Slide Rule

My favourite author is Nevil Shute. He wrote many novels including No Highway, which I studied for my O Levels in 1968 and A Town Like Alice. Both have been made into movies. Nevil Shute was an aeronautical engineer by profession and he also wrote an autobiography entitled Slide Rule.

Now, I have a question for the young people (below 30). Do you know what is a slide rule?

If you have never heard of a slide rule, do not feel embarrassed. I once put this question to my nephew, a polytechnic graduate, and he too did not know what it was. To my surprise, so did a few other young people I put the same question to.

Here’s another question. You must watched documentaries of the 2nd World War and seen some of those amazing fighting machines like air craft carriers, submarines or even Hitler’s inter-continental ballistic missile, the V2. In fact, at the time of the Korean War, in the fifties, when the jet fighter started to be used, or during the early part of the space race in the 60’s, the electronic calculator had not arrived yet. To design, produce and operate these engineering marvels must have required an immense amount of mathematical calculations and data crunching. How on earth were they able to do it when they did not even have a simple electronic calculator? Has this question ever occurred to you?

The answer is the slide rule and its cousin the log book (which we learned to use in secondary school). According to my dictionary, the slide rule is “an old-fashioned instrument that looks like a ruler with a middle part that slides, used for calculating.”

Do you know that the ubiquitous calculator that even the vegetable seller in our wet markets use nowadays was not around until the 1970’s. I remember my university days in the early seventies. We had to use the slide rule for all our calculations. Although, the scientific calculator was available by then, we were not allowed to use them for our exams. The reason is that they were simply too expensive and very few students could afford one. For example, did you know that an HP scientific calculator cost more than $1,000! I had the chance to use one courtesy of my brother-in-law who worked as a refinery technologist.

(Well, actually at that time, he was courting my sister, and maybe wanted to impress me by lending me his precious HP scientific. I remember bringing it to class and getting my class mates all envious.)



Although, I have been advising my readers to get rid of things they do not need (in my other blog ), I am really glad that I did not throw away my slide rule. In fact, it is still in very good condition complete with protective case and instructional manual. Mine was an expensive model from Faber Castell. It was made of 'Geroplast' and cost slightly more than $30. The cheaper ones were usually made of bamboo and imported from China.





The slide rule is one of those human inventions that was seen as an essential tool one day and then became obsolete practically overnight with the arrival of the pocket calculator. Here’s an interesting snippet about the slide rule from Wikipedia:

“Throughout the 1950's and 1960's the slide rule was the symbol of the engineer's profession (in the same way that the stethoscope symbolized the medical profession). As an anecdote it can be mentioned that German rocket scientist Wernher von Braun brought two 1930s vintage Nestler slide rules with him when he moved to the U.S. after World War II to work on the American space program. Throughout his life he never used any other pocket calculating devices; slide rules obviously served him perfectly well for making quick estimates of rocket design parameters and other figures. Aluminum Pickett - brand slide rules were carried on five Apollo space missions, including to the moon, according to advertising on Pickett's N600 slide rule boxes.”

How to use the Slide Rule? Sorry to say that apart from simple multiplication and division, I have forgotten. And I am too lazy to read up the instruction manual just to explain it here. But if you are really interested, I have listed a few websites below which explain in detail how to use the slide rule.

Still, I hope you learned something new today.

Wikipedia Slide Rule Site
Eric’s Slide Rule Site
How a Slide Rule Works
Another great slide rule site