What I Learned Today

OSU offers a course called ME 412: Design of Mechanisms. Sadly, it is only offered during the winter term, and I am here for the fall term. So I contacted the professor to find out more about what sort of books and other materials the course uses, for my own investigation. Imagine my delight when he gave me a copy of the latest edition of the textbook and sent me on my way!

This textbook, Design of Machinery, may well be the best textbook I’ve ever read. Really. Unlike some books that pay lip service to being clear and accessible, this text really is clear and accessible. It is also annotated with lots of amusing cartoons and very clearly illustrated examples — the latter being crucial since we’re talking about physical devices and how they move. The book comes with a DVD with animations that I haven’t been able to play with, since it is Windows-only. But, of course, there are linkage animations galore online. And even better is building them yourself, physically.

Chapter 1, “Kinematics of Mechanisms,” is charmingly written and touches on the broader subject of what it means to be an engineer, and how one of the biggest challenges is learning how to “structure the unstructured problem” to go from a concept to a problem definition to a solution. One tip the book offers is to use “functional visualization” (meaning, focus on the desired behavior of the solution, but no one kind of “embodiment”) so as not to limit your creativity and be restricted by a specific kind of solution early on. It also encourages you to make cardboard models of linkages that you design (as above) — a philosophy I think makes a lot of sense.

The chapter also includes the text from a paper given by George A. Wood Jr. titled “Educating for Creativity in Engineering.” Two of my favorite quotes from the paper are, “To me, the creative moment is the greatest reward that the profession of engineering gives,” and “If a person decides to be a designer, his training should instill in him a continuing curiosity to know how each machine he sees works.” Yes! Yes!

On a more concrete level, I learned that kinematics is “the study of motion without regard to forces,” while kinetics is “the study of forces on systems in motion.” The first half of this book focuses on kinematics, reserving forces for the second half. I can already tell that kinematics alone provides ample material to keep me busy!

“Once you become familiar with the terms and principles of kinematics, you will no longer be able to look at any machine or product without seeing its kinematic aspects.”

It’s already happened. At a conference last week, after ironing a shirt in my hotel room, I sat down and drew my first kinematics diagram — of the ironing board.

I’ve already started working through Chapter 2, “Kinematics Fundamentals,” which is fascinating but slower going, as it’s dense with new information, terms, and concepts for me. But I’m already impatient to get to the end of this chapter, where there are 15 pages of problems to do! Starting with… drawing kinematics diagrams of familiar objects like ironing boards. Ooops, jumped the gun on that one!

I recently had the pleasure of seeing tea being made into tea bags, right before my eyes! While in Boulder, CO, for a conference, I stopped by the Celestial Seasonings tea factory. They have not only a wonderful gift shop but also a free tea-tasting bar filled with great art and a free tour of their factory facilities.

After donning a hair net (plus beard net for whiskered men), we entered the factory and got to see black tea being milled (chopped up), filling the air with the most delicious odors. We walked past bales of herbs piled to the ceiling, filled with hibiscus and chamomile and tilia and all sorts of other things. We entered the tea room, where actual tea (black, green, and white) is stored, and then the “world famous” mint room, which of course is filled with mint. It turns out that a room full of mint bales, kept closed 99% of the time, builds up an overpowering mintness. Two feet into the room, my nose started to tingle and then burn faintly. I couldn’t get back out because of the flow of people coming in, so I edged over to the spearmint side of the room since it was less painful than the peppermint side.

Next we entered the main assembly room floor. This was so awesome I’m having trouble putting it in words. It was heaven for any tea-loving geek — like Willy Wonka’s Chocolate Factory, but with tea! Little conveyor belts sent half-assembled boxes of tea zooming around the room, pausing to be folded or stamped or sealed or wrapped in plastic, all by amazing automated machines. I wanted to stop and stare and figure out all of their gears and mechanics, but the tour kept pushing onward. Perhaps most intriguing was their “Robotic Palletizer”, which picked up packed cartons tea boxes in groups of six and stacked them precisely on a pallet. Later I saw the whole pallet being spun so it could be wrapped in plastic, a 6-foot stack of tea cartons all wound up like a cocoon. I could have spent the whole afternoon watching this busy, enchanting process.

Right there at the factory, the various herbs and constituents are magically converted into a lovely beverage experience. They mill, mix, and bag the tea (using unique no-string teabags so as to save frightening amounts of paper), then deposit the bags into boxes that are sealed and sent off for distribution and sale. You can get some glimpses of this geeky awesomeness through the Celestial Seasonings virtual tour; click on the tea cups marked “3” and “4”. Enjoy!

High-speed photography can capture athletes in action. But you need really high-speed photography to capture events like a nuclear explosion.

At the recent National Radio Science Meeting, I first encountered the idea of a rapatronic camera. These cameras have exposure times as short as 10 ns. They were developed in 1940 to capture the rapid expansion of a nuclear explosion, and they were gems of ingenuity. No mechanical shutter at that time could possibly open and close that quickly, so Harold Edgerton came up with a non-mechanical way of controlling the shutter: he put a Kerr cell between two polarizing filters oriented at 90 degrees from each other. Normally, no light would penetrate between the crossed polars. But when voltage is applied to the Kerr cell, it rotates the polarization of the incoming light 90 degrees—permitting it to pass through the second filter. By only activating the Kerr cell for a very short time, you obtain an ultra high-speed shutter.

You can view Edgerton’s hand-drawn circuit diagram to see how it worked.

Likewise, there was no way to mechanically advance the film fast enough to permit a single camera to take a sequence of high-speed shots, so in these tests they’d set up an array of the cameras, each with a slightly different delay. (Although I immediately wonder if you couldn’t have an electronically controlled refractive material behind the single lens to direct the light across a series of film segments so you wouldn’t have to physically move anything.)

The results are stunning:

At left is an explosion from Operation Tumbler-Snapper (1952), about 1 ms after detonation. The spikes along the bottom edge are evidence of the tower’s guy wires being vaporized by associated gamma rays. At right is an explosion from Operation Hardtack II (1958). This one was suspended from a balloon and the spikes here are the balloon’s mooring cables being vaporized. A beautiful ghostly array of such images is available from a google image search on “rapatronic”.

One thing I haven’t been able to determine is the etymology of “rapatronic”. It may be that Edgerton just coined it (with “rapa” for “rapid” and “tronic” for “electronic”—but that’s just a guess). Please share if anyone knows more!

You can read more about Edgerton and his various innovations aside from the rapatronic camera. Brilliant guy!

I had no idea what a broad range of topics the field of “radio science” covers. I recently attended the National Radio Science Meeting in Boulder, CO, to talk with other researchers about the latest advances in radio astronomy data analysis (e.g., hunting for pulsars). Other topics in the multiple parallel sessions included lightning detection, antenna design, remote sensing of rain, “biophotonics”, “metamaterials”, space plasmas, and “telemetry for monitoring and biosensing”. Intrigued by some of the talk titles, I attended one of the latter sessions.

One goal of this field is to develop and test low-power, efficient radio communications for implantable medical devices (IMD). One envisioned application is for people in very rural areas who don’t have regular access to a doctor. Internal sensors could monitor blood pressure and various nutrient levels, then report them to an external base station they could visually check. As one presenter imagined, “Low potassium? Push a button and find out what you should eat for the next week!”

The devices are still under development, and in the initial work they’re focusing on the ability to monitor blood pressure. They aren’t yet up to human trials. Researchers from Texas A&M and Mississippi State University described how they’d started with rats. They showed pictures of the rat surgeries needed to implant the tiny antennas and then described the experiments, which aimed to evaluate whether the simulated response from the antennas was the same as what was observed when it propagated through rat muscle, fat, and skin. Unfortunately, the presenter noted, they’d been forced to euthanize all of the rats after the tests, because they hadn’t coated the antennas with a “biocompatible material” and therefore by animal testing rules they could not let the animals live. (It seems odd to me that this oversight would not have been caught during the protocol review process!) At any rate, the results showed a not very good match between the simulated response and what they actually got, which they attributed to differences between human skin (in the simulation) and rat skin (in reality).

As a side note, I kept wondering if these tests really qualified for the “in vivo” term the presenters applied, since the rats went to sleep for the surgery and (presumably) never woke up. The point at which they were euthanized was never specified. I started wondering whether live fat/muscle/skin tissue has different dielectric properties than dead tissue, which I assume it must, since circulating blood probably affects any signal propagation. This particular experiment seemed perfectly designed to test both cases. But I wasn’t quite up to asking this question after the talk.

The next presenter (from the same group) continued on to describe their subsequent experiments with larger animals (pigs). Pig skin apparently is a much better match to human skin (insert obligatory “white meat” joke here), and they got an excellent match with their simulation. In this case, they used a proper coating and the pigs were permitted to live. The presenter also commented on how very expensive these particular bred-for-experimentation pigs are (about $10,000 each), although I had to wonder whether one must purchase an entire pig to do a radio antenna transmission test, or whether one can give it back afterwards to be used for other experiments, or possibly time-share with other researchers. But again I wasn’t actually able to ask a question, being more sort of transfixed in a rather distasteful fascination and slightly nauseated by all of the graphic surgery images!

These talks didn’t spend much time on other important IMD constraints, like where power for the wireless transmitter comes from and how to dissipate the excess heat generated without cooking the animal (or human) internally. They noted that the devices had a 25 day lifetime if in continuous use, or 1.7 months if only transmitting periodically, so I’m guessing that limit was based on some nonrenewable power source being exhausted.

Overall, the envisioned future of such devices is certainly promising—and I was kind of disappointed to see how premature such investigations apparently are (if this represents the state of the art). I would also have liked to hear more about the kind of technology used for the sensors that collect the data to be sent by the antennas!

As kids, I think the first encounter most of us have with the idea of an “engineer” is “the person who drives the train”. By the time I started my undergraduate studies, however, I knew that the College of Engineering wasn’t just about driving trains. But I always wondered how a purely functional role could have the same name as what I now saw as an engineer: someone with a very active role in design and problem-solving. Or as wikipedia puts it, “An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems.”

Recently I picked up some books at the library on steam locomotives and other fascinating train topics. And suddenly, I realized why the train-driver could also lay claim to the title of engineer. Historically, at least, the railroad engineer did not just drive the train. He (these were generally men) also had to be a top-notch engineer, familiar with all of the inner workings of his engine, as he was continually required to maintain, lubricate, tend to, and sometimes even repair the engine. One book noted that the “iron horse” was just as temperamental and required as much attention and grooming as the organic horse it had replaced.

Today, it seems we have a very different view of machines and their users or operators. Most of us who drive cars do not expect to have intimate knowledge of how they work; instead, we hire car mechanics to deal with the details and fix problems. No doubt today’s train engineers are also much more removed from their engines than those of the 1800’s. Computers likewise (or our attitudes about them) have evolved as well, so that users need not understand operating systems and file systems and network protocols, disk scheduling and memory allocation and pipelining, kernels and shells and scripts. Instead, one can hire an IT expert to maintain the machine and fix it when it breaks.

Is this trend a result of the growing sophistication and complexity of these machines, or a shift in our social attitudes towards the desirability of being involved in details? Or both? If it’s an evolution in the machine, are there other machines out there in their infancy and still requiring that the engine be a part of the engineer?

I can see the allure of both the low and high levels on this abstraction spectrum, for computers. I personally enjoy tinkering with the configuration of my computers and knowing what’s going on under the hood, even up to spending hours buried in an ancient Linux machine to get a wireless card working—but sometimes that loses its appeal when I just want things to work. And in truth, when the machine is reliable enough that I don’t need to be checking and tinkering constantly (as with my Mac), I’ve found that I stop doing it. Yet I still feel a tug of curiosity about other machines as well—I’d love to take a basic automotive mechanics course, and learn more about how trains work, and I’m fascinated by pulleys and linkages and astoundingly clever machines of all kinds. But then, I’m an engineer by inclination—or perhaps, I have a wish to be (in a friend’s charming coinage) an “engine-er”: someone who knows and tends and cultivates the engine, akin to a farm-er or a sail-or.