mancini tube upper control arm failure....

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lo234me said:
I just purchased my complete front end with rack & pinion steering from CAP. I hope that my welds are good. I wonder if I should have them inspected buy someone who knows a good weld from a bad weld????
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Post pic closeups on site. I`ve always thought they should have gussets tieing arms to tube. Wonder how many of these guys actually have an engineer designing this stuff, or at least signing off on them? This was debated on Mopar muscle mag, a few years ago. Where an engineer wrote in and pointed out that the torsion bar system provided a good percentage of supporting the front clip of car, and deemed them unsafe. The editor went to the defense of the aftermarket systems, stateing, well they been holding so far, without front sagging etc. But I`ve noticed some systems provide a pipe connecting firewall down to upper uca mount, somehow. Does CAP have warrenty for failure? if so they probably will just replace your broken part, not the resulting damage to car or other involved cars/lives, property damage etc. It`s a wonder street cars pass inspection with non factory front end systems? I was thinking of a RMS system in the future, but now i`m hesitant
 
mopar head said:
Post pic closeups on site. I`ve always thought they should have gussets tieing arms to tube. Wonder how many of these guys actually have an engineer designing this stuff, or at least signing off on them? This was debated on Mopar muscle mag, a few years ago. Where an engineer wrote in and pointed out that the torsion bar system provided a good percentage of supporting the front clip of car, and deemed them unsafe. The editor went to the defense of the aftermarket systems, stateing, well they been holding so far, without front sagging etc. But I`ve noticed some systems provide a pipe connecting firewall down to upper uca mount, somehow. Does CAP have warrenty for failure? if so they probably will just replace your broken part, not the resulting damage to car or other involved cars/lives, property damage etc. It`s a wonder street cars pass inspection with non factory front end systems? I was thinking of a RMS system in the future, but now i`m hesitant
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The failure in those pictures are from a poor weld. Don't lump the RMS system in with that other junk. Mine has been in my car since 2005. There are cars out there with 60,000 miles on theri RMS system with no problems. Do your homework. I have never heard a complaint or of any type of failures with the Rms set up . It may not be as cheap as others but it's your saftey we are talking about.
 
Wow, those pics are just sickening. :pale:

So, CAP = Crap and never buy from them. Got it.
 
abodyjoe said:
The failure in those pictures are from a poor weld. Don't lump the RMS system in with that other junk. Mine has been in my car since 2005. There are cars out there with 60,000 miles on theri RMS system with no problems. Do your homework. I have never heard a complaint or of any type of failures with the Rms set up . It may not be as cheap as others but it's your saftey we are talking about.
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Point taken Joe, But if your using these systems on the street, Beware! Your 100% liable! Both companys have a disclaimer, off road only!!!! and if a knowlageable insurance adjuster notices that non factory system, good luck recovering any damages period! Neither company claims to have an in house engineer. homework done. I don`t care how good a weldor you are, In real life, welds fatigue, something I would inspect frequently, and if they crack from inside out you`ll find out the hard way. Good Luck
 
engineers have designed some of the biggest disaster known to man. In a lot of cases the at home guys just understand this stuff and how it all works together. It's hard to explain. You have to see it in action to understand I guess.

As for the welds go. It's no different the a weld on that bridge you drive over everyday. Or the building you work in. A bad weld is a bad weld. Even if your using all stock stuff you better be under there checking things out. Just had a friend find a stock upper arm with a crack in it. The stock stuff is far from bullit proof too. And let's not get off subject here. The failure in that picture is a bad weld. Plain and simple
 
So his 40 year old stock part has a crack in it? How old do you thing that tube A-arm was?

Sure it was a bad weld.... So what. An after market part like that should not have a bad weld. Like was posted above.... These things are poorly designed. Gussets could be and should be added for strength. But then they wouldn't look as cool.

I feel no pity for the destruction of that car.
 
The point is that the weld was bad. That's what broke and what caused the crash. No crap a part like that shouldn't have a bad weld. That's what the thread is about. As far As a bad design. Who knows. It may be a good design that just welded bad. Those arms don't need to be gusseted if the proper material was used and welded correctly. Even with a gusset that arm would have broken with a crappy weld like that.

And the point I was making about the stock arm being g cracked is that even though you have stock stuff under there it's not bolt on and forget it.
 
abodyjoe said:
The point is that the weld was bad. That's what broke and what caused the crash. No crap a part like that shouldn't have a bad weld. That's what the thread is about. As far As a bad design. Who knows. It may be a good design that just welded bad. Those arms don't need to be gusseted if the proper material was used and welded correctly. Even with a gusset that arm would have broken with a crappy weld like that.

And the point I was making about the stock arm being g cracked is that even though you have stock stuff under there it's not bolt on and forget it.
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I am with you on this joe. Bad design or not, that weld should not have broke like that. The tube should of snaped in half before that weld did that. I have seen dune buggys that have rolled going 80+ MPH tubes all bent and snaped in half but not one broke weld. Good welds should not brake.
 
That looks really bad. Most of what I think has already been covered... just like my ex... lack of penetration! :toothy10:

Some stuff in this thread reminds me of a story of "piss" and "cheerios".

I guess having a pair of upper control arm tabs pull off a stock frame rail is a product of bad design as well? Maybe bad welding tool. You know those Chrysler engineers know everything. sheesh!
 
In the July 2009 Mopar Muscle they put a Cap k-frame and upper arms in their project '68 Barracuda. They talk them all up about how strong and light they are. Now people all the the country will read that and more junk will be installed breaking out on the public roads putting people's lives in danger.
 
abodyjoe said:
. Just had a friend find a stock upper arm with a crack in it. The stock stuff is far from bullit proof too.
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at least his pix are not blurry - at least where the crack is......lol

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That crack is from rust. I have also seen stock arms crack in the same location from bad handling (as I suspect - monkeys doing the R&R on the bushings). I have also seen bent stock arms (easy to spot is you sight through the bushings).
 
I have to disagree Jim - I dont believe rust was the cause of the crack.
 
Jim Lusk said:
That crack is from rust. I have also seen stock arms crack in the same location from bad handling (as I suspect - monkeys doing the R&R on the bushings). I have also seen bent stock arms (easy to spot is you sight through the bushings).
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the entire point wasn't to decide why the stock one cracked. it was to point out that even if your running stock stuff that you need to still check it from time to time.


it was in reply to this comment.

I don`t care how good a weldor you are, In real life, welds fatigue, something I would inspect frequently, and if they crack from inside out you`ll find out the hard way.
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340sFastback said:
In the July 2009 Mopar Muscle they put a Cap k-frame and upper arms in their project '68 Barracuda. They talk them all up about how strong and light they are. Now people all the the country will read that and more junk will be installed breaking out on the public roads putting people's lives in danger.
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oh they will tell ya how great the set up is. not because of anything they found by installing it but because they are a sponsor in the magazine..lol
 
Jim Lusk said:
That crack is from rust. I have also seen stock arms crack in the same location from bad handling (as I suspect - monkeys doing the R&R on the bushings). I have also seen bent stock arms (easy to spot is you sight through the bushings).
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That's definitely a stress crack, not a rust issue at all! Almost looks like the bushing pressed in was a little oversize, appears that the outer part of the wall is pushed out. Maybe just a bad installation. Either way, stock parts fail too! They rust, they flex, and over time they fatigue. All your stock parts have 40 years of metal fatigue built in now, even if they don't look bad it doesn't mean they can't fail.

The CAP A-arm that failed is right at the weld. Its probably just a bad weld. If it had failed in the middle of the tube or somewhere else, I'd say bad design. But if its just a cold weld,it has nothing to do with design at all. All the aftermarket A-arms have threaded ends welded onto tubes, not sure if all of them are just butt-welded though, a better design would be for it to have a shoulder on the end that fits into the tube. But even that design still wouldn't make up for a bad weld, and there's no reason a butt-weld can't be strong enough to support the front end. So yes, there are stronger designs, but it doesn't mean its a bad design.

Also, the fact that it failed while the owner was driving down the road at 45mph doesn't mean it was caused by regular driving. A hard launch and landing could have cracked the arm at the weld, but not enough for immediate failure. Drive around for a few months, hit a few potholes, and the crack completes itself and the arm fails. Don't get me wrong, I have CAP a-arms on my car and I'm concerned, but it may not have been entirely on the manufacturer. It certainly might be a poor weld that slipped through and failed under normal conditions, but it also might have been damaged on the car.

Yes, it shouldn't happen, but even the best QC in the world can't prevent all failures. If you get a bad tube for example, how would you know? If it was heated improperly and all the carbon migrated to one place making it brittle, how would you know? Without an detailed engineering analysis (which would destroy the part btw), you wouldn't.

Tubular a-arms in general are a much better design than the stockers. They will be stronger, lighter, and less prone to flexing if built out of the right materials. But unlike the stockers they depend on welds for the strength of the part, so if you have a crappy weld, you have a crappy part.

On that note, we all love powder coated parts. But realistically they hide cracks. If parts are left bare, you can see even small cracks begin to form. Of course, then you have a corrosion issue to deal with, and rust will hide cracks too.
 
Also, the fact that it failed while the owner was driving down the road at 45mph doesn't mean it was caused by regular driving. A hard launch and landing could have cracked the arm at the weld, but not enough for immediate failure. Drive around for a few months, hit a few potholes, and the crack completes itself and the arm fails. Don't get me wrong, I have CAP a-arms on my car and I'm concerned, but it may not have been entirely on the manufacturer. It certainly might be a poor weld that slipped through and failed under normal conditions, but it also might have been damaged on the car.
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if ya look at what the guy says, the arms were bought in december of 2008, it is now may 2009. thats not even 6 months. and on top of that from what i understand the car is from the detroit area. so in reality how much could use could those arms actually of gotten? not too much in my opinion.
 
abodyjoe said:
if ya look at what the guy says, the arms were bought in december of 2008, it is now may 2009. thats not even 6 months. and on top of that from what i understand the car is from the detroit area. so in reality how much could use could those arms actually of gotten? not too much in my opinion.
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I agree, its unlikely they got much use. But it only takes one event to damage the part. Hit a curb, bounce the car after a hard launch, even a big pothole (none of those in Detroit right?) could cause a failure of correctly built aftermarket parts or even stockers. In SoCal while they were repairing I5 Caltrans left a really big step off at a few overpasses, they ground down the asphalt for paving and obviously left the concrete under the overpasses. I must have seen a dozen cars on the side of the road with busted suspension, so it can happen!

I personally think a crappy weld is much more likely, but there are a lot of ways to break stuff. I'm still planning on keeping a very close eye on my CAP UCA's.
 
Tub A arms are used on off road stuff all the time. Never seen one brake like that. I have seen them all twisted up after hiting some thing or after a crash, but never a weld brake. I have been in this white car as it has gone over 4 foot deep whoops at over 80 MPH. As for pulling the front end up then coming down hard? Well just watch the vid. We do it all the time. O ya and we have jumped it too. Ant no thing.:-D


http://www.youtube.com/watch?v=6bR_qvarkwc

AlumiCraft10.jpg
 
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