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07-01-2009, 11:27 PM | #1 |
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Own PolTec Endlinks? Beware of Catastrophic Failure
I have PolTec Heavy Duty spherical bearing endlinks from the Fall of 06. A while back, I had noticed one was cracked a little bit, but other car problems pushed it out of the priority fix it should have received. Leaving it alone was a problem. Today, it failed outright, thankfully in a bump rather than a turn. If you have these parts, check them. If they're cracking at all, replace them.
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07-01-2009, 11:36 PM | #2 |
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WOW thats insane! looks like a major stress riser is from the setscrews. i've never seen metal peel away like flaky baklava. mmm delicious baklava...
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07-01-2009, 11:38 PM | #3 |
Former Vendor
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I guess I know what you're doing tomorrow. I'll set some links aside for you.
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07-01-2009, 11:39 PM | #4 |
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07-01-2009, 11:40 PM | #5 |
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wow, just wow. and great pics too. i have always wonderd how long there CF lat links hold up, but looking at this i know now
get yourself some of the best ones out there, from one of the two guys above |
07-01-2009, 11:43 PM | #6 |
Scooby Guru
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Well, since Clint saw my post, it looks like there'll be a set on my desk when I get down to TiC tomorrow morning.
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07-01-2009, 11:45 PM | #7 |
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man......should let poltec know about this...
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07-01-2009, 11:46 PM | #8 |
Scooby Guru
Member#: 71092
Join Date: Sep 2004
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Location: Licking County, Ohio
Vehicle:2005 2.5RS Wagon Regal Blue Pearl |
Thanks. This was actually my first use of my new macro extension tubes and my new camera that has Live View in it. It's astonishing how easy macro shots like this are when using Live View. It's like doing them on an old large format view camera. Me likey.
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07-01-2009, 11:47 PM | #9 |
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Improper heat treatment????
I have seen some 7075 peel like that, but never THAT bad |
07-01-2009, 11:47 PM | #10 |
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07-01-2009, 11:55 PM | #11 |
Former Vendor
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I've only see decay like that once before. Ironically, and scarily, it was on all the nuts on a bridge in columbus. It was kind of fun to peel the layers of grain apart, until it occurred to me that perhaps I shouldn't be making the bridge any worse...
That was a few years ago. I've checked it out a couple of times a year since then, and they still haven't fixed it. I'd love for one of the metal nuts to pop in here, and drop some knowledge as to what would cause this. |
07-02-2009, 12:16 AM | #12 |
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well...it is severe intergranular corrosion and exfoliation
extrusions are prone to this.....milled, from cold rolled stock, wont do this |
07-02-2009, 12:18 AM | #13 |
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I'm thinking vibration thru the allen screw, weaking the metal, then corrosion. im getting more and more iffy on some of these garage shop made parts. esp for suspension.
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07-02-2009, 02:13 AM | #14 |
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It looks like the spacers were hitting the housings quite a bit. I'm sure that didn't help anything.
-Mike |
07-02-2009, 03:17 AM | #15 | |
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Quote:
6061 alloy isn't as notch sensitive as 7075 and more corrosion resistant. It has to do with ~6x more copper in the 7075. I've seen a problem similar to this before with 6061 forgings that used extruded blanks. Long stringy large grain structure that didn't like to have the grains cut. Nice crack initiation points. Almost the same part and application with a cast blank had very fine grain structure after forging and didn't have the intergranular cracking problem. The machining in the area of interest for these parts was the same. For the links shown that thread form for the set screw is one hell of a stress riser and guaranteed to cut grain structure. The hole for the bushing is bad enough. Nice pictures Ty. What body, lens, and tubes did you shoot with and at what f. Could you get a plan view shot of the set screw thread where you think the cracking could have initiated and as high a magnification as you can. Better than 1:1 would be great. Edit: I don't have access to a microscope right now but some photomicrographs would be very interesting. A really screwed up heat treat could have done bad things to the grain structure. Last edited by Web Foot STi; 07-02-2009 at 03:23 AM. |
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07-02-2009, 07:23 AM | #16 | ||
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Quote:
Quote:
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07-02-2009, 09:41 AM | #17 |
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Wow. That's some serious damage. I'll stick with Perrin and/or Kartboy.
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07-02-2009, 10:14 AM | #18 |
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07-02-2009, 10:39 AM | #19 |
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You guys might laugh but, with my STI suspension, I'm running Cusco's links in the front which look like factory links but, they have real ball and sockets instead of the plastic sockets in the factory ones and I'm running stock end links in the back. 24mm F/24 mm rear. So far the only problem I have is they sometimes come loose after a couple track days and I have to tighten them.
I've run Kartboys too and wasn't real happy with fitment. |
07-02-2009, 10:49 AM | #20 | |
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Quote:
So yeah, I'll take my Perrins over those pieces. |
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07-02-2009, 10:55 AM | #21 |
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Congratulations, you got the one set of Perrins that didn't fall apart as soon as they looked at your car
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07-02-2009, 11:44 AM | #22 |
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07-02-2009, 12:06 PM | #23 | |
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Quote:
I know what you mean about needing focusing rails. Metallurgical Microscopes have 3 axis stages for a reason. For my camera I picked up a Kirk rail in the used department of the local "Pro Photo Supply" store. It would be interesting to see the grain boundaries at the thread roots and really see if the cracks started intergranular, or where the grain was cut. Also, did the crack prorogate along the grain, or through the grain? You are right about optical depth of field at high magnification. With an unpolished specimen. You can move in and out to see things, but the photos suck. For that kind of work you need an electron microscope The smaller companies that I have worked for always have contracted that out. I'm not a Metallurgist, but have worked with them. I'm just a dumb Mechanical Engineer. PS: I double checked my definition of "intergranular" and came up with these two sites. First one has an ugly macro picture of Al and the second has a nice photomicrograph of 7075. http://corrosion.ksc.nasa.gov/intercor.htm http://corrosion-doctors.org/Forms-i...ergranular.htm Oh and here are another thoughts of what bad things that steel set screw could do: http://corrosion-doctors.org/Corrosi...ea-effects.htm http://corrosion-doctors.org/Forms-E...y-assisted.htm This dumb engineer likes this site. |
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07-02-2009, 02:16 PM | #24 |
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07-02-2009, 02:42 PM | #25 |
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It split with the grain. Its like like it was metal Plywood and it came apart between the layers.
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