propeller spinner bulkhead cracks

[fehdxl]

Curious what you guys think may have caused my propeller spinner bulkhead to disinigrate. I don't know myself yet...looking for ideas. Thanks! -Jim

[Walt]

I would suspect the main culprits to be vibration and fatigue. As soon as one of the supports cracks then the others will follow quickly as they are now overstressed from the lost support of the broken mount.

I would suggest you get the prop balanced as this is a telltale sign of excessive vibration. I would aslo look closely at your baffling and exhaust system, these are also very succeptable to excessive vibration.

[fehdxl]

Thanks Walt. It was dynamically balanced 400 hrs and 2-1/2 years ago...how much do these thing change? Thx, -Jim

[DanH]

Originally Posted by fehdxl

Thanks Walt. It was dynamically balanced 400 hrs and 2-1/2 years ago...how much do these thing change? Thx, -Jim

Did it take a lot of weight, and is that weight attached to the spinner bulkhead?

[fehdxl]

Dan, I don't remember how much weight. Screw, nut, and a couple washers? I can remove and weigh in a couple days. Yes, attached to the spinner buikhead flange. Whatcha thinking? Thx, -Jim

[Walt]

Originally Posted by fehdxl

Thanks Walt. It was dynamically balanced 400 hrs and 2-1/2 years ago...how much do these thing change? Thx, -Jim

How old is the spinner and what aircraft is it on? How many hours on it before balancing?

[rv9av8tr]

engine prop balance weights get bolted to the starter ring gear. Spinner back plate cracking is most likely due to centrifigual forces from the spinner not being perfectly centered.

[fehdxl]

Originally Posted by Walt

How old is the spinner and what aircraft is it on? How many hours on it before balancing?

Unsure of exact age...could go back to '66 since it's on a V35 Bonanza.

Are you thinking just old age fatigue in this case?

Thx!

-Jim

[fehdxl]

Originally Posted by rv9av8tr

engine prop balance weights get bolted to the starter ring gear. Spinner back plate cracking is most likely due to centrifigual forces from the spinner not being perfectly centered.

I'm trying to visualize the ring gear on the -540 for the RV-10...where would it bolt to? Drill a new hole? Guess I'll have to take another look when I return from this business trip.

Thx!

-Jim

[az_gila]

Is there a lip (or step) at the cracks?

If so, it could be that the metal "ring" was not a tight slip fit and the bolts stressed the material when the bolts were tightened up?