Hello Everyone, I am an engineer and I wish to implement a gym system that generates energy from the user. I am originally an electrical engineer by trade, and have limited knowledge in mechanical design. This is why I need your help. My current design follows the outline of a basic cable machine commonly found in gyms for exercising the triceps, biceps etc. I have the brief design sorted: A rectangular frame is used to support all the components and weights used A pulley system is used to provide a means for the user to pull a weight up and down The rotation of the pulley is transferred to a shaft The shaft is connected to a motor The motor is therefore run by the users energy The output voltage of the motor is fed into electronics where the resulting energy is stored I require advice upon the mechanical aspect of this project. I wish to make a system that is: Efficient Feasible to implement within 3 months Can handle a weight of 10kg Current component parameters are: Motor with 15V rated output and 6mm diameter D-Shaped shaft Frame material is 45mm-by-45mm Rexroth beams I have provided some basic design sketches to give you a visual idea of what I am thinking: The first image is the frame. It is 1 meter in height, and 0.5 meters in width and length. There is also a middle beam connected across the top as shown in the image. This middle beam is where the pulley and motor are connected, and is illustrated in the second image. The second image is a basic representation of how I wish to connect the components together. As shown in the second image, I wish to screw the motor under the middle beam, connect it to a coupling shaft, have the coupling shaft connect to the pulley, have the whole shaft supported by hook-like supports, and have the pulley rotate by having the cable pulled up and down by the user on one end and connected to a weight on the other. Please give feedback on my design, and I need better ideas so I can improve the project.