Roll Cage 4130 Chrome Moly is it legal for LSR vehicle

[ronnieroadster]

Is it legal to use 4130 chrome moly for a lakester roll cage? My build requires 1 5/8 diameter tubing if moly is legal I need to know what the tubing thickness should be.
 Thanks in advance for any guidance.
 

[geh458]

Hi,

I can not answer your question directly, but let me be the first to ask you if you've acquired a rule Book yet?  I don't recall what numbers it give for CM wall thickness, but those that I've talked to about my planned project have recommended not using Chrome-moly tubing, something about it becoming brittle, and snapping in a crash versus folding up, helping to absorb an impact.

[Pete1]

Is it legal to use 4130 chrome moly for a lakester roll cage? My build requires 1 5/8 diameter tubing if moly is legal I need to know what the tubing thickness should be.
 Thanks in advance for any guidance.
 

1 5/8 x .095 4130 was legal this year.
You should be highly familiar with the welding characteristics of 4130 before
using it. It is excellent stuff done properly.

[panic]

As Carroll Smith put it some decades ago (paraphrased, memory isn't what it was):

"The advantage of moly vs. mild steel creates a narrow safety envelope in which, to have value, the anticipated crash must be serious enough to overwhelm the lesser metal, but not sufficient to overcome the greater. It's pretty small."

[johnneilson]

There have been quite a few discussions about proper construction techniques here on this site.

The other qiute from Carrol Smith (on 4130) is this "if you don't heat treat you end up with an expensive part with the same strenth as 1020- and brittle weld areas".

John

[ronnieroadster]

 Thanks for everyones impute. Yes the material cost is more the Tig welding will be done by a certified welder but considering the weight advantage I feel its worth it.
 

[geh458]

Less weight in an LSR vehicle, isn't always a good thing.

[Dr Goggles]

Thanks for everyones impute. Yes the material cost is more the Tig welding will be done by a certified welder but considering the weight advantage I feel its worth it.
 

Unless you're looking at the outer limits..... like a liner, the rewards are debatable. It's stronger for the same weight , or lighter for the same strength but time and time again we see the same advice, use mild steel tubing.

[Milwaukee Midget]

Mild steel is so much more practical and readily accessable, and facilitates quicker repairs and remedies, if necessary.

Ask yourself this question - "If I needed to fix or add a weld to my chassis on the salt, would I have the capability to do it?"  You said that the chassis builder would be a certified welder - is he coming with you if something breaks?

Yeah, there are hundreds of folks at Speedweek who can weld anything from tungsten to wicker, and a number of them would be happy to step up and lend you a hand, but you kind of need to be as self sufficient as you can. 

Keep it simple, keep it practical, keep it fixable.

I'd spend the extra money on dyno time.

[maguromic]

As Mr. Midget says, think of it like you are going to Mars and need to fix it to get back home. Murphy's Law has a front row seat on the salt.  Tony

[Peter Jack]

If you're planning on running on the salt weight often becomes your friend. This is like no other form of racing. If you check the build threads you'll find that more often than not weight must be added to increase the speed. Air becomes tough stuff to push.

If I were building a cage for the salt I'd invest in a load of DOM tubing.

Pete

[Pete1]

Some of you guys think totally different than I do and that is NOT meant as bad.
I have a VERY strong aversion to checking out before my time.
If I decide to go LSR racing, I would want to be in a car that was built WAY over
enginered to be as safe as possible. That would include the strongest alloy steels
and engineering practices available. If I did not have the money to have the work
done by qualified people, I would go to school and learn how to do it myself, which I did.
Previous crashes at the salt can be analyzed and studied but you can never foresee the future.
Previous crashes at Indy, formula 1, World of Outlaws NASCAR and others can be studied
but eventually there will be one that is different. The same applies to Bonneville.
It boils down to each crash is different. You can't build a car too strong.
The rule book is a guide. It doesn't hurt a thing to go WAY past that...
If you can't afford it, either wait till you can or gamble with an early racing carreer at that
GOLDEN SALT FLATS in the sky.

[Dr Goggles]

Some of you guys think totally different than I do and that is NOT meant as bad.
I have a VERY strong aversion to checking out before my time.
If I decide to go LSR racing, I would want to be in a car that was built WAY over
enginered to be as safe as possible. That would include the strongest alloy steels
and engineering practices available. If I did not have the money to have the work
done by qualified people, I would go to school and learn how to do it myself, which I did.
Previous crashes at the salt can be analyzed and studied but you can never foresee the future.
Previous crashes at Indy, formula 1, World of Outlaws NASCAR and others can be studied
but eventually there will be one that is different. The same applies to Bonneville.
It boils down to each crash is different. You can't build a car too strong.
The rule book is a guide. It doesn't hurt a thing to go WAY past that...
If you can't afford it, either wait till you can or gamble with an early racing carreer at that
GOLDEN SALT FLATS in the sky.

I think you'd be surprised at the even spread of opinions.

I don't think there would be many experienced racers who would disagree with the intent of your post, but I think you might be surprised at the reaction to regarding all who come here as an homologous group.

Your contention that people regarding mild steel as acceptable as being tantamount to "gambling" makes me think you may have not considered the nature of injuries sustained in an accident and the possible and practical ways to avert those injuries.

As Carroll Smith put it some decades ago (paraphrased, memory isn't what it was):

"The advantage of moly vs. mild steel creates a narrow safety envelope in which, to have value, the anticipated crash must be serious enough to overwhelm the lesser metal, but not sufficient to overcome the greater. It's pretty small."

If you give me an explanation in your own words of the meaning of the above statement I will put more weight in your opinion.........

So , what you contend is, at the very least, we should use CrMo of the minimum dimensions , or bigger or we are foolish?

Roll cage material is but a small part of the safety package....fire-suits, extinguishers, proper design of the cab and intrusion protection...the HANS, the helmet...the chassis..........

Mostly we can't defend our brains against sudden deceleration.

The car I drive is so over engineered in the drivers area it is ridiculous. The chance of me being crushed or mortally injured by a physical object in an upset is , I hope, small. If I somehow get it into the air at 200mph and then stop abruptly It's not going to be the cage material that determines my outcome.

I can choose between super-strength and protection or ultra-lightweight in an effort to minimise inertia............. it's not a simple argument.....

[Tman]

Is this poster R Sangiovani? Or someone using the same nick?

[Milwaukee Midget]

My advocacy of mild steel is purely practical.  You need to build your car out of the legal material you feel most comfortable racing with.

Of the few accidents that I'm aware of on the salt where a driver was injured, I can't think of one where the difference between mild steel and chrome moly would have made a difference in the outcome.

While Pete1 is correct when he says no two accidents are the same, the nature of the crashes that tend to occur in NASCAR, Outlaws, Formula 1 and Indy are those of the collision variety, where a car hits another car, a wall, or some sort of obstruction.  Rollovers and getting airborn are, unfortunately, the common crash scenarios in LSR.  I would recommend building accordingly.