Flywheels vs counterweights

[Putt-Rite]

Motors have progressed over the years from flywheeled to counter weighted cranks.

I assume that counter weighted cranks accelerate faster (are more responsive to the throttle), but do flywheeled motors run more smoothly?

 

[enfieldbullet]

the fly wheel stores momentum and smooths out the torque provided by the reciprocating pistons. it also reduces the tendency of the motor to stall whenever a load is applied.

counter weights reduce vibration induced by the dynamical imbalance of the reciprocating assembly(pistons and rods).

they are not mutually exclusive, an engine can and most do possess both.

more flywheel mass = less acceleration but smoother torque curve.

as far as counter weights go a crankshaft with less mass will be able to rotate faster and will accelerate faster.

you might be interested in checking out v8 crankshafts. the classic 'cross crank' is a heavy, counter weighted crankshaft that produces the bubbling sound normally associated with those engines. then there's the 'single plane' crankshaft that is what's used in F1 engines and which can rev faster because it doesn't have the heavy counter weights.

 

[Till]

There is only one powerstroke within four strokes of a four cycle engine, so power is delivered with high cyclic irregularity.
To compensate for that, you have to increase the gyrating mass. Momentum is "stored" and will be "released" between the powerstrokes to smoothen the irregularity. So every engine has some kind of a "flywheel", even if it's really small and if it doesn't look like it at first sight.
Counterweights add to the gyrating mass, so the flywheel in modern engines can be smaller by that amount.
If the engine is equipped with massive crankwebs, or a large blower fan for aircooling or a prop, this adds to to gyrating mass, too, so the conventional type of flywheel becomes redundant.
But the gyrating mass is still in there. The engine will not rev up faster unless the gyrating mass is reduced... eg. lighten the flywheel or removing counterweights... causing cyclic irregularity.