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I could be wrong, but I thought that the primary source of vibration here is the cylinder heads flopping around, which is why we have split baffling between the two (or three) heads. I have no idea if the prop vibration has a bigger impact than the heads, but you might want to consider both.
Interesting analysis. EFII has been using Stainless Steel for at least the last 10 years in their System 32 with screwed fittings into the prime ports. Thanks for the engineering work! The sharp notch appears to have been eliminated also about 10 years ago.
Final Engineering Verdict
At 1.2 IPS, the 6061 aluminum tube is a failure risk in high-vibration engine environments. Switching to 7075-T6 or 304 Stainless Steel moves the stress far enough below the material's fatigue threshold to ensure the part will not crack under normal operating conditions.
So if my assumptions were in the ballpark the math supports the failure and I believe the assumption to be correct and the engineering change to ss as a correct remediation to the problem.
The sharp notch is not ideal but is the reality of manufacturing simplicity. (Endmill vs a pipe). There is proven evidence this is not the weak link it the chain as it has a much higher moment of inertia due to the large diameter.
As we know it’s in the execution.
Fly Safe
