SolveSpace is a free and open source 3D CAD application that is designed to be easy to use and highly efficient for both 2D and 3D design. The software is available as a desktop application as well as a web-based version. The app provides a 3D workspace that is ideal for creating 3D models, drawings, and assemblies. The software allows users to create sketches and use a range of tools for extruding, revolve, and lofting 3D models. It is also capable of creating complex assemblies with the help of a range of tools for constrained motion, inverse kinematics, and motion simulation. SolveSpace also provides support for parametric modeling and is capable of importing and exporting files in a range of formats. The software is developed by a community of volunteer developers and is licensed under the GNU General Public License.
Sketchup is not for modeling precise machine parts, let alone simulating them.