C-2 L79 Engine problem

[Duke W.]

Re: If it works, don't fix it!

I'm not a fastener engineer, but I understand the basics, and material properties apply to fasteners as they apply to any structural element.

If a fastener or any structural element is repeatedly stressed beyond the elastic limit then it is definitely "weakened", and and it will eventually fail.

My suspicion is that this test repeatedly loaded the fastener to beyond the elastic limit, but few fasteners are designed to function in this stress range. Most are stressed well within the elastic limit when torqued to specification, and they can be used repeatedly until thread wear or corrosion dictate replacement.

I can design any test to "fail" - like the old "three ball test" where plain motor oil causes the balls to seize, but the whazzo additive didn't. Therefore my engine will seize without the additive. But the fact of the matter is that the unit loading on any friction surface inside the engine is nowhere even near the unit loading of this "test", so the "test" is not valid, because it is not representative of what's going on inside the engine.

Fastener failures are rare, but the causes can be fatigue, corrosion, over-torqueing or under-torquing, or in some cases, design error, where the joint simply doesn't have enough clamping force to carry the load even if all the fasteners are properly torqued.

Duke

[Dennis H.]

Re: If it works, don't fix it!

"Midwest Fasteners had quite an elaborate setup on the stage"

Sounds like they were putting on a show so the final result would be buy our fasteners. I have reused GM fasteners for many many years and can't recall ever having one fail during torque other than threads giving away. But to have one snap in half during torque, never happen to me.