Possible cause of 185 crankshaft failure?

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Postby flyalaz » Tue Sep 05, 2006 11:52 pm

Never having started a poll before, I hope I filled out the lines the right way.

I got to thinking about the way I first saw someone working on their Rotax 185 one day, probably shortly after my (old) engine failed, and also the way I have heard other people work on their own.

Reasoning that if you are applying torque on the mag nut, and are stopping the crankshaft from turning by sticking a long screwdriver or bar through the prop bolts, and vice versa, the force is going from one end of the shaft to the other.

The narrowest and therefore weakest point from A to B is right where the prop shaft comes out of the crank lobe. Which is where they all break. All things being equal, I believe repeated torque operations of this type may contribute to the weakening and eventual failure of the prop shaft.
The mag end is larger in diameter, plus it doesn't have to swing a prop load either.

I use a thick rubber strap wrench from Canadian Tire that grips the mag and prop hub, that eliminates this possible cause from happening. Wildfire has a tool for the mag end, p/n R-929, but nothing for the prop end.

If anything comes of this, it might at least eliminate improper technique and a possible cause of failure.

Thanks for your interest,
Karl
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Postby flyalaz » Thu Sep 07, 2006 11:12 am

Come on guys, don't be shy. There is no way to see who does what in the poll. It's like voting- nobody will know how you vote.

Without enough people voting, no statistic will be valid.

Karl
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Postby flyalaz » Wed Sep 13, 2006 4:10 pm

Gee, what engines are you guys using?

It's just a mouse click, honest! Non-members can't vote so any statistic arrived at should be as honest as we are right?

Ignore question #3, it doesn't make any sense, but the other ones all apply, so come on guys, lets see how things add up!

Karl
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Postby bdiedenhofen » Thu Sep 14, 2006 9:25 am

You're absolutely right. I never thought about this. Thanks for bringing this to light. I will definately trap the end that I am torqing in the future.

Thanks,
Brian D.
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Postby JPXman » Thu Sep 14, 2006 2:20 pm

I fly JPX engines and daffy fly's Solo's... so there's two non-voters :)
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Postby flyalaz » Thu Sep 14, 2006 7:25 pm

That's cool.

Though the poll applies to the rotax because of known events, I think the practices, both good (probably) and bad (possibly) are being applied to other motors as well and the more info that comes out, the better it is for us.

"The truth is out there"

Blue skies,
Karl
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