Bill;
A well-balanced V-8 isn't bad at all but a well-balanced I-6 or V-12 is
a thing of joy. In a V-8 there is still a "couple" that can't be
compensated with balance weights.
Some late 4-cyl engines are using a balance shaft that runs parallel to
the crank; this improves its overall balance but doesn't compensate the
vibration completely.
Aircraft engine cranks are a special case, though. Propellers are a
"flexible" load and those cranks aren't subjected to torsional stresses
like an automobile engine connected to its semi-rigid load through a
clutch. A drag race would wind up most aircraft engine cranks like a
piece of spaghetti.
But then there's the radial aircraft engine-- a VERY short, rigid crank.
Some planes with radials even returned from missions with entire
cylinders shot off. Sitting behind that big air- cooled bullet- shield
was a psychological morale booster, or so I've read.
Regards, Neil Tucson, AZ
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