Chassis steel specs..

[Warpspeed]

Strength itself may not be the most important factor, especially if strong also means brittle.

Glass is stiff and strong.
Rubber is soft and weak.

Hit each with a very large hammer. Which survives the "accident" best ?

In an accident, you want the structure around you to ABSORB the impact energy without failing or tearing apart.

Very stiff and very strong structure may be superior right up to the point where it suddenly fails completely.

Something else, which is much more forgiving, may deform massively without losing much strength at all.

[Bubstr]

If I remember correctly from log ago school days, for the 4000 category steels they have a high carbon content with chromium, nickel and molybdenum for alloys. for each specific number there was 3 or 4 ways it was tempered or annealed. One annealed was cooled in a controlled furnace. Brought down to temp.slowly and is softer. Two normalized, air cooled. This is a little harder. Three Water quenched. This is tempered hard stuff. Four was oil quenched. this was harder yet, if offered in the steel you want.

So you could get at least 3 kinds, maybe more of 4130 or G41300 steel, all with the same alloy makeup.

What I know about it is just enough to ask questions.

Is it possible that NHRA needs to mandate structure design rather than material used, or both?

[Ed-vancedEngines]

I know this,
I see remains of cages after serious crashes made from mild steeel and the cages are intact in one pice just bent.

I see remains of serious crashes of cages made of the .083 Chromolly and I see cage material torn or sheared. I see jagged tube ends from the tearing. I see welds or material surrounding the welds fail.

I like light weight but if I am in a serious crash I would feel much more secure knowing my cage isn't going to break up.

In the older days the C/M cages were mandated to be .095. Now they are .083. What is there to make them safer except more tubes used now. Those same more tubes are now used in Mild Steel cages and that is the safest in my opinion.

Ed

[Ron E]

OK. We an all agree that a properly fitted and welded joint is better than a sloppy fit and welded by someone like...say. Me. No matter the material.

However, I'm still searching for the logic in NHRA's backing MS down to 8.50. Having read through such discussions in various places, the conclusion seems to be MS is at the very least equal to, or better than CM in a crash. So, whats the drive behind such a rule change? Is there a chrome molly lobby I don't know about?

[Bubstr]

OK. We an all agree that a properly fitted and welded joint is better than a sloppy fit and welded by someone like...say. Me. No matter the material.

However, I'm still searching for the logic in NHRA's backing MS down to 8.50. Having read through such discussions in various places, the conclusion seems to be MS is at the very least equal to, or better than CM in a crash. So, whats the drive behind such a rule change? Is there a chrome molly lobby I don't know about?

In the first post there was a link to an article. In that article it was stated that a couple guys was dismissed from the SFI because they had no dog in the fight. This meaning, they where no longer active chassis builders. Did they loose all their knowledge because they retired?

This is pure speculation, but it would seem SFI and SEMA influence the rules to improve business. Now I can say that because I have no dog in the hunt. Being retired I have nothing to gain either way. I just don't like the little guy getting hosed, or in this case tubed all the time. This 7.50 rule means more professional built chassis and the longevity of them chassis is shorter which means more professional built chassis. That's good business. It's also bad for the hot rodder that made the sport by using his intelligents and mechanical skills to be competitive. This sport is turning into a Indy car buy a ride type deal, even in the lower tiers.