control arm failure at the track this weekend

[DILYSI Dave]

"We do FEA" means not much. It's a tool, but only that. It doesn't magically make parts not break.

 

[sheizasosay]

I would only be guessing but I would think that if a part looks like it has a problem revealed with FEA then it definitely will have a problem in the finished product, but if a product looks good after the analysis it doesn't mean it's guaranteed good to go. Is that true or a bad guess?


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[skyline247]

I would only be guessing but I would think that if a part looks like it has a problem revealed with FEA then it definitely will have a problem in the finished product, but if a product looks good after the analysis it doesn't mean it's guaranteed good to go. Is that true or a bad guess?


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It depends. Sometimes the product can look good in FEA, and then fail in reality. It comes down to how the part is modeled. I won't get into boundary conditions, but essentially, you need to get the loads, moments, etc. that are acting on the component correct if you want realistic answers. For example, the control arm that failed here could have undergone analysis, but if the loads on it weren't large enough, it wouldn't have predicted the failure that happened. Usually companies will supplement FEA with testing to validate the results. Computer modeling helps reduce time and cost of exhaustive testing, but worst cases will probably be tested regardless.

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[Thekid760]

And Steve Poe also already pointed out that there was a KB A-arm failure that same week at the track.


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but the question is, which or whose bushing?

There are a bunch of different ones out there,

something like these?

http://www.stage3motorsports.com/pr...Whiteline-Anti-Dive-Control-Arm-Bushings.html

http://www.stage3motorsports.com/c=...tang-Whiteline-Bump-Steer-Correction-Kit.html

 

[Norm Peterson]

I would only be guessing but I would think that if a part looks like it has a problem revealed with FEA then it definitely will have a problem in the finished product, but if a product looks good after the analysis it doesn't mean it's guaranteed good to go. Is that true or a bad guess?

It's not nearly as simple as that, because "doing FEA" says nothing about how extensive the analysis was or how detailed the model itself was. There can be orders of magnitude differences between two analyses for the same part with both legitimately being Finite Element Analyses.

I suspect that a FEA performed at this point to either validate or exclude the various root causes mentioned would be in somewhat greater depth than what might have been performed when the part was originally designed.


Like Dave said, FEA is only a tool. It can be a very good tool, but it's still only as good as the input data going in and the engineering evaluation of what comes out.


Norm

 

[sheizasosay]

It's not nearly as simple as that, because "doing FEA" says nothing about how extensive the analysis was or how detailed the model itself was. There can be orders of magnitude differences between two analyses for the same part with both legitimately being Finite Element Analyses.

I suspect that a FEA performed at this point to either validate or exclude the various root causes mentioned would be in somewhat greater depth than what might have been performed when the part was originally designed.


Like Dave said, FEA is only a tool. It can be a very good tool, but it's still only as good as the input data going in and the engineering evaluation of what comes out.


Norm

I understand and I appreciate the extra info on FEA. I am just curious if they(BMR) even use it. Granted they could "do" the FEA inadequately, but what is the issue is that BMR has had problems with S197 A-arms and have revised it several times. It brings the design and manufacturing process into question....I would say the testing phase, but they don't road race and that is the ultimate test. Maximum Motorsports designs parts and then puts them through a season with a pro driver in a race car and if the part is problematic, they aren't gonna sale it. Cortex has the same philosophy. Mr. Poe is filling that role....except he is a customer. Ultimately post #45 is what I am walking away from this whole thread with.

 

[Norm Peterson]

Even Ford's OE arms probably aren't 100.000% failure-proof under track driving conditions, taken over the entire population of arms produced. But I would expect Ford's analyses to have gone a bit deeper into evaluations of any potential failure modes if only because the cost of such analyses can be spread out over more cars/parts and/or because of a larger database of experience to draw from to begin with.

If it sounds like I'm still being a little vague, it's because I'm trying to be. Any further thoughts that I might have - either way on this - are at best unsubstantiated conjecture.


Norm

 

[ArizonaGT]

Like Dave said, FEA is only a tool. It can be a very good tool, but it's still only as good as the input data going in and the engineering evaluation of what comes out.


Norm

All models are wrong, some are useful.

 

[DILYSI Dave]

All models are wrong, some are useful.

Love that.

 

[ocpony]

Even Ford OEM redesigned the A-ARMs. 2011 also comes with larger front brakes which increases the stress on the A-Arms.

It appears Ford increased the curved section to increase its strength.


I guess I will be adding some reinforcing to the BMR A-Arms I was fixing to install. Figures I just prime them and was ready for the Red Candy paint.

 

[jmauld]

I'm not sure if that is a strength redesign, or if they made the piece easier/cheaper to produce.

 

[908ssp]

Even Ford OEM redesigned the A-ARMs. 2011 also comes with larger front brakes which increases the stress on the A-Arms.

It appears Ford increased the curved section to increase its strength.


I guess I will be adding some reinforcing to the BMR A-Arms I was fixing to install. Figures I just prime them and was ready for the Red Candy paint.

My 2010 has control arms like the above 2011. It also has larger diameter ball joints.

 

[Philostang]

Anybody have a pic of the 2011+ GT arms? Or better, one of the 2011+ V6 arms? If they're only putting them on the Brembo equipped cars (like the GT500s), then there's likely a good reason they're doing so there and not on the more plebeian varieties. If they're on all the newer cars, then it might strictly be a production motivated switch.

Still, those things do look stronger. =)

Best,
-j

 

[kevinatfms]

except for the balljoint flange which looks much thinner. i havent worked on a newer car in a while but im suspecting that its the entire model line change to ease production. also the larger balljoint is added due to the 05-09 balljoints ability to wear out after 15-20k miles.

 

[Sky Render]

except for the balljoint flange which looks much thinner. i havent worked on a newer car in a while but im suspecting that its the entire model line change to ease production. also the larger balljoint is added due to the 05-09 balljoints ability to wear out after 15-20k miles.

You can get a good look at mine when we install all those parts.

 

[DILYSI Dave]

Does the new control arm / ball joint bolt on? No changes to the knuckle to accommodate the larger ball joint?

 

[sheizasosay]

My 2010 has control arms like the above 2011. It also has larger diameter ball joints.

Have the GT500 control arms changed at all with the s197? Just curious if the 2010 GT just switched to the already made GT500 . I know there ball joint diameter is larger since they came out.


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[19COBRA93]

As far as I can tell, based on part numbers, '05 to mid-'10 had two part numbers. One for the V6/GT, and one for the GT500. Starting on 08/03/2009 (mid year '10 production run) the part number switched to one part number for all V6, GT, and GT500. So it appears to be a running change for all models. Probably a financial decision more than a strength thing. But that's just a guess. Since that change in '09, there have been several part number updates, but are still the same for all models.

 

[TheViking]

Starting on 08/03/2009 (mid year '10 production run) the part number switched to one part number for all V6, GT, and GT500. So it appears to be a running change for all models. Probably a financial decision more than a strength thing.

I heard they did it to correct the ball joint problem V6/GT's were having.

 

[19COBRA93]

I heard they did it to correct the ball joint problem V6/GT's were having.

Likely so. Mid-year '10 they went to a larger ball joint. So the arms aren't interchangeable before and from 08/03/2009 without swapping out ball joints.