AROUND THE WORLD

A globe themed stirling heat engine.

I individually designed and manufactured a Gamma-type stirling heat engine. Using provided engineering drawings and SolidWorks part files, I modeled the standard components of my engine, such as my mounting block and heat sink. I then chose to model the remaining 7 unique parts of my engine (including the flywheel, bedplate, and base) to give my engine the appearance of a spinning globe, because I love to travel and experience new places around the world! Throughout the semester, I learned how to machine aluminum, steel, brass, and wood using the manual mill, CNC mill (ProtoTRAK), vertical bandsaw, and lathe.

My engine reached a maximum speed of 867 rpm, and won the award for Best Design.

Overview

Course: Machine Design and Manufacturing

Focus: Ideation; Mechanical Design; Manufacturing 

Timeline: August 2017-December 2017

Ideation

At the beginning of the semester, I brainstormed overall themes for my engine, sketched the entire engine concept and the 7 unique components, and specified which materials I would use for each component. My theme concepts ranged from the environment to artificial intelligence to The Beatles! 

Modeling

I created 3D models of all of the standard parts on SolidWorks from provided industry level engineering drawings. After sketching and planning the overall aesthetic appearance of my engine, I modeled my original design pieces to work within my chosen theme of a globe. Once each piece was modeled, I combined all of the parts into a SolidWorks assembly to ensure the machine would physically assemble as intended. I also performed analysis on the center of mass of the engine and moment of inertia of the flywheel, to ensure that my design was structurally stable and could perform basic functionalities. 

Evaluation

Throughout the semester, I learned about geometric dimensioning and tolerancing (GD&T), a concept that manufacturing engineers use to determine how imperfectly a part can be machined before inhibiting the performance of the entire project or assembly. In the second half of the semester, I began adding GD&T dimensions to my own engineering drawings, and gained a better understanding of how I could use those specifications throughout my mechanical engineering career. I also performed a tolerance stack up on my heat engine, so that I was able to visualize the effect of machining parts imperfectly on the success of my project. 

Let’s Go Around the World!

Throughout the semester, I practiced and employed methods for ensuring precise measurements and setting datums, such as using a dial indicator to find the center of my heat sink before drilling holes around the circular cross section. I also learned about many important engineering practices that will be useful to me in industry, such as selecting different types of metals based on project objectives, and using different manufacturing techniques like casting and injection molding. 

This project taught me how to think flexibly to solve assembly issues. Because my flywheel included 3 aligned parts, it was complicated to attach all of the pieces to each other, to design a mechanism to connect the flywheel to the rest of the engine, and to ensure that I would not offset the center of mass of the entire engine by adding too much weight. By the end of the semester, I redesigned the structure of my flywheel 5 times, but each time I learned an important lesson about stability in assemblies, and best methods and practices for design for manufacturability and design for assembly.