Today's Message Index:
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1. 06:26 PM - Re: Re: Can not turn over prop (Damien)
2. 07:44 PM - Re: Re: Can not turn over prop (rparigor@suffolk.lib.ny.us)
3. 08:53 PM - Re: Re: Can not turn over prop (FLYaDIVE)
Message 1
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| Subject: | Re: Can not turn over prop |
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
----- Original Message -----
From: "Roger Lee" <ssadiver1@yahoo.com>
Sent: Monday, August 20, 2012 6:14 PM
Subject: RotaxEngines-List: Re: Can not turn over prop
>
> 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.
>
> --------
> Roger Lee
> Tucson, Az.
> Light Sport Repairman - Maintenance Rated
> Rotax Repair Center - Heavy Maint. Rated
> Home 520-574-1080 TRY HOME FIRST
> Cell 520-349-7056
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=381411#381411
>
>
>
Message 2
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| Subject: | Re: Can not turn over prop |
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
Message 3
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| Subject: | Re: Can not turn over prop |
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>
.
False brinelling gets it's name from the Brinell Scale of Hardness. Not to
be confused with the Mohs Scale of Hardness.
Now the questions are: What caused it?
Was it poor preventative maintenance?
Such as way, way over due oil changes?
Poor quality of oil?
Too many short runs with not enough heat generated to drive out the
condensed moisture in the oil?
Improper matching of mating materials?
Poor tolerances on rotating surfaces?
Poor tolerances and excessive lateral movement on the rotating surfaces?
Leaking of the cooling system into the crankcase?
Barry
On Sat, Aug 25, 2012 at 10:44 PM, <rparigor@suffolk.lib.ny.us> wrote:
> 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
>
> *
>
> *
>
>
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