Join Date: Aug 2006
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Re: Transmission output flange fell off Yanmar 2QM15 - Theories re: why?
Originally Posted by JeffBurright
- This is the same nut that originally failed. I reused it by filing off the older calked spot. The threads look good on the nut still, nearly perfect with minor scoring. I plan to replace this nut now that we're back to civilization and a better repair is clearly needed. However, couldn't a person just chisel in a new calking in the old nut in a new location around the rim?
- I agree that the inside of the flange looks and feels suspiciously smooth. The thing is, the schematic drawing, while tiny, does show longer teeth. Also, I found a machinist here who had an old rusted out flange that was unusable but did have fuller teeth. It would make my month if I didn't need a new flange, but the evidence so far seems to point the other way.
- From what I can tell, the flange does go all the way onto the spline. When the nut is torqued as far as I can get it, turning the flange turns the gears in the transmission. However, those tiny teeth seem such a tenuous hold on an awfully long spline, and if the calking on the nut is the only thing keeping this whole show together, it seems like an awfully weak link.
Here's a picture of the spline. Apologies, I'm not near the photographer that my wife is.
Agree that the flange and shaft seems an odd pair.
Looks like a "bodge job"..
I had a prop shaft flange split along the keyway once.
First we found that the key was just a bit of scrap iron, did not fit at all
Had to get the original drawings from the manufacturer to get a new flange made.
We then discovered that the nut should be conical fitting into a conical recess on the flange locked with a set screws.
But some genius had modified the flange to take a custom made hex nut where only the corners had contact with the flange and no set screw at all
So the old flange had been sitting on the cone only (probably a long time).
When it started to slip the scrap iron piece split the flange hub.