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Date: Tue, 30 Jul 2013 06:05:29 -0400
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From: Charles Brown <browncc1@verizon.net>
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Subject: Re: [LML] Re: Potential Problem-Engine Vibration
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Good info Paul.  I am a little chagrined to find that, after loading =
"Vibration" on my iPhone and going out to collect data, things were a =
bunch smoother than I recalled.  The only thing I changed was new spark =
plugs.  But I think it's clear that the vibration in my Legacy/IO550 is =
much less than what I hear Bob and Steve describe.

Kyrilian, would you care to examine vibration data from a test ride?  I =
have about 8 files of 15sec X 100Hz data taken with the iPhone secured =
to the instrument panel and I don't know what to make of it.

Charley


On Jul 29, 2013, at 10:23 AM, Paul Miller wrote:

One thing to keep in mind is that the prop balancing on the ground is =
not as accurate as when the scimitar is loaded in flight. This comes =
directly from one of the SX300 guys testing one of the Scimitars for =
Hartzell on his Lyc 580.   What he did was run the cables through the =
heat duct and perform the balance in flight conditions.  He reported =
that balancing the scimitars was not easy.  I had a hard time finding a =
good balance on the ground on the Legacy but it was passable.  I may try =
the in-flight balance next time at the 2300 rpm mark.  Our Legacy =
scimitars are simply cut shorter than the longer bladed scimitars for =
ground clearance.

Second, the engine and cowl moves a lot and the clearances are very =
tight in the Legacy.  At 2700 RPM and low airspeed the cowl is different =
shape than at cruise and the engine is in a different position relative =
to the mounts that at 2300.  The torque on the engine mounts is much =
different at 2300 versus 2700.  I found a lot of interference showed up =
as the RPM came down from 2700 to 2300 and then the engine and cowling =
were slightly separated so that the banging was transmitted.  I believe =
at other settings the engine was up against parts of the cowl and the =
actual vibration was transmitted.  I had the nose gear interference as =
well plus the baffling hit the prop governor cable in cruise.  Lots of =
areas where interference fits are really tight.  My point is that there =
are many factors that can affect vibration with changing throttle and =
RPM and it isn't just the prop/crankshaft combo that can be at issue.  I =
was seeing almost two inches of cowl movement between rest and flight at =
certain locations.   Thats a lot.

Not to take anything away from the issue under discussion except to say =
that, in my Legacy, vibration amplitude did change with varying RPM as a =
result of mechanical interference.

Paul
Legacy


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<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><div>Good info Paul. &nbsp;I am a little chagrined to find that, after =
loading "Vibration" on my iPhone and going out to collect data, things =
were a bunch smoother than I recalled. &nbsp;The only thing I changed =
was new spark plugs. &nbsp;But I think it's clear that the vibration in =
my Legacy/IO550 is much less than what I hear Bob and Steve =
describe.</div><div><br></div><div>Kyrilian, would you care to examine =
vibration data from a test ride? &nbsp;I have about 8 files of 15sec X =
100Hz data taken with the iPhone secured to the instrument panel and I =
don't know what to make of =
it.</div><div><br></div><div>Charley</div><div><br></div><br><div><div>On =
Jul 29, 2013, at 10:23 AM, Paul Miller wrote:</div><br =
class=3D"Apple-interchange-newline"><meta http-equiv=3D"Content-Type" =
content=3D"text/html charset=3Dbig5"><div style=3D"word-wrap: =
break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
after-white-space; ">One thing to keep in mind is that the prop =
balancing on the ground is not as accurate as when the scimitar is =
loaded in flight. This comes directly from one of the SX300 guys testing =
one of the Scimitars for Hartzell on his Lyc 580. &nbsp; What he did was =
run the cables through the heat duct and perform the balance in flight =
conditions. &nbsp;He reported that balancing the scimitars was not easy. =
&nbsp;I had a hard time finding a good balance on the ground on the =
Legacy but it was passable. &nbsp;I may try the in-flight balance next =
time at the 2300 rpm mark. &nbsp;Our Legacy scimitars are simply cut =
shorter than the longer bladed scimitars for ground =
clearance.<div><br></div><div>Second, the engine and cowl moves a lot =
and the clearances are very tight in the Legacy. &nbsp;At 2700 RPM and =
low airspeed the cowl is different shape than at cruise and the engine =
is in a different position relative to the mounts that at 2300. =
&nbsp;The torque on the engine mounts is much different at 2300 versus =
2700. &nbsp;I found a lot of interference showed up as the RPM came down =
from 2700 to 2300 and then the engine and cowling were slightly =
separated so that the banging was transmitted. &nbsp;I believe at other =
settings the engine was up against parts of the cowl and the actual =
vibration was transmitted. &nbsp;I had the nose gear interference as =
well plus the baffling hit the prop governor cable in cruise. &nbsp;Lots =
of areas where interference fits are really tight. &nbsp;My point is =
that there are many factors that can affect vibration with changing =
throttle and RPM and it isn't just the prop/crankshaft combo that can be =
at issue. &nbsp;I was seeing almost two inches of cowl movement between =
rest and flight at certain locations. &nbsp; Thats a =
lot.</div><div><br></div><div>Not to take anything away from the issue =
under discussion except to say that, in my Legacy, vibration amplitude =
did change with varying RPM as a result of mechanical =
interference.</div><div><br></div><div>Paul</div><div>Legacy</div><div><br=
></div><style></style></div></div><br></body></html>=

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