It is believed that the Romans learned by the method of trial and error, which is just another way of saying try and fail. By means of observing and analyzing unintended failures, they deduced rules of thumb.
For multiple arch bridges, one rule was to have the dimension of the spans be no more than an order of magnitude greater than the dimension of the piers between them. Although there do not appear to be any records explaining the architectural or technical purpose of the stepped rings surrounding the base of the dome of the Roman Pantheon, there should be little doubt that they were introduced to contain the concrete dome and thus prevent cracks from opening up in it.
And, as Vitruvius so explicitly explained, the Greeks learned that a stone lintel spanning more than about three column diameters was prone to crack and fall. In his book, he advised that when longer spans were desired, timber lintels should be employed.
Such stories of success and failure in ancient engineering are instructive not because we still use rules of thumb to design masonry arch bridges or stone temples. The stories are relevant to modern engineering design because they reveal in their simple contexts the way engineers accumulate knowledge and engineering advances.
Experience, both good and bad, guides us in extending the state of the art toward new limits. Those limits are seldom well defined in advance. It is the essence and adventure of engineering for us to be the pathfinders who push against and through the frontiers of knowledge and bring back news of what lay beyond and how to reach it.
As the ancients did, we find ourselves now and then designing things that do not work as intended. But the overwhelming number of engineered things large and small do work, and do so safely and reliably in service to society, advancing civilization. Engineers today may not be designing ancient monuments, but they are working in the grand tradition of those ancient engineers who did.
As seemingly distant in time, technology, and scale from those ancient structures as the integrated circuit and digital computer and other modern electronic devices may seem, they and all engineering marvels are our contemporary masterpieces of engineering design and execution. They have their origins in the same conceptualizing and synthesizing processes that the ancient engineers employed. Like our professional ancestors, today’s engineers are essential to civilization.
Straying just a bit off the course I have to comment about TV's outlasting consumers' interest. It remains to be seen if LCD back lit flat panel monitors will ever achieve the life expectancy of CRT TV's.
Back in the late 1940's my parents were early adopters of televison in their home. Their Magnavox TV saw the factory authorized repairman several times a year to keep that sucker working! There were lots of silly engineering mistakes in that early set design. One that comes to mind involved the main power supply subchassis. It consisted of a pair of 5U4 rectifier tubes. The subchassis was mounted on the inside wall of the cabinet such that those tubes were horizontal. Well, they were designed to be operated base down, not base to one side. Thus, the filament ribbons (cathodes) would eventually sag sufficiently to short out!
Once the vacuum tube count was greatly reduced, TV's became more reliable requiring fewer repairs during their expected service life. With the advent of modern solid state designs TV's became carefree devices that would last as long as their CRT's.
Early CRT's had metal to glass seals around their faces as the body of the tube was a metal cone! But, it was typically the electron gun that would wear out as the cathode emission would drop off. CRT boosters were quite popular. They were devices installed in series with the CRT socket to boost the filament voltage to squeeze a few more months life out of a tube.
Back when all computer monitors were CRT's I almost never replaced them due to failure. Flat screen LCD's have been quite the opposite, typically going dark due to failed backlights and/or failed switch mode power supplies to drive them.
Though MTBF has diminished for modern TV's, the pace of available new features has accelerated. So, you are right that for consumers today their interest will most likely wane faster than the failure rate of their TV's compared to yesteryear.
"Quality Junk"? Good design will yield a quality product at the targeted price point! To suggest that the production of "junk" that meets "specifications" is acceptable is nothing more than an inferior, lazy design shortcut.
It is CRAZY when "legal representatives" overrule engineering opinions, especially in Regulatory Commissions' decissions. It seems the permits were given before explosions, e.g. BP Gulf and paying small fees approved by inspectors instead of serious safety corrections - WV cosl mine, etc. in last years.
Larry S.; Quality means different things. In manufacturing 'quality' is conformance to specifications. A process can be Six Sigma and still produce junk, but it is 'quality junk' if it conforms to specifications.
And there is always the demand to always make things 'less expensive'. The trick is to stop making things 'less expensive' before the point of making them 'cheap'.
And a tangent: Despair.com has a take on building the pyramids = when you have an unlimited supply of expendable labor, there's nothing you can't do. Still, there are ancient structures that rival modern buildings.
"The most successful employees were also the employees who made the most mistakes"
Rob, exactly correct. Most of the innovations are happened by accidently, similar to Einstein discovered force of gravity. If employees are not making any mistakes means, the productivity and innovation are less associated with him. He is just doing whatever he knows , that's all.
Henry, civilization and engineering are closely co-related and related in a bilateral way. Technology can bring up the living standards of citizens and this in turn can uplift the civilization. Most of the technologies we are using now a day's are either digitalized or extended versions of the older ones.
Excellent point—engineering and civilization DO go hand-in-hand.Several years ago, my company sent me to Egypt to call on a distributor concerning issues with atmospheric gas burners softening (another word for melting) during extended periods of firing.Propane gas was used as the fuel.If you recall, propane gas has a heating value of approximately 2500 Btu/Ft³ so the orifices must be sized accordingly or you will definitely have problems.While there, I had an opportunity to visit the pyramids.Pictures, in no way, do them justice.They are massive—massive.I would love to know the mechanisms used to hoist those stones upward and into place.I have always thought that for such an undertaking, there would be some form of documentation as to how this was accomplished.In our day, time is "of the essence".It is definitely hard to believe the "ancient" engineers worried that much about time.They seemed to be more in tune with achieving quality.
Rob, I believe some engineering schools are starting to take note of this fact, as well. Most notably, it's being incoporated in the curriculums at Olin College of Engineering in Massachusetts.
Good points, Larry. When it comes to TVs, though, I think they last well beyond the period consumers want to own them. Consumers give up well-made, perfectly well-running TVs in order to gain new features.
Good point about failure, Chuck. I remember a few decades ago IBM -- then considered a master of business organization -- did a study and found that the most successful employees were also the empolyees who made the most mistakes. The conclusion of the study was that employees should be encouraged to take more risk.
On April 21, NASA launched a novel project, putting into orbit three satellites that employ an off-the-shelf commercial smartphone as the control system.
The legacy endpoint devices that control our critical infrastructure (utility systems, water treatment plants, military networks, industrial control systems, etc.) are some of the most vulnerable devices on the Internet.
In a switched-capacitor filter, capacitors and switches take the place of resistors and accurately reproduce the characteristics of continuous-time Bessel, Butterworth, and elliptical filters.
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