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Old 06-23-2013, 10:02 PM
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Default RE: OS 1.20 Go Boom....!!!

ORIGINAL: earlwb

I think I would agree that the rod went first. The rod looks like it was cast and then machined. I remember cast rods letting go before in the past. The rods probably has some sort of a casting flaw in the metal from when they were made. I have a couple of engines I need to make new rods for myself where the rod had broken.

You don't think that the engine exceeded its max RPM rating in the air with the 16x6 prop do you?
With the 16x6 (which is a recommended prop size by OS) it was turning 9000-ish on the ground. The engine RPM range is 2000 - 11000 and it makes peak HP at 11000. Under load in the air it never exceeded 10000 I am quite sure and like I said, I do not abuse my stuff and run it wide open all the time. I come downhill idling 90% of the time so it's not over revving on the downlines.

When the engine popped, I had just left a knife edge climb out configuration where it climbed out at about 2/3 throttle and I started to power up to 3/4 - full. If I had to guess, it was turning maybe 8000 when it let go. It certainly was not at full song.