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Horror of the week 04/02/10


Tony
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Owner of a late Alfa hit an unremarkable pothole and the wheel broke in half... In my 500 hundred years in the trade i've never seen or heard of a wheel breaking in half.

 

In true wim fashion, first time ever here is the evidence.

post-2-1265230393.jpg

 

post-2-1265230408.jpg

 

post-2-1265230421.jpg

 

post-2-1265230455.jpg

 

What's concerning is the initial injury is not that severe so this suggests a build issue :huh: ...... By the way the replacement wheel cost £600.

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You can see in the first image that the impact was unremarkable, so why did the wheel snap like this?

 

Could the alloy have been too thin on this particular wheel? Maybe it's suppose to be 2 parts and they just glued the front of it on!!! :huh:

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And I thought I was unlucky to suffer a flat spotted wheel from a pot hole, and the new wheel is only £150 (although I'm still waiting for Ford to stock the wheel after 2 weeks).

 

If it was me I would have took it back to Alfa and said this damn thing could have killed me, and demanded some compensation :huh:

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You can see in the first image that the impact was unremarkable, so why did the wheel snap like this?

 

It could have been a weld as it looks as if the the front end is cast and the back end is rolled. Would have caused a stress raiser or even weakened the material at the fusion and/or heat affected zone, so the impact initiated the brittle fracture.

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You can see in the first image that the impact was unremarkable, so why did the wheel snap like this?

 

It could have been a weld as it looks as if the the front end is cast and the back end is rolled. Would have caused a stress raiser or even weakened the material at the fusion and/or heat affected zone, so the impact initiated the brittle fracture.

 

 

Errrrr i don't think i would be buying a replacement one of those. Straight to Aftermarket methinks !!!

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You can see in the first image that the impact was unremarkable, so why did the wheel snap like this?

 

It could have been a weld as it looks as if the the front end is cast and the back end is rolled. Would have caused a stress raiser or even weakened the material at the fusion and/or heat affected zone, so the impact initiated the brittle fracture.

 

It's shocking, but not really surprising that it broke where it did. The whole wheel is a short cantilevered tubular beam. The fixed end is well supported and quite stiff. The free end is entirely unbraced and is being flexed continually about the fixed end by the weight of the vehicle. So, a short tubular cantilever with the load reversed once for every revolution of the wheel. For a wheel about 2 feet diameter that's one reversal for about every 2 yards travelled or about 900 reversals per mile. Give it 10,000 miles and that's 9 million reversals.

 

If there is insufficient material at the point where the tube joins the fixed part of the wheel, or if there is an inadequate radius at that point or some poor machining that creates stress raisers, then there is a terrific case for induced fatigue failure, possibly with some embrittlement and the propogation of fine cracks. Now throw in a few shock loads and the last one is the straw that breaks the camel's back.

 

I think I would want to do some crack detection on the other wheels before I drove on them again.

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