Design Heavy-Duty Agricultural Subsoil Ripper

I need a complete engineering design for a sub-soil ripper that will mount to a Category 3 three-point hitch and run behind a 100-150 hp tractor. Its primary role is deep tillage on broad-acre farms, so durability is far more important than cosmetics... (Budget: $250 - $750 AUD, Jobs: 3D CAD, 3D Modelling, 3D Rendering, AutoCAD, Autodesk Inventor, CAD/CAM, Finite Element Analysis, Mechanical Engineering, Solidworks)