Proceeding Paper Preliminary Design and Validation of a 3D-Printed Continuously Variable Transmission for an Electric Vehicle Prototype † Marcos R. C. Coimbra 1 , Társis P. Barbosa 1 and César M. A. Vasques 2, *   Citation: Coimbra, M.R.C.; Barbosa, T.P.; Vasques, C.M.A. Preliminary Design and Validation of a 3D-Printed Continuously Variable Transmission for an Electric Vehicle Prototype. Eng. Proc. 2021, 11, 11. https://doi.org/10.3390/ASEC2021- 11178 Academic Editor: Filippo Berto Published: 15 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Telecommunications Engineering and Mechatronics, Federal University of São João del-Rei, Alto Paraopeba Campus, Rodovia MG 443, km 7, Ouro Branco 36420-00, MG, Brazil; mrafaelcc@live.com (M.R.C.C.); tarsisbarbosa@ufsj.edu.br (T.P.B.) 2 proMetheus, Escola Superior de Tecnologia e Gestão, Instituto Politécnico de Viana do Castelo, Rua Escola Industrial e Comercial de Nun’Álvares, 4900-347 Viana do Castelo, Portugal * Correspondence: cmavasques@gmail.com † Presented at the 2nd International Electronic Conference on Applied Sciences, 15–31 October 2021; Available online: https://asec2021.sciforum.net/. Abstract: This article discusses the progress made in developing a new 3D-printed continuously variable transmission (CVT) for an electric vehicle (EV) prototype competing in the Shell Eco- marathon electric battery category, a global energy efficiency competition sponsored by Shell. The proposed system is composed of a polymeric conic gear assembled in the motor axle and directly coupled to the rear tire of the vehicle. The conical shape allows to implement a continuous variation of the gear diameter in contact with the tire. The motor with the gear was mounted over a board with linear bearings, allowing the speed ratio to change by moving the board laterally. A 3D-printing slicing software with an optimization algorithm plug-in was used to determine the best printing parameters for the conic gear based on the tangential force, maximum displacement and safety factor. When compared to the original part with a 100% infill density, the optimized solution reduced the component mass by about 12% while maintaining safe mechanical resistance and stiffness. Keywords: continuously variable transmission; powertrain design; electric vehicle; 3D printing; Shell Eco-marathon 1. Introduction The automotive industry has been heavily reliant on the use of fossil fuels for decades. However, due to rising diesel and gasoline prices, as well as environmental pollution and fossil fuel depletion, it was concluded that alternate vehicle propulsion methods were required. Electric vehicles (EVs) have been intensively studied and appear as a possible solution for reducing global warming emission gases in this scenario. To put it in perspec- tive, the transportation industry alone accounts for over 30% of global warming emissions in the United States; thus, switching to electric vehicles would be a very responsible and environmentally sound option [1]. International conferences, such as the United Nations Framework Convention on Climate Change (UNFCCC), also show international pressure for the development of sustainable technologies. According to Miyamoto [2], the Kyoto Protocol, which was signed in 1997, had an indirect impact on climate change discussion by boosting the number of worldwide patent applications for renewable energy, emphasizing the need for international cooperation on the subject. The Shell Group sponsors an international competition called the Shell Eco-marathon, which focuses on lowering vehicle fuel consumption and is competed in by university groups of enthusiastic automobile teachers and students all over the world [3–8]. This and similar events foster several automotive technology developments, including the demon- stration of distinctive car designs, energy management systems, powertrain innovations, advanced use of materials and manufacturing methods, mechanical design and the devel- opment of new 3D-printed automotive parts [9–14]. A continuously variable transmission Eng. Proc. 2021, 11, 11. https://doi.org/10.3390/ASEC2021-11178 https://www.mdpi.com/journal/engproc