Made By Monkeys

Look ma -- no hands!

Uri Geller's claim to fame is that he can bend a piece of flatware - just by thinking about it!! His website also says he does assorted kinds of important investigative work the government, but it's so highly confidential he can't talk about it.

Well I recently did him one better and cleaved this cast pewter serving fork cleanly in half. Okay, I needed the assistance of my right arm to manage it, but I'm fairly scrawny, even for a girl.

Now, please, don't start in with the jokes about bad cooks in the kitchen and tough, stringy cuts of meat. I was in the process of carving up a tender, store-bought honey-baked ham when I broke the fork in two.

At this point, astute engineers will recall that pewter is a finicky material and that pewter alloys are notoriously brittle, especially when cast. And they know that you never, ever, ever, ever, ever, ever design in a slender cross section that will be subjected to high bending stress. Though possessing a lovely finish and artistic design--after all, it was purchased at a tony Museum Shop--my fork was sentenced to a premature demise given the poor choice of material and silly geometry.

To make a long-lasting serving piece, the makers could have traded off their artsy fartsy design by thickening up the cross section (around about 3X or so) and using a more sensible material like stainless steel. But then it wouldn't be art, would it?

My friend Jon Titus ups the ante on party tricks involving flatware one better:

"Your pewter fork may have been a cheap substitute alloy that felt heavy but didn't handle stress well. Remember those metal spoons made of Wood's metal or Rose metal that melted in hot coffee [typically used in solder applications]? I loved to pull that trick. Give someone one of these teaspoons and watch as they saw it melt when they stirred their coffee or tea."

Red dye is a beast in plastics and especially in cheap plastics, which won't win any prizes for outstanding color stability and UV resistance The kind of plastics that, well, designers most likely chose for the seats in England's new £800M Wembley Stadium. According to the gossipy London Metro, 17,000 seats have faded from a pleasing red to the kind of pink color not typically associated with British soccer fans. So here's the vicious design challenge: ABS and PVC have great color stability and UV resistance but are expensive. But ABS is pricey. And PVC ranks right up there with disposable diapers on the hate list of tree huggers here. Advice to designers: Think beige -- it's the new red, isn't it?

The US National Transportation Safety Board issued a damming report on Tuesday. It cites a lack of engineering know-how about the epoxy used to hold the anchor bolts holding 4,600-lb ceiling panels in place. The epoxy failed, leading to a ceiling collapse last year in the $14B public works project in whch a woman died. According to the NYT article Collapse of Big Dig Ceiling in Boston Is Tied to Glue

"“We’re talking about the wrong glue here, in effect,” said Kitty Higgins, one of the five members of the board, which said that the epoxy selected dried quickly but lost strength weeks later. “The knowledge of the engineering community seems to be deficient,” said Bruce A. Magladry, director of the board’s office of highway safety."

At the time of the collapse last year, engineers speculated wildly in forums online about this engineering who-done-it.

Though widely used in a wide range of demanding and critical applications including the assembly of aircraft components, epoxies require a more nuanced understanding than their mechanical counterparts. Design engineers need to know how they perform under specific environmental conditions (moisture, thermal) and the exact mode of loading, as well as curing considerations.

So perhaps it's no surprise that the Big Dig debacle does not set a precedent for the misapplication of epoxy: In one notable example in the automotive industry, the liquid adhesives originally used to bond rearview mirrors in place on car windshields often failed prematurely, causing many mirrors to shear off and wind up in the surprised driver's lap. (Your's truly included.) Ford ultimately substituted a high-strength, pressure sensitive tape in that application.

Warning: This article may contain content that is not safe for work!

Just recently my significant other was going about his business in the loo when suddenly he felt an ominous movement directly beneath him. Understandably perturbed, he investigated further and discovered a radial crack in the wood composite toilet seat he’d installed just the week before.

At this point I should note that my husband’s weight is appropriate for his height, which is the first question that Research Mechanical Engineer John Hunt delicately raised when I rang him up. A wood composite expert with the Forest Products Lab of the US Dept of Agriculture, he was surprised to hear about the failure. It turns out that the rather lowly toilet seat is actually a highly engineered structure designed to sustain high bending loads while in use. Otherwise we’d fall in.

Unlike the case with, say, lithium ion batteries, he hadn’t heard of any recalls or advisories on toilet seats of late.

So why did the seat crack?

Plastics often get a bad rap for being flimsy and cheap., But big hunks of metal aren't immune to failing catastrophically.. Ken Russell, a forensic engineer and professor of materials science at MIT, describes the disastrous effects when monkeys substituted poorly cast aluminum for forged steel in a motorcycle brake. The SEM micrograph shows crack-inducing pores and oxide film in an aluminum casting with hydrogen porosity of the kind he describes..

When it comes to lingerie, my requirements are pretty straightforward: comfort and appearance. No small engineering feat, given that fabric per se is an unwieldy and challenging structural material. The fact that it is weak in compression is particularly problematic in a bra, whose main job is to lift and support a distributed, cantilevered load. Brush up on the physics of bras here.

Aluminum is a wonderful, awesome material. Heat treat it properly, and you can get a strength on par with structural steel. Okay, maybe only ordinary structural steel, but you still get a two thirds savings in weight.

It's why design engineers love aluminum. Plus it won't rust.

But screw up the heat treating, and well, you get this thing called grain boundary embrittlement that's really, really bad. Cracks can form, which can lead to a complete failure of the part.

Click on the image to see detailed view of the failed zinc casting.

Rolling luggage has to be one of the greatest engineering innovations of all time, so it's a real pity that their telescoping handles are so frequently a dismal failure. On a recent trip (to India, natch) the cheaply-cast zinc parts in the handle assembly on my husband's High Sierra brand bag (above) decided to give up the ghost. First he had difficulty getting the handle to extend, which seemed like the worst luck in the world-- until he couldn't get the handle to retract again.

You try checking a 22-inch bag with an 18-inch handle sticking out of it. Talk about needing a chill pill!

My husband and I got into a debate recently over the pros and cons of eating rust flakes. I said that I couldn’t imagine anything good about ingesting something that could be scraped off the bottom of an ocean tanker, with the exception of barnacles. We once ordered a barnacle appetizer in Portugal. It was delicious.

My husband, on the other hand, argued that in small doses rust is probably relatively harmless. And not only would the iron oxide potentially satisfy the NIH’s recommended daily intake for iron, he pointed out that as an added benefit you wouldn't have the adverse effects associated with red meat, which is a good source of iron.

We got onto this rather strange line of conversation because I noticed some rust-colored flecks floating in my ice water. While it may taste a little weird, I didn't think we had a heavy metal problem in our drinking water here in Cambridge, Mass.

EW's own Alex Mayhew-Smith nominates Nigella Lawson’s Living Kitchen Citrus Juicer as a strong made by monkeys contender, mainly because designers elected to trade off any notion of functionality for a really cool-looking design.

"We were given one as a present. The form is sort of new and interesting but there are many reasons this kitchen device annoys me.

Click to view detail

Here's a lovely before-and-after shot of an Amco enameled aluminum juicer after only a few cycles in the dishwasher. Though this particular juicer came with no instructions whatsoever, the product description online clearly states "dishwasher safe."

Designers apparently missed the materials science class in which aluminum's susceptility to water corrosion in the presence of anything that dissolves the passivation layer was covered. I recall learning that aluminum parts could literally be destroyed in even a brief cleaning operation with detergents with high pH levels.

What happened to my juicer is also what guarantees that beach chair salesmen never lose their jobs, as salt water dissolves the passivation layer that ordinariliy protects aluminum from its otherwise high rate of oxidation.

The story of Napoleon’s buttons is one of those great cautionary tales about the potentially dire consequences of ignoring the chemical properties of substances.

Most engineering students probably first heard about this historical wardrobe malfunction (apologies to Janet!) in an introductory chemistry class: As the story goes, the tin buttons on the coats of Napoleon’s troops literally crumbled to a powder after being exposed to the bone-chilling cold of a Russian winter. The culprit? A metastable material, pure tin undergoes a structural transformation at low temperatures (below 0C), essentially decomposing into dust. This transformation is called tin pest, which can be avoided by combining tin with other elements, like, you know, lead.

Prized by design engineers for its enviable strength-to-weight ratio and high modulus, titanium has made its way in recent years into all sorts of high-tech products from turbine engines to bicycle frames.

Now, a new toothbrush with a titanium dioxide core in its handle has hit the market in Europe and the US. Developed by the Osaka-based Shiken Corp., the Soladey toothbrush leverages the electrochemical behavior of titanium dioxide to reportedly reduce bacteria in your mouth. Studies have shown that exposure to UV light induces antibacterial activity in titanium dioxide (TiO2).

The winter sports season is upon us, along with the usual spate of bruised buns and broken bones.. But while most skiers who run into trouble will do so on their way down the slopes, for the really unlucky there's the occasional freak accident going the other way. The latest incident, as reported in the Concord Monitor, was a lift malfunction in New Hampshire:

"A young man was hurt in a chairlift accident at the Mount Sunapee Ski Resort in Newbury yesterday.... The incident involved a mechanical failure of the North Peak triple chairlift."

No details on the actual failure mode, though I'm reasonably confident that lawyers are already busily at work finding out. But it does bring to mind another case involving a chairlift calamity in New Hampshire. In this instance, a fractured housing caused a lift chair to separate from the cable, sending it and two occupants plummeting to the slopes below.

My friend, forensic engineer and metallurgist Ken Russell, investigated the case on behalf of the ski area, who was being sued by the parents of the injured teenage skiers for poor design and assembly and a suspected overtightening of the fastener holding things together. Ken's job as forensic engineer was to figure out what caused the housing to fracture.

Try as he might, he couldn't find a good metallurgical reason for the failure -- as he reported in Design News

"Radiography and optical and scanning electron microscopy showed a sound microstructure remarkably free of cracks and porosity. A small specimen machined from the subject housing and loaded to failure had a strength consistent with that of the exemplar. So, the housing was plenty strong enough. The test showed only 6 percent ductility, which is to be expected of the aluminum-silicon alloy used."

The expert for the plaintiff saw Ken's report and immediately changed his tune -- concluding the failure was due to "sympathetic oscillations set up in the cable instigated solely by the powering mechanism, which caused the chair to strike a tower and fracture the housing."

Wow -- good thing kids don't try and get those chairs swinging or anything!

View crack detail.

My husband is known for his creative special effects, usually involving food, like the time he grilled eggplant slices and formed them into stacks vaguely reminiscent of that famous leaning tower in Italy. Just as he sliced into his own architectural wonder, a live beetle scuttled out from under his stack, which seemed like a really interesting, if slightly repulsive, way to work protein into the menu.

The other night, however, he truly outdid himself. As he was taking one of our Waechtersbach ceramic dinner plates from the cupboard, he heard a cracking noise emanating from it. Upon inspection, he observed a radial crack about 3 inches in length.

When it comes to structural integrity, plastic parts often get a bad rap. But when they fail, often the result of metal fatigue, metal parts can fail catastrophically as forensic engineer Ken Russell relates in his Calamities Column in Design News.

In the Case of the Acrobatic Airplane, he describes his investigation into a twin-turboprop airplane that was forced to land on one wheel when the other failed to extend. My worst nightmare, actually.

"The landing gear retraction mechanism involved an up-lock hook that engaged a pin. The hook had partly fractured and jammed so the wheel could not be lowered. Many airplanes of the same model used the same hook without incident. So why did this particular hook fail? Examination of the failed hook with a simple hand lens gave the answer. The fracture was next to a hole that had been reinforced by a washer spot-welded in place. The spot weld was defective in burning a hole through the bracket. Fatigue cracks started at this weld defect and ultimately caused the accident.  (The figure above is an SEM photo of a small region on the fracture surface.)"

Read the full analysis here.

Modern dish racks are constructed of metal wires with a protective coating (typically nylon or polyvinyl chloride) that protects against the highly corrosive world inside a dishwasher. So when Mark Skillings emailed this image of this-dish-rack turned-rust-bucket from his 2003 Whirlpool Gold dishwasher, I briefly wondered just how sharp his knives are.

Clearly, the coating had been compromised. Mark assured me that in the five years he owned the dishwasher, he never washed knives in it because "It's murder on the blades and handles."  Maybe that explains all the cuts on his hands!

Rusted dish racks are among the most common consumer gripes about household dishwashers. In addition to the obvious scratching from sharp objects, the causes are numerous, including defects in the coating and degradation due to aging.