[miyu1975]

Can someone tell me the differences? Are counterweighted engines just smoother or what??...

 

[jrvssgl]

Counterweighted Engines may be a little smoother, not a lot, however the highlight of them is that it will eliminate most Engine/Propeller operating limitations. However Counterweighted Engines need a smooth hand on the throttle and do not like to slow down suddenly as this can cause serious damage to the counterweights. Also not much of a recommend for Aerobatic flight.

 

[chaskuss]

Can someone tell me the differences? Are counterweighted engines just smoother or what??...

As Jarvis mentioned above, the added counterweights can be de-tuned, by careless engine management. Another item is that those counterweights, add weight to the engine.
Counterweights are used to eliminate or at least modify objectionable engine/prop harmonics. It's not done for the comfort of the pilot and passengers. Of course, if a blade comes off the prop, the pilot will be VERY uncomfortable.
Charlie Kuss

 

[Allen Barrett]

Whoops

Counterweighted Engines may be a little smoother, not a lot, however the highlight of them is that it will eliminate most Engine/Propeller operating limitations. However Counterweighted Engines need a smooth hand on the throttle and do not like to slow down suddenly as this can cause serious damage to the counterweights. Also not much of a recommend for Aerobatic flight.

Hang on a second here Jarvis. Most all of your statement is correct. However, not being recommended for aerobatic flight can certainly be argued. If the statement were true, IO-540's and AEIO-540's wouldn't have them.

 

[DanH]

Fundamental to understanding their function, a Lycoming "counterweight" is not really a counterweight. They're mounted 90 degrees to the crankthrow, so they only thing they counterweight is themselves.

Calling them counterweights is mere poor terminology in common use, like "radiator" for heat exchanger or "shock absorber" for damper. They are tuned centrifugal pendulums, or to be more precise, the particular type used in a Lyc is a bifilar pendulum absorber. Their purpose is to eliminate torsional vibration at a particular tuned frequency.

Having considerable mass, a pendulum absorber can be arranged on a crank to serve a dual role of pendulum absorber and counterweight to piston/connecting rod mass. However, that's just the designer being thrifty with weight. If he only needed a counterweight, a mass solidly fixed to the crank would be fine.

Ryan, there's a decent discussion of pendulum absorbers in Schwaner's "Sky Ranch Engineering Manual", although the pendulum equations on pg 425 of my edition contain errors. Regardless, the book is a worthwhile addition to your personal library, along with his magneto manual. A more technical discussion can be found in any of the classic books on vibration.