tech/safety questions

[josht]

are there any tracks on the east coast that let you run with shaved door handles?

I am looking at a eight point cage for the 68 Pontiac GTO, what material should the cage be made out off?

Does it have to be bolted in or is welding the roll cage in allowed?

Consideration is on saving weight, as they should all perform the same?

I was looking at these 8 Point Roll Cages from S&W:
Part number:
11-1003-CM 68-72 Chevelle, GTO, Tempest, Skylark, 442, Cutlass, 1-3/4" x .083" wall moly tubing. $399.95

Part number:
11-1003 1968-1972 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" x .134" wall tubing (mild steel) $169.95

Part number:
11-1003-DOM 68-72 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" X .120" Wall DOM tubing. $399.95

Between DOM and Chrom Moly which one is lighter?
Is one easier to weld if that is a track requirement?

[jason@gmachine]

Use at least DOM .120 wall.

Chromoly is not lighter than DOM, they are the same weight. The onlt weight saver is the ability to use .095 wall 4130 instead of .120 DOM. That is where the weight savings come into play. And chromo is stronger.

IMO i would never use a bolt in cage, its just not safe. Take the time and weld it in.

Jason

[MonzaRacer]

If it was me I would buy a kit with the proper dimensions and bolt in then I would weld it in if it fit my needs.
S&W are a great bunch and I used to sell thier products and all are top notch.
After installing it (ie welding it) you could remove the bolts and weldthe holes up. Remeber to talk to your welder about welding chrome moly to steel. SOME welders use thier favorite wire or welding rod and it sometimes wont take on the steel to chro-mo weld.
Been there had to have a floor pan replaced as the guy doing the welding wouldnt use the proper wire(he bought his stuff years ago at big lots and its cheap chinese stuff that doesnt weld well on disimilar metals/dirty metal) as it can be welded it just takes good wire and proper technique.
Also cheap Chro-mo is a bitch to get welded unless you know EXACTLY the metalurgy. A friend of mine bought an Alston roll bar from the original Alston chadssis compnay before it got sold to the guy in Illinois. They had a bad load of Chro-mo and had to replace his cage,,,he goes back and buys from the new owners a few years later and he got swindled too on cheap stuff. My worry is in it being incosistent or not even Chro-mo (technicaly)and not passing tech.
Good luck.
Lee

[jason@gmachine]

Remeber to talk to your welder about welding chrome moly to steel. SOME welders use thier favorite wire or welding rod and it sometimes wont take on the steel to chro-mo weld.
Been there had to have a floor pan replaced as the guy doing the welding wouldnt use the proper wire(he bought his stuff years ago at big lots and its cheap chinese stuff that doesnt weld well on disimilar metals/dirty metal)


When welding 4130 or DOM 1020 cage work you always use mild filler rod or wire, never use 4130 filler, unless you are going to heat treat the chassis or part you are welding. 4130 can easily be joined with 1020 and i have done this many times. If a welder is not skilled enought to weld 4130 to 1020 then welding a cage might be a little over thier head.

The chinese stuff is a no bueno when welding. The phrase "you get what you pay for" is very important with cage welding and welding in general. I suggest not buying any welding materials from anywhere other than a certified Miller/Lincoln dealer such as an Airgas. For body work or other oddball welding jobs the cheaper stuff will work just fine. But when it comes to yours or someones elses life, i would not trust anything less than the best.


I say this because we have a customer that got a car caged about a year ago from a "builder" and well it is very scary. He is now taking a sawzaw to it and we are building a new cage in it. It was so bad that it did not even pass tech at Irwindale Dragstrip open night. All to often i see unsafe welding and cagework. Dont trust your life to just any "builder" or "welder", make sure you do some research and see for yourself what quality looks like. Now im not saying that every cage builder expect for my shop are not of quality, im just saying that there are many that are down right scary. I know many builders that are great and there is a long list of professional shops that can build great cages.


Jason

[jason@gmachine]

I was looking at these 8 Point Roll Bars from S&W:
Part number:
11-1003-CM 68-72 Chevelle, GTO, Tempest, Skylark, 442, Cutlass, 1-3/4" x .083" wall moly tubing. $399.95

Part number:
11-1003 1968-1972 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" x .134" wall tubing (mild steel) $169.95

Part number:
11-1003-DOM 68-72 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" X .120" Wall DOM tubing. $399.95



I would pick the DOM first, because of the thickness of .120 wall. This is because the .083 wall moly does somewhat concern me, i would never use less than .095 moly, IMO the .083 is to thin for cagework. I would not even consider the Mild no matter how thick it is. Anyone that has seen mild bend in a wreck will know what im talking about. The mild will fold like a "noodle". The DOM seems to be the best bet in this case. Whatever one you pick, please stay away from the Mild, your life will thank you for this.

BTW, a roll bar is different than a roll cage. So a 8pt roll bar is not the same as a 8pt cage. just FYI.

Keep it safe and have fun.

Jason

[josht]

I was looking at this 8 Point Roll Bar from S&W:

Part number:
11-1003-DOM 68-72 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" X .120" Wall DOM tubing. $399.95

you wrote that bars are not cages, help me out here please...

S&W calls the 10 point roll cages but the 8 point roll bars. Jegs & Summit, can not find DOM both have mild steel (you wrote that mild steel is NOT recommended). Both have 8 & 10 point listed as roll bars but then list them as roll cage kits.

I need to purchase a kit for various reasons, is there a specific one to purchase?

thanks

[Camaro Zach]

I would pick the DOM first, because of the thickness of .120 wall. This is because the .083 wall moly does somewhat concern me, i would never use less than .095 moly, IMO the .083 is to thin for cagework. I would not even consider the Mild no matter how thick it is. Anyone that has seen mild bend in a wreck will know what im talking about. The mild will fold like a "noodle". The DOM seems to be the best bet in this case. Whatever one you pick, please stay away from the Mild, your life will thank you for this.

BTW, a roll bar is different than a roll cage. So a 8pt roll bar is not the same as a 8pt cage. just FYI.

Keep it safe and have fun.

Jason not sure if you understand it or not but DOM IS MILD STEEL! it is just seamless "drawn over mandrel"

[jason@gmachine]

not sure if you understand it or not but DOM IS MILD STEEL! it is just seamless "drawn over mandrel"

When i refer to MILD that means HREW 1020, that is a welded seam. In this industry it is very common to refer to HREW 1020 as MILD.

Not sure if you understand it but DOM is stronger in tensile strength
than HREW 1020 (mild) steel. I do not know the exact numbers off the top of my head but I have them on my desk at the shop where I build cages 6 days a week, for both race and street. I would never use HREW 1020 (mild) in cage work. Yes, DOM is made out of 1020 but it’s the actual process on how its made that makes the difference. DOM has more accurate ID and OD measurements than HREW 1020 and IMO welds and bends better. DOM also has a more constant spring back reading when bending. I could go on for days and get extremely technical about cage work and materials used. There is no reason to make it complicated; I try to keep it simple so the average joe does not get confused. So, that is why I use the term MILD for HREW 1020.

Thanks for the very professional comment,

Jason

[jason@gmachine]

I was looking at this 8 Point Roll Bar from S&W:

Part number:
11-1003-DOM 68-72 Chevelle, GTO, Skylark, Cutlass & 442, 1-3/4" X .120" Wall DOM tubing. $399.95

you wrote that bars are not cages, help me out here please...

S&W calls the 10 point roll cages but the 8 point roll bars. Jegs & Summit, can not find DOM both have mild steel (you wrote that mild steel is NOT recommended). Both have 8 & 10 point listed as roll bars but then list them as roll cage kits.

I need to purchase a kit for various reasons, is there a specific one to purchase?

thanks

Here is the part number you are talking about.

https://static1.pt-content.com/images/noimg.gif

the reason this is called a ROLL BAR is because it is simply a supported main hoop that will prevent the roof from coming down during a roll over. It does not have forward mounting A-Pillar bars with a forehead bar to make it into a CAGE.

A Cage has a structure that wraps around the drivers head. This pic below is thier addition to this ROLL BAR to make it into a CAGE.
https://static1.pt-content.com/images/noimg.gif

If you add this to the ROLL BAR then weld it all up, you will then complete the ovberhead portion of the CAGE to make it a CAGE.

Here is what a CAGE looks like.
https://static1.pt-content.com/images/noimg.gif

This is considered to be a 6pt cage.

Now, I do not use any MILD (HREW 1020) in cage work simply because i know from experience that it’s not strong enough. MILD (HREW 1020) is weaker in strength than DOM but the cost is much less. I have seen MILD (HREW 1020) in an accident, and it will fail well before the DOM and even more so before the 4130. For some track time and mainly street use I suggest nothing less than 1.75" by .120 wall DOM and for race applications I suggest nothing less than 1.75" by .095 wall 4130 Chromoly. Summit and others sell these cages as "MILD" and not DOM. I personally think those cages are a joke. They are not safe and i will never install of even drive a car with one in it. They sell the "MILD" because they can make easy money off of it. The cost of the steel in those is only about 60-100 dollars. They never fit right and still offer only a min amount of protection. Cage building is a skill that takes lots of practice and patience.


Your best bet is to get a well known shop to build a custom setup for your specific application. It will cost you more, but in the long run you will be happier. I get customers all the time that are kicking themselves in the foot because they did not get a custom setup first.

I hope this post explained what you were looking for. I’m just trying to help you out!

Jason

[Camaro Zach]

When i refer to MILD that means HREW 1020, that is a welded seam. In this industry it is very common to refer to HREW 1020 as MILD.

Not sure if you understand it but DOM is stronger in tensile strength
than HREW 1020 (mild) steel. I do not know the exact numbers off the top of my head but I have them on my desk at the shop where I build cages 6 days a week, for both race and street. I would never use HREW 1020 (mild) in cage work. Yes, DOM is made out of 1020 but it’s the actual process on how its made that makes the difference. DOM has more accurate ID and OD measurements than HREW 1020 and IMO welds and bends better. DOM also has a more constant spring back reading when bending. I could go on for days and get extremely technical about cage work and materials used. There is no reason to make it complicated; I try to keep it simple so the average joe does not get confused. So, that is why I use the term MILD for HREW 1020.

Thanks for the very professional comment,

Jason Thanks buddy, just wanted to clear it up for the people that don't know. So they would understand that DOM is not some exotic metal.

[chicane67]

Beyond all that has been said...

It is going to up to the sanctioning body (and the class in which you build your chassis to) to what your roll cage requirements will be.

We can talk all day long about material... but it doesnt mean shee'ot if doesnt meet the requirements for your chosen class, in the respective sanctioning body.

To further the material thought process, unless your entire chassis (frame/unibody etc) is made up of ChroMo... you will be inspecting it for cracks 10 times more than all other materials combined. Not to mention that you'll need someone that knows ChroMo and the requirements to properly weld it. Embrittlement is the biggest issue with ChroMo.

Any new chassis requiring a 'stamp' or certification will be required to be at a minimum of DOM to meet SCCA rules and regulations. SCTA-BNI, USFRA requirements are different... as are that of the American Iron Series.

There is nothing wrong with Mild Steel. In fact, if you wad up your car... MS and DOM are going to be the ones who win the war... unless your entire chassis is made up of ChroMo. Ask the chassis builders of Land Speed Record and NASCAR chassis. But in my opinion... I would choose DOM.

Some people believe that 4130 chromemoly cars are stronger than mild-steel cars. Not necessarily true. While 4130 tubing is a stronger material, because it’s made out of an alloy steel, the rules let us use thinner material (.083- and .065-inch wall). Thus, a stronger material that has a thinner wall is about as strong as a thicker-wall mild steel. The 4130 chassis is going to be 20- to 25-percent lighter because it’s made out of thinner material; there’s simply less steel in the car. Basically, what you’re paying for when you buy a 4130 car is weight reduction. In a basic cage, you pay about $XXX extra to save 70 to 80 pounds.

Now, some guys would pay a fortune (as would I) for 70 to 80 pounds. But, you have to ask yourself: “Could I spend $XXX somewhere else, and be better off?” If you have cast-iron cylinder heads on your engine, and you want a 4130 chassis, you’d be better off buying aluminum heads. If you’re going to go fast you probably should consider 4130, but remember the difficulties and challenges involved with using it. The only real disadvantage to 4130 is that it must be TIG-welded for any serious effort. That means every single accessory, bracket and tab has to be TIG-welded. For the first-time, build-it-yourself type of guy, this is not the way to go. In fact, he shouldn’t even consider it. Chromemoly is for a higher-skilled, more capable fabricator. Mild steel, on the other hand, is extremely forgiving.

Just a few thoughts... and an opinion. When you study rule books from different sanctioning bodies long enough... and talk to those doing the actual 'Tech' inspection... you learn a little more than hear-say.

Straight out of the ECTA, on this very subject:


Mild Steel vs. 4130 Material

There is a myth that a chassis constructed of 4130-chrome molly is “stronger” than mild steel one. While 4130 is a stronger material, the rules allow us to use a thinner wall thickness (.083 8 .065). Therefore, the 4130 structure will be 25 to 30% lighter than mild steel. This may or may not be a consideration in your planning. Other factors to consider are the cost (about $900 more for 4130) and ease of construction. A mild steel chassis can be MIG welded (Metal Inert Gas) while the 4130 tubing requires the TIG method (Tungsten Inert ~Gas) and must be done by a professional.


Mild Steel Wall Thickness

Although the rulebook only requires .120” wall tubing thickness in a mild steel application, it would be wise to use .134 (11 ga.). You must be aware that .120 wall tubing can vary by production runs and can be within acceptable industry mill spec standards yet being under the minimum .120 nominal wall thickness! Since NHRA has instituted the .118 minimum, I have had to repair many “new” cars as thin as .113!
When ordering tubing from a steel supplier, specify ASTM A51 3 Type 5, DOM (Drawn-Over-Mandrel). This material is a cold drawn electric resistance welded tube with all flash removed. Each tube is tested for soundness of weld. It is made from 1020 steel in walls up to 10 gauge and 1026 steel in walls heavier than 10 gauge. Normalizing and cold drawing over a mandrel makes DOM a uniform and precision Product. It is preferred over seamless tubing for it’s excellent O.D. & I.D. concentricity.
Cold Drawn Seamless Tubing (ASTM A519) is another good choice but availability in .134 wall thickness is limited. It is made from 1026 steel, produced to OD & ID dimensions; and it is furnished in “As Drawn” condition. Cold Drawn Seamless offers good surface quality and increased mechanical properties over hot finished seamless tubing.

[jason@gmachine]

I agree with 90% of what chicane67 is saying. He has many good points about the weight reduction and rule books.

I do have a different stance on a few things though!

Personally I think any 4130 that is less than .095 wall is to thin for cage work, this is because I spent years seeing chassis made of that just get torn up and the .095 sections staying together.

The other thing is that:

"The only real disadvantage to 4130 is that it must be TIG-welded for any serious effort. That means every single accessory, bracket and tab has to be TIG-welded. For the first-time, build-it-yourself type of guy, this is not the way to go. In fact, he shouldn’t even consider it. Chromemoly is for a higher-skilled, more capable fabricator. Mild steel, on the other hand, is extremely forgiving."

I do not agree completely, MIG welding 4130 will work great and actually is preferred in many applications because with TIG there is more of a tendency to find cracks. Now some may think I’m crazy but I learned from some of the best fabricators in the industry. Several class 1 cars and TT's are MIG welded 4130 and they actually hold up better and need less prep than TIG 4130. Herman Motorsports is a good example of this, they MIG weld 4130 chassis all the time, and we even had a MIG welded 4130 NASCAR chassis that was one of our main cars. It is very common in off-road to see MIG welded 4130, and the forces those chassis see are far greater than the forces seen in road-racing and NASCAR. In fact I’m building a CLASS 5 right now for my race team and on the rear 4130 trailing arms I went with MIG welding because of the problems with TIG cracks. The chassis will be 90% TIG welded though, because I can TIG to the level required. NOW, a proper TIG weld is stronger, but not by much, over a proper MIG weld. So:

Should the first time builder use 4130 and MIG it?
NO, only an experienced MIG welder, one who is very confident welding cages. Certification does not matter in this, I have seen many so called "certified" welders just weld some down right scary stuff.

Is it ok to MIG weld 4130 in cagework?
YES, in fact not only are many chassis MIG welded but 90% of production Long Travel 4130 off-road suspension kits are MIG welded and are even race proven, ex. Camburg Engineering.

Does every bracket have to be welded via TIG if the entire chassis is?
NO, those brackets welded via MIG will be less prone to cracks if welded properly by a professional welder.

Is 4130 recommended for a higher skilled builder?
YES, it is less forgiving than DOM or MILD.

Is this post an attack on chicane67?
NO, this is not directed toward him, its just different strokes for different folks.:cheers:


Jason

[chicane67]

I dont take that way... its all good.

Now, most of what I did post... is right out of the rule books. It doesnt fully support what I do think and believe to be true... just like your point on tubing thinner than 0.095". Out of experience there is romm to move in certain directions, specifically when dealing with rollcage design and materials. When you get into full tube chassis... the world is a little different. I too have mucho experience in the full tube world... and we MIGed 4130... but just like you said, an experienced MIG welder is the key.

I started way... way... back in '90 building class 7 and class 10 unlimited chassis and LT "water pumpers" before they became the norm. I then went into the road race world in the ranks of SCCA... and then into SCORE Trophy Truck and Pro Truck world... and it all shares pretty much the same views. So yeah, I agree with what you said... I just dont steer 'first timers' into the more difficult direction up front.

I actually use various diameters and wall thickness' throughout the chassis. For main hoops I like 0.120" and everything else you hang off of it can be whatever. Some attributes just dont need to be 0.120" or 0.065" for that matter.... the design and its execution when fabricated has more to do with it than whats on the surface in this thread.

:bananna2:

[josht]

With all that has been posted, I don't think that the guy doing my body work has enoughf experience welding cages. He does great body work but was not familiar with the differences between DOM & chrom-moly.

The best thing would be to send the car out for a cage....

Any recommendations for places in Nassau County, New York?

Thanks

[jason@gmachine]

I dont take that way... its all good.

Now, most of what I did post... is right out of the rule books. It doesnt fully support what I do think and believe to be true... just like your point on tubing thinner than 0.095". Out of experience there is romm to move in certain directions, specifically when dealing with rollcage design and materials. When you get into full tube chassis... the world is a little different. I too have mucho experience in the full tube world... and we MIGed 4130... but just like you said, an experienced MIG welder is the key.

I started way... way... back in '90 building class 7 and class 10 unlimited chassis and LT "water pumpers" before they became the norm. I then went into the road race world in the ranks of SCCA... and then into SCORE Trophy Truck and Pro Truck world... and it all shares pretty much the same views. So yeah, I agree with what you said... I just dont steer 'first timers' into the more difficult direction up front.

I actually use various diameters and wall thickness' throughout the chassis. For main hoops I like 0.120" and everything else you hang off of it can be whatever. Some attributes just dont need to be 0.120" or 0.065" for that matter.... the design and its execution when fabricated has more to do with it than whats on the surface in this thread.

:bananna2:




Good points. I love off-road but my partner is really into the whole pro-touring thing and road racing. Right now we have the CSULB SAE team Baja chassis in out shop because I’m donating my time to show them how to weld it up and offer our welders as well. Because I’m not a student I can’t touch the chassis but I stand there with them and give them pointers as they go. It's made of .058 wall 4130. Really thin stuff but the entire chassis with engine and driver is only like 500 lbs. It’s a neat little project they have going.


Jason

[jason@gmachine]

With all that has been posted, I don't think that the guy doing my body work has enoughf experience welding cages. He does great body work but was not familiar with the differences between DOM & chrom-moly.

The best thing would be to send the car out for a cage....

Any recommendations for places in Nassau County, New York?

Thanks


Never get a car caged by a body shop, muffler shop, or even a performance shop. Only take cage work to race fabrication shops that build them on daily basis. If a builder does not know the difference between DOM and 4130 then they should not even be welding on sub-frame connectors. That is actually scary that a welder does not know the difference. Anyways,

I don’t know any shops off the top of my head but if you find some post up their names and websites/ photos of their work. I will take a look at the work from a fabricators POV and give my opinion.

Jason

[josht]

Well I talked to the bodyguy. He is going to contact some people that race at Englishtown to see who built there cages. He does have a Tig welder but said he does not do it often enoughf to consider welding a chrom-moly cage.

[jason@gmachine]

awsome, please keep us posted on what your findings are.


Jason