Broken Jag rear - WARNING!

[Tom Wells]

Hi John,

Thanks for the opinion.

On this unit, nothing was modified, ground or otherwise touched. We used 3.8S axles and wishbones without any changes whatsoever. Just powder coated & installed.

Current analysis being done on the failure indicates possible impact failure - more to come but don't hold your breath

[podly]

Hi Tom,
I took a picture of my Dads Shamrock Cobra lower swing arm to show you what John Crawford was talking about. It shows the factory weld on the left, and the steel reinforcing sleeve on the right. The half shafts are done in the same manor. I put the picture in my gallery if it doesn't show up here. Good luck!!

Greg

[Tom Wells]

Hi Greg,

Thanks for the illustration. It confirmed my understanding of John's comments.

Note, however, that mine broke in the unmodified portion of the wishbone between the shock mount and the hub Yours is unmodified in that same region, apparently.

We are doing some metallurgy, mostly out of curiosity. If there are any results at all, we'll post them here - but it'll be some time before we can see any results...

Tom

[Monster]

Tom,

I just came across your post. I had the same thing happen to me coming home from "Snakes to the Lake" Cobra run this year in late Sept. We were driving "spiritedly" through the mountains when I cam around a turn and a pickup truck decided that he would pull in between me and the car in front. I was going about 50mph and had to down shift 3rd to 2nd, when I did my RT control arm broke on the inside weld (yes, it was on the weld and we noted that it appear to be possibly an issue of poor penetration. The weld was not ground and appeard to be original. We had not hit anything and suspension travel is correct as well). Luckly we were slowing and I was able to stop in a matter of 40-60ft and some how with no further damage. I was able to get the car on a fellow Cobra owners trailer (which I'm sure you know is a task with a broken suspension) get it over to another Cobra owners house that was in the area and make an inner sleeve which we cross drilled and button welded then seam welded into place. I was able to then drive it home that same day. I am not driving it much currently until I can re-build both arms. I have considered both the sleeve approach and/or also adding horizontal braces to the arms. I believe that the issue is the torque stress applied to the arms since they have to absorb all of the transferd power. I am considering adding an upper arm from the top of the hub carrier to the frame which would compensate for the toque applied to the lower arm and reduce the strees placed on it, but I will need to work out the geometry.

good luck keep us posted,

Mike "monster"

[tommyboy]

Hello Tom,
Sorry to hear about your misfortune. I hope you and your car are back up and running soon. If you need answers to the failure of your rear suspension or any other area, please contact me by e-mail(tgw@packereng.com). I work for Packer Engineering and we are involved with all sorts of failure analysis type of situations. Check us out at our website :

www.packerengineering.com

Good luck, Tom.

[Tom Wells]

Hi Tom,

Just got word that the cast stays on for at least another four weeks. That'll be four months - sheesh, it gets old...

Car should be ready in Feb, I hope, & with luck and calcium so will I.

I'm more interested in preventing a recurrence but so far the only thing that looks like it might work would be to take turn 3 a bit slower

Tom

[CowtownCobra]

...or use a solid rear axle