Development of a Lightweight Connection Rod for Motorbikes Fabricated with Hybrid Manufacturing

Connecting rods for motorcycles today are commonly produced via casting or for racing applications by forging. Within this project, a lightweight connecting rod was developed for use in motorbikes. The aim was to improve the efficiency and smoothness of the engines by reducing the rotating masses. The manufacturing process was a combination of additive manufacturing and conventional gravity casting. On the material side, 17-4 PH and Ti6Al4V were used for the additive manufacturing. For the casting material AlSi10Mg. Initial preliminary tests showed that a material connection could not be created due to the different material properties. Therefore, the focus was placed on a form-fit connection. Cylindrical sleeves with different internal structures were printed and cast. Subsequently, the force necessary for pressing out was determined in shear tests. The force was found to be dependent on the number of connection points. The maximum necessary compressive force was 14 kN. The gap between the shell and the core due to shrinkage was determined optically. It was in the range of 3–25 µm. Further preliminary investigations included casting and solidification simulations, metallographic analysis of the microstructure, radiographic examination and corrosion tests. The findings of the preliminary investigations were incorporated into the design of the final component. A simulation model was created to predict any distortion that might occur during the casting process. The maximum displacement was 1.15–10.1 mm. The final component was installed in an engine and tested on the dynamometer. A significantly smoother engine running was observed. Finally, the connecting rod was subjected to a compression test. The maximum force applied was 76.6 kN. The connecting rod did not experience any significant deformation.