DYNATRAC SAFETY RECALL on 1550 Steering Knuckles

My replacement knuckles arrived yesterday.

This whole thing is certainly unexpected and inconvenient, I'm grateful it was posted here for those of us yet to be contacted.

I think $245 is reasonable. This isn't $xxx/hr caliber work, but good shops that charge higher fees are justified, so I don't have any issue paying the difference if there is one. I'll just have this knocked out when I have the brake and ABS lines run along the upper control arm and across the axle which I already planned to do.
 
Knuckles showed up yesterday. Hope to get things back together tonight. Just need to find the ball joint torque specs.
 
bhaner said:
After this I would bet they are... I think it is going to cost them quite a bit.
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I worked in orthopedic implants for a few years and had to deal with occlusions and whatnot occasionally in both forged and cast parts. While I'm no expert at metallurgy or casting, I think their issues with the forged aluminum parts should be fairly easy to resolve. The part may cost a little more. But other than what they are out what it costs to replace the existing forged components on the market. Because of where the issue is pronounced (from their press release it sounds like it consistently occurs in 1 area), my guess is this is caused by an inadequate aluminum casting process that is causing the defect (occlusions/porosity/etc) to accumulate in the same spot. Depending on how bad the occlusions/porosity/etc are they'll reduce fatigue strength.

To fix it going forward:
They can optimize their casting process so that the occlusions form in a different area, or in a area that gets machined off.

They can implement non-destructive testing (xray, ultrasonic, or possibly eddy current) to identify parts with severe occlusions and wee them out.

Again, not my area of expertise but that's my understanding of the issue.
 
Primo82 said:
I worked in orthopedic implants for a few years and had to deal with occlusions and whatnot occasionally in both forged and cast parts. While I'm no expert at metallurgy or casting, I think their issues with the forged aluminum parts should be fairly easy to resolve. The part may cost a little more. But other than what they are out what it costs to replace the existing forged components on the market. Because of where the issue is pronounced (from their press release it sounds like it consistently occurs in 1 area), my guess is this is caused by an inadequate aluminum casting process that is causing the defect (occlusions/porosity/etc) to accumulate in the same spot. Depending on how bad the occlusions/porosity/etc are they'll reduce fatigue strength.

To fix it going forward:
They can optimize their casting process so that the occlusions form in a different area, or in a area that gets machined off.

They can implement non-destructive testing (xray, ultrasonic, or possibly eddy current) to identify parts with severe occlusions and wee them out.

Again, not my area of expertise but that's my understanding of the issue.
Click to expand...
We used eddy current inspection for neck cracks in aluminum cylinders (both scuba & scba)...these high pressure cylinders are extruded in one piece from a slug of aluminum to form a cylindrical cup, then the open end is closed with the application of heat and spinning the cup at high speed. In our industry, the defects were formed along the molecular boundaries of the various metals in the alloy...I'm not sure how they are formed in a forging...
 
Brute said:
We used eddy current inspection for neck cracks in aluminum cylinders (both scuba & scba)...these high pressure cylinders are extruded in one piece from a slug of aluminum to form a cylindrical cup, then the open end is closed with the application of heat and spinning the cup at high speed. In our industry, the defects were formed along the molecular boundaries of the various metals in the alloy...I'm not sure how they are formed in a forging...
Click to expand...


I'm assuming this part is cast into a blank roughly the shape of the steering knuckle. There are several forging processes that could be used, but they all basically rely on pressure and heat. I would not expect this defect to be caused by the forging process alone. My guess is these are material defects that were introduced during that casting process.

I'm most familiar with investment casting. I'm guessing the cast isn't optimized. And either the impurities are accumulating at that point in the knuckle due to the casting design. Or they're getting defects in that part of the material based on now the molten aluminum is filling the mold. For instance, if the point that's fracturing is pretty far from the gate vestige (where the molten aluminum is introduced) then the aluminum could be partially cooled by the time it reaches the defect area and could cause porosity and other issues.

Based on the announcement I'm leaning towards impurities are accumulating at that spot causing fracturing. I don't know though, I'm just spit balling based off my other experiences.

And that is cool, I had no idea that is how tanks were made. Cheers.
 
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