0.3 percent or more of Nickel
0.06 percent or more of Niobium
0.6 percent or more of Silicon
Stainless Steel- Alloy Steels containing by weight 1.2 percent or less carbon and
10.5 percent or more of chromium, with or without other elements
and a minimum of 50 percent iron.

Glossary of Terms
AGA- American Gas Associations.
AISI- American Iron and Steel Institute.
API- American Petroleum Institute.
ANSI- American National Standards Institute. Formerly the ASA- American Standard
ASME- American Society for Mechanical Engineers.
ASTM- American Society of Testing Materials.
AWWA- American Water Works Association.
Bales- Term associated with banded lifts of pipe.
Barlow’s Formula- An equation, which shows the relationship of internal pressure to
allowable stress, normal thickness and diameter.
Bevel- The angle formed between the prepared edge of the end of the pipe and a
plane perpendicular to the surface of the member. The standard bevel for line
pipe is 30 degrees to facilitate welding.
Billet- A solid semi-finished round or square product that has been hot-worked by
forging, rolling, or extrusion. For seamless tubular products, the billet is heated
and pierced to form a hollow tube.
Black Bare- Term associated with pipe surface whereby the pipe will not be coated with
mill oil spray and grease spots and cutting oil will not be removed.
Black Dry- Term associated with pipe surface whereby the pipe will not be coated with
mill spray oil and all grease spots and cutting oil will be removed.
Black Oiled- Term associated with pipe surface whereby material ordered in this
manner is protected with a varnish- type oil on the O.D. for temporary
corrosion protection during transit and short-term storage.
Bundles- Term associated with practice of packaging NSP 1-1/2 “ and smaller pipe.
Pieces per bundle vary depending upon size.
Burst Test- A destructive hydraulic test employed to determine actual yield and ultimate
strength of both seamless and welded pipe.

Buttweld Pipe- See Continuous Weld.
Chamfer- A beveled surface to eliminate an otherwise sharp corner.
Chemical Properties- Normally associated with a limited number of chemical elements;
however, depending upon the specification, practically a full
analysis may be required. Minimum or maximum limits are
established in Standards.
Cold Work- Deforming metal physically at a temperature lower than the recrystallization
temperature. Mechanical or hydraulic expansion employed to achieve higher
mechanical properties.
Conduit- Pipe serving as a duct for electrical wiring.
Coupling- Threaded sleeve used to connect two lengths of pipe.
Continuous Weld- In common usage, a phase for continuous butt-weld. Furnace-
welded pipe produced in continuous lengths from coiled skelp and
subsequently cut into individual lengths, having its longitudinal butt
joint forge welded by the mechanical pressure developed in rolling
the hot-formed skelp through a series of welding rolls.
Cut Lengths- Pipe cut to a specific length as ordered.
Die Stamping- Permanent marking placed on a pipe as required by some
Double Extra Strong- Standard pipe weight designation (XXS). Sometimes described
as XXH (double extra heavy).
DRL- Double Random Length ( 35’ minimum average or as defined in specifications).
DSAW- Double Submerged Arc Weld.
Ductility- The ability of a material to deform plastically without fracturing, being
measured by elongation or reduction of area in a tensile test or by other means.

Eddy- Current Testing- Non-destructive testing method in which eddy-current flow is
induced in the test object. Changes in the flow caused by
variations in the object are reflected into a nearby coil or coils
for subsequent analysis by suitable instrumentation and
ERW- Electric Resistance Weld. See High Frequency Welding.
EW- Electric Weld. See High Frequency Weld.
Elongation- In tensile testing, the increase in the gage length, measured after fracture
of the specimen within the gage length, usually expressed as a percentage
of the original gage length.
Expanded Pipe- Pipe which has been enlarged circumferentially by mechanical or
hydraulic pressure.
Extra Strong- Standard pipe weight designation (XS). Sometimes described as XH
(extra heavy).
Flattening Test- A quality test for pipe in which a specimen is flattened between
parallel plates that are close to a specific height.
Galvanization- Covering or iron or steel surfaces with a protective layer of zinc (weight
defined in specification).
High Frequency Welding- A technique employed in the manufacture of electric
resistance weld pipe. Typical radio frequency power for
welding is supplied at 450,000 cycles per second.
Hot Stamp- Permanent marking placed on pipe as employed by manufacturer or as
established by specification.
Hydrostatic Test- Normal mill test as required by specifications. The pipe ends are
sealed and high-pressure water is introduced to predetermined
pressures as required by specifications.
I.D.- Inside Diameter.
Impact Test- A test performed at a specified temperature (usually lower that ambient)
to determine the behavior of materials when subjected to high rates of
loading, usually bending, tension or torsion. The quantity measured is the
energy absorbed in breaking the specimen by a single blow, as in a
Charpy Test.
Ink Mark- Continuous printing identification associated with NPS 1-1/2 and smaller
pipe. Detail is normally limited to the trademark and “ Made in USA”.
Kip- A unit of weight equal to 1,000 pounds used to express dead weight.
Lifts- Term associated with separated segments of pipe (banded or unbanded for ease
of handling).
Magnetic Particle- One of several methods of non-destructive testing. A non-
destructive method of inspection for determining the existence
and extent of possible defects in ferromagnetic materials. Finely
divided magnetic particles, applied to the magnetized part, are
attracted to and outline the pattern of and magnetic leakage fields
created by discontinuities.
Magnetic Properties- The properties of a material that reveal it's elastic and inelastic
behavior where force is applied, thereby indicating its suitability
for mechanical application; for example, tensile strength,
elongation, hardness, and fatigue limit.
NPS- A dimensionless designator for such traditional terms as “ nominal diameter”,
“size”, and “nominal size”. Corresponds to actual outside diameter only in sizes
14 inches and over.
Normalizing- Heating a ferrous material to a suitable temperature above the
transformation range and then cooling in air to a temperature substantially
below the transformation range.
O.D.- Outside Diameter.
Oiled- See Black Oiled.
PE- Plain End.
Pickling- Pipe immersed into acid bath for removal of scale, oil, dirt, etc.
PSI- Pounds per square inch.
PSIG- Pounds per square inch gage.
R & D- Reamed and Drifted. Pipe commonly used in water wells which has a special,
heavy-duty coupling and a guaranteed I.D. clearance.
SC- Square cut plain end pipe.
Skelp- A piece or strip of metal produced to a suitable thickness, width and
configuration, from which welded pipe is made.
SMLS- Seamless.
SRL- Single Random Length ( 16-22 ft. for standard weight ASTM pipe or as defined in
Stencil- Paint spray identification placed on pipe. Specification size, wall, grade, test
pressure, method of manufacture and normal mill characters and mill
identification are usually included; however, detail varies by specification.
“Country of Origin” is included.
Stretch Reduction- A technique employed in the manufacture of continuous weld pipe
and in certain instances in the manufacture of seamless and
electrical resistance weld pipe. It involves one or several “matter”
sizes which are stretched-reduced or rolled under tension through a
number of stands to achieve a variety of standard pipe diameters
and walls.
Strip- A sheet of metal in which the length is many times the width.
TBE- Threaded End Bolts.
Tensile Strength- In tensile testing, the ratio of maximum load to original cross-
sectional area. Also called ultimate strength. Usually expressed in
pounds per square inch.
TO- Threads Only.
Tube Round- See Billet.
Ultrasonic- An electronic method of nondestructive testing utilizing sound waves.
Yield Strength- The stress at which a material exhibits a specific deviation from
proportionality of stress and strain. An offset of 0.2% is used for many
metals including steels.


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2,279 Posts
I downloaded an image that Rockrat put up on his website and I use that to play around with designs. That is pretty much how I came up with what I wanted.

I did a lot of searching and looking at other vehicles too.

An important thing to remember when making a cage is nodes, that is, having tubes meet/welded at the same point or close to the point, it increases strength and leave less opportunity ove movement under stress. This definition of mine is kinda poor... look this up too or if I have some time later I'll pull it off of one of the threads I have saved, I just need to find it.

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10,738 Posts
One of the primary important things that specs miss out saying specifically:
You are building a SAFETY CAPSULE for the occupants. Everything within that capsule must be attached to the same thing. It has to be a unit, not a conglomeration.

Bodies separate or move from frames, engines move from frames, transmissions, steering, suspensions can move or dislocate. If your cage moves one way, and your seat moves another, and your harness moves yet another -- well you can imagine.

Notice a fighter pilot's seat belts are tied into the part that ejects, not the airframe.

Are your seats mounted to the frame? Are your belts?

Using small plates on the floor, even both sides, isn't strong. But good safe practice is to run a long plate between the cage bottom ends connecting them together, both top and bottom of the floor. That strengthens the cage bottom and attaches it to the body stoutly.
Remember - CAPSULE!

Look at how your body attaches to your frame - and the condition of the mounts. Once the cage is securely and safely tied to the body as a capsule, then it's your option to tie the frame to it.
Remember CAPSULE.

NASCAR rules etc differ a little as to frame vs body attachments, but notice NASCAR does not race open vehicles. A cage built inside the body cannot separate by far - it's trapped.

Picture this (but don't try this at home kids) a severe accident - where the frame goes one way, the cage another, and the body another. Where are the drivers legs? Torso? Head?
Take a walk around a junk yard, notice all the broken body mounts.
Notice car makers that install cages, or build them in, like Targas etc, all attach them to the body, not the frame -- remember CAPSULE.

The cage itself - remember - the idea is to take the impact energy from the side where it hit, then transfer all that energy PAST the occupants to the other side where it can dissipate.

Braces can come loose - welds break etc. Look at where the end will go if it does - does it become a spear? (I helped remove a guy that crashed bad, the brace behind him broke, went through the seat, in his back and out the front of his chest. We had to cut the brace behind him to get him out. We left the tube in him so he wouldn't bleed to death till he got to the hospital. Amazingly he lived, but I don't know for how long.) Look, Think, remember CAPSULE.

Whenever possible, all portions should extend past the driver and occupants as a solid piece without joints or welds. Ends should be pointed away from occupants.

The best off road set-ups have been shown here - where the cage has a lower section that ties from side to side and the seats and belts are mounted on it - a true safety capsule. Maybe someone has those pictures and can show them.

If you guys want the *.pdf of the documents that Rockrat posted, let me know I can e-mail them to you.

The first one has very good figures showing design.

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278 Posts
In reply to:

How do you guys feel about cross braces behind the seats

[/ QUOTE ]

Part of the reason that brace exists is to give something to which you can attach the 5 point harness. If your seat didn't brake away, that'd be one heck of an impact to push that brace into the seat. While stopped, being rear-ended at freeway speeds might do it, especially if you were close to the vehicle ahead of you. That'd be a really good day NOT to have any back seat passengers.


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93 Posts
I was more thinking along the lines of the flimsey stock sammy or whatever seat backs bending back onto the cross brace from the enhanced weight of the occupant brought on by a rear impact. Without a cross brace the seat would fold back at the hinge line and the occupant would lay flat rearward, but with a cross brace there, the seat would fold wherever the cross brace is, and so would the occupants back bone. The weight of the occupant above mid-back is pretty substantial. I guess a sturdy racing seat would take care of this problem. Just food for thought.

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2,678 Posts
It is the canadian equivelent of the SCCA, same standard i just couldnt find this bookmark SCCA
Roll Bar Tubing Chart

Minimum Tubing Size

Under 1500 lbs.
Mild Steel
1.50” O.D.x .120 wall

Alloy Steel
1.50” O.D.x .090 wall

Over 1500 lbs.
Mild Steel
1.75” O.D.x .120 wall

Alloy Steel
1.75” O.D.x .090 wall

(It is recommended that vehicles weighing in excess of 3200 pounds use 2.00" tubing).

Roll Cage Specifications

Roll Cage Division Requirements: A Roll cage is mandatory in the Super Sport and Unlimited Divisions. The roll cage must be designed and made so that, when correctly installed, they substantially reduce body shell deformation and so reduce the risk of injury to occupants. The essential features of Roll cages are sound construction (designed to fit the particular vehicle), adequate mountings, and a close fit to the body shell. Tubes must not carry fluids. The safety cage must not unduly impede the entry or exit of the Driver/Co-Driver.

Division Requirements: Bolt-in roll cages are allowed in the Super Sport SS1class and below; fully welded cages are recommended. At least one door bar must be used on both sides of the vehicle. The use of a NASCAR style door bar incorporating at least 2 bars that extend into the door and are supported by vertical upright bars is recommended. The factory side impact bar may only be removed if using a NASCAR style cage design.

Super Sport SS2 & Special Race Prepared Division Requirements: Fully welded roll cages are required. Bolt-in roll cages are not allowed. The roll cage must be welded to a major structural frame or be a part of the major structural frame. A NASCAR style roll cage is highly recommended.

Door intrusion bars are required on both sides of the vehicle. A minimum of two bars is mandatory, and three or more are recommended. The use of a NASCAR style door bar incorporating at least 2 bars that extend into the door and are supported by vertical upright bars is recommended.

The cage should be triangulated at as many points as possible and the liberal use of gussets, welded at each joint, is mandatory.

Basic Design Considerations: A roll cage is comprised of a structural frame or hoop, a perimeter roof hoop, door bars, fore and aft bracing and diagonal supports all arranged in such a manner so as to prevent occupant injury in the event of a rollover and to structurally improve the integrity of the vehicle.

The top of the roll cage main hoop shall not be below the top of the driver's helmet in a closed car and a minimum of two (2) inches above the driver's helmet in an open car when the driver is in the normal driving position with helmet on. It shall not be more than six (6) inches behind the driver.

The two vertical members forming the sides of the hoop shall attach to the outermost main chassis member.

If certification of roll cage construction cannot be provided, an inspection hole of at least 3/16” diameter must be drilled in a non-critical area of the main hoop to facilitate verification of wall thickness. This should be at least three inches from any weld or bend.

Material: The roll cage hoop and all braces must be of seamless, ERW (Electric Resistance Welded), DOM (Drawn over Mandrel) or CREW (Cold Rolled Electric Welded) mild steel tubing. Chrome alloy tubing, such as 4130, can be used but is not recommended since the strength of the area adjacent to the welds will be impaired if the structure isn't normalized, and because of the difficulty in making satisfactory welds. The size of the tubing to be used must be determined on the basis of the weight and speed potential of the car. Refer to chart below. The main hoop and support braces must be of the same size.

Fabrication: The main vertical hoop must be of one continuous length of tubing with smooth continuous bends and no evidence of crimping or wall failure. All welding must be of the highest possible quality with full penetration and will be subjected to very critical inspection. Arc welding, particularly heli-arc, should be used wherever possible. Gussets should be welded at the junction of any tubes.

On vehicles of Space frame or Frameless Design: It is important that the structures be attached to the vehicles in such a way as to spread the loads over a wide area using spreader plates. It is not sufficient to simply weld the bars to body or frame material. The roll cage must be designed in such a way as to triangulate the designed structure of the vehicle. Considerable care must be used to add as necessary to the frame structure itself in such a way as to properly distribute the loads.

Vehicles With Non-Metal Floor or Roof: The floors of these vehicles require 16-gauge steel or equivalent to be added, fabricated and fastened in such a manner as to prevent occupant legs from protruding from the vehicle in an accident should the non-metal floor material be destroyed.

Similarly, the roof area requires similar material to be fastened so as to remain a part of the vehicle if the non-metal material breaks up. It is recommended that all removable tops be additionally secured to keep them on the car in the event of a rollover.

Bracing: The braces must be of the same size tubing as used for the roll bar itself. All roll cages must be braced in a fore or aft direction with the braces attached within six inches of the top of the verticals and at an angle of at least thirty (30) degrees from vertical. A diagonal brace must be used to triangulate the main hoop and it is highly recommended that this brace be attached at the top on the driver’s side and attached to the bottom on the “passenger” side.

An additional horizontal bar to support the main hoop is recommended. In addition, this bar should be installed at the height no more than 2” above or below the driver’s shoulders while seated in the driver’s position. The shoulder harness should be attached to this bar. A head restraint is recommended.

Mounting Plates: The main hoop and braces must be attached to the frame of the car whenever possible. Mounting plates must be used for this purpose. In the case of cars with unitized or frameless construction, mounting plates must be used to secure the structure to the floor and body of the car. The important consideration is that the load be distributed over as large an area as possible, with 4”x 4x1/8” the minimum size desired for spreader plates. The plates must be tack welded or continuous welded to the car's frame. On some vehicles this exact size is not an option and square area of the spreader plate must be calculated to spread the maximum load expected in the worst-case scenario.

Other Designs: Deviations from the above will be considered.

Roll Bar Padding: Roll bar padding should be used to protect the occupants in all areas of possible contact. It must be of material readily available that is designed for this purpose.

Roll Cage Tubing Chart

Minimum Tubing Size

Under 2700 lbs.
Mild Steel
1.50” O.D.x .120 wall

Alloy Steel
1.50” O.D.x .090 wall

Over 2700 lbs.
Mild Steel
1.75” O.D.x .120 wall

Alloy Steel
1.75” O.D.x .090 wall

It is highly recommended that vehicles weighing in excess of 3200 pounds use 2.00" mild steel .095 walls.


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278 Posts
In reply to:

Without a cross brace the seat would fold back at the hinge line and the occupant would lay flat rearward,

[/ QUOTE ]

You're absolutely right. A stock seat would, and sometimes does fold back in a rear-impact. (I had racing seat in mind when I wrote that.)

I have PRP (Premier Racing Products) seats in mine. I'd be very surprised to see those fold.

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1,171 Posts
This whole rollcage/rollover idea made me think of something else that's related...crumple zones & energy dissipation. In racing they talk about how the shedding parts dissipate the forces of the crash, in production cars they design in those accordian folds so the car can bend at exact places and protect the passenger compartment. I guess I'm thinking more of exocages here..building a structure that basically keeps the whole vehicle intact...of course an exocage is primarily for extreme offroading situations, low speed flops and rock grinding and such, but maybe from an onroad standpoint an exocage doesn't allow much destruction and the forces could be higher?

It could be that building protection for a mostly onroad truck should be different from a mostly offroad truck?

Your thoughts?

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2,678 Posts
Your bringing up crumple zones and absorbtion is of great importance.. What some peole fail to see when buiding a cage is they try and make it indestructible,I want to roll many times and still have my cage intact ready for the next roll. In my opinion that is way off base when building any cage, once it has been hit hard ( it has done its job ) replace it.. Ther was a controversy on the zuwharrie board awhile back about the petroworks sport cage that folded in someones rig. My opinion was asked during what seemed to be a bash session. Here are my thoughts. Do i like the petroworks and was also asked or told that it was a crap cage since it folded. My reply was this I dont care for the design of the cage MY opinion do I think it is a crap cage NO the tubing bent which in escence ABSORBED the impact which inturn takes pressure away from the driver. Final comment the cage has to be replaced why (it did its job) the guy walked away... Again my thoughts and opinion

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3,632 Posts
That is a great point , I've built cages for dirt modified cars for years . Once they get wrecked , any section of that cage gets replaced if it was affected at all . Who cares what the pipe costs , it's harder to replace a good driver .

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2,871 Posts
Discussion Starter · #19 ·
The key to crush or crumple zones is to have a controlled crumple. uncontrolled and you can wind up outside
the cage. For most applications the core cage needs to be pretty rigid. the further out you go, the less you
want, and in some cases you triangulate to allow it to bend and give.

That's not an easy thing for the average Joe in his garage, and some engineer's aren't up to the task. With
the winged sprints and modifieds the wing itself creates a crush zone over the driver's head. The cage
immediately around the driver needs good triangulation and the area's just fore and aft need some
triangulation, but some diagonals go to the mid point of a straight run and will actually cause the section to
bend under impact.

If the primary cage over the driver's head is bending much I would not give it very high marks. A dilemma is
the concept of a family cage over the back seats. From a competitive point of view and best protection
of the driver, you should construct that section to allow bending. From the perspective of protecting passengers,
you want it to hold up better.

Exo cages actually can be set up easier to have crumple zones, and a stock position rollbar, with strategic
bracing, could provide the core capsule. That bar needs to be tied to the frame, and the seat and the
belts/harness tied to it. Obviously this is not a trivial approach to take. It has to be well thought out.
You might tie into the under-dash spreader bar for the purpose of some of the seat mounting, then tie that into a cage or exo cage.

Materials come into the picture as well. 4130 CrMo is in my experience generally well thought of for cage
and chassis material. But, it is so strong that it can become too rigid an not absorb impact, just transfer
it to the rest of the car, including the driver. I noticed that in the cage spec RR posted, mild steel was
recommended and "alloy" (4130 presumably) while allowed, was not recommended. I would think this
would be for 2 reasons. It is easier to get strong welds in mild steel, and the mild would tend to be a
throw away cage intended to bend and protect the driver in the event of one event not several.

The other problem of 4130 is to develop the full possible strength in a welded section, it is supposed to go
through a treatment most shops are not equipped to handle.

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