Pneumatic Marchetti Engine

Introduction

This was completed as my final project for a graduate level course entitled Integrated Computer-Aided Design in a team of six people. We were tasked with creating a machine of our choosing. After much consideration, we settled on a Marchetti engine since it is a purely mechanical system and has a unique cam-action. Creating a fully mechanical system, as opposed to a mechatronic system, allowed us to highlight the skills we learned in the course. 

Introduction
Background

A Marchetti engine was conceptualized as an airplane engine. It is an inherently balanced engine due to its internal mechanism. The butterfly-shaped cams act as a flywheel. The original designs for the Marchetti engine were powered by combustion. However, due to University rules and regulations, we opted to create a pneumatic version. 

Design

The design of our Marchetti engine was a challenge because there is little information available about Marchetti Engines as they are mostly historical. As a result we performed thorough analysis of the engine components, such as creating a torque profile, calculating the force per piston, determining the force of friction due to fluid shear, and determining the moment of inertia. Additionally, since we were creating the first functional pneumatic Marchetti engine, we carefully designed a custom timing mechanism and pneumatic system.

All CAD was done using SolidWorks. Master Modeling was used since it made making changes to the engine much simpler. I, personally, created and managed the master and created all the components of the engine.

Manufacturing

SolidCAM was used to generate G-Code for many of the engine components. All of the components were machined over the course of a week by myself and my teammates. We used a CNC mill (Haas Mini Mill), a CNC lathe (Haas TL-1), ProtoTRAK CNC mills, and manual mills and lathes. Some key challenges included maintaining concentricity of certain components through various operations and ensuring tight tolerances were achieved so the engine would be able to run.