This article reviews a permanent display on the first floor of the Potter Engineering Center that showcases pre-digital analytical marvels at Purdue University in West Lafayette. The display includes about 200 slide rules from Purdue alumni, including astronauts Neil Armstrong, Jerry Ross, Richard Covey, and Roy Bridges. Another Purdue alumnus, Eugene Cernan, the last man to walk on the moon, has promised to send his slide rule, as well. The exhibit is indicative of the attachment—some might say outright affection—that these and other engineers have for an old standby with a long history. The calculator and the computer may have usurped the slide rule’s place in the engineer’s toolbox, but that does not mean the old rule has been forgotten. The oldest slide rule in the exhibit does not date back quite that far, but it does hail from the mid-1800s. In addition to antique specimens, the exhibit includes slide rules made of metal, wood, bamboo, paper, and plastic, as well as two 7-foot-long rules. The oversize slide rules were used in classes to teach students how to use them.
At Purdue University in West Lafayette, Ind., a permanent display on the first floor of the university's Potter Engineering Center showcases pre-digital analytical marvels. In all, the display includes about 200 slide rules from Purdue alumni, including astronauts Neil Armstrong, Jerry Ross, Richard Covey, and Roy Bridges. Another Purdue alumnus, Eugene Cernan, the last man to walk on the moon, has promised to send his slide rule, as well.
The exhibit is more than just a curiosity. It is indicative of the attachment—some might say outright affection—that these and other engineers have for an old standby with a long history. The calculator and the computer may have usurped the slide rule's place in the engineer's toolbox, but that doesn't mean the old rule has been forgotten.
"If these slide rules could talk, they'd tell stories of amazing projects," said James Alleman, a Purdue professor of civil engineering who began collecting them about 15 years ago. "There was a point in time when the slide rule was king," he said. "During a period of about 400 years, anything anybody built that was of any magnitude would have required a slide rule."
The exhibit is arranged in a series of panels detailing the history of slide rules, starting with Scottish mathematician John Napier's 1614 discovery of the logarithm that made it possible to perform multiplication and division by addition and subtraction. Six years later, English mathematician Edmund Gunter devised a logarithmic ruler with a set of dividers for adding and subtracting. In 1632, countryman William Oughtred used Gunter's approach to invent the first slide rule.
The oldest slide rule in the exhibit doesn't date back quite that far, but it does hail from the mid-1800s. In addition to antique specimens, the exhibit includes slide rules made of metal, wood, bamboo, paper, and plastic, as well as two 7-foot-long rules. The oversize slide rules were used in classes to teach students how to use them, according to Purdue alumnus and retired civil engineering professor Robert Miles, who helped design the exhibit and provided the funding for it. "Taking a course to learn how to use a slide rule was mandatory at one time," he said. "And from then on, you used it for the rest of your academic career."
It's not just the folks at Purdue who think slides still rule. When SpaceShip One made its X Prize-winning flight, it carried some special mementos, including spaceship designer Burt Rutan's 1961-vintage college slide rule, a Pickett 3-T.
That bit of news spread like wildfire through The International Slide Rule Group, an Internet-based network for collectors of slide rules and associated mechanical calculating instruments. The group discusses everything from how best to clean old slide rules to sightings of slide rules in the latest "Ben Affieck saves the planet from extinction" movie.
This group isn't the only Web-based entity devoted to the slide rule. Walter Shawlee, president of Sphere Research in Kelowna, British Columbia, maintains the Slide Rule Universe Web site (http://www.sphere.bc. ca/test/sruniverse.htrnl), which is as information-rich as it is hard on the eyes.
Slide Rule Universe, which has been in existence since 1997, offers reference material on the care, feeding, and use of slide rules, a slide rule marketplace, and even step-by- step instructions on building a slide rule from scratch.
The site was born out of Shawlee's rediscovery of his junior high and high school slide rules, both Keuffel & Esser models.
"It grew out of a nostalgic longing," he said. "I poked around on the Internet, found other collectors, and started the Web site as an exercise to document my growing obsession. Once the site was up, I got more and more requests from people who were looking for particular models, and the marketplace grew from there."
Shawlee, who was part of the team that put together The First Edition Oughtred Society Slide Rule Reference Manual, said he gets calls all the time from teachers who need slide rules to use in the classroom. They still use the slides to teach logarithms because they find that students retain more when they learn with slides than with calculators, Shawlee said.
"People are desperate to get their kids smarter," he said.
"And it's these people whose desire for slide rules touches me more than the collectors who want something different, and more exotic."
Still, Shawlee admits to falling prey to the lure of the exotic himself. He owns up to having roughly 1,000 slide rules in his personal collection, and favors pocket rules, and those he terms "the unusual, and the stunning."
"A slide rule offers extraordinary technical beauty," he said. "There's hundreds of years of history in one that survives despite our best efforts. It's like selling puppies: Someone puts one in your hands, and you have to have it."
Another fan. Mike Konshak, a senior advisory development engineer for StorageTek in Louisville, Colo., may only have been collecting for a year or so, but he has already got more than 800 slide rules to his name. And, he's the happy proprietor of Mike's Slide Rules: Calculators for Hairy-Eared Engineers (http://www. konshak.com/ MK_Sliderules.htm). The affectionately named site is an Internet museum dedicated to engineers and their slide rules.
Konshak's collection includes a 10-year-old basic K&E model he still uses at work, and probably his most prized specimen: his 87-year-old father's slide rule.
"My dad was career military, and had a plastic slide rule that he used every day," Konshak said. "Somewhere along the line, it broke, and either he or my mother epoxied it back together so he could keep using it. It's a Sterling 584, a cheap model that most engineers wouldn't look twice at. But I remember him using it as I was growing up."
Unlike many collectors who favor the exotic and the pristine, Konshak favors a slide rule that shows its lineage. "I like to see someone's name on a slide rule," he said. "I like to know who the person was who owned the slide and what they used it for."
Many of the slide rules in Konshak's collection are donated by people who want to see their mother or father's prized possession gain a little bit of immortality. "It's just not something you ever consider discarding," Konshak said.
Still, he admits that his passion for slide rules has cost him about $10,000 in approximately a year. The slide rules he buys average about $200 each. In the '60s and '70s, when there were few collectors interested in them, and eBay didn't exist, the same slide rules sold for around $20 each.
But more than the monetary value, it's the engineer behind the slide that drives Konshak to collect. "You can really see something of the person and what they did in the markings on a slide rule," he said. "Sometimes, I wonder if a particular slide was used in a project that changed the world."
Shawlee, curator of Slide Rule Universe, pointed out: "If some cataclysmic event happened, most of our digital world would vanish forever. But people would still find things, like slide rules, that go back 200 years."
Part of the charm is the slide rule's reliability. As Purdue's Alleman observed, "Calculators and computers are more powerful than slide rules, but they become obsolete so quickly, you can't develop a personal attachment to them."
Slide rules, it seems, heave earned a permanent place in the hearts and minds of engineers.