The .118 is for mild steel either DOM or ERW, however.125 DOM is around the same price as C/M and the C/M will (if you chose) certs quicker. There is no such thing as .125 ERW, only what they can call .120 (ASTM specs can be minus 10% on wall and still be called .120) which measures at .114. This spec allowance make the tubing mill extra money considering that the tube starts out as flat sheet and then rolled round then welded. Just as easy to maken the flat .120 and roll/weld it, but that .006 the ASTM gives them makes them more tube and money. SO to make a NHRA spec chassie out of mild steel (full cage door car) you have to use 1 5/8 x .134 wall tubing. Well you would think that with the minus 10% that ASTM gives you will bring that down to .120 wall , one would be happy----EXCEPT that .134 wall is a short run order and it measures out at .134.
That is a potential problem with any weld, but much more so with chrome-moly. The tubing isn't getting brittle over time. The heat effected area starts out brittle from welding and things go downhill from there. It just takes some use for the part to begin failing. Mostly because of this potential problem some race sanctioning organizations don't allow chrome-moly chassis/frames or rollbars.
Hey, Craven & CUda340; On the use of brake clean... The article mentions "chlorinated" solvents. ANY chlorine-containing substance, when burned, will generate phosgene gas. Including a lot of the "freons". What is it about brake clean, other than the chlorine, that mixes w/argon to make phosgene gas? Not being funny... I'd like to know. Haven't heard that one before. & what do you prefer for brake clean equivelent? TIA. Marcus...
There are two kinds of Brakleen, flammable and non-flammable. The non-flammable kind is the one with chlorinated hydrocarbons.
& while I'm asking Q's... & cracking cr is being discussed... In the Nov.'67 R&C, V-Rod plans, it calls for 4130 C.R. tubing for the front axle, radius rods, & frame. 4130 plate for other chassis parts. It appears Tex welded Tom Medleys' V-rod w/an arc welder. ??? From reading in this thread, cr goes away rather quickly? I didn't realize this was such a problem. Did Kent Fuller have lots of trouble w/his rails' tubing cracking? Or his V-Rods frames cracking? Was thinking of building one or two, of these things. They'd be light-weights, but I'd rather not have "issues" that I don't need. Since I really don't know, I'd appreciate some input. TIA. Marcus...
Al; Thanks, I do know about the difference twixt the brake cleans. At work, the only stuff we use is the non-chlorinated. Brand is LPS... boy, that stuff is good. Expensive, but it's my favorite. No oily residue, lousy smell, etc. I got the impression from Cuda340 that something else was in the brake clean, that mixed w/the argon, chemically, maybe during the burn process. Never heard that, but seriously wanted to know. FWIW. Marcus...
I am not a expert or trained metal specialist. About 99 % of all oval track midgets and sprint cars are made of chrome moly. From what I read the IMCA type modifieds and NASCAR cars are ERW tubing. The welding of Chrome Moly and the condition N is where the cracking starts. As stated earlier gas welding was the first method of welding Chrome Moly. If you read any of the posts about MIG welding body panels, a MIG weld will crack if you try to hammer and doly it, while a gas weld or Tig weld is softer and can be hammered.
Here a link to the artical about clorinated brake clean (or anything with clorine in it), and welding. http://www.brewracingframes.com/id75.htm Pretty nasty stuff!!!!!!!
The test(s) you are referring to are called PMI or Positive Material Identification. Two of the most common are XRF and OES. XRF is demonstrated in the video posted. I use this equipment daily and have been for over 12 years. The unit the guy is using is a very good unit, I use the upgraded model of that instrument. The other test OES is commonly used to test the lighter elements, carbon being one of them. The "spark test" Craven is refering to could be one of two test; first one being the OES test or secondly is grinding the sample and looking at the sparks, which is old school and unreliable. The guy in the video is more than likely a sales guy, if you notice the instrument id'ed the second alloy as 304ss, but it does not meet the elemental requirements; only someone who knows how to use the equipment correctly would know that. The only way to correctly determine what any metal is is through PMI testing. There are many other methods, but they are unreliable. In the past most alloy techs would use OES to determine the difference between 4130 and 4140, it can be done using XRF and only a handful of techs know how to do this. However XRF can not determine the difference between 1018, 1020, 1026 etc...only OES testing can do this, but XRF can determine the difference between 10xx and 41xx. The 10xx material will id as carbon steel. 2507ss should never be used to build a rollcage. I doubt SFI would ever recommend it to be used either.
It is my belief that NHRA specifies the TIG process for chromoly (4130) so that inexperienced builders will stay away. As long as you can qualify the weld procedure, the process does not matter. In simpler terms, if the weld is stronger than the base metal then who would care what path you took to get there?
Thanks for the replays Gent's Got an email from SFI today; This material is stainless steel. Stainless steel is not considered an equivalent to 4130 chromemoly for the SFI Chassis Specs due to its slightly lower tensile strength and much higher elongation So I'll be NOT useing the Super Duplex! Also got a phonecall from Grinder1, and he actually had the right Chrome Moly stashed in his warehouse. Br Kjell ................................. Taildragger&fenderless
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