Pleuel

Pleuel, short for Pleuelstange, is the connecting rod in piston engines. It transfers the reciprocating motion of the piston to the rotating crankshaft, converting linear movement into rotary motion. The Pleuel connects the piston via a piston pin (Kolbenbolzen) at the small end and the crankshaft via a bearing at the big end.

The rod typically has two ends: the small end attaches to the piston and allows a pivoting motion as the piston moves. The big end couples to the crankshaft journal and is fitted with a bearing, which can be a plain bearing or a bushing. The Pleuel experiences significant bending, compressive, and torsional loads during operation, and its length and cross-section influence engine geometry, compression ratio, and crank-throw behavior.

Common designs favor lightweight yet strong cross-sections, with I-beam or occasionally H-beam shapes to optimize stiffness and weight. Materials range from forged steel and cast iron to aluminum alloys in high-performance applications; aerospace uses alloys such as titanium in some cases. Manufacturing often involves forging or casting, followed by precise machining to achieve tight dimensional tolerances and surface finishes. Journal diameters, big-end bore, and rod length are specified to match engine design and bearing clearances.

Lubrication and bearing wear are critical considerations. Adequate oil supply to the big-end bearing reduces wear and overheating; improper lubrication or misalignment can lead to bearing damage or rod failure. Pleuels must withstand high cyclic stresses and are common failure points in engines under high load, detonation, or oiling problems.

Pleuel is used across a wide range of piston engines, including inline, V, and flat configurations, as well as in some high-performance and aircraft engines.