The development of energy storage systems has gained increasing interest in recent years, as global energy policies and protocols demand to regulate and use available energy efficiently. Inertia flywheels constitute a simple means of energy storage, which has been integrated into different mechanical systems such as die-cutting machines, internal combustion engines, modern systems such as regenerative braking in automobiles, uninterruptible power systems, etc. In this research work, the design process of a flywheel-based experimental test bench to be used as an up-to 130 kilojouls energy storage capacity, and also to test small capacity internal combustion engines, and to diagnose the performance of engine starters. Setting the requirements and main specifications, the paper presents the followed design process, including the solid modeling, the calculations for the dimensioning of the final concept and prototype. Some experimental performance plots obtained during the preliminary tests performed are presented.