While trying to track down play in the front end I found a lot problems. One tie rod was about to fail, my steering box was pathetically worn, etc. These were all things I had expected because they're wear parts - things you would expect to fail over time. What shocked me was that my swaybar links had egged out the holes in my factory a-arms to an extreme.

I've already bought a new AGR box, a complete front end rebuild kit (Moog centerlin, idler arm, inner/outer tie rods, and "extreme duty" tie rod adjusters), new swarbar bushings/links, and Koni Sports. Since I've been upgrading things on the car as they break I would like to take the next step with the front end and upgrade to tubular A-arms and coilovers but I'm not sure how well suited they would be for daily driver use.

Questions: I'm planning on buying everything from Spohn. Is this a good idea or a bad idea? Should I go with delrin or poly bushings? I'm leaning toward delrin but I don't know how it wears. If the material doesn't have any problem with miles then I would like to use it. Should I reinforce the inner fender since the spring location is going to be changed to the same place as the shock mounting location or will the bolt in reinforcement plate be enough? Finally, what spring rate would you guys suggest? I’m already used to my fairly stiff w6s ride and wouldn’t mind if the ride stayed the same or got a little harsher but at the same point I might swap to a ls1 in the future and would prefer not to have to swap springs.

Thanks for any and all thoughts/opinions.

 

in my opinion, not some experience with this setup.. yeah, definately possible problems
factory stuff might be heavy and big, and take up too much space, or whatever your particular problem is with it.. but 9.9 out of 10 times its better suited to be driven then anything you buy on the aftermarket

I think it was after redraif's mishap with her tubular a-arms breaking while she was driving one of those places put up there "for racing only" disclaimer ;0

 

I've not heard many member complain about the ovaling that you mention; however, I think the problem is common. I had the holes welded and rounded again, then made sure that my endlink bushings (1LE, which have rounded heads) fit snuggly into the holes. Sorry about that rant. I'd like to know more about Spohn's tubular A-arms as well--some members report that they'll lower the car some.

JamesC

 

No disclaimer like that here.

I plan on spending the extra money for chrome moly and everything is already TIG welded. I'm not so concerned with a failure (I didn’t even know it was possible) as I am about possible ride issues, etc.

I don't feel comfortable simply welding the hole shut and going on with life. These holes are huge – way big enough to be seem huge with the end links still installed. Whatever I end up buying will be a stronger material than stock and I will take much better care of my end links.

I don't see how new a-arms could lower the car - they're just a link between the spindle and the frame but I guess anything is possible. If it does lower the car too far I will be able to compensate with the coilovers.

Keep the comments coming!

 

The fanciest material in the world and the pretiest welds doesn't mean squat if it's a bad design in the first place. In my opinion most if not all of the aftermarket A-arms out there are underdesigned for highway and road race use. 1" tube with no gussets is just not going to cut in on the street.

On top of that I highly doubt Spohn is heat treating their A-arms after welding. Without heat treating 4130 it's as weak as regular mild steel at the welds. Also keep in mind that most companies will step down in wall thickness when using 4130 to save weight. In an ideal world this would work fine, but without the heat treat you are asking for trouble.

If you don't want to fix your stock arms, go to the junk yard and get another set. The weight saved with tubular arms is completely not worth the risk, unless you are after the bling (which most people are) it's not worth it.

P.S. An a-arm can lower a car if the spring seat is lower than stock, if you are using coil overs then it's a moot point. On that note, you are not gaining anything by using coil overs, you can get a set of weight jackers for half the cost of coil overs and be able to use cheaper stock size springs. Hint, there are tons of cirlce track springs that will work just fine.

 

Great post. You bring up quite a few things for me to ask the guys at Spoon. I was already planning on e-mailing them about bushing material so I will include this as well. Thankfully the tube is 1.25" and has a gusset Oddly, the only picture I could find of a broken A-arm (scroll down for links) showed the break in the middle of a tube, not at one of the welds.

You’re right that the chrome moly version has thinner walls (1.25" x .095" vs 1.25" x .120"). I’m not sure how these thicknesses compare to other company’s products. If I had to guess both sets probably have the same overall strength (maybe an edge toward the chrome moly version) but the chrome moly version saves an extra 2 lbs (whoopie). I will defiantly ask about head treating.

The decision for chrome moly stemmed from the egged out hole in the factory arms. I’m trying to prevent it from happening again so I figure that a stronger material + better end link upkeep will prevent it from happening again.

As for the bling factor, that was never a part of my goal with the tubular a-arms. I just assumed that it would be worth the upgrade akin to boxing your LCAs. I would be surprised if the tubular arms aren’t stiffer than the factor stamped steel version. I had read about weight jacks through one of crazyhawaiian’s threads but I’m fairly intimidated when it comes to finding springs (or the jacks themselves). Coilovers are a convince to me and really aren’t that expensive as compared to buying new springs, the weight jacks, and the spherical upper mount I decided I wanted when I was first thinking about lowering the car. I agree that coilovers pose no significant advantage over weight jacks + adjustable shocks because everything is adjustable either way, but they’re the way I want to go with my car.

Incidentally, I found redraif’s cardomain page with the broken A-arm by accident while searching google for broken A-arms. I took the time to read through the page and it looks like it was a fluke because of bad materials. I’m assuming that the replacement never broke because there was no follow up with another breakage. I also found the thread she posted but it’s far too long for me to actually want to read it all.

So, to recap. The e-mail will include questions about heat treatment, material advantages for street driving, and bushing material. I'm also going to ask about spring rates and how much a new set of springs would cost if I decide to change them at some point in the future.

As always, keep the comments coming.

 

I got a response. That was nice and fast Italics = me. Regular font = them.

A-arms. First and foremost, are these safe for a daily driver application with occasional track use (autocross and paved track romping)? The car will defiantly be cornering hard at the track. Is there one material I should favor over the other (steel vs chrome moly)? I'm personally leaning toward chrome moly to help prevent the sway bar holes from getting egged out again but I read on thrirdgen.org that chrome moly isn't that strong at the welds unless you heat treat it. I'm not sure if this is true or not but if it is, do you guys heat treat your A-arms? Also, what bushing material is better suited for street use? I would like to pay the extra money for the delrin bushing if it can stand street driving (not fan of poly squeaks).

Yes, they are not "drag" pieces, they are built to be road raced. or street use I would run the poly or the delrin. The delrin will give a little more road noise since it's a very stiff bushing. Either material will hold up, we know how to properly TIG weld 4130 and have never had a durability problem with it.

Coilover kit. I only have two concerns here. First is whether or not I should reinforce the inner fender beyond the plate that you supply (ie weld tube on the inside of the engine bay to provide additional reinforcement).

A STB would be a good reinforcement, you don't need to do anything
beyond that.

(more coilover questions)My second question is about springs. What spring rate would compare to the stock ws6 suspension? I don't mind the fairly stiff factory ride but at the same time I don't want my brains rattled every time I drive down a bumpy road. I realize this might be somewhat vague and I'm sorry. Also, are replacement springs available incase I decide I want to change my rate in the future? I'm planning a ls1 swap down the road, which will mean a lighter front end.

The 300# springs would be equal to your factory springs. The springs are only $39.95 ea., so changing spring rates isn't a costly deal. We've found that the 300# springs also work well with the LSX swap.

---

That pretty much cleared up all of my questions. I will most likely be ordering around Saturday or Sunday and will be sure to post a review once everything is installed.

 

Just a few comments:

First your sway bar mount hole's egged out because the bushings wore out and allowed the bolt to rub. You'll notice new endlinks have a small lip that keeps this from happening, this is usually the first part to wear.

Of course they know how to properly TIG weld, that still doesn't negate the need for heat treat to take full advantage of 4130's properties. Yes TIG does have a smaller heat affected zone, but it still has one. Unless Carol Smith and my stack of metalurgy books are all lieing, it needs done. I would go with the mild steel units.

You're never going to feel the flex in the a-arm, it's just so small that it's insignificant. If I were you I would have gotten a set of poly bushings and another set of stock a-arms. To each his own, enjoy your new a-arms.

 

Once again I’ll say that it doesn’t matter how good the material is and how good the welder is, your still welding a material that gains most of its strength from the heat treatment that it undergoes. I worked for Pratt and Whitney for a while, what little 4130 they did weld (mostly TI and Inconel) all HAD to go in the oven after welding, FAA wouldn’t let it in the air if we didn’t.

Yeah getting rid of unsprung weight does help handling, but I wouldn’t tout it as being key to well handling car. Being worried about a few (less than 5 total) pounds of unsprung weight in the front while you’re still running a 300 lb live axle in the back is kinda like worrying if your arms look fat when you weigh 400 lb’s.

You’ll probably never have problems with these tubular arms, I personally believe (and so do the experts) that 4130 steel is a waste of money if you don’t properly heat treat after welding. I have personally pulled apart many samples on a tensile tester and have seen the results, it fails next to the weld every time. I wouldn’t be so worried if you’re running coilovers, this removes the largest load off the a-arm. When you run the spring in the stock location, you are trying to bend the a-arm in half. Tube is strong in tension and compression, not so much in bending. Race teams look at a-arms as a “timed” piece, meaning that it has a usable lifespan and should be replaced to prevent failure on track. You’re going to time it out much quicker on the street.

When it comes down to it I think the original poster is looking at these arms for the wrong reason. He’s freaked out because his stock sway bar mount holes got ate up by worn out sway bar mounts. Lack of maintenance caused his failure, not metallurgy.

 

your sway bolt holes elongated because the bushings wore, slack developed, and the bolt was then allowed to rub on the arm.
if you dont maintain the endlinks, then that elongated hole will occur in any sway bar mount..

 

You do have to use 100% argon when TIG welding 4130. What happens when you don't use the proper shielding gas is that you get oxygen embrittlement. This causes the weld to crack. Heat treating won't fix this problem. MIG welding is imperfect in that you don't get gas flow after the arc is stoped. Also mig abruptly starts and stops the weld puddle which introduces contaminents to the weld. With TIG you can slowly bring the metal up to temperature and slowly cool the weld pool all while emersing it in argon.

Let me do some searching and I'll post the proof that 4130 needs to be heat treated.

Let me clarify that it's not the end of the world if it's not, your just not going to get the full strength of 4130 without heat treating. Like I said before, I would save my money and get the mild steal.

 

The reason I stay away from moly is fatigue. This is not because of the metal itself, but because manufacturer's run thinner wall moly than steel. Moly is stronger, not lighter. Due to it's strength, manufacturer's run thinner wall chrome moly, thus causing moly parts to be lighter. The issues is that over time the thinner wall will fatigue more, thus "wear out". - Every heard the pro-stock guys talking about needing "new pipe"? Their chassis is worn out, and is flexing too much. - Just for note, mild steel vs chrome moly tube chassis kits have about 150# difference. 150lbs, and that's a complete tube chassis! - For pro stock fine, you have to have it(and all the rest of the high $ fancy stuff) or the rest will out run you. For the rest of us, is it worth extra $ for weight savings to have a part that can/will wear out faster?

 

Wow, lots of new posts.

Completely true, it was caused by lack of maintenance. However, I'm willing to bet that even with perfect maintenance the holes would egg out eventually. Stronger material is just another way of me prolonging the life of the new arms.

It’s 12 pounds total savings (10 for the steel version) but I can certainly see your point given the massive rear.

I understand thinner walls = lighter but if they’re both the same strength how does one wear out faster than the other? That’s like saying that a piece of 10 gauge metal will fatigue faster than a massive stack of laminated paper of the same strength just because it’s thinner. I might be wrong but it doesn’t make sense to me.

You bring up a great point about the Torrington bearings. How quickly would you say they wear and how easily are they replaced? I assume it wouldn’t be that hard to live with if it was a decent interval. I’m curious about how other companies that sell coilovers for imports get around this or if they don’t at all.

I would like to refocus the thread if I may. My main concern at this point is whether or not I should buy mild steel or if I should buy chrome moly. Are the arms on par in strength and the only advantage is the 2 lbs of difference or are the chrome moly arms stronger than the mild steel despite thinner walls?

 

A thinner material has more of a tendency to buckle under loading with the wall thickness being discussed here. I said the same thing a while back about chromoly and that I'd take my chances with mild steel first, all the reasons above are why. If there is any one of the many pieces of the puzzle left out while constructing something from 4130, you're left with a part that may fail because of that. It might not either, its all dependant on what loads the part sees and what sort of use and abuse the car sees and the part might never see enough stress to fail even given a few shortcomings here and there.

 

4130 is also "notch sensitive" which means that any scratch or ding is going to propagate into a crack. Think of 4130 like a piece of wood, it has a very defined grain strutcture and if you happen to put a notch in that grain structure at any point the whole piece is compremised.

We had a huge rule change in the SAE mini-baja series last year. Previously teams were allowed to use a steel member that was equivalent to 1" .120 wall mild steel. Things were getting a bit out of hand in that teams were using 1.5" .049 wall 4130 tubing. On paper it was just as strong as the 1" .120 wall mild steel, and even tensil testing proved it was as strong in pure tension and compression. The problem was that in a roll over the tubing was collapsing the first time it hit the dirt, then the whole cage would cave in the second time it hit. We called it the pop can effect. It wasn't pretty, luckily no one was hurt but some guys took some pretty nasty spills in the midwest competition. The rules now limit the teams to .083 wall tubing.

I vote for mild steal, no I retract that, I vote for a set of good bushings in a set of stock arms. I'm up to 180,000 miles and my sway bar bushing holes aren't "wore" out.

 

nope.
and because these exact same stamped A arms are used on ALOT of other cars over the last few decades, you can easily prove it... just look at any S10, blazer, monte carlo, impala....ect.. list goes on.. or another Fbody..

 

Your absolutely correct in everything you said, except for one part

This is simply not true, pick up any text book, tensil test any welded piece of steel (4130 or otherwise) and it will fail in the heat affected zone unless heat treated.....Period.

All I've been saying is that 4130 is affected more so than mild steel. In his application I think mild steel is a better choice for the simple strength to dollar ratio. He most certainly doesn't need 4130 to keep his sway bar mounts from wearing.

Boogie: I don't mean to sound like I'm anti-4130, I'm not at all. You just have to treat the material with respect if you are going to rely on it's properties to keep your car on the road. You don't have to heat treat 4130, it's a very good idea especially on a critical component like an a-arm. Just out of curiosity, do you know if those 5140 parts were heat treated? How often are they replaced? I bet the answers to those questions would surprise you.


EDIT: Ok I found what I was looking for, if you look at the attached chart you'll see how much strength 4130 looses in its annealed state. You'll also see that it's still stronger than 1020 steel in its annealed state, but not near as strong as it could be with a proper heat treat. The heat affected zone is the annealed part of the tube. So this is where the failure will happen every time. You can also see how drastically 4130 looses strength when compared to other steels. I'll post up more when I find it.

 

Unfortunately that isnt true. You can read about the 'pop can' effect above, its a fact of life with thin materials. I know I'm getting off on the same sort of off subject like before but its things I know a little more about... on a steel building they often try to reduce the thickness of the web area as much as possible on an "I-beam" especially in the beams (horizontal member), to reduce the structure weight and the overall cost. To some extent the vertical area on the I <---- is dead weight. Often in areas its thicker than it needs to be and even in a building, especially in an area with seismic activity, the structure weight is as important as it is in a race car. You can analyze on paper and load test in-situ or in a lab all day long with different yield strengths and once the web starts to get to a point where its 'thin', the usual common denominators of the beam failing in bending, axial loading, or shear (at the connecting ends typically) become less of a problem and buckling of the web is the main issue, especially when subjected to frequency loading like the type experienced in an earthquake... a load that is quite similar in expression to a vehicle suspension traveling over bumps in a road. When doing design of thin web beams, checking for buckling of the beam becomes a necessity rather than something you just ignore because you know it wont be a factor. It would be similar to making a piece of tubing out of a sheet of 1/4" thick steel and tin foil, one you know just wont fail from any sort of side load along its length and the other is as strong as... tin foil. Remember that picture I posted before of the bridge? I know its a bridge but it was thin wall tubing. What you saw was not heat treated, but we felt it wasnt necessary. We did heat treat one part and it may or may not have helped but the trussed bridge section still failed the same, the main upper bridge member still failed in what appeared to be a buckling failure more than anything else. We did make some sections with thicker wall tubing for the upper and lower members and then the angled truss sections, a super thin .035 wall tubing, failed in buckling. You generally dont experience those types of failures until things get thin, there just isnt enough load transfer area to resist any forces that are not perfectly aligned to a perfectly straight member.

Unfortunately, you can talk to all the knowledgeable people and experts you want to, nothing can explain what the part will do in use. I can tell you it will fail, and Nick can tell you I'm full of it. It doesnt really matter who or what, fact is really nobody knows. The only way to really honestly determine the failure point, in general, of the parts from say... Spohn, is to take a 'sample' of the a-arms or whatever part he makes and take them to a lab and break them. Subject them to different types of loads and directions, impact, etc and see what exactly fails. Then you can sit and argue all day long about how strong the part is and where it fails or doesnt fail, whats working and what doesnt, and then you put it on a car and it turns around and fails in a different manner when some guy curbs the car and drives off a cliff... and the other 99 people driving on Spohn arms put 200k miles of racing abuse on them and they never even whimper. Its like anything else, you take a shot and hope that the part itself is made in a manner where its giving you close to its best and it never sees anything near a failure point. Thats probably what happens with most of the broken a-arms I've seen from places like PA Racing, Pro Fab, etc.... a little bit of poor fitting, little bit of poor welding, weakening of parent material, part stress, and maybe factor in a little abuse and you have a recipie for disaster. I'm sure thats what happened with those Ford GT parts, some guy in a lab did some finite analysis and testing with million dollar equipment on a quater million dollar salary and shaved off every unecessary ounce of weight and it hit the manufacturing platform and a stress riser was introduced somehow in production from a 10 cent part and you end up with a bunch of junk parts.

And I would still opt for the mild steel. But thats just me. I take my chances in the engine compartment and others take them on moving suspension parts. Choose your poison.

 

Moly is stronger, therefore also more brittle, meaning it would be more likely to break than bend. - Not that it would, but that's part of the physical properties of being stronger/more ridgid. As has been stated, because it's thinner wall, it is more prone to give anywhere it's over stressed or nicked/cracked, etc. Stronger materials can/will(especially in an instance like this where thinner wall is used) fatigue faster under the same stress because the physical properties of it will be less likely to give/cushion. - as stated here by BMmonteSS
- Think of the titanium engine parts. Yes, they're lighter and stronger, but because of that they are more brittle, thus more prone to stress and wear much faster. Would you buy a $2000 dollar set of rods for your motor because they would be better performing, even though they wouldn't last the lifetime of the engine oil? especially since it will never be noticable in/on a street car? I doubt it. Same thing goes for the a-arms.
...so there's only a 2lb difference(not even the 5 BMmonteSS was allowing for) between the mild steel and the moly arms? and you have to pay more money? - IMO, it'll never be worth it, or noticeable, even a purpose built/perfectly tuned street car. Pro stock, Lemans, etc...then you'll be able to tell, but then you can afford new stuff every season or less.......

 

His website says its 4130N.

Take a gander:
GENERAL METAL INFORMATION PART-3 from Aircraft Spruce

 

The annealed term in that chart is refering to the "dead soft" condition. The term Heat Treating is actually a very broad term, you can vary the temperature, time, and cool down period in the oven to achieve a wide range of properties.

The problem is you cover the entire heat treating spectrum when welding. Somewhere along that tube you are going to have the dead soft state. I noticed in my testing that if I used higher heat and moved quicker the tube would break closer to the weld than if I would use lower heat and welded slower. Unfortunately I don't have actuall tensil tests with hard numbers. My testing consisted of butt welding tube and then putting it in a tubing bender to see where it would break. At the time we were debating whether or not pre-heating was necesary to prevent cracking at the weld. We determined that the tubing was thin enough that the tubing would preheat itself ahead of the weld puddle enough to avoid cracking. Thicker sections of 4130 do need to pre-heated in an oven to prevent this.

Edit: Boogie, care to explain how you can take a metal to it's melting point in a localized area, then let it air cool without affecting it's heat treatment properties?

 

The higher heat treated 4130 requires heat treatment after welding to gain what strength is lost from welding. The normalized is closer to the natural 4130 properties so he likely isnt losing much from just welding and painting/powdercoating the part and sticking it in a box, if its welded properly. At least thats what I know... not that I know much. Welding isnt exactly my best subject area, I would rather leave that to someone else and hope they are doing it right. The stuff I was using was TIG'd and not heat treated and the welds seemed ok but the guy doing the welding was really good. One place we refused to cut corners.

Like I said, break a random sample of parts and see what happens. Otherwise its a bunch of guesswork. Thats if you even care where it is going to break when its loaded to the point of failure. I'm not sure anyone does, I think they just want to run the part and hope its fine while they own the car.

 

So I decided to go for the mild steel but feel free to keep up the debate if you guys want to. The soda can effect that everyone's mentioned scares me, especially since the A-arms will most likely see some rocks hitting them during the course of their life. This was the thing that finally won me over to the mild steel.

If all goes according to the master plan I shall be ordering everything Saturday or Sunday. I will be sure to post the results once everything gets here and I have a chance to install everything.

 

I'm not sure a rock would do it, unless it got positioned between the pavement and the arm. Not planning on doing any thirdgen offroading, are you? I think its more prone to problems, if any, from the varying continual loads applied by the car itself. Even .035 is pretty hard to collapse, takes some force to do it. Cant just push it with your finger or something so it would take a fairly serious loose flying rock at a fairly serious speed to do any damage IMHO to a .035 let alone .090 wall thickness.

 

Wow, Dean I almost didn't recognize you without all the insults

Couple things I would like to clarify, the industry standard for destructive testing of a weld REQUIRES that the coupon fail in the HAZ. The whole purpose is to guarantee that the weld itself is stronger than the base material. I think you were leaving out some key info to your welder friend, or he would concur. Any piece of welded metal is going to be weaker in the HAZ, that's a fact of life. I pointed out my testing as proof that it is a weak point, and then backed it up with a chart showing how much weaker it is at the point on the tube. FYI, I had 2 welders of 25+ years experience looking over my shoulder when I did this, I also had them each do a coupon to test as well. There coupon broke in the same location as mine. This proved to us that the weld was strong enough and that tubing material was the weak link. We never got to test the part after heat treatment.

Where you run into problems is when a designer/fabricator looks up the properties of 4130 and decides that he can cut his material thickness in half. The truth is that 4130 is only marginally stronger than regular mild steel when not heat treated. It appears that Spohn has made his 4130 a-arms 13.3% thinner. I say this is within the design criteria for un HT'ed 4130, I can't say for certain without testing. If he were to heat treat he could theoretically cut that down into the .049" range with a 1.5" tube. You can see where the weight savings would be there. Of course turning a product like that loose on the public would be suicide.

The sole purpose of the shielding gas is to protect the weld puddle from atmospheric contaminants. 4130 is especially susceptible to hydrogen embritlement because of its grain structure, hence the reason for extra attention while welding. The shielding gas in no way shape or form has anything to do with heat treating the weld area. Don't confuse weld induced cracking with heat treatment. TIG is used because 4130 needs to be slowly (relatively) brought up to temperature and cooled while welding to prevent stress cracking. Hence the reason for preheating. This is why MIG is not the preferred method of welding 4130, it starts and stops the weld bead way too quickly.

Let me throw this out there, annealing takes place at 865 deg C, Normalization takes place at 870 deg C, and welding takes place at 1370 deg C. How in the world are you taking your weld puddle up to this temperature without exceeding either the annealing or normalization temperatures of the weld area and surrounding metal? Also these heat treating techniques require that the metal be brought up to these exact temperatures and held for a period of time then slowly allowed to cool at a rate that is around 100 deg per minute. I know I can touch my welds 5 minutes after I finish.

Once again, I'm not anti 4130, I'm just trying to lay out ALL of the facts so Johnny Q public can make an informed decision. The truth is most people see 4130 and get all star eyed thinking its way stronger and way lighter than anything else. When in fact, without heat treating it is only marginally stronger and there is no weight difference unless thinner material is used. Also extra care has to be taken to make sure that welded 4130 is not going to crack right down the middle of the weld (heat induced cracking).

Here's some links of interest

Properties of 4130 @ different levels of heat treatment

Explanation of different levels of heat treatment

Explanation of Hydrogen embrittlement

 

I was thinking definitely the heating and maybe the cooling process were fairly different from a weld with no control on the cooling would have some effect but I didnt know the facts you posted. Thats great. I'd imagine you are compromising the higher strength heat treated materials pretty significantly because the part isnt being heated evenly from the weld to where the heat level drops somewhere below annealing, thats why they require heat treatment afterwards to correct what you did when you welded the part in the first place. Then there's the controlled cooling situation that isnt identical, obviously, to when a part is heat treated.

 

Thats just it Dean, there are two completely and unrelated things going on here. The first problem that you keep harping on is hydrogen embrittlement, which like I said is easily avoided by welding with the proper process and shielding gas.

The second issue is the heat treatment issue, which is completely unrelated to the first problem.

Hydrogen embrittlement will cause the weld itself to fail, ruining the heat treat causes the parent material to fail in the HAZ. Every piece of welded material has this happen, 4130 happens to be affected by it more. Carol Smith covers this extensively in Prepare to win and goes into it in depth in Engineer to win. I also have serveral material science text books that discuss it in depth. Like I said, it's not the end of the world, just something that needs to be known to make an educated decision on whether or not it's worth the extra money.

I tried to link to info that was available on the net that way people could see for themselfs, that way they wouldn't have to take my word for it. Dean, do you have any tech to back up your arguement? I don't mean to sound harsh, but I've brought the tech, and you've called a friend. It's ok you've admitted that welding isn't your forte, it just happens to be something that I've done a LOT of research on and my education has tought me alot about, not to mention that I work with welders, weld inspectors, and weld teachers on a daily basis in the gas industry. I'm around it a LOT.

 

BMmonteSS -
- The way I understand this is that with the gas shielding done properly, the weld is strong, the issues is that(say...3/4" from the weld...) you have screwed the heat treat and it is prone to give in that area unless you re-heat treat the part after welding, correct? This would be because you control the heat in the area you're welding, but you cannot fully control the disperssion of the heat through the metal, nor can you fully control the cooling time. - This would make sense to me because of heat transfer though the length of the welded materials. - so basically, just because you perfectly controlled the heat of the weld doesn't mean you can grab the pipe 1" from the weld directly after welding.(which is kind of a given.....) - Plus, you have gone past the temp of the heat treat to make a proper weld. Am I correct?

I have never welded moly and am just learning to TIG. I've done almost everything up to now with a stick. I've borrowed a MIG a few times for some minor body work and it deffinitely makes building exhaust systems easier. - Everything I have previously done has been mild steel, and I learned soley from my father(certified when he was younger)

...and by the way, I need some stuff welded....... j/k

 

Yeah, you pretty much got it. The heat treat is blown in any area that was taken above 865 deg, it's the simple fact that there is more material at the weld that makes it stronger (as long as it's not hydrogen embrittled). Some where along the tube you are going to have the fully annealed or soft point, which is going to be your weak link in the chain, where this happens depends on how much heat you put into the tube while welding.

TIG is great for hose that can learn to pat their head while they rub their stomach. Once you get the method down you will love it. When you get a chance to weld 4130, just remember to keep it super clean and slowly bring down your heat at the end of a bead, you'll know if you do this too fast because you'll get a little crater in your bead..

 

It's Carrol Smith, the god father of the Indy car and one of the most respected names in road racing, HUGE difference from Carrol Shelby the god father of bling. And yes believe it or not TIG as we know it today has been around for over 50 years. The last time I checked my text books were all written in the last 10 years. I also hate to tell you when parts are heat treated they aren't done so in an argon atmosphere. The shielding gas has nohing to do with heat treatment and everything to do with protecting the weld puddle from absorbing contaminants from the air. I dare you to prove me wrong.

Come on Dean do your homework or bow out of the discussion. Hidding behind the fact that your just regurgitating what your friend told you isn't an excuse. If I did something like that you would call me on it, and rightly so.

 

You don't need to drop the money for tubular A-arms for the street.

I don't know of any road race 3rd gen that's running tubular arms. There might be one or two out there, but the numbers are low.

Save your money on the arms, pick a set up at the junkyard, paint them up, and put in new bushings and ball joints. You'll be good to go on the street or track and your wallet won't be as light when you're done.

 

I'm not sure that I agree with all of Dean's posts being deleted from this thread. I guess I missed the thing that finally sent things over the edge but why not just delete that post? A few of his posts were very useful to me, thankfully I quoted the thing that's the most important (IMO) so I will post it again for the benefit of those who will be looking for this thread in the future.

"What I do not like about coilovers on a 3rd gen (and I actually had a part in discussion of developing his coilover kit in private correspondences through phone and email) is the fact that the Torrington bearings uses to pivot the springs in steering may have long term continual maintenance on a daily driver. If I had a track only or weekend only playcar, I would opt for the coilover kit."

Also, to whoever asked about off roading - there will be none of that. I just happen to have a fairly long gravel driveway that's fun to tear up/down sometimes

 

Great, now it looks like I'm argueing with my self

Gummie, I think the reason that all his post's were deleted is because he has been banned upteen times now, and refuses to sit out his due time. He just keeps popping back up under a different user name. Dean is very knowledgeable about some things, it's just his delivery and take my word for it attitude that rubs everyone the wrong way.

 

Yea, I guess I was talking to myself too... thought I saw the post count drop last night and I was kind of wondering... had a suspicion. Confirmed.

So to recap... we have some welders with experience saying when done properly with the right gas mix that its ok, and some say or think otherwise. I'm not sure myself on the low yield strength (~90ksi) 4130 losing enough strength to drop it to the 1020 range but I cant see how you would think that 4130 heat treated into the 150-200ksi range through specific heating and cooling processes that affects the entire piece equally would be equivalent to later heating one small portion that inevitably has relative hot and cool spots and is allowed to cool in an uncontrolled process. To me, it doesnt make much sense if you consider the heat of the weld and that you've gone past the temperature used for heat treating, it would be similar to heating a spring to the point where you ruin the temper, the properties it had are gone from what you did.

I dont think anyone is arguing about embrittlement when the welding is done like its supposed to be done, its the material strength from whatever specific heating and cooling processes were used to give it that strength.

 

I know about his past but he wasn't being very agressive in this thread, at least with what I had read up until deletion. If he did get aggressive then why not just delete the aggressive post and give him a warning? He did post some useful info (the bearing) as well as some relevant info as to material strengths. I'm very pro-Dean right now because he was extremely helpful in my other thread (he even took a picture for me), which you can find here

Don't forget the 'soda can' effect. This is pretty much the only reason why I’m going to pass up the chrome moly and get the mild steel. Granted, everything else aftermarket on my car is already 4130 (crossmember and torque arm) and everything else will also probably be 4130 in the future (panhard bar, LCA’s, etc). Gotta fix the front before I can move on to the back.

P.S. – this double quote thing is very cool

 

You guys have forgotten something,why not gas weld it? 99% percent of all small airplane frames are gas welded,not tig. And there reason for it was because after welding the joint you can go back over and normalize the weld zone.You can do the same if you TIG weld it then go back over the weld with gas. You probably wont find that info in any new textbook. I learned it from some old airframe engineers when I was looking at building a airplane.

 

Actually that’s in every welding text book I have. The problem with gas welding 4130 is that your weld is not protected by an inert gas, and why it’s no longer allowed by the FAA. Hydrogen embrittlement is why TIG welding was even developed, and people learned about it by welding with gas. You are right though, you can return the entire piece of metal back to its dead soft state by heating it like you mentioned, this at least gets the whole piece in one state of heat treatment, even if it’s the weakest state.

 

There is also the requirement to back purge the tubing being welded. One starts to wonder whether 4130 automotive parts are really properly welded.

RBob.

 

Oh, I was wondering why the plane I wanted to build the fuselage is TIGed. I really dont see the reason for tubular arms, the stocks dont weigh that much and also could be lightened and reinforced enough to make a difference. I think most people wouldnt even feel the difference.

 

RBOB


Edit to add that I think there is widespread missuse of 4130 in the a automotive world. Believe it or not rocket chassis, one of the leading dirt track late model builders in the country uses MIG to weld their 4130 chassis' together. Every book in the world says it's not the right thing to do, but they do it anyway. I asked why they didn't use TIG, and their answer was that it took too long. They turn out a race car a day there, and with TIG they could only do 2 a week.

 

gotta love america - quantity before quality.....that's got to be unsafe.
- I've seen some horrific crashes in my years being around drag racing. After recently having the unfortunate event of watching my father t-punch the concrete retaining wall at a little over 125mph and having him get out with out a scratch and only the car hurt from the firewall forward(plus post impact 1/8 slide on the roof). I think for the 150lbs difference, I'll just stick with mild steel. I've seen too many moly cars desintegrate after the initial impact. The first hit is ok, past that you may never walk(or breathe) again.....I guess thats the same as the mini-baja thing you were talking about.

 

Gas Welding is still FAA approved. And after welding 4130 with gas you can go back and normalized the tube and weld. The tubing will the same strength as before you welded it. To heat treat it the whole thing would have to be brought up to temp then quenched to allow proper heat treating. The only reason to go with 4130 is for using a lighter weight tubing that has the same strength as mild steel. You can use a smaller wall thickness to loose weight but retain the strength needed. On a suspension part it would wise to use mild steel or 4130 in the same wall thickness as the MS.

 

That extra strength is also its weakness, as it becomes more brittle The problem is that(especially with thinner wall) it is more likely to give after the initial impact(like the 2nd roll, etc). As for using the same thickness, then what would you be gaining? Yes, it would be stronger, but if the mild steel part is up to the task, you now have a more expensive piece that is still doing the same job and is more prone to break than bend.....

 

Hence why race teams inspect often and replace religiously.