Geometric Modeling and Digital Restitution of a Single Cylinder Steam Engine of the Grasshopper Beam by Henry Muncaster

This paper shows the result of the process followed in the geometric modeling and digital restitution of a single cylinder steam engine of the Grasshopper beam designed by Henry Muncaster and published in the ‘Model Engineer’ journal in 1957, as a previous step to explaining the operation of the invention. For this, the Autodesk Inventor Professional 2023 software has been used in order to obtain its geometric modeling and virtual recreation, as well as AutoCAD Mechanical 2023 to obtain its graphic documentation from the available plans. However, during this process discrepancies in the dimensions of some elements have been found. This introduced geometric incompatibilities during the assembly of the different components of the invention, for which reason some of them have had to be resized so that the degrees of freedom of the mechanism of the invention could be restricted correctly and thus allow correct relative movement between them. In summary, a series of dimensional, geometric and movement (degrees of freedom) constraints have been applied to make the 3D CAD model coherent and functional. Furthermore, the graphic documentation of the invention (assembly plans, exploded view and dimensioned plans of each element according to the standards) has been obtained from the model. Finally, the simulation of the operation of the invention has been carried out, obtaining a realistic virtual recreation of the steam engine.