Cracked rocker

[cgarr]

I've seen plenty, burnt, pitted, broken but have never seen one crack in the nose area?




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[Tippy]

Had to have been porosity or contamination during casting

[DRACO A5OG]

Whoa, what a Night Mare.

Master CGarr, is this yours or a customers?

[chris_seven]

It's not really a surprise as the material used is quite 'notch sensitive'.

The crack could initiate from any small surface defect such as a notch of a 'nick' on the edge of the pad.

The shape of the crack would suggest that it's path has been dominated by the microstructure of the casting and the defects introduced due to how the part solidified and subsequently cooled.

The question is when did the crack propagate - was it during manufacture, during operation or whilst being refurbished.

[JFairman]

I took it to Photoshop and lightened the shadows a little and cropped the top down.

Could you see this crack before refurbishing it and machining some metal off?
It seems like 911 rocker arms have at least doubled in cost over the last 10 years.
Are they plain old cast iron or something else?

You do really nice work

[cgarr]

It's just a cast rocker. I'm sure it was there before I ground the pitting out of it. I have seen pockets open up in the surfaces before after grinding but never any cracking like this.


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