In internal combustion engines, the crankshaft is the "backbone" that converts linear piston motion into rotary motion to drive the wheels.
: In this design, the spindle is permanently attached to one of the crank arms (usually the drive side), simplifying installation and increasing stiffness. Engine Crankshafts CrankHD
: The most standard modern setup, consisting of a left arm, a right arm, and a separate spindle . They typically use square-taper or splined (like Shimano Octalink) interfaces. In internal combustion engines, the crankshaft is the