# Slide Rule

Does anyone still remember their SlideRule? Does anyone still use their SlideRule? Remember the nice grippy slippy slide just so and no reading glasses BackInTheDay?. A fun trip down memory lane here http://www.sphere.bc.ca/test/exchange.html http://www.hpmuseum.org/sliderul.htm

Could someone describe the purpose and uses of a slide rule here, for those youngsters who were born into the calculator age?

At its simplest, you can do multiplication and division on a vanilla-flavoured slide-rule.

In short - take two ordinary rulers. It's easy to see how to use them for addition. If you want to add X and Y using rulers A and B,

• line up the 0 on A with X on B,
• opposite the Y on A is (X+Y) on B.

If the scales are logarithmic, then
• line up the 1 on A with the X on B,
• opposite the Y on A is (X times Y) on B.

A slide rule of a different sort - Circular designed 1931. Equivalent to a 65mm conventional slide rule (on outermost ring)

• Log Log with Trig functions (Sine and Tangent Trig function on reverse side)
• Shown here with solution to 2*pi.

I still have a couple of slide rules that I will not part with. I use them to illustrate a point I make in speeches about the rate of technological change; namely that our cultures are very much slower to change than our technologies. After all, we still talk about the poor buggy whip makers that were ruined by the advent of the horseless carriage. Yet, buggy whips are now a high end luxury item still very much in use while I know of no company that still makes slide rules. -- HansWobbe

uh, that might be because whipping your partner with a sliderule doesn't have the same cachet... --PhlIp

Thoughts of catholic engineering schools spring to mind... -- IanOsgood (whose father owns a functional slide rule tie clip)

See http://wiki.rubygarden.org/Ruby/page/show/SlideRule for a sliderule simulation:

I lost my slide rule some time in the last 10 years, and would love to find it again. It was about 15 or 20cm long (6 or 8 inches), and was my Dad's way back in the 60's in Germany. I now own a circular aviation slide rule, but it only does multiplication, division, and a bunch of aviation specific functions. No trig, powers, etc. -- StefanVorkoetter

Since my last post, I've re-found my slide rule (although it's missing its cursor), and have gotten hooked on the hobby of slide rule collecting. I now own several, including a circular mathematical slide rule. -- StefanVorkoetter

Another collection of good slide rule simulators (using scanned images of real slide rules) can be found at:

There are an abundance of slide rule simulators showing up as mobile apps for Android or iPhone. At least one of them allows you to pinch/stretch the screen to increase the apparent size of the slide rule, increasing the precision.

Also, don't forget, there are wristwatches which have a "slide rule bezel," for the truly geeky. They are usually marketed towards pilots, as many pilots still use a circular slide-rule device known as an E6B (the military designation of such a device used by the US Army Air Corps during World War II). If you know what you're doing with such a watch, you can multiply, divide, and find square roots and logarithms. Their small size limits their precision, though.

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