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Date: Mon, 21 Feb 2011 11:32:36 -0500
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Subject: Re: [LML] prop balance
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Jack,
 
The 12 pound harmonic damper is present to reduce negative torque  between 
power strokes.  It has a steel ring suspended in silicone.   It does not 
help balance the prop - it should be totally neutral with  respect to balance 
but not circular momentum.  On fixed-pitch prop (likely  wooden or composite) 
driven engines, there is often a 100 rpm increase because  of added 
momentum and a reduction in the negative torque by damping it.   Constant speed 
prop users may find it difficult to measure the effect.   Another benefit is to 
move the CG forward - usually a plus in the 320/360 series  aircraft.
 
The person in Redmond is wrong.  He is misinformed about the purpose  of 
the damper.
 
I have such a damper and I do balance my prop.  Because I am in  a 
partnership that owns a simple balance device, I have no  constraint on performing a 
balance or just checking the last balance to insure  it has not changed (it 
has not).
 
Go balance that prop.  Weights/longer bolts can be affixed where  the 
damper is mounted to the starter ring.  However, be careful that any  large area 
washers not stick out far enough to come in contact with  the cowling in 
dramatic + or - G maneuvers.
 
Geeeeze!
 
Grayhawk
 
 
In a message dated 2/21/2011 7:26:04 A.M. Central Standard Time,  
jraddison@msn.com writes:

Question?
On my LNC2-360 (BIB plus high comp pistons) there is  an add-on "balancer" 
bolted to the face of the starter ring gear.
It is  supposed to balance the engine with its internal weights that are 
supposed to  arrange themselves to cancel or dampen our any sensed vibrations.
The  "balancer" is about 2 inches in debth and almost the diameter of the 
ring  gear; it is all self contained and you would have to take the prop off 
to get  it off and take it apart if one was at least currious what was 
inside of  it.

It's difficult to know if a 4 cyclynder Lycoming is as smooth  as it can 
be, because it's not a real smooth engine under the best of  conditions.

I inquired to a local experienced prop balance person  in Redmond and they 
concluded that because of the dynamic balancer on the ring  gear, he would 
not attempt to balance the engine with his expensive balance  work, as he 
thought the attached dynamic balancer would change the internal  weight at will.

Does anyone have any experience with these  dynamic balancers attached to 
the ring  gear???

Cheers

Jack Addison  N360JS
near  Redmond, OR
=

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<DIV>Jack,</DIV>
<DIV>&nbsp;</DIV>
<DIV>The 12 pound&nbsp;harmonic damper is present to reduce negative torqu=
e=20
between power strokes.&nbsp; It has a steel ring suspended in silicone.&nb=
sp;=20
It&nbsp;does not help balance the prop - it should be totally neutral with=
=20
respect to balance but not circular momentum.&nbsp; On fixed-pitch prop (l=
ikely=20
wooden or composite) driven engines, there is often a 100 rpm increase bec=
ause=20
of added momentum and a reduction in the negative torque by damping it.&nb=
sp;=20
Constant speed prop users may find it difficult to measure the effect.&nbs=
p;=20
Another benefit is to move the CG forward - usually a plus in the 320/360=
 series=20
aircraft.</DIV>
<DIV>&nbsp;</DIV>
<DIV>The person in Redmond is wrong.&nbsp; He is misinformed about the pur=
pose=20
of the damper.</DIV>
<DIV>&nbsp;</DIV>
<DIV>I have such a damper and I do balance my prop.&nbsp; Because I am in=
=20
a&nbsp;partnership&nbsp;that owns&nbsp;a simple balance device, I have no=
=20
constraint on performing a balance or just checking the last balance to in=
sure=20
it has not changed (it has not).</DIV>
<DIV>&nbsp;</DIV>
<DIV>Go balance that prop.&nbsp;&nbsp;Weights/longer bolts can be affixed=
 where=20
the damper is mounted to the starter ring.&nbsp; However, be careful that=
 any=20
large&nbsp;area washers&nbsp;not stick out far enough to come in contact=
 with=20
the cowling in dramatic + or - G maneuvers.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Geeeeze!</DIV>
<DIV>&nbsp;</DIV>
<DIV>Grayhawk</DIV>
<DIV>&nbsp;</DIV>
<DIV>
<DIV>In a message dated 2/21/2011 7:26:04 A.M. Central Standard Time,=20
jraddison@msn.com writes:</DIV>
<BLOCKQUOTE  style=3D"BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARG=
IN-LEFT: 5px"><FONT    style=3D"BACKGROUND-COLOR: transparent" color=3D#00=
0000 size=3D2    face=3DTahoma>Question?<BR>On my LNC2-360 (BIB plus high=
 comp pistons) there is=20
  an add-on "balancer" bolted to the face of the starter ring gear.<BR>It=
 is=20
  supposed to balance the engine with its internal weights that are suppos=
ed to=20
  arrange themselves to cancel or dampen our any sensed vibrations.<BR>The=
=20
  "balancer" is about 2 inches in debth and almost the diameter of the rin=
g=20
  gear; it is all self contained and you would have to take the prop off=
 to get=20
  it off and take it apart if one was at least currious what was inside of=
=20
  it.<BR>&nbsp;<BR>It's difficult to know if a 4 cyclynder Lycoming is as=
 smooth=20
  as it can be, because it's not a real smooth engine under the best of=20
  conditions.<BR>&nbsp;<BR>I inquired to a local experienced prop balance=
 person=20
  in Redmond and they concluded that because of the dynamic balancer on th=
e ring=20
  gear, he would not attempt to balance the engine with his expensive bala=
nce=20
  work, as he thought the attached dynamic balancer would change the inter=
nal=20
  weight at will.<BR>&nbsp;<BR>Does anyone have any experience with these=
=20
  dynamic balancers attached to the ring=20
  gear???<BR>&nbsp;<BR>Cheers<BR>&nbsp;<BR>Jack Addison&nbsp; N360JS<BR>ne=
ar=20
  Redmond, OR<BR>=3D</FONT></BLOCKQUOTE></DIV></FONT></BODY></HTML>

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