Forshock 85TA

ok people, sounds like things have moved along...

Her car may not reflect you tastes (or mine ) but its hers, as is the money and direction it goes (hopefully straight now )

So, lets see what happens with the AJE stuff and call it a day shall we?

camarodarrell

Just for information purpose: I was driving my fathers 1992 astro van 20 mph in a neighborhood and the STOCK A-arm broke, the balljoint and surrounding metal broke off, no impact and going in a straight line. Not a camaro but still GM.

RTFC

OK So now you're telling us Jason had records of the bad batch of arms and never notified you before the break? Even worse. And you bought his line of BS.

Forshock 85TA

Im gonna have to agree with him on this one, i wont make it a habit

Dewey316

interesting. So hers where the only arms that were sold thru PA that had this problem...according to PA's records.

So if "Some have" been sent something, who did you send them to? Apperently not the only person that PA sold a bad set of arms to.

I'm with Dean on this, sounds like a line of BS.

snm92rs

iTrader: (1)

SWEEEET

redraif

Telling you what I was told.

Just reporting on our conversation. What he told me was wrong with the parts is exactly what My experts who inspected them found. So how it happened, why, and to how many parts...I'm going on what I was told.

Not saying the whole thing was handled properly! I'm with you...I would have thought that once a pattern was established, ie... parts outsourced were breaking... phone calls and recalls would have been made. Esp if I was truely the only individual that recieved a set from this batch. I should have been te easy one to track down. In that regard I'm disappointed in PA's efforts, but at this time he is making a real effort to straighten things out with me!

Will say again, all are lucky I had not gotten on the hwy when the part let loose.

Will keep you all updated.

iroc-si

Just wish to clarify, did you mean to say that? If you substitute the word streetcar for racecar then you make sense.

A racecar needs all parts to be their lightest, for a given required strength to get maximum performance. The ultimate racecar would fall apart as it came over the finish line. Now only the top level cars would consider doing exactly that, but a car that just works race after race after race is never going to be the fastest that it could be. Most true racecars that are competatively raced require certain parts to be replaced after X number of racing miles. Now most of us accept that this applies to things like brakes on all cars but at more competative levels this also applies to suspension components.

"compromising design strength for lightness" is done throughout the racing world but is done with a lot of research into each and every part to make sure they are stong enough for the particular race application. Outwith the intended application and they will break. Streetcars have to cope with all sorts of rough road conditions, potholes, kerbs etc, and thus cannot fail as their drivers cannot usually cope with unexpected failures.

Getting back to the reason of this thread....

I'm glad to hear that this fail didn't cause too much harm. It is a shame that PA didn't treat you right initially, but they do seem to be good to work with in the end. They do have good customer service (when you get through) unlike folks like Spohn who told me that it was just tough luck that their parts didn't fit...... and yes I spoke directly to Steve.....

I've found that most small to medium sized car parts companies have a poor record for getting back to you, and the only approach that works is repeated phoning.

Si.

RTFC

Si,

The parts you speak of are factory one off parts that are not availiable to the public and areprototype parts. The drivers are paid profesionals working under a blanket catastrophe clause in the case of death or disfigurement.

This is an oiver the counter part that is mass produced to the general public and they damn well know it is being used daily on street cars- Its what make 95% of their business and they and anyone else in the simular public aftermarket parts business know that.

Now if these parts are made to have a shelf life, PA needs to disclose that they are wound up so tightly for lightness that they may break and should be replaced in regular intervals for safety.
They know their customers can not afford to replace parts frequently in 99% of cases. Customers should not be prototype dummies and are not paid or insured to be.

Dean

JPrevost

The break down;
PA part breaks on the street under normal street driving.
Part was broken from fatigue, a normal problem with street parts that see many miles (cycles).
PA has disclaimer on website that states it is not responsible for the part being used on the street.
PA claims to have known there was a problem and that they have records of the "bad" batch but didn't attempt to contact the owners of their defective products.
PA goes above and beyond to rectify the situation... but why? Is it their reputation that they're worried about or is there a legality that they're trying to hide?

My assumptions; The part wasn't designed by an engineer. Instead the normal coil-over LCA just got a spring pirtch installed without understanding the bending forces that would lead to failure EXACTLY where the part in red's case failed! Right behind the spring pirtch is the highest bending moment force. This is why the product fatigued to death.... or was it? Nope, mild steel, even defective steel (so long as it's mostly steel) doesn't get weak from fatigue unless the part was improperly designed!!! You can put a piece of steel in a vice and jump up and down on it all day so long as you don't go past it's yield point and it would not get weak. Aluminum on the other hand WOULD, but NOT steel. Their part is a terrible design. It's great for coil-over but when you put the spring in there there is a huge bending moment at the spring perch. Since the distance from the wheel to the perch is longer than that from the bushings to the perch, the break would be more likely to occure between the perch and the bushings. Reason being is the wheel (in equilibrium) has a greater moment over the bushings.
For the street, nothing beats the GM LCAs. For racing with coil-overs, the PA units are GREAT. For imbetween I'd go with Spohn. He might not engineer his parts the best but they're definatly stronger than most (including OE).
I sure hope PA starts using engineers with half a whit because as it stands, I can see tons wrong with their products. It's not my place to bad mouth a company and I won't, because I think some of their stuff is great, but they have a lot of work to do before I recommend their stuff.
Here's a hint as to what should be done with perch LCAs; boxed steel, not tube! Tube is great for compression and tension, not bending. Squeeze a tube in a press along it's axis and then push on the center of the tube with a heavy force, watch the resulting carnage.

Side topic; Why is it some of you guys were trying to calculate the spring rate change of Eibach Pro-kit spring with a coil cut? Don't you guys know that the Pro-kit is a progressive, not linear. You can't calculate the rate like you would a linear spring! Sport-lines yes, Pro-kit no.

91formulaSS

The front Pro-kit springs are linear. It's the rears that are progressive. evenly spaced coils = linear

JPrevost

I didn't notice the evenly spaced coils. I'm not doubting you because you sound like you know, but how did you find this out? When I called Eibach (4 years ago) they said it was progressive... I didn't ask if all springs where

91formulaSS

I read it here https://www.thirdgen.org/techbb2/sho...t+spring+rates

but all you have to do is look at the spring, and take a few quick measurement if you don't believe your eyes.

(bad angle) but you can still see how the rear springs get wider at the top, the fronts don't

91formulaSS

here you can see both stock and pro-kit springs are linear

JPrevost

Yeah, I looked at some old pictures. You're right, definatly appear to be linear. Thanks for the heads up. Now back to the broken A-arm... anybody else a little curious as to why they just welded in spring perchs? Because I was bored at work today I through their design into Solidworks and ran an FEA simulation. I'm suprised it didn't break from just lowering it after installing them!

91formulaSS

because you've actually done more engineering on these things thank the people that manufacture them.

MrDude_1

umm, because they designed a coil over a-arm for drag cars, and people wanted ones that took the stock coil.....





if you have solidworks and everything to test/engineer it, why dont you figure out something and post it up?

JPrevost

ummm... because I don't work for free.
If they hire me to design a superior product that'll be cost effective and easy to replicate then I'll do it... for a price.
It's a real shame how some companies work these days... it's a wonder they're still in business.

MrDude_1

um, since you seem to be REALLY intrested in this subject...

and you have the tools at your disposal...



why wouldnt you do it as part of your hobby thing for fun and benifit us all? its not like PA is going to change their design to match what you come up with... lol






















on a unrelated side note... i hit a pothole yesterday.... went over the a arms best i could... cant magnaflux them or anything.. lol, but no visible damage... (powdercoating is off so i can look at them)

anesthes

iTrader: (12)

Anyone wanna share the alignment specs ?

I had mine done the other day by a buddy. No matter how hard he tried, we ended up with 2 degrees of caster on the right side. Dunno if my strut towers are bent, or if the k-member isn't to spec.

Curious if anyone else has similar results?

Also, I hit a pothole the other day. The left a-arm hit the k-member and has a ding in it now.. Bumpstops would be a good idea.

-- Joe

JPrevost

Because that's just it, I have the tools at my disposal, not you and apparently not PA. How do you know PA isn't going to change their design to what I came up with? They obviously have an issue already with it and have a "fix" by adding in little misc braces (a solution, weak, but still a solution).

Also, how would it benifit everybody? I fail to see how 99% of the people that bought these A-arms would be able to replicate my design over their's seeing as their's is pretty simple and nobody bothered making their own... so.. umm... no work for free . Besides, it's obvious their design is sub par, I'm sure after this thread that they're taking considerations towards redoing the design or dropping the perched arms completely... I hope.

AM91Camaro_RS

well then, thanks for telling us that you have software to design a better arm...

Lo-tec

1 deg neg camber, 4 deg caster, .05" toe in per side, using ground control camber/caster plates. Ground control sells foam bumpstops that go on the strut shaft under the mount for $8 each.

MrDude_1

its in the FAQ on the main page: https://www.thirdgen.org/newdesign/faq/thirdgen.shtml

you'll find factory, and reccomended performance specs...

DAMN... you must have hit it HARD...

MrDude_1

yea.. no ****.... lol

JPrevost

What part of my message didn't you understand. What good is it if I just through up my work for free? You guys paid PA for the arms, not me, so make them pay me and I'll give them my services. Want me to build you some stronger arms, pay me and I'll do it. I might charge you $1000 an arm but that's because I don't want to do it and again, I paid $$$ for my software, why should I give it and my work away for free? I fail to see why you think I should do that. What I will do is show you their design simulated. Hopefully you know some engineering and can derive for yourself the problem with their arms. This is all the help I'm going to give. Expect the FEA in the evening or tomorrow mid day.

kretos

I have to tottaly agree with dean on this one, if he knows where all the bad ones are why are people not getting called to be informed, and having the bad ones replaced.

the answer is because he really couldn't give a ****, the reason redraif is getting a new set is because this topic had over 200 replys and was a slap in the face to him pumping out product.

If i were a person who had bought a set of "defectice" a arms from him, i would be suing him and his company over negligence. Having made a defective product, knowing it was defective and failing to notify people it was defective is illegal. It wouldn't matter its application, street, strip or "off road" it boils down to he knows there was a bad batch and people arn't getting called.

Forshock 85TA

Im with him (JPrevost), its his work so leave it be, what he shares is up to him. I do Industrial Automation/Programming and there is no way i would give you my source code...

Anyways would be nice to see the stats

Kat

iTrader: (4)

I'm kinda curious how the Spohn A-arms would compare to i PA's in that program....

Kat

Dewey316

What scares me is that you (as in spohns company) don't know.

In this day and age it is hard for me to beleive that there are companies building stuff like this, with out first doing some basic design tests on computers.

soulbounder

I'm sure we'd all be surprised if we knew how many aftermarket parts received no real engineering at all.

AM91Camaro_RS

i do understand not giving out your work. that makes perfect sense. it just that he (JPrevost) comes in here and says that he's designed something better but then doesn't care to tell why its better. he says that if PA wants to hire him....he'll let them use his design but its pretty unlikely that they'll say "oh, this guy said he has something better, he says we can hire him, i guess we'll hire him!" if i designed something and thought that there was a market for it and i thought that i could build and sell this piece, yes, i'd keep my design to myself. if i couldn't build it and sell it or wanted to charge rediculous prices...i'd probably throw the design out to see if someone else could build it for the good of other people. see what i'm saying??

redraif

Well Jason did make the situation right with another customer prior to me...prior to this thread! And again getting things made right was never the intention of this thread. I wanted to educate myself! Which I got a crash course for sure! This thread got a life of its own! Would Jason have given me a new set even if this thread did not exist. I feel he would have!

As far sueing... honestly I did not want to destroy anyone. I just wanted it all made right. I'm not that vendictive. The cost of sueing his company would have taken time and $ I did not, do not have. Plus what would some huge lawsuit have done for US as a automotive community... made venders afraid to even try to offer parts for us, drop what they already carry, destroy PA so he can't sell any products for us... Honestly, I don't think there would have been a good overall out come for the time and $ spent. At this point, we are working things out in a fair manner!

In retrospect....looking at this thread... hopefully enough have seen it that they will think about what they both buy and sell. Realize peoples life's and cars are at stake and take it more seriously in the future! BUILD better stronger parts, & call if there is a potential problem!

JPrevost

http://www.absoluteastronomy.com/enc..._of_safety.htm
Read that if you're not an engineer or need a refresher.
Here is only 2000lbs on the spring perch. Joints are restrained.
Now check out this FEA;

Notice something odd about the FOS? This is using Max von Mises Stress with the materials yield strenght, not ultimate. When a steel goes past it's yield point it can fatigue like a paper clip in the hands of a bored colleague. When I did the ultimate strength test the min FOS was at .87 , still below 1! And that's just a 2000lb force on the perch. You'll see more than that on the street with crappy shocks and no bump stops. I could have thrown in a cornering simulation but it wouldn't be pretty.
Here is the stress;

JPrevost

I would if you didn't have other options for LCA's. There are enough out there that are plenty strong enough so why would I give out my R&D for free? I give enough to this community already so don't **** me off by telling me that my work should be given away for free.

Forshock 85TA

holy crap! Thats junk, i would atleast hope for a 3 or 4, preferably an 8...

Kat

iTrader: (4)

Kinda funny how you "assume" what we know and don't know. The reason I asked him to run it though his program cause well everyone uses different stuff and it would be a good direct comparison.


Kat

Dewey316

Funny how I read your post. If you don't want assumtions made, then elaberate on your posts.

I will also add that at least one of your employers parts (granted an older design), that I put into solid works, showed the exact results of where my peice failed, and showed the exact conclusion that myself, my engineer father, my engineering studen brother, and several ME friends all thought was the case.

I obviosly don't have his new design arms to take measurements of, but I would imagine that the actualy problem with mine, in the same conditions would still be an issue. I don't really want to get into a pissing match about these things, its not my place. I know how my car reacts, and where it puts forces on parts that your 'average' camaro does not. So I am not going to bash them. But if you are insinuating that my assumtion is wrong. Then buck up, and at least tell us all a little about the process, and why my assumtion was so incorrect.

RTFC

OK college boys, How about we see this same FEA/FoS test results on a genuine GM stamped steel arm for comparisons.

That has nothing to do with givng out design ideas. It a simple baseline test showing what we are in fact using that is tried and true not to break unless extremely corroded or misused.

In all fairness, its the appropriate thing to do since you have shown the PA results with *this* "computer" simulation.
Dean

cali92RS

You say college boy like its a bad thing?

Kat

iTrader: (4)

Thats the thing, I can't. I feel any of that info could be used for other co's to make a better product that are in direct competition for Spohn. I singed a paper saying that I can't release any info about that kinda stuff. Sorry.

Kat

HorseflyDF

The front end of this car is very heavy so
be careful when and if you decide to use aftermarket
suspension components.
We are living in an age where for the most part
people think its ok to steel lie cheat etc...just take
government as an example.

Also I would like to add while I like
the design of the front end suspension from the factory
the unibody body flex is ridiculous. The factory sheet metal
used for the unibody is a joke and its sad that GM
got away with using such weak material. IF wieght was
an issue the sensible thing to do would of been to scale
down the dimensions of the car. Not put a weak
uibody contruction damn I never felt such bending
some kind of joke.

Co worker purchased a 98 firebird with only 11,000 miles,
from another co worker.
After owning the car only a few months
the linkage for the brake pedal broke at 40 mph.
The Gm dealership response was to claim that the car
had been in an accident that weakened the linkage.
If it was in an accident it had to happen at the factory.

He will never buy another GM car again.

He owned a 240sx put 175,000 miles on it and it
was still running and now he purchased an
ALtima he will not even drive the firebird anymore.
or any gm car again. Japanese have whats called integrity.
The US have thiefs and crooks.

Dewey316

Kat, I am going to go on my assumptions until you prove to me otherwise. No offense, because trust me, I understand the NDA and no compete clauses, etc in contracts. Most of Steve's stuff is so overbuilt, that it last, but do not show much engineering.

My statement earlier was also a blanket statement, although I did respond directly to you. The second statement in that post, was the part that you should read. I was not going out of my way to pick on your company. I actualy mention Spohn to a lot of people, and send many people his way. Because, I would trust their lives to an overbuilt and underengineered peice, over something that is underbuilt, and underengineered.

You made a point of trying to discredit my statement, and then can't really say anything to actualy counter. Maybe a more pointed question, would help. How many licensed ME's are on staff there?

RTFC

College is a great thing for knowledge, it does nothing for intellegence or common sense.

The street smart thing to do if we are all going to talk above everyone and then run some figures on one product design with a certain program would be to common sensibly run that same program on a baseline product so you have a reference to look at.

Any ol' scientist can and usually does make up figures to meet his agenda- the same for political and enviromental wacko groups. You can make figures to back any stance in your favor when you do not provide another reference to the equation.

91formulaSS

I couldn't agree with you more.

Dale

iTrader: (12)

JPrevost,
can you explain the colors in the pictures as to what means what?

I am a draftsman, but no company I have worked for has used a program like that. I'm sure their are others watching this post that are possibly less understanding than even me.

cali92RS

You are correct, that would be the most definitive thing to do. But JPrevosts model is useful in showing WHERE failure would occur under loading. And for that, no comparitive model is needed.
I bet the stamped GM piece would be a bitch to model. I know CATIA v5 (pretty much same as solidworks) and i wouldnt even know where to begin.

Dale, FEM analysis is used at pretty much every company where engineering is performed for the last 15-20 years.
In both models, the scale is shown to the right, the top model shows the FOS (Factor of safety...the higher the number, the higher the redundancy the part has built into it, and the more expensive it will be) distribution over the part. I cannot think of anytime you would want an FOS less than 1.
The bottom model shows the stress distribution. again the scale is on the right. The higher the number is, the quicker is will fail in thhat reigon.

soulbounder

Red = bad in the pictures above. Normally you would expect to see an FoS no less than 4 when it comes to something you would want to trust your life with. The first pic with the 2k lbs. load shows FoS less than 1.

askulte

If someone has access to a laser scanning CMM, then the stock part could be modeled fairly accurately, but it would involve many hours getting the model cleaned up with the various compound curves in the piece. I doubt anyone will offer to pay the $5k a scanning house would want to make a solid model of the piece, and mesh it for an FEA analysis, just to have a baseline. I've never heard of a stock f-body a-arm failing, so I'll make an engineering judgement (i.e. guess, based on either an engineering education, or proper experience) that it's built strong enough, with enough safety factor that failure will be a very remote possibility. Modeling an aftermarket a-arm, made of tubes, bar stock, and straight length is much easier than every curve, fillet, flange, and pocket on the stock stamped a-arm. In this case, using FEA will let you try alternate designs, to see if the strength (and factor of safety) improves, flexes less, and also lowers localized high-stress points on the model.

Sure, you can make any graph or model show anything (just change max stress to green instead of red, leave min at blue, and most marketing people would think it's great w/o looking at real numbers!). Add fillets to all the corners, build up some areas with thicker material, or even change materials in the model to see how you can improve it. Basically, use the FEA model to quickly try out different ideas to see how the part can be improved (strengthened or lightened, for a racing application).

Dale

iTrader: (12)

so if red= bad. That part sucked from the beginning.

My first drafting job was in a mfg plant where we built dock equipement about 10 years ago. We didnt have this program still when I left 5 years ago. The engineers busted out the formula books, pens n paper.

But then again, it is all theory. Some things break when they shouldnt, and some things didnt break when they should.