2.670- Mechanical Engineering Tools- Week 1 by Melis A. '08

In an engineering class with a lecture format, you get to learn a lot about physical principles and how other people have applied them. A formula is written on the board, you think about it, figure out how it was derived, do a couple sample problems, maybe see a real life application, and then move on. Right now, I’m taking Mechanical Engineering Tools (2.670), a class that breaks this mold. The course teaches us the fundamentals of machine and computer tool use so all the Mechanical Engineering students will be equipped to handle upper level classes. But instead of taking us around the machine shop and giving a boring explanation on how to use each machine, we get to learn by making a spiffy Stirling engine! Actually, the class is divided into four sections, and actually manufacturing the engine is only half of the process. The machining is divided between time in the Pappalardo Lab and the Lab for Manufacturing and Productivity. In the other two sections we learn how to draw and use CAD, and optimize our engine.

Here’s a picture of a modified engine (from the 2.670 course website):

The first day of class was like Christmas and Hanukah and New Year’s all rolled into one. We were given a complete toolbox, raw materials to make our engine out of, and a really nice drawing set. As you can tell, this is a very expensive class for MIT to run and we’re all really grateful that they have managed to keep the course running despite all of the logistical difficulties. Anyway, they split us up into sections and sent us on our way:

Sections 1 and 2: Making the engine

In the Pappalardo Lab and the Lab for Manufacturing and Productivity, our job was to take the stock materials and use various machines to whittle them down to precise parts for our engine. We were given instructions and parameters for each part, and learned how to ream, countersink, take a rough cut and finish pass with an end mill, use a drill press, deburr, tap, use a lathe, etc. We had a lot of help from the professors, undergraduate assistants, and technicians. The technicians are super-cool guys who work magic with the machines and seem to absolutely love their jobs. All lot of them have turned away high paying jobs for the opportunity to work at MIT and they all have great stories to tell. Basically, they’re a lot of fun.

Section 3: Drawing and using CAD

Sketching is a crucial part of product design. There is nothing like using a pencil and paper to draw out a possible design to get the creative juices flowing, and in the real world it’s really important that you can communicate your ideas through drawing. So, in our drawing class, we learn that there are many different way to represent a physical object (isometric sketches, orthographic drawing, solid modeling, etc) and we learn how to utilize these techniques. We started off with some very basic isometric drawing (when you hold a part with a vertical edge towards you and then tilt it until the other horizontal edges diverge at 30 degree angles) and we’re working our way to sketching more complex objects. Here’s an example of an iPod that I drew on the second day of class (the assignment was to pick any object and sketch it.)

We’re also learning to use SolidWorks, which is a really powerful 3D CAD program. I’ll try to post an example of something made on SolidWorks soon.

Section 4: Optimizing our engine using MATLAB

This section has changed from previous years. In the past, it focused on teaching MATLAB, but now Dynamics and Vibrations (2.003) teaches MATLAB so the focus has shifted to using MATLAB to optimize our engines. A normal, unmodified Stirling engine runs at about 500 rpm, but we hope that we can use this class to make some run at around 1000. First we learned about the Carnot cycle and engine basics. Next, we analyzed the efficiency of the engine using thermo, and then we made some computer models to analyze the effect of temperature and phase difference (between the two pistons) on the work of the engine. As a group, we also analyzed the losses that might limit the performances of the engine and brainstormed possible remedial actions.

This Friday, we will all run our engines and have various competitions to decide the fastest modified engine, the fasted unmodified engine, and the most attractive engine. I’ll post an exact time and place for those of you who want to watch, it’s going to be quite a spectacle!