Calming crankshafts

Think of the crankshaft in an early-days single-cylinder motorcycle engine. Peaking at maybe 3000rpm, with a 100mm stroke, its piston is stopped twice per revolution, once at top centre, once at bottom centre. Between those extremes, it accelerated and decelerated at a peak rate of 650 times the acceleration of gravity to a maximum piston speed of around 50ft/sec.

For each pound of piston, gudgeon pin and con-rod-small-end mass, that required a