Hello All, I have been in the background studying for my build project. Grayhawk, your information about the harmonic damper is an educational point of significance. I know nothing about dampers, is there a book that I can get to learn about this subject. Does a damper have to be specific to an engine or is the design universal to any recip?   Thank you for any advice in advance,   Sincerely,   Mr. Slava Harlamor slavaharlamor@sbcglobal.net   --- On Mon, 2/21/11, Sky2high@aol.com <Sky2high@aol.com> wrote: From: Sky2high@aol.com <Sky2high@aol.com> Subject: [LML] Re: prop balance To: lml@lancaironline.net Date: Monday, February 21, 2011, 10:32 AM 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 =