Okemo 2 caged car crashes

[3rdgendennis]

Thanks. I'll be looking more closely at what I'm ordering in the future. I've always ordered DOM, but never looked at ASTM specs of the materials.

[Mopar 151w2]

There is a lot of DOM, SAE1005 hydraulic tubing around (at the scrapyard), wich is so soft that it's ASTM spec doesn't even include tensile strength - only rated burst pressire.
Also, I would not be surprised if ASTM a500 DOM , SAE 1015 tubing had a tensile strength less than or equal to ASTM a513, ERW, SAE1026. If you are building something nice, look into ASTM a519 CDS (Cold Drawn Seamless)tubing. It is available in the US because Thyssen-Krupp has built a new tube mill in Alabama (IIRC), which is capable of making CDS. According to the Rally America rules, this is the only mild steel tubing which actually meets FIA rollcage specs. R/A allows "DOM" as an acceptable substitute. Demand for this tubing sufficent to permit it's manufacture is driven by the NASCAR market, and is a result of the Penske South initative to develop true seamless tubing with consistent wall thickness- initally made by OD skiving or grinding seamless tubing. Remember - DOM tubing is made by redrawing welded tubing, it is not truly seamless!

[walterclark]

After a couple years, I am still sorting all this ASTM lingo and metal grades stuff out. Being involved in the email discussions after the change to the cage rules last Feb spurred me to read a lot more. Not enough to be sure, but way further along than I was last year at this time.

To add to what John just wrote... in either ASTM 513 Type 5 DOM or ASTM a519 CDS grades 1020 or 1026 seem to be preferred for cages and mandated by some rules including FIA Regs Appendix J Article 253 (where they specify tensile strength and min/max % ingredients that cross reference as 1020/1026) . Strong but still form-able.

And further. The above are going to be found only (my research) in round tubing...which is fine for cages. But if you are fabricating a chassis where parts of it are going to essentially act as a cage but you need to use square or rectangular structural tube, then you are probably going to want to find A500 Class C, which is an ERW structural tube that is close to the above DOM and CDS in terms of strengths and available in square and rectangular shapes.

[jkale]

Walter,

I am curious about the cage failures you referred to last week regarding the materials used not being as strong as they should have been..

I am very curious about which imported steels are not doing their job.. When I order my material from my suppliers, I almost always order a513 type 5 DOM, but it comes in 2 different finishes. One of them is just raw bare steel( kindof how cold-rolled round-stock looks).. The other is scaly, and I need to clean the hell out of it to get it weld nicely when tig welding. The material that does not have this "scale" on the outside is almost always stamped with U.S.A. while the scaly versions either read "Wheatland Tube Co", or just "INDIA".. This is just coming off of the materials that I have in stock currently..

I am wondering if these other companies are using some sort of corrosion inhibitor on the surface immediately after the tube has been drawn(while it is still hot)..?

I am also wondering if these types of surface coatings have any adverse affect on the strengths of the steel. I have a hard time believing they do, because when working with T45(Custom Cages UK LTD. kit), that tubing had a similar, but not quite as thick coating on it that would only require a quick sandpaper scuff to prep..

[walterclark]

Mike Hursts comments were mainly related to supplies of 4130 (for NHRA funny car cages) and A500 (ERW) which I guess is used by some racing bodies. The 4130 had inconsistencies that resulted in deformation testing at the fab shops being all over the place and the ERW was reported failing along the seam during cage fabrication where bent. As I understand it both are Chinese origin sold by what used to be American manufacturers that source offshore now. But for more detail I would suggest you contact Mike as he is the source so that makes my information 3rd hand at best. He is with SFI but also still maintains his Rally America position as director of competition. His RA email is mikehurst@rally-america.com I am not sure what his email is at SFI.

[jkale]

Ok, good. I will get a hold of him to get some details, but it sounds like it is not affecting any materials I use frequently.

As far as what you said about ERW: that is exactly why our rules should incorporate something in it preventing fabricators from using ERW in the safety structure around the driver. You brought up a great point yesterday too, regarding fabricating tube chassis and the inability to use DOM square tubing. I never even thought about that exception..

[Mopar 151w2]

I would beg to differ with regard to ERW used in cage fabrication, for a simple reason - there are thousands of cages out there made with it, and there is nothing wrong with them. No one is suggesting doing new main hoops or door bars with ERW, given what may be in the current pipeline - but banning it altogether is throwing the baby out with the bathwater. I don't think, personally, that you will find the sleazy, badly made tube sold as conforming to a513, or even a500, or even as "Mechanical Tubing".
Further, there ARE plenty of goobers out there using Harbor Freight PIPE benders, to bend tubing, and the dies are sized wrong. 1 5/8 tubing is mentioned in a lot of specs, as an alterrnate - because 1 1/4" nominal schedule 40 measures 1.660 dia., the 1 5/8 (1.625)tube can be bent in those dies with little deformation. 1" nominal measures 1.315, and 1 1/2" nominal is 1.900 - so trying to bend 1 1/4, 1 1/2, or 1 3/4 tubing in a cheezy bender will result in significant distortion - enought to split marginal tubing at the weld, and enough to cause significant loss of strength with ANY tubing. There wasn't a lot of tube bending equipment around in the 60's' What you could find tended to be conduit benders (like Greenlee and Hossfeld), which came in pipe sizes, so the 1 5/8 spec evolved from that. Look at stuff for the drag race market - It's still the same size today. That's also where the .134 wall spec for 1 5/8 comes from - standard for schedule 40 pipe, the better grades of which ain't too bad - and it's weldable with a common arc welder with good fit-up and skill - remember, a MIG welder was exotica in '75!

[jkale]

I would beg to differ with regard to ERW used in cage fabrication, for a simple reason - there are thousands of cages out there made with it, and there is nothing wrong with them. No one is suggesting doing new main hoops or door bars with ERW, given what may be in the current pipeline - but banning it altogether is throwing the baby out with the bathwater. I don't think, personally, that you will find the sleazy, badly made tube sold as conforming to a513, or even a500, or even as "Mechanical Tubing".

It doesn't make sense to use a material that is known to split and tear at the seam after being cold worked.

There are so many options of affordable seamless tube available, why would you choose to use a material that is known to be inferior?

It really doesn't matter how many cages there are out there made of erw. What matters is what the competitors of NEHA are using to keep themselves alive in the case of a collision with something.

Suck it up John, That ERW baby needs to be tossed in the hot bath water!

And as far as tech inspection is concerned, it would be fairly easy to come up with a Roll Cage Registration sheet that competitors with new cages/chassis would fill out. It would have simple information on it such as: roll cage material, tube dia. and wall thickness on certain important components, fabricator, ect. I feel like there are many ways this can be beneficial and it really won't be any extra work. Plus, that way, at tech, Don and Walter don't have to prove what the material is. It will be right on the sheet..

..just an idea we were throwing around the other night..

[KevinGale]

It doesn't make sense to use a material that is known to split and tear at the seam after being cold worked.

It doesn't make any sense to race cars up mountains either. Have you seen the trees and the drop offs on Mt Washington.

My point being there isn't any such thing as absolute safety. Any new cage that is being built would of course avoid ERW. Not because it is so horrible but because better stuff is available at a reasonable cost. But I don't personally see any reason to exclude a well built cage just because it is ERW. I don't think it should be a recommended material but I think the cage should be judged on it's construction. And that is all we can really do anyway.

[walterclark]

John may want to clarify what he meant but I read it as existing cages made from ERW should not be disallowed simply based on being ERW, but new construction requirements should be tighter.

What I just stated is oversimplified to be sure, but I think along the lines that we have been moving.

One of the tricks is going to be to define "existing". Another is an issue John brought up a while back about the dividing line between chassis and cage on a "tube" frame car. Since a number of good cars are build with a rectangular/square tube chassis onto which round tube is welded for supports and cage elements, and the rectangular is not made in "DOM", simply requiring DOM and/or CDS everywhere is not realistic. The fact is that what is needed in tubing is a defined range of strength and form-ability. It appears that A513 type 5 in 1020 to 1026 (e.g. most DOM) is a good choice in these regards. I would suggest that an A500 or A519 that comes close in terms of strength should also be acceptable. To that end we may want to specify the min/max range of tensile strength and perhaps a min/max carbon, etc. content as our requirement for new construction. Then include recommendations such as A513 Type 5 1020-1026 and A500 Class C for material meeting those requirements.