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Gary Flom holds up two of his 200 slide rules.

U alum Gary Flom shows off some of the 200 slide rules in his collection.

Let it slide

University of Minnesota alumni preserve the history and use of the slide rule

By Steve Linders

Sept. 26, 2006

Ah, the slide rule.

There was a time when no self-respecting University of Minnesota engineering or mathematics student would be caught on campus without one. Efficient by nature, sleek by design, these handsomely crafted tools of the trade could be seen hanging from their proud owners' belts ready for calculating at a moment's notice.

Although they came in a variety of shapes and sizes, most slide rules were 12 inches long and arrow-straight, crafted from a perfect blend of mahogany, enamel, glass and just enough steel to guarantee sturdiness, accuracy and longevity. Yes, engineering students could always count on their slide rules. If life were a mathematical equation, the slide rule was a constant--after all, they'd been around since the 1600s. Up until the early 1970s, the device essentially ruled campus, allowing students to efficiently multiply and divide by sliding identical scales back and forth and making quick estimations. Then along came the HP-35 electronic pocket calculator in 1972, and everything changed for engineering students.

The allure of the slide rule University of Minnesota alum Gary Flom (Math '76) understands the slide rule's powerful allure. Of all the educational mementos he kept from his college days--textbooks, diplomas, awards, photographs and yearbooks--his slide rules are the most coveted and beloved. "They are just the neatest things. They take me back to a different era," says Flom, who has more than 200 slide rules in his personal collection. Flom, an Atlanta-area ear, nose and throat physician, has joined thousands of people around the world who collect, trade and use the devices for fun. In fact, he's such a slide rule fanatic that he holds a leadership role in the Oughtred Society, perhaps the largest organization dedicated to the preservation of the slide rule, with thousands of members in more than 20 countries. He also is an active member of The International Slide Rule Group, which has 1,100 members, and has co-authored a book called The Oughtred Society Slide Rule Reference Manual. Flom also carries a three-and-a-half-inch slide rule with him everywhere he goes.

"I use it to calculate gas mileage and the price per unit in the grocery store, and to solve really challenging equations," he explains. "When I'm using it, I get some pretty interesting looks from people."

Flom first learned to use the tool when he was a student at St. Louis Park High School in suburban Minneapolis.

"My first was a typical standard-issue slide rule," he recalls. "It had about a 10-inch scale with a two-inch slider. I also had a slide rule holster that I used to wear on my belt. It had a sheath with a leather loop, and it hung like a sword."

By the time he came to the University, Flom was quite adept at using the slide rule. He still wore it on his belt and, depending on which social circles he was in, it was either a status symbol or the epitome of nerdiness, he said. But by his second year of college, electronic calculators had begun to invade University classrooms.

"My first was a typical standard-issue slide rule... I also had a slide rule holster that I used to wear on my belt. It had a sheath with a leather loop, and it hung like a sword," says Gary Flom.

So, like many other students at the time, Flom tossed his slide rule into a box and didn't think about it again. Then one day about seven years ago, he came across that archive of college mementos. At the bottom of the box he discovered his old slide rule.

"I was sitting there looking at this thing, and I wondered if I could still use it," Flom said. "I started doing some simple calculations, and one thing just kind of led to another."

University alumnus Darrell Rinerson (Physics '69, EE M.S. '77) bought what he calls his first "real" slide rule in Minneapolis.

"It was a Post Model 1460 made of bamboo, and it was controversial," says Rinerson. "Back then, Japanese products weren't known for being high quality, so people didn't really know if it would hold up."

Rinerson, founder and current CEO of Unity Semiconductor in Silicon Valley, still has that bamboo slide rule, along with about 800 others from all over the world.

Both Rinerson and Flom say their interest in the calculating devices is more about the future than the past.

"Slide rules evolved over hundreds of years as the by-product of people's natural curiosity about how to solve problems more effectively," explains Flom. "I think it would be a shame if tomorrow's generation of engineers and mathematicians forgot about the slide rule, because it represents the engineer's natural curiosity."

Edited from an article in Inventing Tomorrow, summer 2006, a publication of the Institute of Technology.