The Story Of O-rings

As usual, I greatly enjoyed the latest issue of your magazine, and I am delighted that it will now be published four times a year. I particularly enjoyed the articles on Glenn Curtiss and Niels Christensen.

Regarding the latter (“Ring Master,” by George Wise, Spring/Summer 1991), you emphasized O-rings’ physical design but not the materials from which they are made. If Christensen had invented the O-ring much earlier than he did, when only natural rubber was available, its practical applications would have been severely limited, since many of the fluids to be sealed would have rapidly caused the rubber to deteriorate. Fortunately, Du Pont and others have come up over the years with a succession of O-ring materials to handle almost any fluid, even at elevated and subfreezing temperatures. These include neoprene, Viton, buna-N, ethylene propylene monomer, silicone rubber, and Kalrez perfluoro-elastomer. For static applications O-rings of hollow all-metal construction have been used, as have composite constructions.

Malcolm G. Murray, Jr.
Murray & Garig Tool Works
Baytown, Tex.

Raising Corn

I found Wheeler McMillen’s “The Ancient Technology of Farming: Ohio, 1910” delightfully nostalgic. While I cannot claim memory from 1910, my earliest memories on an Iowa farm some seventeen years later fit exactly the descriptions recounted. My father continued to farm with horses throughout my boyhood, though removed to Missouri after 1929.

However, in an otherwise flawless story, I’m sure all your old country-boy readers will recognize an error in your caption for the picture on page 46. The two converted Model T’s are not drawing disk harrows as stated. The one in the rear draws a spring-tooth harrow; the one in front is pulling a wheeled moldboard plow (called a sulky plow when fitted with a seat for use with horses). Thanks for the memories.

Robert K. Roney
Santa Monica, Calif.

Going With The Wind

I am always pleased to see each new issue of American Heritage of Invention & Technology , and the Spring/Summer 1991 issue seems to be even better than usual. “The Ancient Technology of Farming” was nostalgic for me. Although I was born many years later, I grew up on my grandfather’s farm, and we had most of the machines that Mr. McMillen mentions. All the other articles, including the one on the Brush wind dynamo (“A Few Words About This Picture,” by Robert W. Righter), were also excellent—that is, except for the last paragraph of Professor Righter’s article, in which he writes of the windmill as providing a “nonpolluting, renewable” energy source that “may serve not only as a historical curiosity but also as an example.”

The word pollution can be used in various ways. A priori it is good to harness a source of energy that will otherwise be wasted. While the process of generating electricity from wind adds almost nothing detrimental to air or water, the actual technology probably ranks on a per-kilowatt-hour basis as the most destructive to nature of all electricity-generating technologies. First, the manufacture and maintenance of the equipment is polluting; this is significant because the technology is so miserably inefficient that a relatively great deal of machinery is needed for a given power-generating capacity. Furthermore, the process of generating the power is noisy and destructive to birds and other wildlife. I’d suggest that the professor consult with the residents of the Altamont Pass area of California, and the investors in wind-power generation there, before he promotes such destruction.

Ralph Kurtzman
Berkeley, Calif.

On the other hand, I would not wish to discourage anyone who is developing ways to avoid the problems associated with wind-power generation. If those many problems could be conquered, wind might become a truly valuable source of energy.

Ahead Of The Game

I was very pleased with the article you did on my early video-game invention (“Postfix: The Patriarch of Pong,” by Frederic D. Schwarz, Fall 1990). It’s true I considered the thing too simple to mention to a patent officer. I still consider it strange that Magnavox, which bought its basic video-game patent from Sanders Associates, has made it stick for all these years. The latest contest was by Nintendo, last September. I wasn’t asked to testify.

W. A. Higinbotham
Bellport, N.Y.

High Praise

Like many other readers I am very pleased to learn that Invention & Technology will now be published quarterly. My special thanks to General Motors for sponsoring a magazine that provides such insight on technology and is such a pleasure to read. I’m a very busy engineering consultant with projects in many parts of the world. Invention & Technology is the only publication of which I read every page, every article, cover to cover.

Robert B. Toth
R. B. Toth Associates
Washington, D.C.