This paper shows the process followed in the assembly of the different elements of a stationary invention by Henry Muncaster, specifically of a single-cylinder steam engine with a crosshead trunk guide whose plans were published in the magazine ‘Model Engineer’ in 1957 as a preliminary step in order to explain the operation of the invention. To achieve this, the Autodesk Inventor Professional 2024 software has been used to finally obtain a coherent and functional 3D CAD model. However, there have been inconveniences derived from the absence of dimensions in the available plans of the invention and certain inconsistencies, so a series of hypotheses have had to be established about the geometries of some elements, estimating their dimension and applying a series of dimensional, geometric and movement constraints (degrees of freedom). Finally, graphic documentation consisting of assembly plans and assembly perspectives has been obtained.