Dynamic analysis of a motorbike engine timing system: Experimental and numerical investigation of the geartrain

• We inspected the elastodynamic behaviour of the timing system of a racing motorbike engine.
• The focus of the paper is on the geartrain which drives the desmodromic valve train.
• The gear angular velocities were measured in firing conditions.
• A lumped-parameter/finite-element model of the whole timing system is proposed.
• The experimental data were employed to validate the model.

The development of high-performance vehicle engines requires advanced investigations in order to provide engineers with proper analysis tools to optimize the system design. The elastodynamic behaviour of the engine powertrain may be critical at high velocities (when the flexibility of the system components can have a major role on the overall performance) with consequences on the valve timing and the transmission of dynamic loads. A thorough numerical/experimental investigation was performed on the timing system of a racing motorbike engine. The timing system included the geartrain, which transmits power from the crankshaft to the camshafts, and the valve train, formed by the camshafts and the cam-follower mechanisms for the valve actuation. An experimental campaign was designed and carried out with the purpose of inspecting the timing system behaviour for different velocities and different design parameters. A numerical model was developed in order to provide a simulation/analysis tool that permits the design optimization of the main system components. The present work focuses on the geartrain elastodynamic analysis, which is the main novelty of a long-lasting activity carried out by the authors in collaborations with Ducati Motor Holding S.p.a. (Bologna, Italy). The experimental campaign, the model development and validation, and some simulation results are reported and discussed.