chromoly tubing for cage ?

[RickM415]

hello,where can i get some chromoly tubing in northen california and what size
i am wondering if its 1 5/8 .83 or .120

i want to build a 10 point cage for my 69 camaro

open to other options

[Blake Foster]

not sure where you can get it but the size depends on what rules your trying to meet
NHRA for a "Roll cage" is 1 5/8 x .083 CM or .118 MS
for road racing it is more dependant on the car weigth but most likley 1 /34 x but i would double check that spec.
also if using it for NHRA it MUST be TIG welded

[deuce_454]

not sure where you can get it but the size depends on what rules your trying to meet
NHRA for a "Roll cage" is 1 5/8 x .083 CM or .118 MS
for road racing it is more dependant on the car weigth but most likley 1 /34 x but i would double check that spec.
also if using it for NHRA it MUST be TIG welded

Thats funny.. if you use Chrome moly for any areospace application it must be welded with an oxy acetylene torch, or the weld must be annealed if tigged....

[Apogee]

I would personally use DOM mild steel over chromoly unless you're planning on post heat-treatment at the weld zones like duece_454 pointed out. There was a big fuss a few years ago about mandating chromoly cages in some of the SCORE desert classes which boiled down to the cost versus safety...the debate was about whether a chromoly cage is really safer than a DOM cage. Racing is an inherently unsafe activity, however nobody wants to pay more for something that doesn't definitely improve the safety of the rigs and/or give them some competitive advantage.

While there's no doubt that chromoly is stronger for the same wall thickness so long as it's welded properly, the debate centered around how rigid you wanted your cage to be? Cars have crumple zones for a reason and that's to distribute the force of an impact over a greater period of time since the impact is typically what does the most damage to the soft and squishy thing inside called the "driver". I think we can all agree though that once a crash begins to occur, the "driver" is really a passenger at that point.

Tobin

[NOT A TA]

I went through the whole cage thing a little over a year ago. Chromo Vs. DOM , sizing, and sanctioning body tech requirements. Here's a couple links to threads you might find informative. Beware of assuming that rollbars and cage structures you see in PT type cars are legal for any sanctioning bodies. Get the rulebooks for any sanctioning bodies where you might run the car.

http://www.lateral-g.net/forums/showthread.php4?t=16317&highlight=chromoly

http://www.pro-touring.com/forum/showthread.php?t=48151

[Blake Foster]

i have herd that the Tig om CM process is acceptable if you wrap the weld and let it cool slowly???? not that any one does it.
i think in reality to make it PERFECT you would want to heat treat the entire cage after welding, but no one is going to do that.
DOM is definatly cheaper. and the fit is not quite as critical and it can then be mig welded..

Deuce454 i know the procees is different but tig and gas welding would be esentially the same? no just that tig would be more controlable would it not?

and what is the BEST filler to use on CM if anyone can shed some light there, we use a 312 rod. only because no one sems to know what if anything is better. my fab guy has been building roadrace cars for 15 years and that is the best material he has found to date.

[mfain]

To support Killer69's point that you should check the rulebook for the type of competition you plan to participate in, I have included an excerpt from the NASA (Road Race) rule book for roll cage tubing size. The Ultimate Track Car Challenge uses the NASA rules, and the unlimited rules for the Silver State Classic are very similar. There are lots of other cage construction "rules" in this and other CCRs (SCCA, Proautosports, NHRA, etc). I've included the website for the NASA rulebook -- pages 59-64 contain NASA cage rules. Some sanctioning bodies let you use thinner wall Chrome-moly because of its strength, but NASA, for example, specifies the same wall thickness for DOM and Chrome-moly.

http://www.nasaproracing.com/rules/ccr.pdf

15.6.18 Roll Cage Tubing Sizes
For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing thicknesses. Minimum tubing size for the roll cage is:
Up to 1500 lbs.
1.375” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1501 - 2500 lbs.
1.500” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.
2501 - 3000 lbs.
1.500” x 0.120” Chrome-moly / Seamless mild steel (CDS or DOM)
1.750” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.
3001 - 4000 lbs.
1.750” x .120” Chrome-moly / Seamless mild steel (CDS or DOM)
No ERW allowed.

[GregWeld]

4130 Chrome Moly tubing can be welded with ER70S or ER80S (stronger)... using TIG... best with a gas lens... and keeping the heat under control or you pull the carbon out. Pre and post heat are only required on .125 wall or thicker. Quenching would cause cracking.

[GregWeld]

312 SS rod -- also called "supermissle" -- EASY to weld with - wets out nice and doesn't magnetize.... good material choice for Chrome Moly tube and has a tensile strength of 120,000 which is higher than the 70 or 80 (which is 70 or 80,000 depending on the rod used as the numbers indicate).

[ccracin]

From what I recall all Nextel Cup chassis are Cold Drawn Seamless tubing.

DOM is not necessarily stronger than ERW (Electric Resistance Welded) for a given alloy. DOM (Drawn Over Mandrel) has a more consistent size and shape so that it has consistent properties in any direction for lack of a better term. DOM still does have a seam that is fused therefore you still have a heat affected zone down the length of the tube. After the tube is formed and welded, it is then pulled over a mandrel to accurately form the shape which provides a more uniform wall thickness, ID, OD. This also does some cold working and can possibly add some strength.

CDS (Cold Drawn Seamless) tubing is formed from a solid carbon steel bar by drawing it over a mandrel to form it's shape. Therefore there is no welded seam. This process also cold works the steel and improves it's mechanical properties.

Chromoly Tube is basically CDS tubing made from 4130 alloy steel. Standard CDS tube is typically 1018 or 1020 carbon steel. The 4130 alloy has greater tensile and yield strength than 1020 while maintaining good ductility. However it does require certain things be done before during and after the welding process to ensure the weld integrity as well as the quality of the base metal in the heat affected zone of the weld.

As said before, Chromoly is not lighter than CDS or DOM. Because it has better mechanical properties, you can typically use less wall thickness for a given tube than CDS or DOM.

I am not a metallurgist or welding engineer, but it is my opinion that you should not attempt to use 4130 unless you are well schooled on the requirements of properly welding this material. I have seen failures that can be attributed to not doing it properly and by people that say gee "I have done it like this for years with no problem". They just got lucky for years. I can't go into the proper procedure because frankly, I don't know it. Meaning there are different methods for different thicknesses, weld processes and weld joint configurations.

Honestly, these same considerations should be taken into account for any structural/safety related weld. I can weld, but when it comes to these types of welds I get a friend and certified professional welder to do it for me. I think it is worth it.

Well, thus ends me running off at the mouth. Don't take this as gospel just me trying to pass on some information I picked up along the way. Sorry for the book. Hope it helps. :cheers:

[GregWeld]

I think Chrome Molly is only ever used where WEIGHT is a major factor -- otherwise - why bother... DOM is fine for most of us...

What book Chad! You only got thru page one! :rofl: :rofl:

[ccracin]

I think Chrome Molly is only ever used where WEIGHT is a major factor -- otherwise - why bother... DOM is fine for most of us...

What book Chad! You only got thru page one! :rofl: :rofl:

That's all I could do, I only type with 2 fingers! :rofl:

[Blake Foster]

I think Chrome Molly is only ever used where WEIGHT is a major factor -- otherwise - why bother... DOM is fine for most of us...

What book Chad! You only got thru page one! :rofl: :rofl:

i would say your 100% correct on this one.
CM is typically 30%-35% lighter that .134 wall dom. so if you had 80 feet of material in a road race cage you might save 50-80 lbs (just guessing here) the DOM is 1/2 the cost of CM if not less. the labor savings is probably 1/2 for the install
that being said i have 3 lengths of CM sitting here waiting for the new project to arrive, but if it wasn't on the rack i don't think i would spend the extra $$$ to use it. if i was building a Comp Eliminator or Prostock car then there wouldn't even be an option it would be CM. but a track day car or super class car, there are alot of other places to loose 50-80 lbs.

[ironworks]

i would say your 100% correct on this one.
CM is typically 30%-35% lighter that .134 wall dom. so if you had 80 feet of material in a road race cage you might save 50-80 lbs (just guessing here) the DOM is 1/2 the cost of CM if not less. the labor savings is probably 1/2 for the install
that being said i have 3 lengths of CM sitting here waiting for the new project to arrive, but if it wasn't on the rack i don't think i would spend the extra $$$ to use it. if i was building a Comp Eliminator or Prostock car then there wouldn't even be an option it would be CM. but a track day car or super class car, there are alot of other places to loose 50-80 lbs.

I know I could stand to lose more weight personally on my body, then I ever could with a 4 or 6 point cage. I bet you lose more weight with Lexan windows or Anvils carbon parts is you have a 1st or 2nd gen camaro.

[RickM415]

ok so lets say i go dom tubing then 1 3/4 .134 would get me in to all the pro-touring events ?...and where to get it in nor cal ?

[Apogee]

ok so lets say i go dom tubing then 1 3/4 .134 would get me in to all the pro-touring events ?...and where to get it in nor cal ?

Based on what I've seen, 1-3/4" x .0120 DOM mild steel will get you onto most tracks, but the design has to be compliant as well as the material. If you go too thick on the wall, you limit your bend radius options for conventional mechanical die/follower type tubing benders, hence the reason I wouldn't exceed .120 on the wall thickness.

Tobin

[RickM415]

ok so now that we got the material figured out ....where can i get it

[ironworks]

ok so lets say i go dom tubing then 1 3/4 .134 would get me in to all the pro-touring events ?...and where to get it in nor cal ?

Define Pro-touring events? I think Silver state has the biggest mandate. The single day non competitive events should not require anything I believe.

[eville]

Check these guys in Hayward. I bet they can hook you up.

http://www.naylorsteel.com/

[nvr2fst]

Define Pro-touring events? I think Silver state has the biggest mandate. The single day non competitive events should not require anything I believe.

SIVER STATE CHALLENGE
ROLL BAR SPECIFICATIONS Roll Bar: A Roll Bar is mandatory in the Grand Sport Division, and recommended in Grand Touring
and Touring.
Basic Design Considerations: The basic purpose of the roll bar/roll cage is to protect the driver in case the vehicle rolls over. This purpose should not be forgotten.
A.
B. C.
The top of the roll bar 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. It shall not be more than six (6) inches behind the driver.
The two vertical members forming the side of the hoop shall not be less than fifteen (15) inches apart, inside dimensions, at their attachment point to the uppermost chassis member.
An inspection hole of at least 3/16-inch diameter must be drilled in a non-critical area of the roll bar member to facilitate verification of wall thickness. This should be at least three inches from any weld or bend.
D. Cars with factory built or factory reinforced roll structures may be allowed in the Grand Sport Division. They will be evaluated on a per car basis. The decision of the Event Director will be final.
Material: The roll bar hoop and all braces must be of seamless DOM (Drawn over Mandrel) mild steel tubing 1010 thru 1025 or alloy tube steel SAE 4130 chrome moly. Proof of alloy, leave unpainted. All NEW roll bars must meet or exceed this requirement.
A. The size of the tubing to be used must be determined on the basis of the weight of the car. (pg. 16)
Fabrication: The main vertical hoop must be one continuous length of tubing with smooth mandrel bends and no evidence of crimping or wall failure. No bend radius will be smaller than 3 times the tube diameter.
A. All welding must be of the highest quality with full penetration. All attachments points must be welded 360 degrees around the tube. Welding must conform to American Welding Society codes.
B. It is recommended that gussets should be welded at the junction of any tubes. Bracing: it is recommended that braces be of the same size tubing as used for the roll bar itself.
A. B.
C.
All roll bars must be braced in a for or aft direction with the brace attached within six (6) inches of the top of the hoop, and at an angle of at least thirty (30) degrees from vertical.
It is required that a diagonal brace 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. See Exhibit A
A headrest is required if not part of the seat.
Revised 1/2010 - Page 15 -
6.
7.
8.
9. 10.
11.
Mounting Plates: Roll bars and braces must be attached to the frame of the car whenever possible. Mounting plates must be used for this purpose. When the main hoop is attached to sheet metal, such as a floor attaching point for unibody cars, the mount plate must be at least 36 square inches (6” x 6” plate) on both sides of the sheet-metal or that provided by the manufacturer. If possible the plate should extend up the vertical wall.
A. A minimum of double-nutted 3/8 inch grade 5 bolts for self-locking or welded nuts shall be used to bolt to the car. No bolts are needed if the bar is welded to the car’s frame. Plates welded to the floor must be at least as thick as the bars tube.
B. In the case of cars with unitized or frame less construction, mounting plates must be used to secure the roll bar structure to the floor of the car. The important considerations is that the load be distributed over as large an area as possible. Plates bolted to the floor must be at least 3/16 inch thick and be placed on both sides of the sheet metal. A back-up plate of equal size and thickness must be used on the opposite side of the panel with the plates through- bolted together.
Removable Roll Bars: Removable roll bars and their braces must be very carefully designed and constructed to be at least as strong as a permanent installation. If one tube fits inside another to facilitate removal, the removable portion must bottom on the permanent mounting, and the mounting hardware used to secure each joint must be grade five (5) or better. It is recommended that the telescope section be at least eight (8) inches in length.
Installations on Cars of Space Frame or Frame less Design: It is important that the 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. 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 and single tube of the frame.
On cars of frame less construction, consideration should be given to using a vertical roll bar hoop of 360 degrees completely around the inside of the car, and attaches with suitable mounting plates. This type of roll bar then becomes a substitute for the frame.
Other Designs: Deviations from the above will be considered. Roll Bar Padding: Roll bar padding must be used to protect the Driver/Navigator in all areas of
possible contact.
Minimum Tubing Sizing: The size of the tubing to be used shall be determined on the basis of the weight of the car.
Under 2200 lbs. 2200 to 3000 lbs.
3000 to 4000 lbs Over 4000 lbs
DOM 1.50” O.D. X .095 wall mild DOM 1.50” O.D. X .095 wall alloy
DOM 1.75” O.D. X .120 wall mild DOM 1.75” O.D. X .095 wall alloy
DOM 1.75” O.D. X .120 wall mild or alloy DOM 2.00” O.D. X .120 wall mild or alloy
Revised 1/2010 - Page 16 -
XI.
ROLL CAGE SPECIFICATIONS
4
4
3.
4.
5.
1. 2.
Roll Cage Division Requirements: A roll Cage is mandatory in the Super Sport and Unlimited Divisions.
Super Sport & Unlimited Division Requirements:
A. The cage may be removable or may be permanently welded, or any combination thereof, providing that all aspects of the cage meet these rules.
B. A NASCAR style roll cage is highly recommended.
C. Material, Fabrication, Bracing and Installation specifications are the same as the specifications for a Roll Bar. See Section X, pages 15 & 16 for detailed information.
D. None of the tubing may show any signs of crimping or wall failure. All bends must be Mandrel type
E. One continuous length of roll bar tubing shall be used as the main hoop. The main hoop must consist of not more than four (4) bends maximum, totaling one hundred eighty (180) degrees +/- ten (10) degrees.
F. At least one (1) diagonal brace must be used in the same plane as the main hoop. One end of the diagonal brace shall attach to the corner or horizontal part, of the main hoop above the drivers' head, within twelve (12) inches of the drivers'-side corner.
G. The forward hoops extend from the main hoop (in a forward direction) to the floor by following the roof and the "A" pillar of the car. There must be a bar connecting the two (2) forward hoops at the top of the windshield mounted as close to the roof as possible.
H. The main hoop must have two (2) braces extending to the rear. The braces shall be attached as near as possible to the top of the main hoop, and no more than six (6) inches below the top.
I. At least two (2) door bars on the driver and passenger sides must be used. The top door bar crossing height between the shoulder and elbow may be angular or horizontal. The second door bar should be horizontal.
J. The roll cage shall be mounted to the floor of the car in six, seven, or eight points. All cage attachment points must be mounted to plates.
K. Welded mounting plates must be at least as thick as the tube wall.
L. The attaching points of a bolt-in cage to the body must use reinforcing plates to sandwich the body. At least three bolts are required for each bolt-in plate and the plate must be at least 3/16 inch thick. All hardware must be SAE grade 5 or better with 3/8 inch diameter minimum. All nuts must be held by a locking system, such as lock washer, or jam-nuts.
M. All welding must be of the highest quality with full penetration. All attachment points must be welded 360 degrees around the tube. Welding must conform to American Welding Society codes.
N. All required bars must be made of the same material and meet with at least the minimum specifications for size and thickness.
O. All roll cage surfaces that may come in contact with the driver must be padded with high- density padding such as Ethafoam or Ensolite.
Specification: See Roll Bar Specification for the roll cage fabrication specification. Main Hoop and Braces: The main hoop and support braces should be of the same size.
Minimum Tubing Sizing: The size of the tubing to be used shall be determined on the basis of the weight of the car.( pg. 16 )

[ProdigyCustoms]

I love these sites. I am able to give advice and share my experiance and make a living doing this. How cool is that.

Know what is even more cool? When a thread like this comes up and really makes me think. Making me think enough that we may change our views on a important decison we are about to make on Project Unfairs cage.

Up until this thread got me really doing some math, we had it in our heads we would use Chrome Moly. But when I do the math, best I can figure we will save 40LBs to 50LBS at best by using .95 Wall Chrome Moly (1.679 lbs per foot) VS .120 Wall DOM (2.089 lbs per foot). Now it is 40LB to 50LBS of which about 2/3 the weight is above the COG. But best I can figure in fast math with out litterly measuring everything the net weight above the COG , deducting the offset weight of the cage material that is below the COG may only be 20LBS different! And while we are watching our weight we are really watching our COG as much as anything.

Like Rodger said. A few trips to the Gym and a little chicken instead of pasta would probably be easier and better for me.

[Vegas69]

Frank, that reminds me of when I picked up my ZL-1 block at Randy Walkers shop in So Cal. He runs pro-street in the PSCA and was contimplating spending 3,4,5 grand to shed 30lbs off the car. He decided to lose the weight. :lol:

[Vince@Meanstreets]

I love these sites. I am able to give advice and share my experiance and make a living doing this. How cool is that.

Know what is even more cool? When a thread like this comes up and really makes me think. Making me think enough that we may change our views on a important decison we are about to make on Project Unfairs cage.

Up until this thread got me really doing some math, we had it in our heads we would use Chrome Moly. But when I do the math, best I can figure we will save 40LBs to 50LBS at best by using .95 Wall Chrome Moly (1.679 lbs per foot) VS .120 Wall DOM (2.089 lbs per foot). Now it is 40LB to 50LBS of which about 2/3 the weight is above the COG. But best I can figure in fast math with out litterly measuring everything the net weight above the COG , deducting the offset weight of the cage material that is below the COG may only be 20LBS different! And while we are watching our weight we are really watching our COG as much as anything.

Like Rodger said. A few trips to the Gym and a little chicken instead of pasta would probably be easier and better for me.

or let the stig drive it. :thumbsup: LOL


That metal supply shop on the corner of Davis and Doolittle can get it. I usually buy my stuff at Alstons if you don't mind a Sacremento trip. Its not cheap. Just go with the DOM. 1 3/4" will keep you safe in most sanctions.


Vince

[mfain]

I found out the hard way that it is far better to build the cage "by the book" the first time than it is to replace bars after the fact. Note also that some of the sanctioning bodies have upcoming rule changes (2011) that mandate two (vice one) doorbar. I also spent a lot of time moving my battery cut-off switch and adding an aluminum firewall between the fuel cell and passenger compartment of my plastic car to conform to rule changes. Another hint is that the sooner you get your car certified by one (any) sanctioning body, the sooner it is "grandfathered" for future rule changes, and you can usually race in other series with an SCCA or NASA certification.

Pappy

[chicane]

Read these two threads about materials selection:

This one (http://www.lateral-g.net/forums/showthread.php4?t=17414&highlight=4130)

And this one (http://www.lateral-g.net/forums/showthread.php4?t=16317&highlight=4130)

[toddshotrods]

This is an awesome thread! :bow: Very timely for me to find it now, as I will need to do a cage for my race rod eventually, and would have been really tempted to fall into the "moly" trap. I was doing it to save weight, but had assumed the savings would be more than thy really are. After reading this thread, and since my main rails are mild steel, it seems logical now to do the cage in mild steel.

One question: Is there any problem with TIG welding mild steel? What filler rod is recommended? Anything special that needs/should be done?

[coolwelder62]

The use of 4130 over mild steel is for wt.# saving's.1.75X.095 4130 weighs the same per foot as 1.75x.095 mild steel tubing.4130 is about 60% stronger than mild steel so you can use a thinner wall thickness than mild steel to abtain the same amount of strenght in your roll cage or chassis.Most of the drag race chassis builder's I've seen use a gas lense as Greg say's and never post heat the tube joint anymore.They just hold the torch over the weld puddle after finishing the weld and let the post flow cool it down.If you keep the ambiant tempure down you should not have any weld joint failure.You will know when your weld temp is right your weld on 4130 will a rainbow of gold to blue.To hot and the weld will turn out all grey & will see small stress cracks if you use a mag. glass.

[toddshotrods]

Thanks coolwelder, but those are moly tips. What about TIG on mild steel? Any issues.

I was going to use moly, but my weight savings would be even less than ProdigyCustoms because of the size of my cage and vehicle. I am seriously thinking about just using DOM and chasing the weight away somewhere else.

[coolwelder62]

DOM tubing can be tiged or mig welded. I like to tig weld every joint on a roll cage.It look's better,I know the weld is better,and it show's I have pride in my work to take the extra time to tig weld it.Mig welding is fine if that's the only way you have of getting the job done.Most Nascar chassis's are mig welded.And if a customer ask for it to be mig welded I will do it as they ask.I will be starting on a roll cage for my 72 camaro shortly.It will be 1.75X.125 DOM seamless tubing.And I will tig weld it all togather.Will post some photo's as I progress along w/the car.:thumbsup:

[toddshotrods]

DOM tubing can be tiged or mig welded. I like to tig weld every joint on a roll cage.It look's better,I know the weld is better,and it show's I have pride in my work to take the extra time to tig weld it...
Thanks coolwelder. :thumbsup: Those are the reasons I want mine TIG'd as well. :cool:

[coolwelder62]

Todd what tig welder are you going to use.A gas lense will make a world of differant's in the weld apearance.Use a 1/16 2% tung. No bigger than 3/32. super sharp point. ground w/tung str. up to grinder wheel or sander.I like post flow about 3-5 seconds.Using a gas lense about 13-15CFM argon.Thanks Scott.

[toddshotrods]

It will be done with a Miller. I work out of two different shops here for fab work. One has an older Miller, can't remember the exact model - I'll get that information. The other has new a Miller Synchrowave 200 ordered. I think the two machines are pretty similar.

Thanks for sharing - copying and pasting that into my little project's "tech" folder. :thumbsup: