sportsterpaul wrote:Thing is, a compensator sprocket greatly reduces shock loads on the rest of the drivetrain.
though logical, this is street legend.
in cases of high load the comp bottoms out. its then the same as a solid.
so it doesnt reduce the shock on the drive train downstream of the sliding cam.
where the comp does its work is when cruising, it absorbs and releases most of the forces created by harmonic vibration of lightly loaded chains.
we all have ridden along side another bike and watched its rear drive chain.
under acceleration the chain acts as would be expected.
also acts as expected under deceleration.
when cruising it misbehaves.
*the top run of the chain whips (vibrates like a guitar string) while the 'no load bottom run' acts very civil.*
what you see on the top run is harmonic vibration.
this whip create forces that are magnitudes above what you may expect from your observations.
that whip
force is transmitted both upstream and downstream.
newton stated
force = mass multiplied by acceleration.
remember acceleration can be positive or negative.
your chain accelerated and decelerates with
each flywheel revolution, because your flywheel accelerates and decelerates in lockstep when cruising.
when accelerating the flywheel rotation increases more then it decreases each revolution. you speed up.
when decelerating the flywheel rotation decreases more then it increases each revolution. you slow down.
this bring up the inevitable question 'what happens when im neither accelerating or decelerating? in other word when im cruising.'
well you know the answer. see asterisk above.
why does that cruising whip happen happen?
because the flywheel rotation not stable during each revolution.
its accelerates when piston pushes on the crankpin, and decelerates when the piston does not.
we all know the piston pushes for only a fraction of each firing stroke.
that leaves the remaining portion of the firing stroke and the other 3 strokes unpowered,hence the flywheel decelerates.
the flywheel accelerates and decelerates with every other revolution.
this hopscotch movement of the flywheel transferred to the entire bike mass.
and it shows up in your chains as whip.
whip, in turn, is turned into "vibratory" force, just as newton stated.
we all know how badly vibration induced forces affects both man and machine.
what the compensator does is allow the variations in flywheel rotational velocity to be absorbed and released thru the compensator spring.
this insulates the destructive effects of flywheel rotational oscillations
that your pistons make when they are lightly loaded .