Monday, December 29, 2008

How To Use A Slide Rule

I ran into one of my dad’s old slide rules while rummaging in boxes and decided to try to figure out how to use it.  My dad was a civil engineer and spent a lot of time with his slide rules before calculators came around.  I googled “how to use a slide rule” and came across this. 

To multiply two numbers on a typical slide rule, the user set the left index (start of the scale) on the C scale to line up with one factor on the D scale. (All labels refer to Pickett scales. Scale labels were not completely uniform between brands.) The user then found the second factor on the C scale and looked on the D scale for the product. By doing this, the user effectively added the logs (lengths) of the two numbers and looked up the antilog.

What.  The.  Heck. 

image

Anyway… back to work…

 

(11) Comments
Posted by Owen at 2223 hrs
Off-Duty

  1. I used one in High School and College.  Sorta cool once you got the hang of it, made you feel smart.

    Posted by yoSAMite on December 29, 2008 at 2257 hrs


  2. Basic Slide Rule Instructions-
    Grip slide rule near an end and hold firmly. Place slide rule in vertical upright position in front of body with arm fully extended. Bend arm 180 degrees at elbow, rotating slide rule behind head and vigorously scratch back.

    I felt pretty damn important when we all received Hewlett-Packard HP-35 hand held calculators in place of the slide, and for the bargain price of about $250 a copy.

    Posted by .(JavaScript must be enabled to view this email address) on December 29, 2008 at 2307 hrs


  3. Those instructions worked great!  My back feels wonderful.

    Posted by Owen on December 29, 2008 at 2324 hrs


  4. Very much fun was knowing that NASA was spending taxpayer dollars calculating rocket launches and orbits with a thing like that.

    And the Navy was building aircraft carriers using them.

    And the Air Force and its H-bombs—oy vey!

    Posted by .(JavaScript must be enabled to view this email address) on December 29, 2008 at 2354 hrs


  5. Hey some of us went to school in the dark ages before calculators. Slide rules were a heck of lot faster to multiply 3.29 times 10.24 than to do it long hand.

    Yeah, no one knows what logarithms are anymore either, I think.

    Posted by Dean on December 29, 2008 at 2355 hrs


  6. Count me in. I liked the slide rule, but they were out even when I started. Still, it was something to play with.

    The HP-35? It’s probably still working, eh? I got the HP-15C as my main calculator and I still won’t give it up. 25+ years and counting, runs like a champ, and still the most usable calculator I’ve seen.

    Posted by .(JavaScript must be enabled to view this email address) on December 30, 2008 at 0007 hrs


  7. I remember whent he geeks in high school carried their slide rulers in holsters.

    I messed around with them and could do simple multiplication and division.  Other than that, I was useless with the things.  I might still have one in the basement.  Perhaps a collectors item?

    Posted by Jim the Fireman on December 30, 2008 at 0909 hrs


  8. The ones I have have holsters and a strap to hook it to your belt.  I think I’ll start wearing it around the office until someone asks me what it is.

    Posted by Owen on December 30, 2008 at 0918 hrs


  9. Slide Rule?  Nothin’ to it.  In NPS in 1974, we all used slide rules except the one guy who had a $600 calculator for addition, subtraction, multiplication and division.  I thought the cost was a little too steep for my Navy pay.

    Posted by Steve on December 30, 2008 at 0934 hrs


  10. The ones I have have holsters and a strap to hook it to your belt.  I think I’ll start wearing it around the office until someone asks me what it is.

    Careful! You don’t want to get arrested for disorderly conduct!

    People just aren’t use to seeing slide rulers strapped to your hip you know.

    Posted by .(JavaScript must be enabled to view this email address) on December 30, 2008 at 1037 hrs


  11. Perhaps this will be a reminder to all of the precious children of the digital age that real life is actually analog. Napier is spinning in his grave.

    Posted by .(JavaScript must be enabled to view this email address) on December 30, 2008 at 1611 hrs


Commenting is not available in this channel entry.