Archive for August, 2003

Zippity-Doo-Dah!

August 27th, 2003 by dstmartin
 

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Sound familiar? It’s hard to imagine life without zippers. We’ll see how engineers made it an open and shut case, today on Engineering Works.

Back in the o-o-o-ld days, getting dressed meant fastening buttons or hooks one by one on your jacket and shoes; took forever. Imagine how late you’d be. An early zipper – called the clasp locker – was displayed at the Chicago World’s Fair in 1893. It used a sliding pull-tab that pulled together rows of hooks and eyes, kind of like a zipper. But not quite. They were awkward and tended to come apart at the worst times. Fine for mailbags and shoes, but not quite ready for your jeans.

A better version, designed around World War I, had tiny metal bars, or teeth, instead of hooks and eyes. It showed up in Navy life vests and Army gear. By the 1930s, people were buying clothing with zippers. Today, zippers are made of plastic, nylon and other materials besides metal. But they still work much like the ones American soldiers wore almost 90 years ago.

Zippers use two simple tools, the wedge and the hook, to form a chain of interlocking teeth. When you pull the tab to close a zipper, tiny wedges inside force the two rows of teeth together. Each tooth is hooked so it meshes with the shape of the opposite tooth. The teeth stay locked together until you pull the tab and the wedges push the teeth apart.

Zippers got their name in 1925 when the BF Goodrich company used the invention on a new rubber boot and coined the term from the sound they made.

Well, time to go.

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Fuel cell cars

August 20th, 2003 by dstmartin

Hop in. We’re going to take a ride in a car some experts say could be the car of the future, today on Engineering Works!

The first thing you’ll notice about our ride is that it’s quiet. All you hear is the tires on the pavement and … nothing. It’s quiet. No engine noise. That’s because the motor turning our wheels is electric. Not a gas tank or fuel injector in sight. The power comes from something called a fuel cell that uses hydrogen, a gas that’s the most abundant fuel in the universe, to produce electricity. No fossil fuels; no gasoline shortages; no smelly exhaust.

The idea behind fuel cells has been around for a long time. Since 1839, long before gasoline and long before automobiles. Fuel cells helped power NASA’s missions to the moon, but engineers have only recently begun to think about using hydrogen and fuel cells to power cars and provide electricity for our homes.

Here’s how they work. Hydrogen enters the fuel cell, a sort of gas-tight can, and a chemical reaction takes the atom apart. One part actually becomes an electric current that’ll run an electric motor. Dump what’s left into the atmosphere and you end up with good old H2O, water. No noxious exhaust fumes.

We might have fuel cells in our future. We’ve got a long way to go before they’re really practical: where to get hydrogen cheaply and easily; building a network of hydrogen filling stations; what to do with the leftover water. But engineers are working on it.

Well, gotta go.

The bridge that couldn’t be built

August 13th, 2003 by dstmartin
 

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It’s one of the most spectacular objects people have ever built. We’ll visit today on Engineering Works!

To most people alive today, the spectacular Golden Gate Bridge has always been there. It hasn’t, of course. Seventy years ago, building it seemed spectacularly impossible to everyone but engineer Joseph Strauss.

People called it the bridge that couldn’t be built: more than a mile of water to cross; sixty mile-an-hour winds; strong underwater currents; earthquakes; and it was the deepest part of the Great Depression. Any bridge across the mouth of San Francisco Bay had to be something special. Strauss’s bridge was special. Nobody had ever built one to do what this one would have to do.

The cables supporting the roadway are almost a yard in diameter and a mile and a half long. Together, individual strands would reach around the world three times. More than a million tons of concrete went into the piers that anchor the cables. For almost 30 years, the bridge’s main span was the longest of its kind in the world.

Construction got underway in 1933 and was completed in 1937, five months late, but more than a million dollars under budget. It survived a major earthquake and terrorist threats. More than a million cars have crossed its 42-hundred foot span.

By the way, a safety net under the bridge’s floor saved 19 men who fell during construction. They called themselves the Halfway to Hell Club.

We’re all the way through for this time. See you soon.

Photo © National Park Service.

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Row, row, row your concrete boat

August 6th, 2003 by dstmartin
 

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Toss a chunk of concrete into the water and it sinks. So why are some engineering students building boats out of this stuff? We’ll go fishing for answers, today on Engineering Works!

The first boats were made of wood. That makes sense. Wood floats. Nobody thought it would work when folks started building ships out of iron plates. After all, iron is heavy. And it won’t float.

Engineers solved the problem of making iron ships float more than a hundred years ago. Think of it this way: if you float a block of wood in a bucket, the water level goes up, just a little. If you weigh the water that rose, it’ll weigh the same as the wood block. If you drop a chunk of iron into the bucket, it’ll sink and the water level will rise again. But this time, that extra water will weigh less than the iron.

Now, imagine that you’ve flattened that chunk of iron into really thin sheets and shaped them into a hollow block. That block takes up more space than the original chunk of iron, a lot more. This time, the water that rises in the bucket will weigh more than the iron, and the iron block will float. Shape the block like a boat and you’re good to go.

The students do the same thing, except they use concrete instead of iron. And instead of hollow blocks, they make long, graceful canoes. Students from across the United States and other countries get together every year for a competition to race the canoes they’ve built. They learn a lot: designing smooth hulls; finding the best mix to get light, strong concrete. … Hey, I’ve got a bite!

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