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Old 11-29-2011, 10:11 PM   #17
Capn Craig
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Join Date: Oct 2010
Posts: 519
RE: 34 Californian props

Had a chance to bring one of the props into house and clean it up a bit, as well take a few crude measurements.* It is definately out of whack.* I found on one of the blades, the same blade that measures significantly different than the other two, what appears to be a crack.* Or it could* be purosity in the casting.* It os also on the 'stretched' side of the blade compared to the 'compressed' side, if the blade is bent the way it measures.* Whether it is cracked or casting purosity, it can't be good.* I'm thinking that an X-ray might shed some light, but I'm also not sure how successfully it could be welded.

The fore and aft ends of the hub do not appear to be particularly flat, so I think it very unlikely that the bore is perfectly perpendicular to either end.* I couldn't find any way to pick up the tapered bore centerline with stuff I have in my shop.***So, my measurements are crude.** Laying the prop on a flat table top, I measured the maximum verticle height of each blade off the table, and noted where it occured.* With the front of the prop down, I got 15mm of difference on one blade*vs. the*other 2 blades.* The other two blades measured within a millimeter of each other.* Flipping the prop over gave a height difference of 8mm of the bad blade*vs. the other two.

I can see how all kinds of wobble and vibration could be induced into the* shaft.* Especially if the RPM hit a nutural frequency of the shaft

So I guess the question is can*it be reliably fixed?* I spent a little time shopping props this evening, New is expensive.* I haven't made up my mind about turning it in to insurance co. yet.*

Picture 1* shown aft side down

Picture 2* shown fore side down

Picture 3* 'cracked' blade low pressure or 'fore side' of blade

Picture 4* 'back side of 'crack'* high pressure or 'aft side' of blade
Attached Thumbnails
engine room and prop 006.jpg   engine room and prop 003.jpg   engine room and prop 004.jpg   engine room and prop 005.jpg  
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