WITH COMPLEMENTS

To the Editor: On page 10 of your September 2008 issue, John L. Hill’s letter states that “…the cosine of an angle is the reciprocal of the sine…” This is incorrect, as any high school plane geometry text could verify. The cotangent of an angle, however, IS the reciprocal of its tangent.

Malcolm Murray
Baytown, Texas

PRODUCT VS. ARTIFACT

To the Editor: I have chided you before for the unremitting grayness of your publication. You know, the charts and graphs, articles extolling the joys of FEA, the eternal lack of respect we engineers tolerate. I always hoped for a remission, however brief or half-hearted. But, saints be praised, no longer.

September 2008 made it all better: Page 34 begins the hilarious saga of (gulp) “affordances.” The lowly tree stump is transmogrified into one of these. Likewise, the most rudimentary of bridges. The chart on the next page turns a product into an “artifact.” Who knew?

The “artifact,” however, must still confront the age-old design question: “What’s it supposed to do and does it do it for costs that are bearable?”

This leap into an etymological Never-never Land reminds me of the New Math my kids were bludgeoned with in the 1960s. I couldn’t help with the homework and in the end they couldn’t add and subtract. Brave new world.

Keep up the good work.

Jack W. Osgood, P.E.
Boston

FREELANCE FALLOUT

To the Editor: The article “Design Futures” in the September issue presents a wonderful world in which we are all freelance “independent contractors” working online from home.

Of course, electronic tools make us more effective, and tasks really are done better and faster because of them. However, a world in which everyone works freelance at home as an independent contractor is a world where there are no paid vacations, no real performance reviews, no physical contact with co-workers, and no walking through the factory for face-to-face meetings with the people who are actually building the product.

Good companies actually work very hard growing their people. Yes, you can do it all yourself, but it will be harder. For example, check the price of tuition at night school these days.

I do not doubt the future the article points to, but I think it might be a mixed blessing. Maybe the VR will be so good that personal presence does not matter.

Dudley M. Jones
Princeton, N.J.

MORE THAN VISUAL

To the Editor: The article “The Route That Forces Take” in the September issue presents an alternative to drawing free-body diagrams of components during design analysis of a structure or mechanism. It urges the designer to draw the “lines of force” to visualize how forces are transmitted through interconnected components. The article does not define “lines of force,” however. It says only that they are analogous to streamlines in fluid flow, as well as to lines of heat and magnetic flux, implying that the force vector at any point is tangent to the line of force. But the force inside a solid does not follow the laws of fluid flow, heat conduction, or electromagnetism, so the analogies aren’t valid.

The image illustrates the load path in a truck steering assembly that failed.

Consider the example given in the article, the failure of a truck steering assembly. Two different load paths, the “intended” one and the “actual” one, are shown superimposed on the assembly cross-section. The article doesn’t explain how the lines of force were drawn, but I suspect they are imaginary lines based on the originator’s intuition about how forces might be transmitted through the assembly. Intuition is, of course, a desirable quality of an engineer, but intuition by itself is not enough; it has to be based on sound mechanics.

Using a free body diagram of the steering knuckle and the principles of statics, I determined the horizontal components of the reaction forces from the kingbolt on the upper and lower flanges of the knuckle. These components form a couple and are not negligible; they may be as large as or larger than the vertical components. In the article, the load paths incorrectly show force being transmitted through either the upper or lower flange, not both. I advise design engineers to stick with drawing free-body diagrams, as they were taught to do, rather than relying on the load path method alone.

Frederic A. Lyman, P.E.
Syracuse, N.Y.

BUY TODAY, PAY LATER

To the Editor:  I read your editorial (“Tomorrowland Today,” August) with interest.

No amount of technology will save us from Wall•E unless we find a way to stabilize and reduce our population.

Every new technology is a two-edged sword. It has benefits, but also costs. Most of them result in the use of more natural resources, which bodes ill with a burgeoning population.

Humans are an intelligent species, but can’t seem to be able to address the tough questions.

Jim Baker
Elkton, Md.

NUCLEAR OPTIONS

To the Editor: I have several comments and suggestions regarding the piece I just read on the Department of Energy’s Deep-Burn R&D program for reprocessing spent nuclear fuel in a Generation IV very high temperature nuclear reactor.

“Deep-Burn” sounds a lot like DOE’s failed magnetohydronamics program that poured millions of tax dollars down a rat hole. I know because I worked briefly for one of the DOE contractors. I personally don’t like the idea of combining ultrahigh temperatures and pressures in the same pot with nuclear materials, especially at a facility like the Idaho National Lab, which has more than adequately demonstrated its inability to clean up nuclear messes from years past.

The most legitimate argument against nuclear power is, and has been, how to safely and economically dispose of spent nuclear fuel. Argonne made a huge stride toward solving this problem by demonstrating how spent nuclear fuel could be turned into vast amounts of clean, safe electricity through years of successful tests in its experimental 20 MW Integral Fast Reactor in Idaho.

Instead of spending our tax dollars on another exotic R&D program like Deep-Burn, the U.S. government should spend it on something with a far better chance of producing near-term tangible results. Let’s build and operate an IFR demonstration plant patterned after Argonne’s 20 MW experimental reactor to determine just how well IFR technology performs on a commercial scale.

I maintain that we don’t have an energy shortage in this country; we just have a shortage of politicians smart enough to promote the development of resources we do have. Let’s not spend huge sums to dump spent nuclear fuel into Yucca Mountain; instead, let’s use it as fuel to produce vast amounts of clean, safe, and affordable electricity.

Robert C. Balhiser
Helena, Mont.

Editor’s note: The U.S. Department of Energy in July selected Idaho National Laboratory and Argonne National Laboratory to lead teams to work on the technology of Deep-Burn, in which plutonium and other transuranics reclaimed from spent nuclear fuel are destroyed while generating energy. According to DOE, the technology can use more of the potential energy in the fuel and reduce the amount of radioactive waste produced.