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Rotax crank failures

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 05, 2014 6:43 pm Post subject: Rotax crank failures

 	  Quote: 	
		  6) The ability to use roller bearings. (I have no idea if they actually should or do). 	


   Interesting point to ponder . . . if they do use

   roller bearings, then in no way will a loss of

   lubrication put a destructive torque moment on

   the crank end of the rod in a mere ten seconds

   of running . . .



   but no . . .



   This excerpt from the 912/914 maintenance

   manual . . .    

 

  http://tinyurl.com/mresg6r



   suggests that the classic pressure

   lubricated sleeve bearings are used on the

   connecting rods.



 

 [img]cid:.0[/img]



 



 



 

  	  Quote: 	
		  As long as the rod and main bearings are good, the idea that the crank can come apart is simply a distraction. Porsche 4-cam racing engines used a similar design, although they keyed theirs. But Still... Your Mileage May Vary. 	


   . . . I've not heard of crank disassembly

   in the field . . . those engines have been

   around for a very long time. It's hard

   to argue with success!



   A short web-cruise did turn up this crank

   failure accident



  http://tinyurl.com/lzhk22s



   which failed to identify any errors of manufacture.

   The press-fit technology is not a high-risk

   process. Interruption fits of highly stressed

   parts has along history of success.



   Also found an AD against a production batch

   of Rotax 912 cranks for suspected vulnerability

   to cracking.



   All incidents of slipped assembly joints

   I found were byproducts of prop strikes.

   I think there's a slip clutch mod that

   reduces probability of a prop-strike from

   over-torque slipping of the joints.



   All in all, a pretty clean track record.



 do not archive.



 



 

   Bob . . .

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tim2542(at)sbcglobal.net
Guest

Posted: Wed Feb 05, 2014 7:26 pm Post subject: Rotax crank failures

From the pics on the Europa site posted earlier, it clear they uses one piece rods. Only way to do that is with roller bearings and a press assembled crank. The main bearings seen are typical automotive style Babbitt bearings.

Also the blueing on the rod beam shows the amount of heat generated when the failure occurred. 

Tim

[quote] On Feb 5, 2014, at 6:41 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:

> 6) The ability to use roller bearings. (I have no idea if they actually should or do).

   Interesting point to ponder . . . if they do use

   roller bearings, then in no way will a loss of

   lubrication put a destructive torque moment on

   the crank end of the rod in a mere ten seconds

   of running . . .

   but no . . .

   This excerpt from the 912/914 maintenance

   manual . . .    

 http://tinyurl.com/mresg6r

   suggests that the classic pressure

   lubricated sleeve bearings are used on the

   connecting rods.

 <34add2aa.jpg>

> As long as the rod and main bearings are good, the idea that the crank can come apart is simply a distraction. Porsche 4-cam racing engines used a similar design, although they keyed theirs. But Still... Your Mileage May Vary

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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