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dgraham7(at)TWCNY.RR.COM
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 Posted: Sat Aug 18, 2012 5:37 am Post subject: Can not turn over prop |
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Hello group. I flew this morning for about 45 minutes to get my annual done. We started to do a compression test and now the prop will not turn forward. It is locked. The prop will turn back about 180 degrees. The mechanic is doing some further investigations. Perhaps a thrown valve ? Do you guys have any ideas? Thanks.
Regards,
Damien
Rotax 912 80 HP
Sent from my iPad
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stabelvej9(at)gmail.com
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| Posted: Sat Aug 18, 2012 6:11 am Post subject: Can not turn over prop |
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You have "something" in the cylinder on top of one piston .......
Don't try to use force!
Get your hand on a endoscope, and check.
Gert Dalgard
OY-GDS / Europa Mono / 914 / Woodcomp
Den 18/08/2012 kl. 15.36 skrev Damien Graham <dgraham7(at)TWCNY.RR.COM>:
| Quote: |
Hello group. I flew this morning for about 45 minutes to get my annual done. We started to do a compression test and now the prop will not turn forward. It is locked. The prop will turn back about 180 degrees. The mechanic is doing some further investigations. Perhaps a thrown valve ? Do you guys have any ideas? Thanks.
Regards,
Damien
Rotax 912 80 HP
Sent from my iPad
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Sat Aug 18, 2012 12:46 pm Post subject: Re: Can not turn over prop |
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This could be an involved answer and I would need some more info. You're welcome to call and we can talk about it. This may be several things and you'll need to rule out each one.
Roger lee
Tucson, AZ
520-574-1080
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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ronlee
Joined: 25 Dec 2006
Posts: 141
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| Posted: Mon Aug 20, 2012 12:39 pm Post subject: Re: Can not turn over prop |
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It could be a valve that a stuck closed after the engine cooled a bit and when the cam tries to open it it stops the the engine from turning. Forcing it will bend or break something in the valve train should that be the problem.
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Ron Lee
Tucson, Arizona |
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Mon Aug 20, 2012 2:14 pm Post subject: Re: Can not turn over prop |
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I talked with them today and think they have found the problem. I don't have absolute confirmation yet, but should have when they do a test I gave them. The cylinders and everything else was clean. The gearbox too.
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Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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dgraham7(at)TWCNY.RR.COM
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| Posted: Sat Aug 25, 2012 5:26 pm Post subject: Can not turn over prop |
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The problem seems to be crankcase fretting, as Roger had suspected. I am
flying the plane again, carefully, but obviously I need to have
this corrected. I am going to contact LEAF and see what they suggest.
Roger, my mechanic and I would still be floundering around if you had not
jumped in to help. Thanks.
Regards,
Damien Graham
N48TK
---
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rparigoris
Joined: 24 Nov 2009
Posts: 796
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| Posted: Sat Aug 25, 2012 6:44 pm Post subject: Can not turn over prop |
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Hi Damien
"The problem seems to be crankcase fretting, as Roger had suspected."
Do you mind explaining exactly what crankcase fretting is and why it prevented you from turning over your prop.
Thx.
Ron Parigoris [quote][b]
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Sat Aug 25, 2012 7:53 pm Post subject: Can not turn over prop |
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Ron:
Fretting wear is the repeated cyclical rubbing between two surfaces, which
is known as fretting, over a period of time which will remove material from
one or both surfaces in contact. It occurs typically in bearings, although
most bearings have their surfaces hardened to resist the problem. Another
problem occurs when cracks in either surface are created, known as fretting
fatigue. It is the more serious of the two phenomena because it can lead to
catastrophic failure of the bearing. An associated problem occurs when the
small particles removed by wear are oxidised in air. The oxides are usually
harder than the underlying metal, so wear accelerates as the harder
particles abrade the metal surfaces further. Fretting corrosion acts in the
same way, especially when water is present.
*Fretting* refers to wear <http://en.wikipedia.org/wiki/Wear> and sometimes
corrosion <http://en.wikipedia.org/wiki/Corrosion> damage at the
asperities<http://en.wikipedia.org/wiki/Asperity_(material_science)>
of
contact surfaces. This damage is induced under load and in the presence of
repeated relative surface motion, as induced for example by vibration. The ASM
Handbook <http://en.wikipedia.org/wiki/ASM_International_(society)> on
Fatigue and Fracture defines fretting as: "*A special wear process that
occurs at the contact area between two materials under load and subject to
minute relative motion by vibration or some other force.*"
The amplitude <http://en.wikipedia.org/wiki/Amplitude> of the relative
sliding motion is often in the order from
micrometers<http://en.wikipedia.org/wiki/Micrometer_(unit)> to
millimeters, but can be as low as 3 to 4
nanometers<http://en.wikipedia.org/wiki/Nanometer>
.[1] <http://en.wikipedia.org/wiki/Fretting#cite_note-0>
The contact movement causes mechanical wear and material transfer at the
surface, often followed by oxidation<http://en.wikipedia.org/wiki/Oxidation> of
both the metallic debris and the freshly exposed metallic surfaces. Because
the oxidized debris is usually much harder than the surfaces from which it
came, it often acts as an abrasive agent that increases the rate of both
fretting and a mechanical wear called false
brinelling<http://en.wikipedia.org/wiki/False_brinelling>
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