When we were recently at a race, a friend of ours mentioned that he had an old style upper control arm fail, where the pin makes the connection to the bar. I had never heard of this. If you look downward at an upper control arm, you will see two inside bushings that are welded in place to eliminate any play from the upper adjustable rod end going down to the bar.
When I was checking to make sure there was no preload on our car, I found that one of the inner bushings was very lose and that this bushing was just spot welded in two places. I then checked the other front upper control arm by using a pen light where the pin goes in. You could see that there was a gap between the welded bushing and the control arm. The bushing was not lose, but because it was just spot welded in two spots, you could see the light.
My guess is that the bushing, on our friends car first broke lose, thus putting extra pressure on the part it was welded to. As a result, it failed. Not good!
Our chassis is # 855 so it's not that old and you might want to check your old style
upper control arms. I am taking them all in and have them welded all around the bushings, rather than just spot welded. This should be a safe fix, thus avoiding a much larger problem.
Pat
Old style upper control arm problem
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Needs a Life!!!
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Joined: Sun Dec 04, 2011 10:38 pm Location: Monument, CO Chassis: 540 |
Pat,
I cannot visualize what the problem is. Can you send a picture? DaveP |
Needs a Life!!!
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Joined: Wed Nov 30, 2011 1:03 am Chassis: 098 Facebook Page: http://www.facebook.com/#!/denny.stripling |
Yeah that sounds really odd. I just looked at the one remaining old style rocker I have and sure enough, those bushings are welded in. Mine are welded about 35% of the way around on the bottom only.
I've never noticed it nor seen a failure of that manner but I suppose an inadequately welded example could have problems there, especially where a pin is used rather than a bolt which would pinch the bushings onto the spherical bearing of the rod end providing more support/less play. ____________
Bay 12, please. |
Denny, my first thoughts were that even if the welds broke it shouldn't do much damage, as it's still acting as a bushing, much like the ones we use on the shocks, which of course are not welded. My guess is the reason it's welded is for convenience of pulling the pins so the bushings don't fall down. Then I looked at the stock to which it is spot welded to on my up-writes, and the metal gauge seems to me smaller and weaker than where the shocks mount to the upper control arm that have the non welded bushings. My friends car is much older than ours and my guess is that is one reason why the metal stock that the bushing attached to might have failed as a result of the bushing breaking loose. Not sure. Just something to look at when you are doing the prep.
Dave, send me a text at 651-303-2670 and I will send you a picture. Pat |
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I've had a hard hit and those tacked in spacers moved but didn't bend the main clevis (this was on the opposite side of the hit, the other cntl arm bent). I thought about welding them around but realized that if I had they likely would have bent the clevis and maybe the arm too. So I tapped it back into position and left as is....
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Needs a Life!!!
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Joined: Wed Nov 30, 2011 1:38 am Location: Sunnyvale, CA Chassis: 068 415 Facebook Page: http://facebook.com/HSERacing |
We see lot of inconsistencies from one rocker to another, especially with those spacers. We disconnect sway bars every event, so they stay in alignment (or we line them back up), but if they have been left for a long, they can gradually (or suddenly) get knocked out of line, and it will be a bear to get the ball in between them. Or to get the bolt out, even w/o any pre-loading.
Dave Harriman
"It looks crazy, I understand. But, we only live once and I am going to give it a good try." - Alex Zanardi |
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