Case Study For A First Year Seminar: A Plan Which (Mostly) Worked

A First-Year Seminar is now required for all students entering Penn State University. The goal is to provide interaction between faculty and small groups of students early in every program of study to personalize the university, to get the students to work collaboratively from the start, and to introduce the students to academic life. Some of the offered seminars are general, applicable to any major, and other seminars are included in courses specific to particular majors. An introductory engineering technology course titled “Manufacturing, Materials, and Processes” has been modified to include a seminar and is effectively required for all students entering a range of majors. One of the goals for this particular seminar class is to acquaint the students with the courses in their majors, and how the courses integrate with the goals of the major. A case study was developed based on a damaged lawn mower, and presented in the seminar. The problem presented in the case study was purposely incomplete, with a series of tasks listed which would be necessary to resolve the damage to the lawnmower. The students were required to search the courses of their major to determine which course provides the tools to accomplish the listed tasks. The case study was re-visited in a subsequent week for concluding remarks about the integration of the courses in the major. The case study is presented in this paper, and suggestions for development of other case studies applicable to first-year students. Additional information presented in a subsequent class is described, as is an evaluation of the benefits of the case study as it was presented the first time. Observations for improvement of the effectiveness of case studies in first-year seminars are also presented. Development of a Case Study Entering freshmen often come with little experience and few skills applicable to engineering tasks, yet they resent spending up to four semesters in preparation for engineering courses. The movement to first-year experiences in engineering is intended to introduce them to the techniques of the profession early in their program of study, and to motivate the students to study in the support courses. Often the students have no knowledge or experience to use as a base for such an introduction. Technical content of case studies for first-year must be (1) limited to that which can be explained in the case study, or (2) is generic enough that all students can be expected to have some experience with the device or subject. In an introductory seminar, the P ge 538.1 case study must also be brief since generally such seminars have limited class hours and it is not desirable to devote more than a period or two to any one case study. This is unlike the sort of case studies prepared for more advanced audiences, such as the excellent case studies written over past years and available from the Carleton University web site. The case study presented below follows these two requirements. First, the centerpiece for the case study is a lawn mower, and for the population served by this case study a lawn mower is almost universally familiar to the students regardless of gender or city/suburb homes. In contrast, farm machinery is familiar to few students and hence would not make an effective example. Secondly, in an attempt to improve the students’ technical knowledge base as it applies to the device described in the case study, a simple explanation of the operation of a 4cycle engine is included in the case study. Descriptions used in the case study must begin from everyday items or from high school general science. The case study presented below was four pages as originally formatted, easily within a single class period for reading and discussion. Case Study Title : I Don’t Know What Happened; It Just Quit! Introduction to Case Study: A lawn mower is a device familiar to most of us. Not everyone has operated one, to be sure, but in this part of the country there is enough rain that if an area is not mowed it will soon grow up to brush or trees. At my house there are some areas that I only mow occasionally, just to keep from having tall stuff growing there. It cannot be called lawn because it is much too rough for that, but it does get mowed sometimes. In midsummer of 1999, I made an effort to mow the usual spots, including one full of poison ivy. The former owner of my house had tossed junk various places out back, and to my surprise I found that some pipes had been left in this patch of poison ivy. I am not very interested in fishing around in poison ivy to see if it happens to have something in it, so some earlier year I had pulled out all the pipes I could see, and then started mowing. This year when I mowed it I got the nasty surprise of the lawn mower finding another pipe. Whether this pipe had been there all along and I missed it previous years, or 1999 was such a dry summer that the soil changed and exposed it anew, or some child had thrown it there the day before, I know not. In any case, the mower came to an abrupt stop. The noise told the story immediately; there is no sound quite like a mower blade hitting a pipe. I tried to re-start the engine, but the rope could hardly be pulled. Since it was very hard to get the engine to rotate, I suspected mechanical damage and tipped the mower on its side. I expected a bent blade but it was not. Instead I found that the engine crankshaft was bent at the bottom of the engine. Background for Case Study: While it is assumed that most people have a passing familiarity with lawn mowers, it is not assumed that very many have ever taken one apart, particularly the engine. Hence a description of what is inside is supplied here. P ge 538.2 At the most basic level, an engine is a device which burns fuel in air to get some heat, uses the heat to expand the air, and the expanding air to apply a force to get a job done. A lawn mower engine is a fairly simple example, but the details are beyond what we must know here, and that is a good thing since a lifetime can be spent studying some of the details. Even though not really necessary for repair of the bent crankshaft, it won’t hurt anyone to have a basic understanding of the operation of an engine, so we will take a detour to think about the thermal and fluid operations of the engine. The first trick that is necessary is to get the right amount of fuel and air into the combustion chamber. The operator controls the amount of the mixture that is drawn in by the position of the control lever, which in turn controls the position of the throttle plate in the intake system. In a conventional engine, the throttle plate is in a carburetor, which also mixes the correct amount of fuel into the air. Should you have the opportunity to study fluid mechanics at some time, the principles will assist in describing this device and understanding its operation, but in short the total energy of the air is the same at all locations as it is drawn through the carburetor. Some of the energy is seen as pressure and some is seen as velocity. Because the area drops in the venturi, the velocity increases. But for the velocity to increase requires energy, which must come from a reduction in pressure, and the atmosphere can push fuel from the float bowl into the reduced pressure of the air stream in the venturi. Getting this explosive mixture into and out of the engine requires some valves and a mechanism to open and close the valves, but we will ignore the mechanism here. The usual lawn mower has what is called a 4-cycle engine. The 4 cycles are intake, compression, power, and exhaust. Shown in Figure 2 is the intake cycle or stroke; the crankshaft rotates, pulling the piston down, drawing air and fuel from the carburetor. At the completion of the intake stroke the intake valve is closed, and the crankshaft pushes the piston back to the top to compress the air-fuel mixture. The power stroke begins with the sparkplug firing, very rapid burning of the fuel (in other words an explosion), heating and high pressure in the cylinder from the burning, and the piston is pushed down by the pressure. Finally the exhaust valve (not shown) is opened, and the crankshaft pushes the piston back to the top and in the process shoves the combustion products out. Figure 2: 4-cycle Engine, top view Figure 1: Simplified Carburetor