Some Trips End Early for Mechanical Reasons

[Grumpy Goat]

... I have a couple of questions. Did they say why the yoke grenaded? Looks to me like there was severe overheating going on in there. ...

I started looking into these failures on the internet and many (most?) cases it is due to improper lubrication of the needle bearings. In one of the images of the fracture above, the impression of a needle bearing seems to be welded or stamped into the fracture surface.

Improper lubrication can come from misalignment leading to whirling vibration which can wear the seals and can exacerbate the loss of lubricant. I guess as the joint wears, the misalignment becomes more of an issue. Also moisture can also reduce the effectiveness of the lubrication.

What is surprising to me is the amount of metal that looks like it fell off in chunks, and not simple friction-type wear.