Kolbenhub

Kolbenhub, also known as piston stroke, is the linear distance the piston travels inside a cylinder from the top dead center (TDC) to the bottom dead center (BDC). It is measured along the cylinder axis and is typically given in millimeters. The stroke is determined by the crankshaft throw, since the piston follows the circular motion of the crank and rod assembly.

In internal combustion engines, the piston stroke together with the bore defines the engine displacement, following the relation V = π × (bore/2)² × stroke. The bore and stroke are commonly referred to as the engine’s two fundamental geometry parameters. A long stroke (greater stroke relative to bore) tends to increase torque at lower rpm and can limit maximum engine speed due to higher piston acceleration and inertia, while a short stroke favors higher rpm and peak power at higher speeds. Piston speed is lowest at the extremes of travel (TDC and BDC) and reaches its maximum near mid-stroke, influencing wear, lubrication needs, and noise.

Design considerations include the balance between torque, efficiency, packaging constraints, and mechanical reliability. Connecting rod length, piston weight, and valve timing interact with the stroke to affect overall engine performance and durability. While Kolbenhub is most commonly discussed in automotive and motorcycle engines, the term also applies to hydraulic and pneumatic cylinders, where stroke denotes the actuator’s travel distance.