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Author Topic: 4130 tubing for cages?  (Read 6300 times)

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Offline norrie

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4130 tubing for cages?
« on: September 15, 2007, 06:56:09 PM »
Wow, tight-nit group here!
This has been touched on in other posts, but I'd like to start another so it's clear...
On the USFRA "pre-inspection" form, and in other references here, it looks like I'm better off with a mild steel cage then with a moly cage. Why is this? I understand that 4130 can work harden and crack, but if it's welded properly, and is approved by a Racing Organization, will I still get hassled by the tech guys?
I ask this because I am more used to moly and have better access to it.
Thanks for any help.

Offline Unkl Ian

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Re: 4130 tubing for cages?
« Reply #1 on: September 15, 2007, 07:41:34 PM »
It can become brittle if not welded correctly.



If you've followed Sprint Car history,you've seen too many pics of cages sheared off.
I guess the answer is "a Secret" .

Offline Dynoroom

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Re: 4130 tubing for cages?
« Reply #2 on: September 15, 2007, 07:59:56 PM »
The answer to your question is you can have a 4130 cage if you like, you will not be "hassled" by tech but the rule book recommends mild steel because most home builders can get it and it's easy to weld with different types of equipment. Cromoly steel was originally developed to be gas welded. Today most folks tig weld 4130, If you anneal your welds with a rose bud when finished (most builders don't) your much safer. Most of the rules regarding safety in the rule book are there because something happened to put it there, they are just trying to keep you safe.
Welcome to the world of land speed racing.

I should also add that most builders use 4130 to save weight. The SCTA has a minimum thickness on tubing no matter what type it is so there is no real advantage to using 4130. Remember weight can be your friend in LSR.
« Last Edit: September 15, 2007, 08:12:08 PM by Dynoroom »
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Offline JackD

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Re: 4130 tubing for cages?
« Reply #3 on: September 15, 2007, 08:17:36 PM »
The requirements for roll cage construction and material vary by types of racing and use.
SCTA is unique in that a race vehicle might be built from end to end by someone that has never built a racer before, they spent a lot of time at maximum speed, and their service life might be expected to be a number of years with multiple owners and drivers.
Making it light weight and then add ballast seems ill-advised.
You might start by calling some of the various advertisers in the SCTA book and get their opinion and then compare it with the information you gather here. :wink:
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Offline hitz

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Re: 4130 tubing for cages?
« Reply #4 on: September 16, 2007, 01:45:00 PM »
[quote author=Dynoroom link=topic=2929.msg35929#msg35929 date=1189904396]
The answer to your question is you can have a 4130 cage if you like, you will not be "hassled" by tech but the rule book recommends mild steel because most home builders can get it and it's easy to weld with different types of equipment. Cromoly steel was originally developed to be gas welded. Today most folks tig weld 4130, If you anneal your welds with a rose bud when finished (most builders don't) your much safer. Most of the rules regarding safety in the rule book are there because something happened to put it there, they are just trying to keep you safe.
Welcome to the world of land speed racing.


I should also add that most builders use 4130 to save weight. The SCTA has a minimum thickness on tubing no matter what type it is so there is no real advantage to using 4130. Remember weight can be your friend in LSR.
[/quote]


  Dynoroom is right on here! This is the first mention of Chromoly being originally be made for gas welding that I've seen on this site. It was recommended by the Experimential Aircraft Association for thin wall 4130N. The tig was used in some aircraft factories but was stress relieved  in controlled ovens after welding. When gas welded, it needs to cool slowly and be protected from cool drafts or as Michael says, "anneal" and cool slowly. .039 (as an example) 4130 tubing was commonly gas welded in aircraft for years. The SCTA recommended low carbon tubing is the best way to go. DOM seems to weld nicer than HREW with tig.

  Have fun with your project!

Harvey
« Last Edit: September 16, 2007, 01:46:48 PM by hitz »

Offline Harold Bettes

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Re: 4130 tubing for cages?
« Reply #5 on: September 16, 2007, 04:56:11 PM »
Howdy All, :-D

I got in some political trouble a number of years ago when I was writing a column for SuperStock and I made some comments about welding 4130CrMo tubing. Seems that one of the big advertisers had chassis parts and pieces and took great exception to what I stated about 4130. :evil:
Well, I cited the AWS (American Welding Society), ASME (American Society of Mechanical Engineers), and the FAA procedures for welding the stuff as a rebuttal.  :-o Being an engineer conditioned me to write the rebuttal in a report format and the "problem" went away but it spoke volumes of the amount of poor info that is abundant in the motorsports ranks "because everybody tig welds CrMo..." :roll: Simply put is that CrMo is very problematic and prone to cracking just outside the welded zone (martensitic failure) UNLESS it is post heated and cooled at a slow enough rate to return the parent material and the weldment back to a "normalized" condition (CrMo is normally supplied in a condition N). :lol:

Additionally, the use of low carbon steel is much more safe in the relationship of being able to absorb the energy of a crash without failure. Although NASCAR is not the mecca of all things mechanical, they very sensibly REQUIRE that the roll cage structures and the vehicles are constructed of low carbon steel. Note that this is in racing that has huge budgets. :-P

Also be wary of the "if it is heavy it is safe" syndrome. Any structure can be made to endure tremendous loads and still be survivable under most conditions. Exotic materials do not ensure anything other than the use of different materials. One should look at material selection in a "truth tree" type approach so that one has opportunity to look at all the positive and the negatives for each. :?

OK, I am done ranting for the moment because I have to get back to my carbon fiber body reinforced with 2.7absolutelyunobtanium that I am welding together in a perfect vacuum using cast off outerspace technology! :wink: 8-)

Best Regards to All,
HB2 :-)
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Offline JackD

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Re: 4130 tubing for cages?
« Reply #6 on: September 16, 2007, 06:28:37 PM »
Selection of materials and joining techniques have been covered here before and with the same result. :wink:
"I would rather lose going fast enough to win than win going slow enough to lose."
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Offline Unkl Ian

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Re: 4130 tubing for cages?
« Reply #7 on: September 16, 2007, 07:19:11 PM »
Howdy All, :-D

I got in some political trouble a number of years ago when I was writing a column for SuperStock and I made some comments about welding 4130CrMo tubing. Seems that one of the big advertisers had chassis parts and pieces and took great exception to what I stated about 4130. :evil:
Well, I cited the AWS (American Welding Society), ASME (American Society of Mechanical Engineers), and the FAA procedures for welding the stuff as a rebuttal.  :-o Being an engineer conditioned me to write the rebuttal in a report format and the "problem" went away...

Good for you.  I despise the "our Advertisers are always right" mentality
common in most automotive magazines. :evil:

Doug Gore did an excellent article on welding 4130,in Open Wheel Magazine
many years ago,including testing yield and ultimate strength with different
filler rods and different processes.Very interesting,but I would rather play
it safe and use mild steel when possible.
I guess the answer is "a Secret" .

Offline Harold Bettes

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Re: 4130 tubing for cages?
« Reply #8 on: September 16, 2007, 10:56:01 PM »
Should have explained myself better :? - Had a great relationship with the editor (the late Steve Collison) and the political hot potato was not with him, but with the manufacturer of chassis parts. It all came out ok, but the myths still persist. :x :lol: That is one of the reasons that the current NHRA rulebook has the requirements that it does on such things.....OOPS that would be another issue  :roll:

The reasoning of "that is the way that it has always been done" is generally somewhat suspect. Unless, that is really the right way!  :wink:

Regards to All,
HB2 :-)
If it was easy, everybody would be doing it.

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Offline norrie

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Re: 4130 tubing for cages?
« Reply #9 on: October 02, 2007, 09:44:28 PM »
Thanks for all the info guys!
I did do a search about this before I posted and I didn't think my particular question was answered, but I would say it has been now.
I work in Pro-Stock and I feel I understand the conditions nessesary to use 4130 safely. The reason I am interested in it for my project is that I plan on driving the car both to and from B'ville from MN, and as my hot rod in general. I want to use it for multiple forms of racing from land speed to the Silver City Classic to drag racing without any more modifications than I have to make (a guy can dream). A lighter car will get better milage on the trip to and from, and will accelerate more quickly in the other forms of racing. I'm just explaining my interest.
Thanks again for all the great info.

divenpuke

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Re: 4130 tubing for cages?
« Reply #10 on: October 08, 2007, 04:06:02 PM »
Would you mind reprinting those articles from the AWA, ASME, & FAA?  I'd like to see them and I don't have handbooks for each one in front of me.  I doubt I'm the only one.

JM

Offline rebelce

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Re: 4130 tubing for cages?
« Reply #11 on: October 08, 2007, 06:34:31 PM »
Hard to serve more that one "Master"

Offline RICK

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Re: 4130 tubing for cages?
« Reply #12 on: October 09, 2007, 09:18:26 AM »
If your'e building a "utility" car that can be driven on and off the track, I would would use 1010 or 1020 mild steel only. The reason a retired pro-stock doesn't make a good super comp/gas car is because it work softens/ flexs, and won't 'react' well anymore. At the same time, the area right at the welds become brittle.
 After inspecting several 'crashed' race cars, the one thing that sticks out is that MS cars bend, and can obsorb impact. CM cars seem to sheer off or fracture tubes near the welded joints.
If it wasn't a weight issue, I would never recomend 4130 again.
 Years ago, we ran a 300 in WB top alcahol dragster. It had a 3 piece chassis. In between round matiance included rubbing it down with a scotch brite and WD-40, to inspect for cracks. Not caused by impact, but by vibration, they were always found next to a weld.--- I thought about that when I saw John Force skating down the track @ 300 with those tiny stubs of main frame tube still hanging from the forward main hoop. ??? Makes you wonder?


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Offline JackD

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Re: 4130 tubing for cages?
« Reply #13 on: October 09, 2007, 11:23:13 AM »
When you consider the weight savings for a utility vehicle vs the long term usability, the answer is clear.
Connecting the various tubes with a method to hold and measure inert gas pressure, saves a lot of inspection time by just watching for leaks that are easily noted with a gauge and spotted with a little hand spray soap.
The added feature that keeps the moisture out is another plus, all for little or no cost, and you can even paint it.  :wink:
"I would rather lose going fast enough to win than win going slow enough to lose."
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