[FMG_V6_btb]

Rotational inertia doesn't depends directly on the stroke, depends on the masses distribution of the rotating parts. Obviously short stroke crankshafts have short diameter, and for that the masses are more next to the center, which means less inertia moment. Due to this fact and the extremely high engine speeds and lineal inertia forces induced by the pistons and rods (part), the correct crankshaft balance by means of the counterweights becomes more difficult. For that reason F1 crankshafts uses some inserts of very dense material in the counterweights (as far as possible from the rotational axle), so why F1 engines does not use knife edge cranks?... because the need to maintain as much counterweight as possible.

Pictured: Ferrari F1 V10 alternative and rotative parts.

Paco.