motormonkey

How do you figure its dirty pool when a shop that knows what it is doing gets passed on inspection the first time?
The point of a shop knowing what it is doing is why you go there, you pay for the experiance. Why go to somebody thats learning to do a chassis of 9.50 or better? There is a lot of "tricks" and secrets in a good chassis that alot of people miss or dont know.
You can make as much power as you want but if you cant make it go it just extra parts. Ever wonder why some people are faster than others?

jdustu

iTrader: (2)

it's funny because the instructer i have this week and the guy last week disagree on just about everything, yet both have been in the field of metallurgy for decades.....

this guy is working on building a cm frame for an airplane, but he's still in the process of practicing his techniques on the tubing right now.....he is pulse tigging it with no post weld heat treat, but said that he has no problem with mig welding cm.....as long as its done the right way....

then i talked to another guy from our proving gorunds in arizona and he said pretty much the same thing.....using a pulsing mig welder, or using the "trigger" technique would be the way to go, but you need to know what you are doing to avoid cold spots, and on the other end to avoid creating too large of a heat affected zone....its easier for the nhra to inspect a tig welded cm cage than it is to inspect a mig welded cm cage, because as has been stated before you can make a cold mig weld look fine much easier than a tig.....obviously if you want a cage certified its best to go by the books, or it could be a huge waste of time and money...

motormonkey

jdustu, Im a little concerned that a welding or metalurgist instructer would "pulse Weld" anything other than sheet metal. Spot welding is so common in the bigginer hot rod frame building and i have seen failures because of this style. It is a cold bead if anything. I recall an editors front end fail by a well known shop because of this but it looked good for pictures. Talk to other chassis builders and see what they say to "pulse welding".

JPMuscle

Thanks guys theres alot of good info in this thread. Il talk around this week and see what i can dig up. Im pretty sure theirs no one local to me that builds NHRA spec stuff other than our local dirt track and outlaw guys. So as for finding somebody to inspect it may be a little bit of a problem. We planned on my car going to the shop this weekend for the work to begin but that may change, depending on what turns up.

For the most part im not to terribly concerned about having the certification, i know i should have done but im not planning on entering events all that much, just building a fun purpose built car. Im more worried about the resale aspect of it, should i ever go to sell it or part it out in the future it will kinda limit my possible buyers, since i doubt most people who would want to do something serious with the car would buy it with out certification. but who knows


thanks again guys,

-john

jdustu

iTrader: (2)

just like anything else, if you do it wrong it could fail.......but pulse welding is a perfectly legitimate way to join metals and keep the haz down, especially welding ss, cm and al.....you want to get the least amount of heat into the metal as necessary, and pulsing is a great way to do that...in no way am i talking about doing it for "style" or looks, but purely for function......whether doing it manually or setting the machine for it, there are many benifits to pulse welding


i know what you are saying about "beginner hot rod" builders "triggering" a mig gun to make a pretty weld, and i know that some guys don't even like to stitch weld for fear of cold spots.......but like anything else it can be done right with experience and a good eye.....

motormonkey

Not to start crap, but pulse is not a penetrating weld. Its bird poop .
Ive never welded anything but sheet metal with the trigger effect. Ive welded just about everything and at no point would pulse welding be acceptable. Im having a hard time with your instructers advising this stuff. Shoot, i have had a pusle option a lot of tigs ive used and cant remember ever using it.
Jdstu, Are you in a certification program? Ive been certified 6t exray mig and tig, and some of what im reading is troubling to me. Ive been building and working on chassis ,cm and mild for a long time and i cant stress enough that at no point do you spot or pulse. The point of keeping the HAZ down is a nice controlled small bead, not starting and stopping with current spiking up and down. That kind of method is going to crystylize the HAZ from rapid up and down heat and cooling and most likely under cut the weld trying to burn it in. From metullargy you should know its not what you see but what you dont see that does the most harm and thats what normalizing helps.
Sorry about being a little vague again. But this could go on forever.

jdustu

iTrader: (2)

yeah, i've got several certs in stick and tig, geared towards structural steels at this point(i'm assuming you meant 6g and not 6t?)......but i take most of what i know from guys that have been doing this for many more years than i, and the 4 top welders i reference all use pulse welding when the job calls for it(they've got a combined 160+ years in the welding industry)

bead control may be a bonus from keeping the haz down, but it's NOT the end reason......take cm for instance, you want to put as little heat into it as possible while still getting enough penatration.....the less overall heat you put into it, the less coarse martensite is formed, the tougher it is and less brittle it is......in aluminum, the more heat you put into the metal the weaker it becomes; pulsing has obvious benefits there.......stainless steel is so prone to warping that pulsing was actually developed for ss to decrease the overall heat input while keeping the peak input high enough to insure penatration.....

unless you meant "the best way to keep the haz down it a nice controlled bead"????? i would not agree, at least entirely, with that.....obviously you want a nice bead(whatever size is proper), but in order to limit the haz as much as possible, pulse welding is added as well....undercutting is a problem with the welder,not the process

maybe you should try it and then you could speak from experience???

there is a lot more to it than just current spikes

motormonkey

Well your right. I wont pulse for my own reasons i guess. Ive welded all things listed and then some and i dont have a problem with warping. Warping comes from to much heat or to big gap or blah blah blah. You know what im saying.Undercuting is the welder and stomping the pedal or pulsing to burn it in spikes the metal and cools the puddle to fast to be any good.
My welds have to pass an xray at any time so i will stick with what works for me.
Its good to hear that you are getting certified so you are better educated than most. Anybody can lay down a bead but it takes more than that to know whats going on. We saw that with 4130 postings. The only reason i mentioned i was certified is ive been through what you are doing now and listening to the guys in your feild is good. Your getting struct. cert and mine is for cars.
Oh you right it is 6g not t. Still learning to type.

jdustu

iTrader: (2)

i figured that's why you mentioned the 6g certs, shows you know what you are doing ......we have a pretty good deal with our training facilities, and the guys that do the training and certifying are top notch and extremely **** about everything, nothing gets the ok without testing, testing, and more testing.....i personally have spent my time getting certified in structural steel, but there is a guy taking a cert course this week that holds certs in ss and al in various forms and thicknesses......part of his job is modifying cages for test cars, and he pulse welds cm

obviously there is more than one way to skin a cat, and you found a way that works for you, and plenty of people(usually myself included) do it that way still.... all i'm saying is don't condemn it when plenty of folks do it and have proven it to work

Silverback

If you have any local NHRA/IHRA tracks then there is definitely a regional inspector that does scheduled cage certifications at predetermined locations. You can usually find/contact them through the sanctioning body, and in most cases they are very receptive to answering questions, including “can I do X and still pass cert for Y?” and they should be able to recommend a local chassis builder that they’ve seen good stuff from also.

Silverback

Why is it dirty pool… because it has nothing to do with doing it right, it can be looked at as “the price of admission” in some cases, and in some cases there’s more to it then that, but I know of cases where the cage is technically illegal, but passed because of who built it. The thing is that I don’t know of any of them that have had cars win consistently enough to have them questioned, but it does happen.

Wonder, no… usually in less competitive classes you might just have someone that has skills that the others don’t, in more competitive classes it’s usually because they’ve figured out a way to cheat, or at least make a pretty serious end run of the intent of the rules without getting caught or called on it.

There is a significant difference between pulse welding with a welder equipped that way (power is always applied, but the amount of heat put into the arc is modulated), and pulse welding as it appeared to be described there and as is being done by a lot of chassis builders now (I believe that it started with the lowrider guys, spread to the 4x4 guys and now is getting into the mainstream motorsports through the import/drifting/ralley and show car circuits). I don’t think that anyone will argue that the latter is the correct way of doing it unless it’s the only way that they can do it and lay down a decent looking weld.

That being said, I’d put at least one of those instructors in the same category as jdustu, take that as you will, but still have a hard time believing that things were described by a certified instructor as they are being relayed here.

FWIW, my dad spent his career (now retired in his 70’s) as an engineer first in the aerospace and then the steel industry and has been involved and in some cases helped develop the welding standards for both industries in the last 40-50years. Funny thing when you grow up with bookcases of this stuff in the house and an interest in it, as well as someone around that you can just “why…” when something just doesn’t seem to make sense. The point is that there are reasons people say that things are done for, and then there are the actual reasons.

If that was the main concern then most in most cases MIG would be the preferred method for welding CM since you can get a full penetration weld with it in 1/3-1/5 the time that you can with TIG as well as a significantly higher arc temp (gas welding happens at just over 5K*F, TIG at about 20K*, MIG at 25K* or more).

The reason that gas and TIG are usually preferred and have been the long term standards for aircraft and in general CM welding is that as you apply a lower level of heat for a longer period of time and you get a larger heated area and the CM doesn’t self quench as hard in the HAZ. MIG is becoming accepted mostly for production reasons and that _it can be done correctly_, not because it is in any way better. Pulse is a step further in that direction, and as far as I can tell is mostly being accepted because if it’s improved weld/bead control, even though it’s probably an inferior weld in CM (but better in aluminum).

Last I heard, pulsed is not acceptable in most materials for many of the most stringent aerospace and similar quality welds (hell, most stringent stuff for aluminum alloys doesn’t even allow AC TIG, it’s DC TIG with He, like as in true “heliarc,” which tends to be faster and hotter). For that matter, in the motorsports industry it’s common practice to “see saw” a tig peddle, running the TIG hotter then you normally would, “flooring” it to make your weld pool, dip, back off let it start solidifying, move over, “floor” the pedal again, dip… this allows perfect looking TIG beads even with crappy weld prep and technique, and would automatically fail most aerospace and nuclear standards, they wouldn’t even inspect the weld, they’d tell you to stop and do it right or get another weldor….

jdustu

iTrader: (2)

maybe i wasn't clear enough; by "least heat necessary" and "less overall heat" i am talking about keeping peak heat at a minimum, and keeping high heat duration at a minimum....depending on the task and desired outcome you would have to balance what is more important and what has a bigger impact on the metal being welded: duration of heat or peak temp.....in the case you describe using a mig without pulse would increase the brittleness of cm much more than a pulsed tig(due to the elevated temps with no break up like with a pulse), or a non-pulsed tig weld for that matter......you may be in and out faster, but the temp is higher for too long...the less the amount of "high" heat, the smaller the haz, the less chance coarse martensite has to form, the tougher the weld is....

reading your next paragraph,its obvious you understand all this

(other than the "self quenching" softer in the larger haz? cm air quenches fine because of the small carbon percentage, but if it doesn't get heated, it doesn't need quenched at all, then why make the haz larger? keep it as small as possible) if your worried about making it even softer, then ht the entire piece

so why belabor the point when it was already made? i never said that mig welding was "better" than tig for cm, only that it could be done and was acceptable in many instances......


i'll ask you again to justify your assertions, because you haven't so far.....and if you can't then shut the hell up, at least when referring to me


by the way, i don't know why the text sizes and fonts keep changing, kind of annoying, eh?

Silverback

it’s like banging your head against a rock… YES, YOU WERE 100% clear, and I understood that. NOW READ WHAT I WROTE. The fact is 100% the opposite of what you wrote. You want to apply a lower heat for longer to heat up a larger area to prevent it from quenching as fast/as much. At least this is the traditional approach to preventing brittle welds in CM and the traditional reason why it shouldn’t be MIG’ed (though anyone that knows what they’re doing should be able to get around that problem pretty easily).

Actually, to make my statement 100% correct it shouldn’t say “brittle welds” but “welds that are more brittle then they absolutely have to be,” since any of these methods will result in a brittle HAZ around the weld, but the issue at hand is HOW brittle/hard it is.

As far as the rest of your comments… in this case you wrote something 100% wrong. Then you took what I said and stated that I obviously understand what is happening and then wanted to know “why belabor….” WELL, because you made EXACTLY the incorrect point, and the opposite of what you would conclude based on the facts that you say you agree with. Now I know that you don’t know what you’re talking about WRT to this (and believe me, I’m not saying that to be mean or anything else, but I’m also not going to waste my time and everyone else’s dancing around that and possibly confusing someone reading this in the future because I wasted my time trying to say “this is what is really the case” without directly contradicting what has already been stated incorrectly), but I’m betting that you totally misunderstood/misrepresented what the one instructor said _or_ he really shouldn’t be instructing the course. Having at one point been an instructor and the director of a department at a technical school (and having written the state and fed approved syllabus for that department as well as the one used by the same department for the local community colleges) I have my opinions on that…

motormonkey

Silverback, no disrespect. I have read everything you have writen and it seems its not from experiance, but from day to day reading.Not that some stuff isnt informative but it seems you change to suit your needs and i think its just not right.This was intended to be helpfull and if i recall you started to fire the first negative shots at welding cm. If im wrong than im sorry.
The "dirty pool" comment and the "faster because there cheating" sounds like every slow racer i have ever met. Why cant somebody just be better?
Next time youre at the track look at the "dirty pool" chassis and the others and see the differance. I admit some differances you wont see.
Lastely you insult track inspectors with your "dirty pool" comments and that is bs. They have a job to do. You know what that is? I will tell you that part of their job is so nobody gets hurt. So next time you fail chassis inspection ,please tell them its because your not a "dirty pool"chassis builder.Hahahaha
Have a good day.

jdustu

iTrader: (2)

my guess is that silverback is a "welding engineer"......lots of reading and very little actual welding??? at least not outside a lab....

i guess i misunderstood what you had said, silverback, and you really didn't have a clue, or perhaps its my fault and i can't explain my self clearly....either way, this isn't really getting any where......

a couple things though:

how exactly would heating up a larger area create a stronger/less brittle weld?

my point was that with pulse welding you can keep the haz smaller and put less peak heat into the weld pool.....cm is air hardened, so keeping heat below the lower critical temp around the weld will lessen the chances of the perimiter weld area from getting brittle....and keeping high heat in the weld to a minimum will give coarse martensite less chance to form......

you've said more than once now that i totally misunderstood and or misreprestented what my instructor said.....and ONE MORE TIME i will ask you what the hell you are referring too? because the first time you pointed that out, you had completely misread my statement(about tig welds gettting inspected), and twice since then you've made the same assertion but haven't pointed out what it is you are referring too????

Silverback

Fine… show me, quote me specifically where I’m not consistent. It is possible that I made some mistake making for inconsistent reading, but I don’t think that I I’ve changed what I’ve said, since it is based in simple fact. I may be mistaken at this point, but if you’re the one that caught both this conversation and a similar one on one of the welding boards, then I will say that we are discussing 2 very different things, here the best way to do it, and on the welding board the inconsistency and lack of logic WRT to NHRA rules and CM vs MS.

Sure, someone can just be better… but like I said, as you get into more and more professional and competitive classes it becomes less and less likely. As you go in that direction, inferior drivers, chrew chiefs, builders… get weeded out quickly and it literally becomes about where you find holes in the rules, the inspection process… that you can take advantage of to give yourself a competitive advantage over your competition. If you start seeing one or 3 competitors/teams that are consistently winning you can pretty much bet that they’ve figured out something that the others didn’t.

I don’t really know what to tell you, I’m not sure that I would call it cheating even though I would guess that most would since many consider “cheating” as anything that gives and advantage that everyone competing doesn’t have. It’s figuring something out that others haven’t. Smokey Yunnick made a career of it, and almost consistently as soon as someone figured it out it was either decided that it was already illegal or a rule was made making it illegal.

Over the years I’ve figured out a number of ways to run a little faster at the dragstrip without actually making the car faster. At this point people that know me will not race against me in a comparable car at least not on any kind of competitive basis. They couldn’t tell you what I’m doing, or how I’m doing it, I can tell you that nothing that I regularly do breaks any rules (well, one thing does come very close to violating a safety reg but I’ve never pushed it far enough that a starter or track official called me on it, or possibly noticed). My brother has said I cheat, I told him we’re bound by the same rules, I go faster then you in the same car despite being 100# heavier then you and you can’t find anything I’m doing to cheat, so…

TRACK inspectors do not do cage inspections, they check for an inspection tag and go on with checking the rest.

Second, I know of cages with sections of .065” wall tubing where it should have been heavier that have certification stickers. I know of more assorted >8.49 legal, MS cages that have thinner then the required .118” wall tubing, again, with stickers. Call it what you want, somehow they got passed.

The few cages/chassis that I’ve been involved with were built to be safe and functional first, and never had an issue with anything that I’ve built/welded going through on the first try. In the range we’re talking about here I prefer the safety and extra rigidity of MS and will give up the 20-40# difference that I would save by going CM for that, in most cases you can save it someplace else anyway.

Now I will admit to playing around with a very fast street car that I have thought about doing things that may not necessarily fit under the letter of the rule book, to build it every bit as safe, but somewhat more functional since it still is a street car, and have wished for the bigtime chassis builder name to prevent from coming under as serious scrutiny, but when that one gets done I’ll probably just talk to the inspector and flat out “I want to ____ because the car is really still a street car, how do I do it so I’m sure that you won’t have a problem with it…”

Silverback

Nope, as a matter of fact I plan on doing a little more welding before going to sleep after I finish typing this.

“air hardened” just means that you do not have to use an oil, brine or water bath to harden it. It’s pretty much completely irrelevant to the rest of this discussion.

When welding CM structures the self quenching of the metal (cooler metal around the weld conducts heat away from the weld and quenches it, hardening it) is the major issue. To over simplify things, the faster you quench CM, the harder it is, the more likely it is to become very hard/brittle and even crack. If you heat a larger area around the weld by heating the weld slower slows down how fast the weld/HAZ cools from self quenching resulting in not as hard/brittle metal in the HAZ since it cooled slower.

First, reread what I wrote about the inspection. I still stand by that.

Second, I really doubt the instructor said that pulsed TIG or MIG is preferred when welding CM

DRVETTE

Bottom line the NHRA does not except mig welds on a CM chassis, Period. And if the statement that silverback has made that, " If you heat a larger area around the weld by heating the weld slower slows down how fast the weld/haz cools." Then how come the leading chassis builder in the country, aka Murf Mckinny and Brad Hadman all tig weld by a process they call cold welding the CM. Which is to weld only 1/4 of a round tube let it cool and then weld somewhere else and come back to that tube only after it has cooled down. If you dont understand that then feel free to give them a call or call Richard Earl another leading chassis builder in florida from SUNCOAST RACE CARS he sits on the SFI saftey pannel and is current with all procedures in welding and saftey in race cars. I visited his shop in 2003 and this is what was explained to me when i purchased my chassis that i built myself from them, i also spent 1 year dedicated in welding CM in chassis aplications before i welded one bar on my car. I also took a bunch of advise from Ed Quay Race Cars another very accomplished welder in CM chassis for race cars.

jdustu

iTrader: (2)

how is cm being air hardened irrelevant to a discussion regarding cm being hardened after a weld??? a weld coming down from its as welded temp is the quickest air quench there is due to the extremely high temps involved in welding....if you can decrease those super high temps, decrease the time it is at a super high temp, and decrease the overall area that is affected by heat at all, you will create a tougher weld and tougher area around the weld, bottom line....


as far as re-reading what you wrote about the inspection, you are basically disagreeing with something you made up in your head......i've already explicitely pointed that out, and you seem to ignore that and keep on assuming you are fully justified in you position, when you are clearly wrong....that's cool, stand by your ignorance/arrogance

with the last statement, all i said about migging cm is that it could be done, not that it was "preferrable" ....and with pulse tig welding, i fail to see a negative to it as long as full penatration is achieved.

DRVETTE

I see nothing wrong with pulse tig welding either. And as a matter of fact the pulse option on a tig welder is really a kind of band aid helping tool to weld with. You can easily pulse with the foot pedal cycling the heat in and out and you dont need the pulse option. That option is usually used when welding aluminum to produce a nicer looking weld, over a long distance. And just to reiterate on the mig welding CM deal. Its not a preferred way of welding CM its the only acceptable way for the NHRA to weld CM. Not bashing anyone here.