X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 25 Feb 2011 09:50:35 -0500 Message-ID: X-Original-Return-Path: Received: from web57504.mail.re1.yahoo.com ([66.196.100.71] verified) by logan.com (CommuniGate Pro SMTP 5.4c2o) with SMTP id 4882284 for lml@lancaironline.net; Fri, 25 Feb 2011 07:59:48 -0500 Received-SPF: none receiver=logan.com; client-ip=66.196.100.71; envelope-from=casey.gary@yahoo.com Received: (qmail 52960 invoked by uid 60001); 25 Feb 2011 12:59:12 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:References:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=BHNj0k2/E3MZq4nfqiRdp+WwQrZ6mF5BVzW9xob4xxH5Sm9NNas8hOzPAtnF25+eewwa3L5fgNGuCb8iNqNBRxMcyqxq3VG5Mqv2AWQ6XptLxykxcIlJlhDmVP3qfFyJh76vgtfeSssdSFeghpjUuoio8EPcFS34Cwlx3PzNm30=; X-Original-Message-ID: <920030.52957.qm@web57504.mail.re1.yahoo.com> X-YMail-OSG: eWsU5pEVM1m.BugoLk3quaPzjr4eBdn1BXwaLp0AVIBXTGw Bp_XEbEn9zjMM1GXumUdL1c4jNljNaXQUR.Wcb_598KlP.v_dzR8kw.OFNo2 pVGqPtzs3NVmmFdYRSaoO35X_qQlBrrRVY5md1TRe3Ni28JHoT71wwRMoiwE hP1XOqUy3ELbCARsX5Pon8CSx4qAMb45VgtSlRNmYP0ceUpoFBUb_SN2GUE3 YTpc4DpvyM6lL0cjvAdR2I0dxzK_EfUwrnlLE1duWg2cY6Z0.PPj3j4da0uy VQLCr_Zyk93pGdZCDvgOQE2gWe3lN3J_WphsGBc09tVd5VyxN33AGKseUXXv 2ozBT_A-- Received: from [96.35.96.95] by web57504.mail.re1.yahoo.com via HTTP; Fri, 25 Feb 2011 04:59:11 PST X-Mailer: YahooMailRC/555 YahooMailWebService/0.8.109.292656 References: X-Original-Date: Fri, 25 Feb 2011 04:59:11 -0800 (PST) From: Gary Casey Subject: Re: prop balance X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-2111745720-1298638751=:52957" --0-2111745720-1298638751=:52957 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable I have only a few comments regarding the flywheel "damper" discussion:=0A1.= =A0 The referenced EPI website is most excellent in its treatment of the = =0Asubject.=A0 I'm impressed.=0A2.=A0 The viscous damper isn't "tuned" to a= given frequency as it only responds to =0Aa change in rpm caused by the to= rsion inputs.=A0 A classic "torsional absorber" is =0Atuned to a resonant f= requency and reduces the amplitude.=A0 A different animal.=0A3.=A0 I'm a li= ttle skeptical as to whether the viscous damper reduces the =0Atorsional am= plitude more than just adding a 12-pound flywheel, but I don't know.=0A4.= =A0 I've heard good things about the viscous dampers when used with a 4-cyl= inder =0Aengine and wooden propeller, but I've seen no technical data to su= pport.=A0 =0AHeavier metal propellers seem to survive okay without the extr= a flywheel.=0A5.=A0 Yes, it's got nothing to do with the radial balance of = the prop.=0A6.=A0 I can't see any way that adding either a flywheel, torsio= nal absorber, or =0Aviscous damper could increase engine power ("100 rpm hi= gher static rpm").=A0 That =0Ajust doesn't make sense.=0AAgain, just my opi= nion.=0A=A0=0AFrom: =0A"Sky2high@aol.com" =0ASlava,=0A=0A= Read this to=A0 get an idea of the instantaneous torque the prop sees throu= gh its =0Afull revolution:=0A=0Ahttp://www.epi-eng.com/piston_engine_techno= logy/torsional_excitation_from_piston_engines.htm=0A=0A=0AMany engines may = have dampers to reduce power pulse effects from the drive =0Ashaft.=A0 The = one we are discussing here is specifically designed to be mounted on =0Aa L= ycoming starter ring.=A0=A0The following text=A0=A0was copied from=A0the ap= propriate =0Aad=A0in the May 2010 Sport Aviation Magazine:=0A=0AMark Landol= l, 405-392-3847, landollskydoll2001@yahoo.com=0A=0AGrayhawk AKA Scott Krueg= er=0APS I have been flying with this contraption on my Lyc=A0I/O 320 for mo= re than 12 =0Ayears.=0A=0AIn a message dated 2/23/2011 8:11:01 A.M. Central= Standard Time, =0Aslavaharlamor@sbcglobal.net writes:=0AHello All, I have = been in the background studying for my build project. =0AGrayhawk, your inf= ormation about the harmonic damper is an educational point of =0Asignifican= ce. I know nothing about dampers, is there a book that I can get to =0Alear= n about this subject. Does a damper have to be specific to an engine or is = =0Athe design universal to any recip?=0A>=0A>Thank you for any advice in ad= vance,=0A>=0A>Sincerely,=0A>=0A>Mr. Slava Harlamor=0A>slavaharlamor@sbcglob= al.net =0A>=0A>=0A>=0A>--- On Mon, 2/21/11, Sky2high@aol.com wrote:=0A>=0A>=0A>>From: Sky2high@aol.com =0A>>Subje= ct: [LML] Re: prop balance=0A>>To: lml@lancaironline.net=0A>>Date: Monday, = February 21, 2011, 10:32 AM=0A>>=0A>>=0A>>Jack,=0A>>=0A>>The 12 pound=A0har= monic damper is present to reduce negative torque between power =0A>>stroke= s.=A0 It has a steel ring suspended in silicone.=A0 It=A0does not help bala= nce =0A>>the prop - it should be totally neutral with respect to balance bu= t not circular =0A>>momentum.=A0 On fixed-pitch prop (likely wooden or comp= osite) driven engines, =0A>>there is often a 100 rpm increase because of ad= ded momentum and a reduction in =0A>>the negative torque by damping it.=A0 = Constant speed prop users may find it =0A>>difficult to measure the effect.= =A0 Another benefit is to move the CG forward - =0A>>usually a plus in the = 320/360 series aircraft.=0A>>=0A>>The person in Redmond is wrong.=A0 He is = misinformed about the purpose of the =0A>>damper.=0A>>=0A>>I have such a da= mper and I do balance my prop.=A0 Because I am in =0A>>a=A0partnership=A0th= at owns=A0a simple balance device, I have no constraint on =0A>>performing = a balance or just checking the last balance to insure it has not =0A>>chang= ed (it has not).=0A>>=0A>>Go balance that prop.=A0=A0Weights/longer bolts c= an be affixed where the damper is =0A>>mounted to the starter ring.=A0 Howe= ver, be careful that any large=A0area =0A>>washers=A0not stick out far enou= gh to come in contact with the cowling in dramatic =0A>>+ or - G maneuvers.= =0A>>=0A>>Geeeeze!=0A>>=0A>>Grayhawk=0A>>=0A>>In a message dated 2/21/2011 = 7:26:04 A.M. Central Standard Time, =0A>>jraddison@msn.com writes:=0A>>Ques= tion?=0A>>>On my LNC2-360 (BIB plus high comp pistons) there is an add-on "= balancer" bolted =0A>>>to the face of the starter ring gear.=0A>>>It is sup= posed to balance the engine with its internal weights that are supposed =0A= >>>to arrange themselves to cancel or dampen our any sensed vibrations.=0A>= >>The "balancer" is about 2 inches in debth and almost the diameter of the = ring =0A>>>gear; it is all self contained and you would have to take the pr= op off to get it =0A>>>off and take it apart if one was at least currious w= hat was inside of it.=0A>>>=A0=0A>>>It's difficult to know if a 4 cyclynder= Lycoming is as smooth as it can be, =0A>>>because it's not a real smooth e= ngine under the best of conditions.=0A>>>=A0=0A>>>I inquired to a local exp= erienced prop balance person in Redmond and they =0A>>>concluded that becau= se of the dynamic balancer on the ring gear, he would not =0A>>>attempt to = balance the engine with his expensive balance work, as he thought the =0A>>= >attached dynamic balancer would change the internal weight at will.=0A>>>= =A0=0A>>>Does anyone have any experience with these dynamic balancers attac= hed to the =0A>>>ring gear???=0A>>>=A0=0A>>>Cheers=0A>>>=A0=0A>>>Jack Addis= on=A0 N360JS=0A>>>near Redmond, OR=0A>>>=3D =0A=0A=0A --0-2111745720-1298638751=:52957 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable

I have only a few comments regarding the flywheel "dam= per" discussion:

=0A

1.  The referenced EPI website is most excel= lent in its treatment of the subject.  I'm impressed.

=0A

2. = ; The viscous damper isn't "tuned" to a given frequency as it only responds= to a change in rpm caused by the torsion inputs.  A classic "torsiona= l absorber" is tuned to a resonant frequency and reduces the amplitude.&nbs= p; A different animal.

=0A

3.  I'm a little skeptical as to wheth= er the viscous damper reduces the torsional amplitude more than just adding= a 12-pound flywheel, but I don't know.

=0A

4.  I've heard good t= hings about the viscous dampers when used with a 4-cylinder engine and wood= en propeller, but I've seen no technical data to support.  Heavier met= al propellers seem to survive okay without the extra flywheel.

=0A

5.&= nbsp; Yes, it's got nothing to do with the radial balance of the prop.

= =0A

6.  I can't see any way that adding either a flywheel, torsional= absorber, or viscous damper could increase engine power ("100 rpm higher s= tatic rpm").  That just doesn't make sense.

=0A

Again, just my op= inion.

=0A
 
=0A
=0A
=0A
=0A
=0A
=0A
From:
=0A
=0A
"Sky2high@aol.com" <S= ky2high@aol.com>
=0A
= =0A
=0A
=0A
=0A
= =0A
=0A
Slava,
=0A
 
=0A
Read this to&= nbsp; get an idea of the instantaneous torque the prop sees through its ful= l revolution:
=0A
 
=0A=0A
 =0A
Grayhawk AKA Scott Krueger
=0A
PS I have been flying with= this contraption on my Lyc I/O 320 for more than 12 years.
=0A 
=0A
=0A
In a message dated 2/23/2011 8:11:01 A.M. Ce= ntral Standard Time, slavaharlamor@sbcglobal.net writes:
=0A=0A=0A= =0A=0A
=0A=0A --0-2111745720-1298638751=:52957--
=0A
Hello All, I have been in the background= studying for my build project. Grayhawk, your information about the harmon= ic damper is an educational point of significance. I know nothing about dam= pers, is there a book that I can get to learn about this subject. Does a da= mper have to be specific to an engine or is the design universal to any rec= ip?
=0A
 
=0A
Thank you for any advice in advance,=0A
 
=0A
Sincerely,
=0A
 
=0AMr. Slava Harlamor
=0A=0A
 
=0A


--- On Mon, 2/21/11, S= ky2high@aol.com <Sky2high@aol.com> wrote:
=0A
From: Sky2high@aol.com <Sky2high@aol.com>
Su= bject: [LML] Re: prop balance
To: lml@lancaironline.net
= Date: Monday, February 21, 2011, 10:32 AM

=0A
=0A
Jack,
=0A
 
=0A
The 12 pound harmonic= damper is present to reduce negative torque between power strokes.  I= t has a steel ring suspended in silicone.  It does not help balan= ce the prop - it should be totally neutral with respect to balance but not = circular momentum.  On fixed-pitch prop (likely wooden or composite) d= riven 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 benef= it is to move the CG forward - usually a plus in the 320/360 series aircraf= t.
=0A
 
=0A
The person in Redmond is wrong.  H= e is misinformed about the purpose of the damper.
=0A
 
= =0A
I have such a damper and I do balance my prop.  Because I am i= n a partnership that owns a simple balance device, I have no= constraint on performing a balance or just checking the last balance to in= sure it has not changed (it has not).
=0A
 
=0A
Go b= alance that prop.  Weights/longer bolts can be affixed where the = damper is mounted to the starter ring.  However, be careful that any l= arge area washers not stick out far enough to come in contact wit= h the cowling in dramatic + or - G maneuvers.
=0A
 
=0A<= DIV>Geeeeze!
=0A
 
=0A
Grayhawk
=0A
 <= /DIV>=0A
=0A
In a message dated 2/21/2011 7:26:04 A.M. Central Stan= dard Time, jraddison@msn.com writes:
=0A
Question= ?
On my LNC2-360 (BIB plus high comp pistons) there is an add-on "balanc= er" bolted to the face of the starter ring gear.
It is supposed to balan= ce the engine with its internal weights that are supposed to arrange themse= lves to cancel or dampen our any sensed vibrations.
The "balancer" is ab= out 2 inches in debth and almost the diameter of the ring gear; it is all s= elf contained and you would have to take the prop off to get it off and tak= e 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.
&n= bsp;
I inquired to a local experienced prop balance person in Redmond an= d 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 wo= uld change the internal weight at will.
 
Does anyone have any e= xperience with these dynamic balancers attached to the ring gear???
&nbs= p;
Cheers
 
Jack Addison  N360JS
near Redmond, OR
= =3D