Chromed cylinder Issue

[T. C. Downey]

Take a flake or two and put in on an anvil and smack it with a hammer.

Who the he-- would have an anvil anymore? Who can see well enough to hit speck of metal?

[GAHorn]

All my shop vises have anvils on them.

[integritywood]

Ok now for a new twist.
Pulled plugs and boroscoped cylinders. Nothing noteworthy showed up. Did cold compression test. All 64-78. Pulled engine to send off for tear down. First sign of trouble thru starter hole.

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Right mag was working before my last 20 min flight to warm up oil. But obviously isn't now.

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Here's the groove chewed in accessory case where gear was rattling around for up to 20 min.

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So somewhere inside we have broken cam gear retainer pieces. Planning to get it tore down for further analysis. Hopefully find more out next week. My ame tried to talk me into putting a low time IO360 out of a crashed chopper in but I don't think I have that much cash!

[GAHorn]

Had kinda a bad day today I guess. I turn 40 tomorrow so I decided to change oil today in preparation to celebrate with a day of flying. Took a short flight to warm up oil. Next dropped oil. Screen loaded with non-ferrous flakes which we identified as cylinder chrome. Probably about 1/2 a tablespoon full with just a slight dusting of ferrous material picked up by a magnet which my ame says is next to nil. Now my question 170hrs since major with overhauled cylinders about 7 years ago 2 of them chromed.About 80 of those hours in last 2 years. ...

Ok now for a new twist. ...Right mag was working before my last 20 min flight to warm up oil. But obviously isn't now.
...So somewhere inside we have broken cam gear retainer pieces. ...!

So, when you made that "short flight to warm up oil"... what do you think you might have missed on your pre-takeoff run-up? (or useful item we could add to our post-flights?)

I also wonder if you know the source/pedigree of that mag gear? (I'm wondering if it isn't from an old prop-strike which wasn't properly addressed.)

[integritywood]

George
Always do my checklist, mags both fine on run up. Can't think of anything I could have done to predict problems before flight.
As far as mag gear. It wasn't gear that failed but the bushing gear runs on, with shoulder to retain gear, that broke. Not sure how prop strike would have stressed that.
I think Someone was looking after me, personally, as oil change wasn't due for another 4-5 hrs and I would have flown a much longer flight the next day. looking at the accessory case wear the gear basically wore through to oil gallery. Don't have IPC in front of me, but I think where pressure relief valve sits. In a few minutes I might have lost all oil pressure and if I was a ways from airport I might have had an opportunity to practice my forced approach for real! So all in all I feel fortunate.

[GAHorn]

A mag check during taxi-in might reveal a dead mag.
A prop strike/sudden-stoppage might damage a mag/gear. All rotating accy's should be checked after sudden stoppage. (Not saying that's the case in this one...just sayin'...)