Numerical methodology for design and optimization of a connecting rod for very high speed engines

Motorsports equipment design is a complex and evolving engineering discipline, whose driving factor for each component is maximizing the weight reduction, ensuring its operation and in-service life imposed by the regulations. The design complexity in this field is because all key components are subject to high and time-varying stresses. Top teams in high-tech categories can invest large amounts of money in developing and applying sophisticated CAE systems. Such economic commitment is not sustainable for all those teams operating in strategic categories where the production of vehicles and their components are in the hands of small realities, such as karts or mini-motorcycles. In these fields, the most common design approach is the trial and error on physical prototypes. Such an inefficient approach leads to high costs, and, for the rough exploration of the design space, a very low innovation for every component. To overcome these limitations, the presented paper proposes a systematic methodology for the structural design of high-speed engine parts, accessible also to small artisan teams. The method is based on the use of commercial CAD and CAE software; it analyses a 3D CAD model comprising all the components of the whole kinematic chain to which the element to be considered belongs. The FE model is built by setting appropriate boundary conditions on all the components of the above-mentioned chain and imposing, on the element to be studied, for each kinematic configuration, all the acting loads, including the inertial ones. This methodology is here applied to the redesign of a connecting rod of the engine for go-kart competitions. The obtained results are critically discussed and compared with the key methods available in the literature: static analysis and quasi-dynamic analysis. The results evidence methods presented in the literature do no work in presence of high inertia loads: for some crank angles, the stress level got is higher than the yield stress. Instead, by using the proposed method, the consistency of safety coefficient values with those available in the literature is obtained. The proposed methodology could lead to an increase in innovation and in a time and cost reduction during the development process of the motorsport engines having a high specific power obtained with high rotation speeds. This could determine a decrease in the cost of race vehicles with an expansion of potential practitioners of these strategic categories.