Hi there,
This is Bogdan from Romania.
I'm a mechanical engineer - specialized in the industrial robotic field, 3D designer and modeler (from time to time and some projects I could make the functional prototype too).
I'm doing product design, industrial design, reverse engineering, ideation, etc.
I have over 15 years experience working on various systems/devices across multiple industries, from concept to launch.
1 - i need to see the drawings/sketches of the workbench you have
2 - based on your input, we should discuss about the materials to be used, the proper methods to apply the physics and engineering rules, etc, etc
3 - besides the spring forces to be calculated will also be necessary a device to adjust the resistive force accordingly with the user's power/muscles system, eventually the leverage lengths (not all the users will be the same, and will be better to have some adjusting possibilities)
4 - in the end, you will have the full set of 3d models of each part and assembly in different cad format (iges, step, stl, x_t), visualization files (screenshots, 3d pdf) and manufacturing files (dxf, dwg, dimensions pdf), bom list, etc
5 - i will try as much as possible to use ots components, but you have to be aware that will not be possible every time (for every part), and some will require manufacturing
6 - if interested, and with a clear analysis of the costs, we could also discuss about prototyping in my workshop (but most probably will become expensive)
Regards
Bogdan