Slashdot Mirror
Stupid Engineering Mistakes
lee1 writes "Wired has bestowed on us a list of the ten worst engineering mistakes of all time. We have the St. Francis Dam designed by 'self-taught' engineer William Mulholland, which burst and wiped out several towns near LA; the Kansas City Hyatt walkway collapse; the DC-10, and more, but my favorite is the one I'd never heard of: a giant tank of molasses that ruptured in 1919 and sent 'waves of molasses up to 15 feet high' through Boston, killing 21."
The Kansas City Hyatt was a disaster, but it wasn't because of bad design, but actually, "Construction issues led to a subtle but flawed design change that doubled the load on the connection between the fourth floor walkway support beams and the rods carrying the weight of the second floor walkway. This new design could barely handle the dead load weight of the structure itself, much less the weight of the spectators standing on it". The original design would have been safe but what seemed an innocuous change completely changed the dynamics of load bearing, a result easily derived by any first year physics student.
Also, while a "top ten" list is always subjective, I think it'd be instructive to at least include Galloping Gertie as honorable mention, another design which had been identified as flawed. This Tacoma Narrows suspension bridge began swaying wildly as it set up its own harmonic resonance in a typical Puget Sound winter wind storm and eventually ripped apart and collapsed into the Sound. Interestingly the original Galloping Gertie could and would have sustained the fatal winds by strategically placed holes in the beams.
about engineering disasters, "To Engineer Is Humnan: The Role of Failure in Successful Design". It's worth picking up a copy from amazon/abebooks/etc...
Amazon.com
The moral of this book is that behind every great engineering success is a trail of often ignored (but frequently spectacular) engineering failures. Petroski covers many of the best known examples of well-intentioned but ultimately failed design in action -- the galloping Tacoma Narrows Bridge (which you've probably seen tossing cars willy-nilly in the famous black-and-white footage), the collapse of the Kansas City Hyatt Regency Hotel walkways -- and many lesser known but equally informative examples. The line of reasoning Petroski develops in this book were later formalized into his quasi-Darwinian model of technological evolution in The Evolution of Useful Things, but this book is arguably the more illuminating -- and defintely the more enjoyable -- of these two titles. Highly recommended.
"I'd rather be a lightning rod than a seismometer." -Ken Kesey
And even those accidents the safety defects were quite minor, nothing major that one could claim that it was poorly engineered. Outward opening doors have been used on all aircraft, Douglas was the first one to make one as a baggage door for a production airliner, improper servicing lead to issues with the locks and finally two accidents, the final resulting in a bulkhead failing that sliced the control cables.
United 232 was a result of a failure of imagination, no one imagined that there would be a failure that massive that would severe all there hydraulic lines, even though they weren't placed next to each other (just near each other as they would have be as they have to run to similar areas of the aircraft). The engineer that designed it probably reasoned, that any failure that would result in all three being severed would be large enough that the aircraft would be lost.
"Slow as molasses in January" is particularly apt (and probably related) as the incident happened on January 15. It's not as slow as you might think -- 35 mph... according to Wikipedia: http://en.wikipedia.org/wiki/Boston_Molasses_Disas ter
Not only did Mullholland build that dam that collapsed, he also built the Los Angeles Aquaduct, that's still bringing water down from the North to supply the city's needs. He's also remembered by Mullholland Drive, along the Santa Monica Mountains. I don't know if he built it, but I do know it was named after him.
Good, inexpensive web hosting
Now, back in the day good wood carvers were relatively cheap, so hiring a crew to gussy your ship up was, all things considered, pocket change. Think of it as the 1%-for-art stipulation that is built into many civic construction projects today. The result was your ship looked shu-weet, and so when it sailed into port everyone noticed, and talked, and generally got your nation some good press.
By the way, that's still a big deal in navel circles, visiting ports and showing the flag. These vessels have to do something, keep in training, and so doing diplomatic/PR duty is as good as many other things. Part of that is looking the part - now we go for angular grey steel & exotic weaponry, back then it was "I can afford to pimp-out-my-ship" gilding.
As to the decoration being heavy, the whole freakin' ship was "heavy", a layer of pretty painted bits was about negligible in effect.
Finally, your considered expert opinion on historical wooden sailing ships aside, the hull was perfectly fine for it's needs. Yes most i^Hg^Hn^Ho^Hr^Ha^Hn^Ht^H unsophisticated folks look at these ships and wonder "however did they stay upright" but they did. Much of the misapprehension comes from not understanding the weight distribution on these craft, the rest comes from not respecting the skills of it's sailors.
And, as has been doubtless pointed out several times already, the ship sank due to late-added lower gunports that were left open and effectively scuppered them.
I don't read ACs: If a post isn't worth so much as a nom de plume to its author then I wont bother either.
The alcoholic beverage made from molasses is rum.
Can you be Even More Awesome?!
the conversions are quite hilarious in Wikipedia:
A large molasses (treacle) tank burst and a wave of molasses ran through the streets at an estimated 35 MPH (56 km/h), killing twenty-one and injuring 150 others.
The collapse unleashed an immense wave of molasses between 8 and 15 ft (2.5 to 4.5 m) high, moving at 35 mph (60 km/h) and exerting a pressure of 2 ton/ft (200 kPa).
Google calculator shows:
35 miles = 56.32704 kilometers
HD Trailers
Well, let's confront your misconceptions:
1. It's actually your great-grandmother's suffering you're reliving. You see, the way to wash the sweat and human oils out of clothes was to take the big pot (like a witch's cauldron) and make Clothes Soup over an open fire. So good job on advancing yourself to 1890.
2. If you went back to freshman chemistry, you'd learn that water and oil do not mix. Which means, if you want to get the human soils out of your underwear, and the human sweat/grease out of your clothes, you're going to have to use soap. Water won't do it. Or, if you don't believe me, just stop buying laundry detergent. You do use it, right, hypocrite? FYI: The water is the medium for the soap, and removed soils. It all has to go somewhere - the soap alone won't carry it.
3a. A liberal arts guy, huh? 'Nuff said.
3b. Just for general info, did you ever see what your top-loader does with your Clothes Soup? The paddle in the middle spins a turn clockwise, then a turn counter-clockwise....and so forth. It also has to spin the drum for the spin cycle (you know, the only major moving part on a front-loader). So you have 2 major moving parts, one of which has to support counter-movement. So you're actually on the WRONG END OF THE SIMPLICITY ARGUMENT. Duh.
You do have the efficienty argument down, though. Front-loaders use 40% less water and much less soap, along with being much easier on the actual clothes because there is no paddle-like implement used to pummel your clothes. Gravity and water do that for the front-loader, off that one mono-dirctional moving part.
4. So...you do change the water in your washing machine from time to time, right?
How do you get it out?
Could it be...........a cute little rubber seal? At the bottom of the drum? Under way more standing water pressure than a front-loader sees?
PS: Check into how long Mankind has been making watertight seals. I bet you'll be suprised. We've had time to actually get kinda good at it.
How the hell did your particular brand of idiocy get modded up?
I have a MechEng/ Materials dual degree, and one of my later courses was actually a "Metal Failures" course, dedicated to this kind of stuff. Most of it was more complicated. My professor was actually a retired PhD who worked on investigative teams that evaluated accidents like these, and acted as the 'expert witness' for technical information in many cour cases.
We studied this case, as well as many on the list above, in detail. In particular, the box beams in question ran horizontally to support the walkway, while the vertical rod was the support for the end of the box beams. The beams could have been made better, but they were good enough for their design loads.
The problem was that the original design called for one continuous vertical rod, with several levels of walkway hanging from it at different heights. However, due to construction issues, the installation was changed (for the worse) so that separate vertical rods were used. This unfortunately got written approval, and shouldn't have. Instead of the successive loads being applied to the rod, the box beam was then holding the weight of all the floors below it, which it was not designed to do.
Imagine one rope hanging from a ceiling, with 3 people hanging at various heights on the rope. The rope can hold the total weight of the 3 people easily, but each climber needs only enough grip to hold up his own weight. Now imagine due to "construction issues" you can't get one long rope, so you get 2 shorter lengths. Ideally, you'd tie the ropes together to create a nearly identical scenario, but in this case, it's like they tied the bottom rope to the middle guy's ankle, and expected him to hold on with the added weight of the guy below him.
Unfortunately, it was just strong enough to hold a few people, but let go when it was fully loaded.
=
"No fair, you changed the outcome by measuring it!" - Professor Hubert J. Farnsworth
The Toronto Skydome beat them by 8 years.
The Romans beat you by almost 2000 years. The Flavian Amphitheater had a retractable roof.
The storage drums were plastic.
And wow, one of the two who died was in a wheelchair. Those folks must have some serious survivor's guilt for not helping that guy when they all ran and drove away.
I read the Wikipedia article and found it very interesting:
The vibration had nothing to do with the resonance frequency of the bridge as a structure, but with the fact that it was wind (as opposed to some other form of energy input, e.g. sound) that was exciting the bridge. At a certain wind speed, the bridge enters a positive feedback loop - when the small motion induced by the wind changes the angle of attack in a way that makes the bridge absorb more and more energy from the wind, eventually increasing the amplitude of the oscillation to a point where structural failure occurs.
To make it short: The bridge did not oscillate at one of its resonant frequencies - aerodynamics caused it to vibrate at an entirely different frequency but managed to pump enough mechanical energy into the bridge to break it anyway.