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> I broke a rear trailing arm at the track!, Holy Cow!
pete000
post Jul 18 2017, 10:39 PM
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I guess those reinforcement kits aren't just for looks after all !
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brant
post Jul 18 2017, 11:09 PM
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Wow
Glad you are ok
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ChrisFoley
post Jul 19 2017, 04:51 AM
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I've never seen a failure like that on a trailing arm. Definitely a rarity.
I expected a tear where the front tube attaches to the box after talking with Matt on the phone quickly last night.
My reinforcing method wouldn't prevent that from happening.
I'm interested in seeing the component up close now.
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Cracker
post Jul 19 2017, 05:34 AM
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Someone (maybe Matt) suggested a difference in the fractures - possibly showing different age. Could it have been cracked (lets say from the tie-downs) and then completing the deed on the track? Please let us know your thoughts Chris - I am very interested in your assessment!

PS: Matt: In which manner do you tie down in the rear - straps straight back or crossed? Also, do not clean the trailing arms prior to giving them to Chris...

Tony
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McMark
post Jul 19 2017, 06:19 AM
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(IMG:style_emoticons/default/yikes.gif) That's a scary failure. Glad it all worked out...
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jd74914
post Jul 19 2017, 06:28 AM
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That's crazy. Glad it didn't result in injury to you or the car. (IMG:style_emoticons/default/smile.gif)

Unrelated, but since you are a data guy have you seen the new multi-point tire temp sensors from IZZE Racing?
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bdstone914
post Jul 19 2017, 06:36 AM
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Have you inspected the other arm for stress cracks ?
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ChrisFoley
post Jul 19 2017, 06:37 AM
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Until I have a closer look I'm attributing the failure to high spring rate and curb hopping. Once a fatigue crack began at the top it didn't take long to propagate around the tube.
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ChrisFoley
post Jul 19 2017, 06:42 AM
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QUOTE(McMark @ Jul 19 2017, 08:36 AM) *

Maybe I'm just seeing what I 'want' to see. (IMG:style_emoticons/default/confused24.gif)

I see a change in the weld where the crack deviated. At that point the crack moved off it's HAZ path and took the shortest route toward the bottom.
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McMark
post Jul 19 2017, 06:47 AM
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QUOTE(Racer Chris @ Jul 19 2017, 08:42 AM) *

QUOTE(McMark @ Jul 19 2017, 08:36 AM) *

Maybe I'm just seeing what I 'want' to see. (IMG:style_emoticons/default/confused24.gif)

I see a change in the weld where the crack deviated. At that point the crack moved off it's HAZ path and took the shortest route toward the bottom.

Yeah, your post made me rethink what I was seeing. Now I see the failure obviously originated from the top side.
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Matt Romanowski
post Jul 19 2017, 08:59 AM
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QUOTE(jd74914 @ Jul 19 2017, 04:28 AM) *

That's crazy. Glad it didn't result in injury to you or the car. (IMG:style_emoticons/default/smile.gif)

Unrelated, but since you are a data guy have you seen the new multi-point tire temp sensors from IZZE Racing?


I have one of the sensors, along with analog versions from Texense and AiM.

For tie downs, we use the hooks on the arms straight (not crossed) to the trailer.
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Cracker
post Jul 19 2017, 09:08 AM
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Chris brings up a great point in reference to the curbing. I have adopted a different approach to curbs this year...I stay off high-speed, significant (height) curbs! When the components and tubs are up to 47-years old like they are on our teeners - I felt a slightly slower lap time and different line was worth the tradeoff of protecting my car from that kind of abuse. Just sayin'...

T
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jd74914
post Jul 19 2017, 09:57 AM
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QUOTE(Matt Romanowski @ Jul 19 2017, 09:59 AM) *

QUOTE(jd74914 @ Jul 19 2017, 04:28 AM) *

That's crazy. Glad it didn't result in injury to you or the car. (IMG:style_emoticons/default/smile.gif)

Unrelated, but since you are a data guy have you seen the new multi-point tire temp sensors from IZZE Racing?


I have one of the sensors, along with analog versions from Texense and AiM.

For tie downs, we use the hooks on the arms straight (not crossed) to the trailer.


Sorry for the hijack again but how do you like it? I've used the Texense sensor (seems to work well and Pierre is awesome) but its $$ and single point.
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gms
post Jul 19 2017, 10:35 AM
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QUOTE(Racer Chris @ Jul 19 2017, 05:51 AM) *

I've never seen a failure like that on a trailing arm. Definitely a rarity.

(IMG:style_emoticons/default/agree.gif)
glad you caught this before something bad happened on the track
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Matt Romanowski
post Jul 19 2017, 10:50 AM
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QUOTE(jd74914 @ Jul 19 2017, 07:57 AM) *



Sorry for the hijack again but how do you like it? I've used the Texense sensor (seems to work well and Pierre is awesome) but its $$ and single point.



No worries. Shoot me an email at matt@trailbrake.net and we can discuss.
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stownsen914
post Jul 20 2017, 05:24 AM
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Jeez Matt, that sucks, but glad it didn't end worse for you!

And thanks for posting too. Good reminder that we need to be checking our 40+ year old cars for stuff like this.

Scott
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GregAmy
post Jul 20 2017, 06:11 AM
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I'll be checking my racer as well, but I have to wonder if the welding on that bit, along with getting jacked down pretty hard there regularly, contributed to the problem. Do you cross-strap and do you jack it down pretty hard to pull down the suspension (I don't do either)?
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jmitro
post Jul 20 2017, 09:16 AM
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wow; glad you didn't have a major accident.

PM sent
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Matt Romanowski
post Jul 20 2017, 12:25 PM
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QUOTE(GregAmy @ Jul 20 2017, 04:11 AM) *

I'll be checking my racer as well, but I have to wonder if the welding on that bit, along with getting jacked down pretty hard there regularly, contributed to the problem. Do you cross-strap and do you jack it down pretty hard to pull down the suspension (I don't do either)?


We put the straps straight back. We don't go crazy pulling it down, so I don't think that was it. The other side doesn't show any signs of cracks or any problems. I'm thinking this might just be a fatigued 40something year old part. I'm heading down to see Chris tomorrow and we'll see what he thinks.
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Matt Romanowski
post Jul 20 2017, 12:33 PM
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Here are some more photos now that the arm is off the car.

Attached Image
Attached Image
Attached Image

I thought people miight like my co-driver's original, single owner Six.
Attached Image
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