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FRONT UPRIGHT FAILURE
While running at the ARRC this past weekendI had the left front upright break at ZIG+ZAG. http://Forums.ImprovedTouring.com/it/smile.gifFortunately I did not make it to 12 before the failure. Is there a recommended replacement period for this part?
After looking at the break point it looks like it had cracked earlier and we were on borrowed time.
There were two times which might have started the break. A light hit on a Armco barrier and a hard hit in wheel from another car. Will zyglow(??)dye testing find these cracks or must you magniflux them?
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Howd it break? its typical the hubs break and take the axle spindle with it as well.
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It broke a couple of inches above bearing opening in the casting. The break is in a section that is about 1.5 inches square at that point.
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Just a guess, but it sounds like the Armco would be the culprit (higher hit).
I'm not familiar with the dye process, but magnaflux would be sure to find the crack.
-T
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Get a magnifying glass and look closely at the break itself. There will likely be two different surfaces visible. The part that looks like sandpaper (uniform rough crystalline texture) is the portion that failed suddenly and literally tore apart. The other surface (something less than half of the cross-section area, I will guess) ought to have "beach marks" - concentric lines, smoother than the big failure. These are the result of a crack working its way across the casting and point at the source of the entire failure process.
There may be a stress riser of some kind (nick, casting imperfection, whatever) on the outer surface of the casting where the smallest of the beach marks is. You might also be able to guess, from the edge where they start, which way the casting was overloaded (from the guardrail hit, for example).
With stock pieces, I don't know if it makes economic sense to Magnaflux uprights - particularly since they will bend in a hit before breaking. This should be a clue big enough to catch, right? Bending = exceeded yield strength of the material = the beginning of complete failure.
Dye penetrant testing should find them too but, again, if you factor in labor, it just might not be worth it. If you ARE going to go the the effort to get the parts clean enough to Zyglow, you may well be able to see the crack with a lens...
Remember too, when inspection shows a crack, you still have to decide whether it is sufficient to warrant replacement. We sent all of the uprights and suspension bits off of a Ralt RT5 to be tested once and EVERY SINGLE ONE came back tagged. The inspector told us that we didn't really need to worry about any of them, however, since we weren't flying them. http://Forums.ImprovedTouring.com/it/smile.gif
Kirk
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When/have you ever changed the hu/bearing in that upright. The area that you describe the crack in sounds like a place where the upright could have been supported in the press for the removal or installation of the bearing/hub.
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Brent Breon
Cendiv ITA #26
www.360racing.com
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Tony:
Contact me off list if you want to know how the part failed and if it was already failing. We have all the equipment here to do just that...
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Bill
92 Saturn SL2
Planet 6 Racing
[email protected]
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The idea of causing a nick while pressing in the bearing is an interesting idea. I think this was impact connected. we will check further and let you all know what we find.
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Tony,
Sounds like an impact failure. I do not think we have seen a none impact related failure in this area of the upright.Call me or bring the part out and we will take a look.
Bob"honda"Clark
