The Wobbler Steam Engine: A Connection Between The Past, Present, And Future Of Mechanical Engineering

The Mechanical Engineering Freshman Experience at Western Kentucky University is a blend of contemporary student success topics with a return to some of the traditional roots of mechanical engineering. Students in this course are provided basic instruction in hand sketching and the safe use of fundamental machine shop tools. Each student designs, documents, and machines their own small steam engine. This experience is a response to the broadening gap between the background of new engineering students and the diminishing opportunties to learn practical skills in modern companies actively moving production overseas. This paper documents three years of this course and will share lessons learned by faculty, responses from industrial constituents, and student course assessments. Examples of engine designs are presented, along with a description and budget for the necessary infrastructure. Introduction Every student who begins the Mechanical Engineering (ME) program at Western Kentucky University (WKU) enrolls in ME 101: The Mechanical Engineering Freshman Experience. As with most freshman seminar courses in engineering, components of this course deal with college life, academic success, introductory professional skills, and ethics. However, this course adds a unique element in an attempt to counteract several evolving trends in the ME profession. As globalization moves through American industry, fewer companies have domestic manufacturing facilities where young engineers are exposed to a range of traditional production processes during a period of onsite practice. Too often, these young engineers will not have mentoring from experienced engineers, designers, and machinists who possess vast knowledge of these processes and their impact on design. In addition, the students who come to college to study engineering now typically possess few of the traditional fabrication skills learned in high school “shop.” Thus, many young engineers never have the opportunity to participate in any of these manufacturing processes. ME 101 is the first in a series of four integrated ME design courses at WKU attempting to deal with emerging issues such as these. The course is not a shop course, nor is it a theoretical course in manufacturing engineering. It is an integrated experience where students spend part of the semester focusing on improving their innate design abilities with practice in basic mechanical sketching and the production of a “proof-of-concept” prototype. The prototype expected from each student is a small steam engine, blending well with concurrent seminar discussions about the historical use of steam and the rise of the ASME. Each student is expected to design, machine, and demonstrate a unique “Wobbler” steam engine powered by P ge 9.304.1 Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright © 2003, American Society for Engineering Education compressed air. Teamwork is encouraged, but each student is responsible for his or her design, prototype, and report. Basic instruction is provided to each of the 50-60 students in the safe use of bandsaws, milling machines, lathes, and drill presses. Student have 24-7 access to a small machine shop where they work to machine these simple engines. Course Overview The Professional Component of the ABET assessment plan for the ME program at WKU has a strong emphasis on design, as documented in the program’s Design Plan. The Design Plan developed by the Mechanical Engineering faculty recognizes that the Engineering design process must be integrated into the Mechanical Engineering Curriculum as a continuous process from the first year to the final semester. This is necessary to provide students with the opportunity to acquire design tools and skills, as well as competency in mathematical and technical analysis, and communication. The Mechanical Engineering faculty accepts the following as a representative statement of the attributes of Engineering Design taught in this department: • Engineering design is the systematic application of the basic sciences, mathematics and engineering sciences to generate and evaluate specifications for systems, components, or processes. • The form and function of the design must achieve defined objectives and satisfy consumer constraints. • Design should include aspects of creativity, complexity, and iterative decision-making to optimize a solution, and compromise between multiple, and sometimes conflicting, requirements . ME 101 is the starting point for the Design Plan. It is the first of four designated design courses across the four years of the ME curriculum before the capstone design course. The Wobbler assignment attempts to meet the three attributes listed above while recognizing the limitations of a freshman class. The time spent on the design project is balanced with an academic success portion of the course, with 1/3 of the course focused on the Wobbler design. The class is team taught, with the author covering the Wobbler portion of the course. Students in this required design course are in their first semester, and are typically taking a material science course, calculus, and chemistry at the same time. Only ME students take this course, with each of the other WKU engineering programs offering discipline-specific design courses in the first semester as well. The freshman design courses in the other disciplines have projects that can be characterized by the three attributes above, but they use design experiences more appropriate to their discipline. Deliverables for the Wobbler assignment include a set of part and assembly hand sketches of the steam engine. Students also build up a cost budget, with materials priced by the inch; their cost must be below $18.75. However, no lab fee is charged to the students, the program bears the full cost. In addition, a spreadsheet has been developed to help students size some of their engine components. Students enter some of their dimensions, and the spreadsheet computes the remaining dimensions. A copy of their spreadsheet must be included. Students are allowed to Page 9.304.2 Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright © 2003, American Society for Engineering Education keep their engine; a digital photograph is taken of each engine for our assessment records. They are required to attend the final freshman event of the semester to demonstrate their engine. At the end of the fall semester, the Department of Engineering sponsors Freshman Engineering Day. The projects from all three Freshman Seminars (ME, EE, and CE) are demonstrated for family and friends. Lunch is provided by the Department, and the number of external visitors to this event has grown every year. The Wobbler demonstration is particularly impressive, as approximately fifty of these highly inefficient air engines are simultaneously powered from a compressor bank outside the building. Students enjoy measuring the speed of their engine with optical tachometers, while watching some of the engines fly apart relatively quickly. Figure 1 below shows a group of the freshmen as they run their engines in unison. Figure 1: Wobblers at Freshman Engineering Day Roots of the Profession A key reason for selecting a steam engine as the project for the ME Freshman Experience is the historical context of the ME profession. The American Society of Mechanical Engineers (ASME) student web site has a wealth of searchable resources on early steam history, boiler explosions, and the rise of codes and standards. Students are shown a presentation on the development of the ME profession, and steam power plays a pivotal role in that story. In addition, students watch a video on the rise of machine tools and their linkage to economic development. Safety Issues In today’s litigious environment, some might be surprised to find freshman engineering students using a machine shop. The author has heard from many faculty and administrators at other institutions who have eliminated all student access to machine tools. P ge 9.304.3 Proceedings of the 2004 American Society for Engineering Education Annual Conference & Exposition Copyright © 2003, American Society for Engineering Education The Department of Engineering is fortunate that WKU has a long tradition in the arts and crafts. Industrial education was a vital element of early Kentucky teacher education, and WKU has its roots in the “Normal School” model of teacher education. Woodworking and agricultural mechanics are still very popular courses within the Ogden College of Science and Engineering. ME students have 24-7 access to the building and machine shop with their student ID. The Department has a strict safety policy regarding safety glasses and always having a shop partner when working. The WKU occupational safety inspector regularly works with the departmental staff engineer and the author to review policies and procedures. The WKU General Counsel has reviewed our policies and plans and given her approval to our efforts. Wobbler Engines A Wobbler steam engine is a valveless oscillating engine with the connecting rod and piston formed as one rigid piece (no wrist pin). The cylinder serves as the valve porting system by oscillating (“wobbling”) on a pivot, moving an air inlet hole back and forth between steam (air) inlet and exhaust ports; see Figure 2 below. Figure 2: Operation of Wobbler Engine Wobbler engines are common beginners projects among hobby machinists. A wide range of web resources are available for students to research their design, with some even providing animated models illustrating how the devices work. Over 150 Wobbler steam engines have been built by freshman over the last three years. Very few appear to copied from public plans, but rather are unique designs developed by the students. Figure 2 below shows a sample of some of the engines built over the last three years.