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912 Vibration

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7suds(at)Chartermi.net
Guest

Posted: Wed Jan 25, 2006 7:29 pm Post subject: 912 Vibration

Group,

A friend of mine is working on a Pulsar with a 912UL 80 hp. It dropped a 

wheel off the runway when turning around and had a slight prop strike. The 

prop was a GSC 2 blade wood ground adjust. Upon inspection there was no 

evidence of the strike so the prop was removed and sent to the Mfg. for 

inspection which revealed micro fractures to the prop end. The prop was 

replaced and there is now a slight vibration at low RPM, higher RPM seems to 

be smoother. The prop was removed and balance checked, balanced and replaced 

but vibration still there. The question he would like to ask is what do you 

feel he should look at, check, replace in the motor?  Also, are the 912 

cranks solid or are they pressed together?

Thanks for any direction I can pass on,

Lloyd

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Jim Shumaker

Joined: 09 Jan 2006
Posts: 106

Posted: Wed Jan 25, 2006 10:12 pm Post subject: 912 Vibration

lloyd

   

  It is not likely that the engine was damaged due to a prop strike with a wooden prop.  Wooden props usually shatter before they transmit damaging forces to the engine.  Try a different prop.  Also look for a difference in tracking along different sections of the blades.  That is, if both blades are set at the same angle using the GSC protractor, they may not be set at the same angle.  Check for proper tracking of the prop and check it for tracking at a couple of different points.  They blades may not be a perfect match at all points along the blades.

   

  Jim Shumaker



Cudnohufsky's <7suds(at)Chartermi.net> wrote:

  



Group,

A friend of mine is working on a Pulsar with a 912UL 80 hp. It dropped a 

wheel off the runway when turning around and had a slight prop strike. The 

prop was a GSC 2 blade wood ground adjust. Upon inspection there was no 

evidence of the strike so the prop was removed and sent to the Mfg. for 

inspection which revealed micro fractures to the prop end. The prop was 

replaced and there is now a slight vibration at low RPM, higher RPM seems to 

be smoother. The prop was removed and balance checked, balanced and replaced 

but vibration still there. The question he would like to ask is what do you 

feel he should look at, check, replace in the motor? Also, are the 912 

cranks solid or are they pressed together?

Thanks for any direction I can pass on,

Lloyd

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_________________
Jim Shumaker

7suds(at)Chartermi.net
Guest

Posted: Thu Jan 26, 2006 3:16 pm Post subject: 912 Vibration

Thanks Jim, we will definitely do that.

---

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ruebd(at)skymail.csus.edu
Guest

Posted: Thu Jan 26, 2006 3:46 pm Post subject: 912 Vibration

Lloyd



Remember that the Rotax 912 uses a gearbox for final drive to the

propeller, so if any damage was sustained by the prop strike, it would

be to the output shaft of the gearbox, not the engines crankshaft.  Even

though wooden props tend to not transmit damage, it is still possible,

and it sounds like your friend may have a bent propeller shaft.  He

needs to have it checked by someone who can put a dial indicator on it.

Duane



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