Archive for March, 2012



21
Mar
12

birdman soars with human-powered wings

Post from Alan Brown:

Dutch mechanical engineer Jarno Smeets has broken new ground by flying like a bird—not inside a vehicle, of course, but with flapping wings attached to a power pack on his body.

Yes, this is for real. Smeets accomplished the feat this past Sunday in a park in The Hague (view the video).

Smeets soared 10 to 15 meters above the ground for about 60 seconds. That is roughly five times longer than the Wright Brothers’ first flight at Kitty Hawk 99 years ago (and about as long as their concluding flight that first day).

This is not the first ornithopter, a vehicle that flies by flapping its wings like a bird. The first human-powered one I can find dates back to 1929, though some question whether it flew or was actually towed by a car on the ground. More recently, in August 2010, a team at the University of Toronto Institute for Aerospace Studies flew 145 meters, though it was also towed until it took off. Smeets’ flight differed in two ways: First, he took off by running; second, it was not human-powered flight.

Smeets calculated that his arms could provide less than 10 percent of the continuous power needed to lift his 180 pound body into the sky. This meant he needed to build a power system.

What he came up with—scavenged from Wii game systems and Android smartphones—would delight any garage mechanic.

Let’s start with the wings. They consist of 185 square feet of lightweight fabric stretched taut over carbon-reinforced windsurfing masts. Each wing weighs just 37 ounces and has a hinge about halfway down its length.

The power pack weighs 40 pounds. It starts with four 5,000 mAh batteries, which power two Turnigy motors. The motors have 1:25 planetary gearboxes, and eccentric shafts that connect to the wing mast and produce up-and-forward thrust.

So how does he fly? The secret lies in some scavenged electronics. This starts with two Wii accelerometers, one on the wing and the other in the back. The first measures the acceleration of his arm, the second the acceleration of the wing.

An Android phone processor calculates the difference between the two in order to determine motor output. There is also a Wii gyroscope to measure pitch, yaw, and roll. The data is used to help stabilize the system.

The system enables Smeets to move his arms freely without any risk of breaking them. The wings mimic an albatross.

“Ever since I was a little boy I have been inspired by pioneers like Otto Lilienthal, Leonardo da Vinci and also my own grandfather,” Smeets said.

What happens next? Smeets says this is an open source technology, and credits the bird flight community with many useful suggestions. He plans to share his bird wing concept with others through his blogs and YouTube channel.

It is an amazing story and I certainly want to learn more. I imagine what it would feel like to soar over the ground, even for 60 seconds. It gives me the chills. Isn’t that what great engineering should do?

20
Mar
12

Exporting Trouble

Post from Jeffrey Winters:

I don’t watch a lot of TV, so I run across memes secondhand. Recently I’ve heard several people independently question why the U.S. is exporting oil when the price of gas here is so high. On the surface—and my guess is that’s how certain news channels present this factoid—that does seem to be a conundrum.

But oil industry operations aren’t superficial. And if you dig into the data from the Energy Information Agency you discover some facts that put the import/export puzzle into better light. The first is that almost all of the “oil” exports is in finished products, and the vast majority of that is in petroleum coke (useful as solid fuel or as an industrial product but worthless in your car), distillates such as diesel, and heating oil. As of December—the most recent month for which the EIA has published data—less than 20 percent of the exports by volume is gasoline.

As for why we’re exporting any petroleum products, a look at the utilization of refinery capacity suggests an answer. Unlike the late 1990s and early 2000s, when refinery utilization was routinely above 95 percent, refineries today have a lot of excess capacity thanks to some of the lowest gasoline sales figures in 30 years. Rather than idling some refineries, oil companies are importing oil that wouldn’t be used in the domestic market, adding value to it, and selling the refined product to countries such as Canada, Mexico, and the Netherlands at a profit.

So, yes, we’re exporting petroleum products at a time of high gas prices. But if we weren’t, that by itself would do little to bring down prices at the pump—and it would put some people in the refinery industry out of work.

16
Mar
12

sam florman and the wiseguys he’s put up buildings with

Back in late January, I received a very gracious personal letter from Samuel C. Florman. Sam is chairman of the Kreisler Borg Florman General Construction Co., and he’s widely known for authoring six books on the relationship between technology and general culture. His most popular is The Existential Pleasures of Engineering—many of you have probably read it.

In his letter, Sam recalled the time, many years ago, when I became editor of Mechanical Engineering and he spoke of the time, in 1982, when he received the Ralph Coats Roe Medal. He spoke of how much technology—and the world, for that matter—has changed since then. Of course, he’s right. Sam has seen many changes since his youth.

He grew up in New York City during the Depression and earned degrees from Dartmouth and then Columbia, with a stint in the Navy Seabees in between. His work in construction began during a vibrant time of growth in the city where it seemed that the skyline changed almost weekly.

With his letter, Sam was also kind enough to send me a preview version of his latest book, Good Guys, Wiseguys, and Putting Up Buildings and promised to send me a final version when it came out this week. He also told me this will probably be his last book, but I have some doubts. He’s still got a lot to contribute—he’s a regular columnist for Harper’s and Technology Review.

The final version of Sam’s book arrived last week and this past Tuesday, The Wall Street Journal ran a review of it. Personally, I think the book is great. Even though the publisher made it out to be about the mob’s influence on the construction industry, it really is more about a slice in time, Sam Florman’s time. It was a time that defined this city’s landscape and its imprint on this country.

At the moment I’m trying to convince Sam to let us excerpt the book in Mechanical Engineering. I hope he does. I’ll let you know.

15
Mar
12

sonic illusions from ancient civilizations

Post from Alan Brown:

When Lincoln Center concert hall opened in 1962, not everyone loved the sound. It took nearly 40 years and numerous minor and two major renovations to create the right acoustic environment for the New York Philharmonic Orchestra.

This story helped me put the accomplishments of ancient civilizations into perspective.

While attending the annual meeting of the American Association for the Advancement of Science (AAAS) in Vancouver, I stepped into a session on archeoacoustics—the study of acoustics in ancient structures—that left me spellbound. It turned out that past civilizations could teach us a lot about sound.

Humanity’s connection with sound traces back to our deepest roots. Paleolithic cave artwork is most often found in caves with the greatest echoes, where small groups of people might have bonded while playing music, singing, and dancing. Similarly, artwork along canyons, such as Utah’s Horseshoe Canyon, occurs in places with greatest echoes.

Archeology’s focus on the physical world blinded past generations of researchers to the sonic quality of the ruins they were investigating.

Not any more.

Take, for example, the sonic illusions at the 1,000-year-old Mayan ceremonial complex at Chichen Itza, a few hours south of Cancun. The main pyramid features 91 steps. If you stand in front and clap your hands, the stairs scatter the sound and reflect it back, with each step having a slightly different time delay. Instead of the sharp clapping sound we expect, it comes back as a chirping sound.

Researcher David Lubman claims the chirps are similar to those of the quetzal, a sacred bird of the Maya. (Click here to listen to two quetzal chirps followed by two handclaps.)

The nearby ball court, about the size of two football fields, is bound on opposite sides by two small temples. They form a whispering court that lets a person in one listen to a conversation in the other. They also let speakers project words onto the playing field, or sound like a whooping bird flying left to right.

In the Peruvian Andes, 1,500 years earlier, the Chavin people built a ceremonial building that also played sonic tricks. One example, according to Stanford University graduate student Miriam Kolar, is the waterway under the stairs leading to the entrance. Pouring water into the channel creates a sound like thunder.

Building itself is a complicated maze of hallways, vents, and chambers. The surprise is that they all work together to amplify sound and direct it towards three openings in the front. Think of it as the ancient equivalent of a bass reflex speaker.

She tested her theory by having musicians play two conch sell trumpets. She said the sound felt like it was coming out of the floor, and vibrated her whole body.

How did they learn to do this? No one knows. Perhaps it was all trial and error. But like Lincoln Center, they eventually got it right.

14
Mar
12

free heat transfer webinar

On Wednesday, March 28, Mechanical Engineering magazine will be having a free webinar, Conjugate Heat Transfer with COMSOL Multiphysics. If you’re invovled with heat transfer, and are interested in tuning in, you can register by clicking here.

14
Mar
12

In the air again

Post from Harry Hutchinson:

My head’s in the clouds. That’s because the rest of me is going to be up there in a few days: I’m going to be traveling again.

There is something unique about being in a place, almost any place. Sure, the Internet has brought the world to our computer screens—or at least, many and various interpretations of the world.

But it isn’t the same as sitting in your hotel in Chiang Mai and hearing the monks chant next door, or having the pork knuckle and black ale at U Fleku in Prague, or watching “As You Like It” at the New Globe in London.

This time, I’ll be flying out of Newark, changing planes and sampling beers in Atlanta, and then pushing on to Sarasota. My destination is a small island that separates Tampa Bay from the Gulf of Mexico. When I get there, I’ll take my tie off, sit in the kayak, and shake fins with the dolphins.

I’m going primitive, right? When I’m on dry land, I’ll be taking photos with a digital camera, speaking asides into a digital voice recorder, updating my friends by e-mail (on a Macintosh notebook computer), and riding a bicycle.

Well, the bicycle sounds a little on the primitive side, yes, but if you caught Frank Wicks’s article “Credit to the Bicycle” in the July 2010 issue of Mechanical Engineering, you were reminded that a bike is a pretty sophisticated instrument. It spurred the refinement of bearings and other mechanical advances that led to later developments. It laid the manufacturing groundwork for the automobile.

To get to the island, I’ll drive my car to the airport, take a shuttle to the terminal, fly on two jet aircraft, and be met at the airport by my sister and brother-in-law in a late model SUV. In a matter of hours, I’m going to cover more than a thousand miles in the air and more distance than a day’s walk—close to 40 miles—on the ground. The jets are likely to be single-aisle narrow-body airplanes, which right now are a source of prosperity for gas turbine manufacturers. You can get more on that in the May issue, which will include Lee Langston’s report on the state of the turbine industry, “Breaking the Barriers.”

I’ll follow the same path in reverse on the way back.

I have a passion for travel. I get to see places that I only dreamed about when I was a kid. It’s time again to say thanks to all the inventors, builders, and others who make it possible.

13
Mar
12

Improving on DIY Wind Power

Post from Jeffrey Winters:

If you spend enough time digging around hobbyist and do-it-yourself websites–guilty as charged–you’ll inevitably run across dirt simple plans for building a vertical-axis wind turbine. Many of those plans tout the ability of the VAWT to turn in very low winds. That makes for a nice display, but it winds up being fairly worthless for capturing energy, since the power of the wind is proportional to the cube of the velocity. Half the speed means one-eighth the power.

The other problem is that while building a Savonius rotor is easy–basically, it’s a pair of half cylinders mounted on an axis–its efficiency is low. That’s because while the wind produces torque pushing on the concave side of one half-cylinder, it’s cancelling some of that torque by also pushing on the convex side of the other cylinder.

There are, as you might imagine, DIY solutions to that problem, and two of them were tested late last year in ASME’s Journal of Solar Energy Engineering. Binyet Emmanuel and Wang Jun of the Fluid Machinery Department of Huazhong University of Science and Technology in Wuhan used CFD modeling to test whether tripling the number of blades or placing a cowling or vanes around the rotating blades would cut down on negative torque and increase the turbine’s coefficient of power.

The results were interesting. The six-bladed Savonius rotor performed only marginally better than the traditional two-bladed one, maxing out at 30 percent efficiency rather than 25 percent. But by adding fixed vanes that funnel the wind into the concave side of the rotors, maximum efficiency jumped to nearly 50 percent.

The researchers cautioned that real-world efficiencies would be a little lower, but it’s gratifying to see that some of those backwoods engineers crafting gear from plywood and sheet aluminum might be onto something.




The Editor

John G. Falcioni is Editor-in-Chief of Mechanical Engineering magazine, the flagship publication of the American Society of Mechanical Engineers.

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