Tuesday, March 8, 2011

Slide Rule Musings.....

One of my AMSAT friends sent me a link with pictures of the early days of Amateur Radio Satellites, and we all joked about all the slide rules in the pictures, which started an ongoing discussion on the email list.
My Dad bought me my first slide rule back when I was about 12 years old. I was studying for my Amateur Radio license, and it just made doing the math so much easier. It was a Post 1445P 8" "Student Model", but it let me do multiplication, division, and logs in the blink of an eye. I can still remember going in to the FCC Field Office in the Federal Building in downtown Chicago to take my General Class exam. I had a big paper bag with my Heathkit HD-10 keyer, some pencils and erasers, and my slide rule. The examiner gave me a big smile when I took it out of the bag.
In the years since then, I've had half-a-dozen linear slide rules, from little 6" ones that fit my pocket protector (yes, I had one...), to the monster 12" ones that cost almost $100, and came with a beautiful fitted leather case. Some of the linear rules had specialized scales on them for doing certain calculations that would be cumbersome on a "regular" rule. I've had a few circular ones, too. The round ones were, like most round slide rules, specialized completely for certain functions. On of my favorites (that I still have somewhere) was my aluminum E6B Flight Computer, still available, by the way, commonly called a "Pilot's Confuser" or "Whiz Wheel". Once you learned how to use it, it sure beat drawing out a wind triangle on the map in your lap while bouncing around in rough air!
Sadly, most of the companies that made slide rules have either gone out of business, or shuttered their slide rule manufacturing facilities. In the end, slide rules helped design the machines that made them obsolete, a rather ironic turn of events for a device that was (literally) hundreds of years old. The only place I'm aware of that you can still buy a freshly-made slide rule is Think Geek, one of my favorite places for funny tee shirts.
With the loss of new slide rules, the market for old ones has gone through the roof. What were once yard-sale $1 items are now going for $50~$150 on eBay, depending on how complex and large they are.
So, if TSHTF and we don't have electricity, I can always get my slide rule out for those important I'm-going-to-help-save-the-world calculations.


  1. Heh... Got both of them around somewhere, and a mini-whiz wheel too! And one from 1936 marked Pan American Airways!

  2. I enjoyed seeing these nostalgic items. Good post.

    I still have several slide rules, both linear and circular, plus an E6B "prayer wheel" back in Kalifornistan.


Keep it civil, please....