Making Your Own Slide Rule

Intro: Making Your Own Slide Rule

I have thought about making my own slide rule, and finally did.  This Instructable is partially a description of how I did it and partially an evaluation of the effort.

STEP 1:

Back in 2008 Instructables member legionlabs published "How to use a slide rule."  In the comment section Instructables member Mr ross made reference to a May 2006 article in Scientific American magazine titled "When Slide Rules Ruled."  Once that article was available on-line in PDF, but has since been removed.  Scientific American still makes it available, but at a cost of about $7 US.  The article included a downloadable PDF file pictured in the graphic for this step.  It is a printout for a fold-up paper slide rule.  I decided I wanted to make one of these just for fun, but mount it on wood and Plexiglass.  After printing the PDF file, I enlarged it with a copy machine to about 150%.  The idea was that the scales would be larger, easier to read, and more precise. 

STEP 2: Construction

I experienced a couple of disappointments with this project, and will discuss them later.  For that reason, I will not give a lot of detailed steps on the construction of my slide rule.  But, I will share a couple of things others may want to use.  

I used Plexiglass screwed to 1/2 inch plywood.  In order to hold the slider (center movable piece) in place and still allow it lateral movement, I used a dovetail router bit to shape the edges of the Plexiglass pieces.  This slight bevel holds the slider down, but allows it movement.  

I covered the Plexiglass pieces with double stick cellophane tape.  Then I pressed the paper scales to the tape.  I covered the paper scales with cellophane packing tape about 2 inches wide.  I trimmed the edges with a very sharp knife.  

STEP 3: Adjustment

The screws near the D, L, & S scales fit into holes no larger than the screw diameter.  The screws near the T, K, & A scales fit into holes that are over-sized so the top slide rule stator can be moved a little left-to-right so the left indices of all scales align properly.  The over-sized holes near these scales also allow the top stator to adjust in and out toward the slider for the desired smoothness of movement.  

The selection of scales available is basically those found on a "trig" rule.  These are the scales found on the Nestler 23 rule favored by Albert Einstein, Werner von Braun, and Sergei Korolev (chief designer for the Russian space program).  This link includes a photo of von Braun's Nestler 23 rule.  Most of the scales were not labeled on the Nestler 23.

STEP 4: A First Problem

I soon noticed that the paper scale and the double stick tape began to separate from the Plexiglass at the ends of the slider.  Although not easy to see, I folded a piece of cellophane tape over the ends of the slider and trimmed it.  There is a slight discoloration and a faint line.  Soon I removed the stator pieces and did the same with them.

STEP 5: Cursor?

I have not made a cursor for this slide rule, yet.  Most calculations I have ever done on a slide rule involve basic multiplication on the C and D scales.  The D scale is directly below the C scale visible in the photo.  It is not difficult to set the factors and to read the answer on these scales without a cursor.  When using the A and B or S, T, & K scales, a cursor becomes more necessary because the answer needs to be read on the C or C1 scales.   See the second photo for this step.  I used a note card aligned with the top edge of the rule as a cursor.  It aligns with 27 on the second scale from the top, which is the K scale.  Follow the edge of the card downward and you see it also aligns with 3 on the D scale.  The cube root of 27 is 3.  Below the K scale is the A scale.  The cursor aligns with 9 on the left half of the A scale.  The square root of 9 is 3.   

Notice one inherent problem with the PDF file that serves as a pattern for this slide rule.  See the first photo again.  The left index for the B scale is aligned with 4 on the left half of the A scale.  The left index on the C scale below it should very accurately indicate 2 because the C scale gives the square roots of numbers on the A or B scales, but the left index of the C scale is a full line width to the left of the 2 indicating 1.99 as the square root of 2.  Calculations done on the C and D scales of this rule are quite accurate, but I found several problems on the A and B scales that are not due to my printer or my construction methods.      

STEP 6: Further Problems

The A and B scales are copies of the C and D scales, but in half-size so they are doubled.  Multiplication and division problems that may be solved on the C and D scales may also be worked on the A and B scales.  Because the A and B scales are smaller, the answers are more difficult to read with accuracy.  Notice the yellow arrow in the photo.  The 1 on the B scale is aligned with the 2 on the A scale.  Move to the right on the B scale and notice the green arrow.  The 3 aligns nicely with the 6 on the A scale.  2 x 3 = 6.  Although not marked with an arrow, the 4 aligns nicely with the 8, too.  But, when you look at the 5 on the B scale, it is at least the width of a line off of the 1 (or 10) on the A scale.  It would appear that 2 x 5 now equals 9.97, or thereabouts.  The PDF file for this slide rule has some problems that make it unfit for anything but practice by a beginner.  

STEP 7: What to Do?

If you merely want to practice learning to use a slide rule, there is a nice virtual slide rule on-line.  It is a replica of a PIckett 10 inch aluminum slide rule.  You can click and drag any part of the rule.  Some readings may be slightly inaccurate, depending on quirks in your Internet browser.  That was my experience.  I learned to use a slide rule with a Pickett 120 Trainer.  It is a printed plastic rule, but quite accurate.  The original manual for it can be downloaded here.  Use your browser's "Find" function to search for "M52."  It is a simple manual, but very adequate and covers the scales on both the virtual slide rule linked above and the PDF slide rule I built.  

Right now I am talking with a friend who studied electronics just a couple of years after electronic calculators unceremoniously drove slide rules from the engineering scene.  He wants to learn to use a slide rule out of personal interest and curiosity.  I may give him the slide rule I built so he can practice.  Otherwise, for someone like him, I would suggest watching the auctions at eBay and buying a favorably priced rule.  An aluminum Pickett 10 inch rule similar to the one used for the virtual rule linked above can often be had for $25 or less plus shipping, even on a "Buy It Now" sale.  Recently I posted an Instructable on how I bought a nice old Dietzgen slide rule for $2.50 plus shipping and replaced the defective/missing cursor glasses myself.  If you have not seen that Instructable, there are some useful links there.  If you saw it when I first posted it, I have since added some links and information.  The photo for this step is my new old rule before I repaired the cursor glasses.   

STEP 8: Other Downloadable Slide Rule Scales.

There are other sites on the Internet with information for those who wish to build their own slide rules.  If you want to be very precise and do it the hard way, this site tells you how to find the logarithms of numbers and etch them onto a scale.

If you want to download copies of just about every slide rule scale ever devised so you can make your own custom rule, this site is what you need.  

If you would like to download PDFs of various classic slide rules and transfer them to your own base construction materials, this is the site you want.  There are even some circular slide rules you can build.  Scroll down about 2/3 of the page to see a nice wooden slide rule built by a man from Spain.  (See the photo with this step.)

Here is a basic circular slide rule design you can build.

In summary, my experience is that you can spend a couple of hours making a slide rule that may not be accurate or work as smoothly as a vintage slide rule you can pick up at an on-line auction.  If your time is worth anything, the slide rule you purchase at an auction site may actually cost less than the one you attempted to build.  

Comments

[Zanderist]

I am an third assiant engineer on board merchant ships. I am 25 years old.

what I have to say is that philosophically the slide rule is the self defense weapon of a jedi knight, if you cant get that, try thinking about a japanese sword, if not that the pracitice of martial arts to disarm someone.

I feel that while the world enters a new age of chaos due to the little black boxes called ICs that make up a hand calculators. As long as engineers willfully learn about the art of slideruler I feel we will never come close to the end.

Modern generations need to understand what a slide rule is and realize that it was all that was needed to land men on the moon, vintage technology is not to be scoffed at and not reguarded as obsolete. How many men since the rise of caclulators have walked on the moon since?

Aggrogance from younger generations to come will be the undoing of the frabic of peace today when they throw away the wonderful gift elder wisedom. I say to anyone reaching this end of my comment, do you got what it takes to make a slide rule.

I have two vintage slide rulers one of my fathers and one of another relative,I am thankful for this tutorial as it will be the first neccesary step in my journey through world of PRACTICAL ENGINEERING.

Thanks to the author, Namaste!

[Phil B]

Thank you for your comment. I have done three Instructables on slide rules and using them. This is one of the three. In one of those I mentioned a friend in the Army Reserves. His group went out for a weekend practice with artillery. Today's field guns are computer guided. But, that weekend the computer was down. My friend's group were older and had been trained in the days before computers. One of the men had brought the charts and a slide rule they used in the old days forty years ago. They were able to complete their gunnery assignments, but the others were not.

[Smokejumper66]

I worked at AiResearch with the Apollo engineers. They spent years calculating by hand and made tables out to four and five significant digits of different commonly used calculations. All they had to do was look up. The HP-35 calculator changed all that in days. Amazing transition period.

[Phil B]

Thank you for sharing your story. There have been several revolutionary changes in recent decades. For one, I think about the change from points and condenser automobile engine ignition to electronic ignition. Timing lights and dwell tachometers are obsolete.

[Zanderist]

Sorry about the double comment.

I would like to add part of my colloege career was to get a degree in electrical engineering which led to me learning about how computers work through logic gates and eventually the idea of tiny men with slide rulers.

I think that situation you described about the field artillery men having to result into slide rulers is likened to a governor on an engine.

How accurate does an artillery shell or cruise missile need to be to under stand the point its useage is trying to make. In matters of war, orders are orders but there are no right or wrong answers to orders, inaccuracy and freewill allow for new orders to be assigned. Good leaders do not go out and destory their enemies entirely, a game of chess is to capture not kill.

modern machines allow for people to carelessly assume they have the right answers, they can assume they found all the correct opinions from the internet.

back to my previous point about the US space program, we landed on the moon with guided engineering from a slide ruler, but yet somehow the program allowed the challenger to blow up from mircomanagement from little black boxes called the modern computer.

I am not asking for a call to arms against modern computers and caculators but a need to slow down and learn what they call in the eastern philsophies, "Zen".

So basically in a nutshell, the Zen of engineering is learning how older vintage tech got us to were we are today.

[BuckR5]

Great page, I was surprised to find here a picture of the rule I made back in 2005 (right under the step 8 title) Yep, I'm the "Spanish man" ;)

[Phil B]

The slide rule you made is very impressive. When I post something like my slide rule, I check to see what others have done that is similar and try to acknowledge those offerings. I want readers to know I did not shoot from the hip, but did some research before posting. I also want them to know about other offerings that may be more suitable to their purposes, and to know how what I am posting is different, in case that is what they want and need. Thank you for your comment.

[Zanderist]

I am an third assiant engineer on board merchant ships. I am 25 years old.

what I have to say is that philosophically the slide rule is the self defense weapon of a jedi knight, if you cant get that, try thinking about a japanese sword, if not that the pracitice of martial arts to disarm someone.

I feel that while the world enters a new age of chaos due to the little black boxes called ICs that make up a hand calculators. As long as engineers willfully learn about the art of slideruler I feel we will never come close to the end.

Modern generations need to understand what a slide rule is and realize that it was all that was needed to land men on the moon, vintage technology is not to be scoffed at and not reguarded as obsolete. How many men since the rise of caclulators have walked on the moon since?

Aggrogance from younger generations to come will be the undoing of the frabic of peace today when they throw away the wonderful gift elder wisedom. I say to anyone reaching this end of my comment, do you got what it takes to make a slide rule.

I have two vintage slide rulers one of my fathers and one of another relative,I am thankful for this tutorial as it will be the first neccesary step in my journey through world of PRACTICAL ENGINEERING.

Thanks to the author, Namaste!

[ATomId]

There are two things about slide rules that have not been mentioned.

1. Some people who have difficulty with math are more visually-oriented, which makes slide rules very helpful so people can see the relations that numbers and operations have to each other.

2. Slide rules are impervious to electromagnetic pulses, so they could preserve mathematics, in case.

[Phil B]

Both are good points. Neither was discussed or even conceived at the time I was learning to use a slide rule. Before electronic calculators, the sight of a slide rule case hanging from someone's belt conferred instant geek status on the wearer. That all went away with the advent of pocket calculators.

[ATomId]

One of my daughters says that geek is more comic books and nerd is more actual science, like math.
I think more people these days have trouble with math than people used to; I think there is a real need now to help people understand math, and see how much fun it can be!

[azcoeho]

When I was in the 11th or 12th grade, I made a slide rule on the Base 8, out of paper glued on balsa wood. I only remember having to use logarithms to convert numbers to fractions of inches to fit on the 10" rule. That was a long time ago, and I not only lost the slide rule, but also forgot everything I knew about logarithms!

[mikeasaurus]

Way to keep the spirit of vintage technology alive. Awesome job, Phil.

[mole1]

Speaking of keeping technology alive, Slide Rule (autobiographical) by Nevil Shute puts it in context. Trustee From The Toolroom is one of his novels that I think most of this group could relate to.

[finton]

TFTT. One of my most favourite stories! Along with A Town Like Alice. Nevil Shute rocks!

[mole1]

Agreed! And don't you think Phil B would get something like the same treatment almost anywhere?

[Phil B]

Thanks, Mike. It might be good to try a slide rule with a different download for the scales in order to see if it would be more accurate.

A few weeks ago I showed my new old Dietzgen rule to the preschool teachers at our church. Basic slide rule is a little advanced for 4 year olds, but the kids like anything that has moving parts. Just a few minutes ago I gave the slide rule I made to the preschool teachers. They plan to have it laying around when parents come for conferences, but doubt any of the parents will know what it is.

[mtdna]

You mention showing slide rules to kids. Have you considered getting a demonstration slide rule? It's a giant slide rule that you hang on the wall so you can show a whole class how to use it. Plus, they look awesome in your living room!

[Phil B]

We had one of those on the wall at my school during my high school years. They come up for sale on eBay periodically. Right now I am downsizing. My wife would not approve were I to buy a demonstration rule. Thank you for the comment.

[snideprime]

I still have the slide rule I used in college in the 60s...I tried to sell it at a yard sale, but few people knew what it was, and no one wanted it. Even when I marked it down. So I will probably own the thing 'til I die, even as I use the much easier calculator!