In this study an alpha type Stirling engine concept based on Scotch Yoke mechanism was proposed with parallel cylinders. A non-conventional crankshaft carrying flanges at both ends was considered. Crankpins were located on flanges. Pistons were connected to the crankshaft by means of slot bearings. Slot bearing was considered to take place on a separate part mounted to pistons. In this engines, the thrust force between pistons and their cylinders is thought to be low enough. The moving components of the engine do not perform any lateral motion and therefore no lateral vibration is present. However, due to masses of pistons and mounted parts, the crankshaft speed will display fluctuations. Friction between the crankpins and slot bearings is also among the concerns. In this study by preparing a thermodynamic dynamic simulation program, some thermodynamic and dynamic aspects of the engine were examined. The power output of the engine was optimized with respect to the area ratio of pistons, the crank radius ratio of pistons and the phase angle between pistons. As the result of these optimizations 5.6%, 1% and 2.4% increments in engine power were obtained respectively. The speed fluctuation of the crankshaft was minimized to 10% of average speed. (C) 2018 Elsevier Ltd. All rights reserved.