5 ms·

How Slide Rules Work

203 points by ColinWright 11mo ago

kingforaday 11mo ago
This would have been helpful for Sam Cooke.
JKCalhoun 11mo ago
Deep dive, for sure. I suspect Cliff Stoll is enjoying this site. I played with creating a logarithmic slider thing [1] in Javascript that I hoped I could package up as a kind of "widget" people could use on their web pages. But I don't really know Javascript that well—or rather how to make an API out of a Javascript thing. Anyway, to test it I tried to make an Ohm's Law calculator [2]. I would love to see a site like the one in this post have some kind of interactive slide rule on the web page itself. [1] https://github.com/EngineersNeedArt/SlideRule https://github.com/EngineersNeedArt/SlideRule [2] https://www.engineersneedart.com/ohmslaw/index.html https://www.engineersneedart.com/ohmslaw/index.html (the yellow slider is not directly user-moveable in this example)
- ErroneousBosh 11mo ago
  It works well enough to get the idea of "set the voltage, set the resistance, read the current off the voltage scale above the 1 on the resistance scale". It might be a little easier to do if the rules were closer, which would probably require a little noodling about with the code to make the "resistance" box sit below the rule scale.
NetMageSCW 11mo ago
The HP-35 wasn’t programmable- it was just a scientific calculator.
clickety_clack 11mo ago
Slide rules are super cool. Such an easy gift to give the engineer in your life. I never spent the time to get quick with it, but I could absolutely see it being quicker than a calculator. You’d just have to be aware of the limits to its precision if you were in a field that required it.
- deepspace 11mo ago
  Quicker than an algebraic calculator, maybe, but very few people could get. faster with a slide rule than an ergonomic RPN calculator. like the HP 41 series. And I say that as an enthusiastic and experienced slide rule user, before I switched to a calculator. One problem with a slide rule is that it only performs operations on normalized mantissas. You have to keep a parallel exponent calculation in your head, and that slows you down. Also, maintaining best precision slows you down.
  - ghaff 11mo ago
    I used an HP-41CV for many years. I needed the financial calcs module which I used in place of the dedicated HP financial calculator in grad school. Eventually gav out on me but was a good calculator for a long time. I did keep a slide rule as a backup for exams in college when calculators were still LED but never really used one after a couple of years in high school.
    - VLM 11mo ago
      The financial people I know all own 12Cs and they've been in continuous production since '81 although the innards are just a very boring ARM processor now. They do what people want, the keyboard feel is infinitely smoother than tapping on a phone, etc.
      - ghaff 11mo ago
        I have an HP-41 app on my phone that the author gave to me when I was doing some product reviews early-on in the smartphone days. But definitely not the same as the physical HP calculator. Yeah, the 12C was the standard in business school. But I needed a new calculator and the 41 with its various modules worked fine and was more general purpose.
  - litoE 11mo ago
    When using a slide rule, keeping track of the number of digits to the left of the decimal point (DLDP) in the result is fairly simple if you know the basic rule: For multiplication, the DLDP in the result is: - the sum of the DLDPs of the multiplicands MINUS 1 if the multiplication is done with the slide sticking out to the right of the ruler's body (for example 2.0 x 3.0 = 6.0). - the sum of the DLDPs of the multiplicands if the multiplication is done with the slide sticking out to the left of the ruler's body (for example 5.0 x 4.0 = 20.0). There's a similar rule for division, but that's left as an exercise for the student.
fjfaase 11mo ago
I have one at home, which is the one we had to buy to use in highschool. In the math classrooms we had a 6 feet version that could be mounted on the blackboard such that the teacher could used for instruction. See for a picture on the Dutch page https://rekenlat.barneveld.com/rekenliniaal.htm https://rekenlat.barneveld.com/rekenliniaal.htm
- watersb 11mo ago
  These TMSLs were also reasonably common in classrooms in the United States in the 1950s. Two Meter Slide Rule
- pinkmuffinere 11mo ago
  Wow that's fascinating! Crazy how things change, no wonder my grandma thinks math is black magic!
gerdesj 11mo ago
It is worth keeping one around. When the "cloud" is raining and your laptop and phone batteries are drained and you suddenly need to navigate your 4823 times table - its got you covered. You will also need to work out how to write with a pen or pencil on paper or try and fix up your atrophied ability to remember arbitrary "facts" short term.
- margalabargala 11mo ago
  Honestly the scenarios where this becomes likely are dwindling with the advent of solar and batteries. Offline knowledgebases and the ability to use them long term are getting increasingly stable, and the likely low point in a societal collapse is probably getting high enough that a slide rule would not be necessary. I have a Casio fx-991ES calculator, and twenty years later I have yet to need to replace the button cell in it thanks to the tiny solar cell.
  - eggy 11mo ago
    And when the EMP washes over your home/office it will most likely be off and most likely survive. If you are doing your monthly finances at the time and it is on, it will be destroyed. The slide rule rules!!! I keep a pocket Pickett for fun...the window has a small crack, and it is missing a very tiny screw (1 of 8). I brought it to my engineering company one day and showed the 20-30-something group how it worked. I then did a full page of calcs they did in Excel, and even with the limits of visual resolution came within an acceptable percentage of their calc.
    - margalabargala 11mo ago
      That's not quite how EMPs work. The wire traces act as antennas, and long wires like power transmission lines will have huge power surges, and small devices like calculators will have basically none. The miniscule increase in length of conductive material if the battery happens to be conducting at the moment won't impact the amount of current induced. Solar EMPs won't be powerful enough to impact electronics. A nuclear EMP can impact electronics, but only over a small geographic area; close enough that if you are in the electronics-frying radius of a nuclear weapon explosion, you either have much larger problems to worry about, or nothing at all to worry about ever again. Here's info from Los Alamos Lab on it: https://www.lanl.gov/media/publications/national-security-science/0424-emp-could-it-happen-to-me https://www.lanl.gov/media/publications/national-security-sc...
jamesgill 11mo ago
Last week I donated several slide rules to Goodwill; a few were very nice. Meanwhile, I still have a pristine HP-41cx and HP-15c, and an HP-25 app on my iPhone.
- incanus77 11mo ago
  I have an HP-15c as well as a 16c and I've been using the latter on a daily basis while writing a byte-level network protocol client. I'm getting faster by the day and on the verge of writing some programs for shortcuts on the calculator. I still use the excellent PCalc as well, but seem to be faster on the physical calculator, which is kind of surprising.
  - ghaff 11mo ago
    When I was writing a shareware program in x86 assembler and doing a fair amount of bit twiddling, the 16C was really handy. Presumably I still have it around somewhere.
watersb 11mo ago
A sort of non-logarithmic slide rule, the E6B Flight Computer, was still in use when I was a student pilot 20 years ago. I still carry one: they don't require electricity (although using one in the dark requires a light source). https://en.wikipedia.org/wiki/E6B https://en.wikipedia.org/wiki/E6B
- KK7NIL 11mo ago
  The main part of the E6B is a very standard logarithmic slide rule. Having it loop unto itself is a neat trick but very ancient. But perhaps you were referring to one of the many other parts of the E6B which I am not familiar with.
egl2020 11mo ago
I still have the wooden 10" Keuffel and Esser that I inherited from my father and that I used in college. These days I use my HP15C unless I want to provoke glee and amusement in my younger colleagues by sporting my Pickett slide rule in my shirt pocket.
- wyclif 11mo ago
  K&E's are classic. What do you think was the most popular Pickett model?
  - VLM 11mo ago
    The microline series, antique stores are full of them. Every high school or lower undergrad boomer had one or a similar clone and they show up in antique stores and on ebay all the time. The 80 and 120 are about the same size and sell for about $20 and I don't bother buying them anymore when I see them. The 80 puts the T scale on top and the 120 more usefully puts it in the slider IIRC so you can chain calculations. Grad students or undergrad STEM students would have something like a 900 series, I have several, very nice. This is a desk rule it will not fit in a pocket. Something like a 600 series is a short pocket model, anodized aluminum, very nice and desirable. The microline series was definitely made to a price point and unless you find one in unusually good condition or its your first collector rule I would not bother picking it up. They stick very strongly and the cursor cracks after half a century and they are slippery in the hand and warp more than most rule and I don't think they're easy to read. They were cheap to make and cheap to buy. Slide rules in the 2020s are an efficient market; something that barely works "the walmart solar calculator of its generation" like a microline series sells for around $20 today, a VERY desirable N600 series sells for like a hundred bucks and I think its a bargain at that price. If you mean most popular as in most desired today not most sold back in the day, that's probably the 600 series or specialty rules like I have a N-16-ES with the electronics engineering scales. The latter sells for about as much as a working HP48 calculator, which is interesting. If you mean popular as in attractive that is surely the Faber-Castell short 83N series, I think that's a 62/83N. I would like one of those LOL. Unleash 1960s German graphics artists on industrial design and tell them to make the coolest looking slide rule possible under 60s industrial design rules, you get the 83N series, very very cool way to spend $300 or so, its the kind of thing you put in a lighted display case to admire.
throw0101a 11mo ago
This education film from 1957 gives a good overview of using one: * https://www.youtube.com/watch?v=oYQdKbQ-sgM https://www.youtube.com/watch?v=oYQdKbQ-sgM "Professor Herning" (?) also has a good series of videos on the use of various scales as well: * https://www.youtube.com/@ProfessorHerning/videos https://www.youtube.com/@ProfessorHerning/videos His playlist starting at the beginning (C and D scales) with a Manheim layout: * https://www.youtube.com/playlist?list=PL_qcL_RF-ZyvWJJkJOk_OujiS3YyWx0nG https://www.youtube.com/playlist?list=PL_qcL_RF-ZyvWJJkJOk_O... * https://sliderulemuseum.com/Manuals/M37_Post_Manheim_Instructions.pdf https://sliderulemuseum.com/Manuals/M37_Post_Manheim_Instruc... Some manuals / books on slide rules: * 1909: https://archive.org/details/mannheimsliderul00coxwrich https://archive.org/details/mannheimsliderul00coxwrich * 1922: https://archive.org/details/cu31924002978561/mode/2up https://archive.org/details/cu31924002978561/mode/2up
- argiopetech 11mo ago
  I also like (and was lucky enough, as a young man, to find a physical copy of) Asimov's "An Easy Introduction to the Slide Rule." It's my favorite introductory text. PDF copies can be found on the web.
inamberclad 11mo ago
For the past 10 years, I've worn a slide rule every day. It's a small circular one modeled after the E6B aviation slide rule, with markers for common aviation conversions.
entaloneralie 11mo ago
I have a little collection of them. I keep the small Hemmi bamboo on the navigation table at all time. https://wiki.xxiivv.com/site/slide_rule https://wiki.xxiivv.com/site/slide_rule
bogardon 11mo ago
For people into watches, check out this video (and the whole series of watch and learn) on slide rules on watches: https://www.youtube.com/watch?v=RuK_77DEUfw https://www.youtube.com/watch?v=RuK_77DEUfw
- jrop 11mo ago
  Wow, I really want a slide rule watch now.
xmcp123 11mo ago
In my head: “Oh yeah, I forgot how to use one of those” This article: “lol, is that the depth of your commitment”
tiniuclx 11mo ago
While I'm a bit too young to have used one in school, my dad did give me his slide rule from when he was a student. It's one of my most prized possessions, if only to show how far humanity has come in terms of computing devices.
- ghaff 11mo ago
  My mother (who ran a biochemistry lab) had a longish one--extra digit of precision I guess. Unfortunately my anti-packrat dad must have chucked it in some move or another. In addition to some cheap student stuff, I think I still have a couple of "normal" professional slide rules but they're not in very good shape if serviceable.
wyclif 11mo ago
My Dad is a retired R&D chemist who worked at the DuPont corporation's Experimental Station. When I was a kid he would bring his old slide rules home from work when he got a new one, and at one point he explained to me how they work but I forgot it all long ago. I still have the slide rules, so this post was a great rabbit hole to go down. In software there's no need for them but I still find them fascinating as a window into how engineers used to get their work done.
- ErroneousBosh 11mo ago
  > In software there's no need for them... ... but in the Real World they work pretty well for the sort of calculations you might need to do in the field (literally, in a field, sometimes) and don't require batteries, are reasonably waterproof, and reasonably robust if dropped.
  - VLM 11mo ago
    The all plastic ones are intrinsically safe in a potentially flammable environment, they don't require power, they're an education in how most engineering materials in the real world have surprisingly wide tolerances so they are far more than accurate enough for most work, for people who learn graphically/visually they are the logical next educational step after counting on fingers. They're pretty useful for teaching amateur people how to implement algorithms. Multiple ways to solve problems, some easier than others, some more efficient than others, with immediate rewards of faster higher accuracy.
    - ErroneousBosh 11mo ago
      > The all plastic ones are intrinsically safe in a potentially flammable environment Never thought of that, and I used to work in an ATEX environment where calculators powered by watch batteries had to be carefully logged and carried across to a "safe" area inside a special (horribly expensive) Peli case.
      - ompogUe 11mo ago
buggi23 11mo ago
To add to this, there's a great set of resources by Joe Pasquale explaining the mathematical theory behind how various functions can be computed by slide rules: * https://cseweb.ucsd.edu/~pasquale/Classes/SlideRule/ https://cseweb.ucsd.edu/~pasquale/Classes/SlideRule/ * Mathematical Foundations of the Slide Rule (PDF): https://cseweb.ucsd.edu/~pasquale/Papers/IM11.pdf https://cseweb.ucsd.edu/~pasquale/Papers/IM11.pdf * Why Does A Slide Rule Work? (PDF): https://cseweb.ucsd.edu/~pasquale/SlideRuleTalkLasVegas14.pdf https://cseweb.ucsd.edu/~pasquale/SlideRuleTalkLasVegas14.pd... The gist of it is: 1. First, define a way to represent any univariate monotonic function f(x) on a graduated scale. (Specifically: select a discrete set of x values, and for each of these x values, place a mark with label x at a distance proportional to (f(x) - f(x_L)) from the left endpoint, where x_L is the leftmost x value.) 2. Then, if we have two such scales f(x) and g(x) that can slide relative to each other, we can compute functions of the form h(x, y, z) = f_inverse(f(x) + g(y) - g(z)). It ends up being surprisingly versatile -- the above resources show how you can compute: 1. Multiplication: x * y using f(x) = log(x) and g(y) = log(y), with z fixed at 1 2. Hypotenuse: sqrt(x^2 + y^2) using f(x) = x^2 and g(y) = y^2, with z fixed at 0 3. Parallel resistors: 1/(1/x + 1/y) using f(x) = 1/x and g(y) = 1/y, with z fixed at +infinity 4. Exponentiation: x^(y/z) using f(x) = log(log(x)) and g(y) = log(y)
jjgreen 11mo ago
In the UK there was a time (late `70s) when slide-rules were allowed in examinations but calculators weren't, no-brainer to learn how to use one just for that. Even better, if you added "(SR)" after your calculations, that indicated that you had used a slide-rule so small errors were permitted.
smusamashah 11mo ago
Here one can play with many slide rules in the browser https://www.sliderulemuseum.com/VirtualSR.shtml https://www.sliderulemuseum.com/VirtualSR.shtml
zeckalpha 11mo ago
Anyone know of a good place to buy a new linear slide rule? I know there's a circular slide rule manufacturer but am not sure if any linears are being made any longer.
- PessimalDecimal 11mo ago
  They won't be new, but Ebay has a lot of old linear rules.
- throw0101c 11mo ago
  As per sibling comment: not much of a market for new ones. Would be curious about someone trying to make some: use Kickstarter to gauge interest perhaps? For used, see perhaps "Where to Buy Slide Rules?": * https://www.sliderule.ca/buy.htm https://www.sliderule.ca/buy.htm
- evilduck 11mo ago
  The used ones aren't that expensive on eBay, especially if you just want a functional one and not a pristine show piece. There's a few 3D print models available for them too, and honestly they are rudimentary technology, you could probably make one with hand tools and patience. I bought a newly manufactured one from ThinkGeek several years ago, some geek-catering company will pop up and supply pent up demand eventually. Curiosity Box fills that niche right now.
- argiopetech 11mo ago
  Faber-Castell had new-old stock in the mid 20-teens, but they ran out (of stock or patience) around 2016–2018. Picked up a 2/83N for under $100, and I wish I'd gotten more. I'd suggest some of those are on eBay now. Most of my like-new rules came from antique malls, though I've also purchased one from Etsy. Estate sales are occasionally fruitful. As long as they were stored properly (e.g., in a desk drawer, like it seems they mostly were after the electronic calculator took over), they don't degrade. Occasionally you see minor yellowing that is cured by some time in the sun. Carrying cases (often leather) are typically more affected by time. I soak new (to me) leather cases in neatsfoot oil and give them at least a week before putting the rule back. You could make your own with prints from the Slide Rule Museum [0]. 3D printing would make quick work of it, but I'm sure wood or metal units could be accomplished. The cursor benefits from spring loading, They also have some pretty nice simulators [1], if that's your thing. [0] https://sliderulemuseum.com/SR_Scales.shtml https://sliderulemuseum.com/SR_Scales.shtml [1] https://www.sliderulemuseum.com/VirtualSR.shtml https://www.sliderulemuseum.com/VirtualSR.shtml
John-Tony12 11mo ago
[dead]
dboreham 11mo ago
I came up on the cusp of the calculator take-over, so although slide rules were around, and we were taught how to use them in school, I never really used them for any practical purpose. However, since they were the buggy whips of that day, you could pick up nice fancy ones for cheap in stationary stores (also now gone). So somewhere I have a good collection of them.
vjvjvjvjghv 11mo ago
When I was in 5th grade, calculators had become pretty affordable and there was this huge discussion whether kids should learn slide rules or use calculators. At the time it was decided we should learn slide rules and I am happy about this because it gives you some level of number intuition. It reminds me a little of AI now. The question of whether students should use AI will probably soon go away and everybody will use AI. Not sure what the results will be.
- ghaff 11mo ago
  Calculators went from something that was really expensive to something that was relatively affordable over a very short period of time. In about 1974, a 5-function TI was about $100 (in 1975 currency). By the next year a full scientific TI calculator wasn't much more and no one, at least in engineering school, was still using a slide rule though I brought one to exams as a a backup. By a couple years later, I was able to buy a discontinued HP calculator for about the same.
gcr 11mo ago
Last year I made my own rotary slide rule for playing Balatro, the poker roguelike! My version has a couple interesting properties compared to ordinary linear slide rules: 1. It has three octaves, so it can scale from 1 to 1k or from 1k to 1m, or from 1m to 1b. This is great for calculating point values 2. It's rotary 3. It can be easily 3d-printed! Source code and .STL files here: https://www.printables.com/model/1026662-jimbos-rotary-slide-rule-calculator-for-balatro https://www.printables.com/model/1026662-jimbos-rotary-slide...
agumonkey 11mo ago
These fascinates me, it's one of the highest simplicity / abstraction level ratio I can think of. A few marks well spaced on two bits of wood, and you get "linearized" multiplication. Nicest ~analog computer I can think of :)
bentley 11mo ago
> I missed my slipstick. Dad says that anyone who can’t use a slide rule is a cultural illiterate and should not be allowed to vote. Mine is a beauty—a K&E 20″ Log‐log Duplex Decitrig. Dad surprised me with it after I mastered a ten-inch polyphase. We ate potato soup that week—but Dad says you should always budget luxuries first. I knew where it was. Home on my desk. Robert A. Heinlein, Have Space Suit—Will Travel (1958)

203 points by ColinWright 11mo ago

This would have been helpful for Sam Cooke.

Deep dive, for sure. I suspect Cliff Stoll is enjoying this site. I played with creating a logarithmic slider thing [1] in Javascript that I hoped I could package up as a kind of "widget" people could use on their web pages. But I don't really know Javascript that well—or rather how to make an API out of a Javascript thing. Anyway, to test it I tried to make an Ohm's Law calculator [2]. I would love to see a site like the one in this post have some kind of interactive slide rule on the web page itself. [1] https://github.com/EngineersNeedArt/SlideRule https://github.com/EngineersNeedArt/SlideRule [2] https://www.engineersneedart.com/ohmslaw/index.html https://www.engineersneedart.com/ohmslaw/index.html (the yellow slider is not directly user-moveable in this example)

ErroneousBosh 11mo ago
It works well enough to get the idea of "set the voltage, set the resistance, read the current off the voltage scale above the 1 on the resistance scale". It might be a little easier to do if the rules were closer, which would probably require a little noodling about with the code to make the "resistance" box sit below the rule scale.

NetMageSCW 11mo ago

The HP-35 wasn’t programmable- it was just a scientific calculator.

clickety_clack 11mo ago

Slide rules are super cool. Such an easy gift to give the engineer in your life. I never spent the time to get quick with it, but I could absolutely see it being quicker than a calculator. You’d just have to be aware of the limits to its precision if you were in a field that required it.

deepspace 11mo ago
Quicker than an algebraic calculator, maybe, but very few people could get. faster with a slide rule than an ergonomic RPN calculator. like the HP 41 series. And I say that as an enthusiastic and experienced slide rule user, before I switched to a calculator. One problem with a slide rule is that it only performs operations on normalized mantissas. You have to keep a parallel exponent calculation in your head, and that slows you down. Also, maintaining best precision slows you down.
- ghaff 11mo ago
  I used an HP-41CV for many years. I needed the financial calcs module which I used in place of the dedicated HP financial calculator in grad school. Eventually gav out on me but was a good calculator for a long time. I did keep a slide rule as a backup for exams in college when calculators were still LED but never really used one after a couple of years in high school.
  - VLM 11mo ago
    The financial people I know all own 12Cs and they've been in continuous production since '81 although the innards are just a very boring ARM processor now. They do what people want, the keyboard feel is infinitely smoother than tapping on a phone, etc.
    - ghaff 11mo ago
      I have an HP-41 app on my phone that the author gave to me when I was doing some product reviews early-on in the smartphone days. But definitely not the same as the physical HP calculator. Yeah, the 12C was the standard in business school. But I needed a new calculator and the 41 with its various modules worked fine and was more general purpose.
- litoE 11mo ago
  When using a slide rule, keeping track of the number of digits to the left of the decimal point (DLDP) in the result is fairly simple if you know the basic rule: For multiplication, the DLDP in the result is: - the sum of the DLDPs of the multiplicands MINUS 1 if the multiplication is done with the slide sticking out to the right of the ruler's body (for example 2.0 x 3.0 = 6.0). - the sum of the DLDPs of the multiplicands if the multiplication is done with the slide sticking out to the left of the ruler's body (for example 5.0 x 4.0 = 20.0). There's a similar rule for division, but that's left as an exercise for the student.

fjfaase 11mo ago

I have one at home, which is the one we had to buy to use in highschool. In the math classrooms we had a 6 feet version that could be mounted on the blackboard such that the teacher could used for instruction. See for a picture on the Dutch page https://rekenlat.barneveld.com/rekenliniaal.htm https://rekenlat.barneveld.com/rekenliniaal.htm

watersb 11mo ago
These TMSLs were also reasonably common in classrooms in the United States in the 1950s. Two Meter Slide Rule
pinkmuffinere 11mo ago
Wow that's fascinating! Crazy how things change, no wonder my grandma thinks math is black magic!

gerdesj 11mo ago

It is worth keeping one around. When the "cloud" is raining and your laptop and phone batteries are drained and you suddenly need to navigate your 4823 times table - its got you covered. You will also need to work out how to write with a pen or pencil on paper or try and fix up your atrophied ability to remember arbitrary "facts" short term.

margalabargala 11mo ago
Honestly the scenarios where this becomes likely are dwindling with the advent of solar and batteries. Offline knowledgebases and the ability to use them long term are getting increasingly stable, and the likely low point in a societal collapse is probably getting high enough that a slide rule would not be necessary. I have a Casio fx-991ES calculator, and twenty years later I have yet to need to replace the button cell in it thanks to the tiny solar cell.
- eggy 11mo ago
  And when the EMP washes over your home/office it will most likely be off and most likely survive. If you are doing your monthly finances at the time and it is on, it will be destroyed. The slide rule rules!!! I keep a pocket Pickett for fun...the window has a small crack, and it is missing a very tiny screw (1 of 8). I brought it to my engineering company one day and showed the 20-30-something group how it worked. I then did a full page of calcs they did in Excel, and even with the limits of visual resolution came within an acceptable percentage of their calc.
  - margalabargala 11mo ago
    That's not quite how EMPs work. The wire traces act as antennas, and long wires like power transmission lines will have huge power surges, and small devices like calculators will have basically none. The miniscule increase in length of conductive material if the battery happens to be conducting at the moment won't impact the amount of current induced. Solar EMPs won't be powerful enough to impact electronics. A nuclear EMP can impact electronics, but only over a small geographic area; close enough that if you are in the electronics-frying radius of a nuclear weapon explosion, you either have much larger problems to worry about, or nothing at all to worry about ever again. Here's info from Los Alamos Lab on it: https://www.lanl.gov/media/publications/national-security-science/0424-emp-could-it-happen-to-me https://www.lanl.gov/media/publications/national-security-sc...

jamesgill 11mo ago

Last week I donated several slide rules to Goodwill; a few were very nice. Meanwhile, I still have a pristine HP-41cx and HP-15c, and an HP-25 app on my iPhone.

incanus77 11mo ago
I have an HP-15c as well as a 16c and I've been using the latter on a daily basis while writing a byte-level network protocol client. I'm getting faster by the day and on the verge of writing some programs for shortcuts on the calculator. I still use the excellent PCalc as well, but seem to be faster on the physical calculator, which is kind of surprising.
- ghaff 11mo ago
  When I was writing a shareware program in x86 assembler and doing a fair amount of bit twiddling, the 16C was really handy. Presumably I still have it around somewhere.

watersb 11mo ago

A sort of non-logarithmic slide rule, the E6B Flight Computer, was still in use when I was a student pilot 20 years ago. I still carry one: they don't require electricity (although using one in the dark requires a light source). https://en.wikipedia.org/wiki/E6B https://en.wikipedia.org/wiki/E6B

KK7NIL 11mo ago
The main part of the E6B is a very standard logarithmic slide rule. Having it loop unto itself is a neat trick but very ancient. But perhaps you were referring to one of the many other parts of the E6B which I am not familiar with.

egl2020 11mo ago

I still have the wooden 10" Keuffel and Esser that I inherited from my father and that I used in college. These days I use my HP15C unless I want to provoke glee and amusement in my younger colleagues by sporting my Pickett slide rule in my shirt pocket.

wyclif 11mo ago
K&E's are classic. What do you think was the most popular Pickett model?
- VLM 11mo ago
  The microline series, antique stores are full of them. Every high school or lower undergrad boomer had one or a similar clone and they show up in antique stores and on ebay all the time. The 80 and 120 are about the same size and sell for about $20 and I don't bother buying them anymore when I see them. The 80 puts the T scale on top and the 120 more usefully puts it in the slider IIRC so you can chain calculations. Grad students or undergrad STEM students would have something like a 900 series, I have several, very nice. This is a desk rule it will not fit in a pocket. Something like a 600 series is a short pocket model, anodized aluminum, very nice and desirable. The microline series was definitely made to a price point and unless you find one in unusually good condition or its your first collector rule I would not bother picking it up. They stick very strongly and the cursor cracks after half a century and they are slippery in the hand and warp more than most rule and I don't think they're easy to read. They were cheap to make and cheap to buy. Slide rules in the 2020s are an efficient market; something that barely works "the walmart solar calculator of its generation" like a microline series sells for around $20 today, a VERY desirable N600 series sells for like a hundred bucks and I think its a bargain at that price. If you mean most popular as in most desired today not most sold back in the day, that's probably the 600 series or specialty rules like I have a N-16-ES with the electronics engineering scales. The latter sells for about as much as a working HP48 calculator, which is interesting. If you mean popular as in attractive that is surely the Faber-Castell short 83N series, I think that's a 62/83N. I would like one of those LOL. Unleash 1960s German graphics artists on industrial design and tell them to make the coolest looking slide rule possible under 60s industrial design rules, you get the 83N series, very very cool way to spend $300 or so, its the kind of thing you put in a lighted display case to admire.

throw0101a 11mo ago

This education film from 1957 gives a good overview of using one: * https://www.youtube.com/watch?v=oYQdKbQ-sgM https://www.youtube.com/watch?v=oYQdKbQ-sgM "Professor Herning" (?) also has a good series of videos on the use of various scales as well: * https://www.youtube.com/@ProfessorHerning/videos https://www.youtube.com/@ProfessorHerning/videos His playlist starting at the beginning (C and D scales) with a Manheim layout: * https://www.youtube.com/playlist?list=PL_qcL_RF-ZyvWJJkJOk_OujiS3YyWx0nG https://www.youtube.com/playlist?list=PL_qcL_RF-ZyvWJJkJOk_O... * https://sliderulemuseum.com/Manuals/M37_Post_Manheim_Instructions.pdf https://sliderulemuseum.com/Manuals/M37_Post_Manheim_Instruc... Some manuals / books on slide rules: * 1909: https://archive.org/details/mannheimsliderul00coxwrich https://archive.org/details/mannheimsliderul00coxwrich * 1922: https://archive.org/details/cu31924002978561/mode/2up https://archive.org/details/cu31924002978561/mode/2up

argiopetech 11mo ago
I also like (and was lucky enough, as a young man, to find a physical copy of) Asimov's "An Easy Introduction to the Slide Rule." It's my favorite introductory text. PDF copies can be found on the web.

inamberclad 11mo ago

For the past 10 years, I've worn a slide rule every day. It's a small circular one modeled after the E6B aviation slide rule, with markers for common aviation conversions.

entaloneralie 11mo ago

I have a little collection of them. I keep the small Hemmi bamboo on the navigation table at all time. https://wiki.xxiivv.com/site/slide_rule https://wiki.xxiivv.com/site/slide_rule

bogardon 11mo ago

For people into watches, check out this video (and the whole series of watch and learn) on slide rules on watches: https://www.youtube.com/watch?v=RuK_77DEUfw https://www.youtube.com/watch?v=RuK_77DEUfw

jrop 11mo ago
Wow, I really want a slide rule watch now.

xmcp123 11mo ago

In my head: “Oh yeah, I forgot how to use one of those” This article: “lol, is that the depth of your commitment”

tiniuclx 11mo ago

While I'm a bit too young to have used one in school, my dad did give me his slide rule from when he was a student. It's one of my most prized possessions, if only to show how far humanity has come in terms of computing devices.

ghaff 11mo ago
My mother (who ran a biochemistry lab) had a longish one--extra digit of precision I guess. Unfortunately my anti-packrat dad must have chucked it in some move or another. In addition to some cheap student stuff, I think I still have a couple of "normal" professional slide rules but they're not in very good shape if serviceable.

wyclif 11mo ago

My Dad is a retired R&D chemist who worked at the DuPont corporation's Experimental Station. When I was a kid he would bring his old slide rules home from work when he got a new one, and at one point he explained to me how they work but I forgot it all long ago. I still have the slide rules, so this post was a great rabbit hole to go down. In software there's no need for them but I still find them fascinating as a window into how engineers used to get their work done.

ErroneousBosh 11mo ago
> In software there's no need for them... ... but in the Real World they work pretty well for the sort of calculations you might need to do in the field (literally, in a field, sometimes) and don't require batteries, are reasonably waterproof, and reasonably robust if dropped.
- VLM 11mo ago
  The all plastic ones are intrinsically safe in a potentially flammable environment, they don't require power, they're an education in how most engineering materials in the real world have surprisingly wide tolerances so they are far more than accurate enough for most work, for people who learn graphically/visually they are the logical next educational step after counting on fingers. They're pretty useful for teaching amateur people how to implement algorithms. Multiple ways to solve problems, some easier than others, some more efficient than others, with immediate rewards of faster higher accuracy.
  - ErroneousBosh 11mo ago
    > The all plastic ones are intrinsically safe in a potentially flammable environment Never thought of that, and I used to work in an ATEX environment where calculators powered by watch batteries had to be carefully logged and carried across to a "safe" area inside a special (horribly expensive) Peli case.
    - ompogUe 11mo ago

buggi23 11mo ago

To add to this, there's a great set of resources by Joe Pasquale explaining the mathematical theory behind how various functions can be computed by slide rules: * https://cseweb.ucsd.edu/~pasquale/Classes/SlideRule/ https://cseweb.ucsd.edu/~pasquale/Classes/SlideRule/ * Mathematical Foundations of the Slide Rule (PDF): https://cseweb.ucsd.edu/~pasquale/Papers/IM11.pdf https://cseweb.ucsd.edu/~pasquale/Papers/IM11.pdf * Why Does A Slide Rule Work? (PDF): https://cseweb.ucsd.edu/~pasquale/SlideRuleTalkLasVegas14.pdf https://cseweb.ucsd.edu/~pasquale/SlideRuleTalkLasVegas14.pd... The gist of it is: 1. First, define a way to represent any univariate monotonic function f(x) on a graduated scale. (Specifically: select a discrete set of x values, and for each of these x values, place a mark with label x at a distance proportional to (f(x) - f(x_L)) from the left endpoint, where x_L is the leftmost x value.) 2. Then, if we have two such scales f(x) and g(x) that can slide relative to each other, we can compute functions of the form h(x, y, z) = f_inverse(f(x) + g(y) - g(z)). It ends up being surprisingly versatile -- the above resources show how you can compute: 1. Multiplication: x * y using f(x) = log(x) and g(y) = log(y), with z fixed at 1 2. Hypotenuse: sqrt(x^2 + y^2) using f(x) = x^2 and g(y) = y^2, with z fixed at 0 3. Parallel resistors: 1/(1/x + 1/y) using f(x) = 1/x and g(y) = 1/y, with z fixed at +infinity 4. Exponentiation: x^(y/z) using f(x) = log(log(x)) and g(y) = log(y)

jjgreen 11mo ago

In the UK there was a time (late `70s) when slide-rules were allowed in examinations but calculators weren't, no-brainer to learn how to use one just for that. Even better, if you added "(SR)" after your calculations, that indicated that you had used a slide-rule so small errors were permitted.

smusamashah 11mo ago

Here one can play with many slide rules in the browser https://www.sliderulemuseum.com/VirtualSR.shtml https://www.sliderulemuseum.com/VirtualSR.shtml

zeckalpha 11mo ago

Anyone know of a good place to buy a new linear slide rule? I know there's a circular slide rule manufacturer but am not sure if any linears are being made any longer.

PessimalDecimal 11mo ago
They won't be new, but Ebay has a lot of old linear rules.
throw0101c 11mo ago
As per sibling comment: not much of a market for new ones. Would be curious about someone trying to make some: use Kickstarter to gauge interest perhaps? For used, see perhaps "Where to Buy Slide Rules?": * https://www.sliderule.ca/buy.htm https://www.sliderule.ca/buy.htm
evilduck 11mo ago
The used ones aren't that expensive on eBay, especially if you just want a functional one and not a pristine show piece. There's a few 3D print models available for them too, and honestly they are rudimentary technology, you could probably make one with hand tools and patience. I bought a newly manufactured one from ThinkGeek several years ago, some geek-catering company will pop up and supply pent up demand eventually. Curiosity Box fills that niche right now.
argiopetech 11mo ago
Faber-Castell had new-old stock in the mid 20-teens, but they ran out (of stock or patience) around 2016–2018. Picked up a 2/83N for under $100, and I wish I'd gotten more. I'd suggest some of those are on eBay now. Most of my like-new rules came from antique malls, though I've also purchased one from Etsy. Estate sales are occasionally fruitful. As long as they were stored properly (e.g., in a desk drawer, like it seems they mostly were after the electronic calculator took over), they don't degrade. Occasionally you see minor yellowing that is cured by some time in the sun. Carrying cases (often leather) are typically more affected by time. I soak new (to me) leather cases in neatsfoot oil and give them at least a week before putting the rule back. You could make your own with prints from the Slide Rule Museum [0]. 3D printing would make quick work of it, but I'm sure wood or metal units could be accomplished. The cursor benefits from spring loading, They also have some pretty nice simulators [1], if that's your thing. [0] https://sliderulemuseum.com/SR_Scales.shtml https://sliderulemuseum.com/SR_Scales.shtml [1] https://www.sliderulemuseum.com/VirtualSR.shtml https://www.sliderulemuseum.com/VirtualSR.shtml

John-Tony12 11mo ago

[dead]

dboreham 11mo ago

I came up on the cusp of the calculator take-over, so although slide rules were around, and we were taught how to use them in school, I never really used them for any practical purpose. However, since they were the buggy whips of that day, you could pick up nice fancy ones for cheap in stationary stores (also now gone). So somewhere I have a good collection of them.

vjvjvjvjghv 11mo ago

When I was in 5th grade, calculators had become pretty affordable and there was this huge discussion whether kids should learn slide rules or use calculators. At the time it was decided we should learn slide rules and I am happy about this because it gives you some level of number intuition. It reminds me a little of AI now. The question of whether students should use AI will probably soon go away and everybody will use AI. Not sure what the results will be.

ghaff 11mo ago
Calculators went from something that was really expensive to something that was relatively affordable over a very short period of time. In about 1974, a 5-function TI was about $100 (in 1975 currency). By the next year a full scientific TI calculator wasn't much more and no one, at least in engineering school, was still using a slide rule though I brought one to exams as a a backup. By a couple years later, I was able to buy a discontinued HP calculator for about the same.

gcr 11mo ago

Last year I made my own rotary slide rule for playing Balatro, the poker roguelike! My version has a couple interesting properties compared to ordinary linear slide rules: 1. It has three octaves, so it can scale from 1 to 1k or from 1k to 1m, or from 1m to 1b. This is great for calculating point values 2. It's rotary 3. It can be easily 3d-printed! Source code and .STL files here: https://www.printables.com/model/1026662-jimbos-rotary-slide-rule-calculator-for-balatro https://www.printables.com/model/1026662-jimbos-rotary-slide...

agumonkey 11mo ago

These fascinates me, it's one of the highest simplicity / abstraction level ratio I can think of. A few marks well spaced on two bits of wood, and you get "linearized" multiplication. Nicest ~analog computer I can think of :)

bentley 11mo ago

> I missed my slipstick. Dad says that anyone who can’t use a slide rule is a cultural illiterate and should not be allowed to vote. Mine is a beauty—a K&E 20″ Log‐log Duplex Decitrig. Dad surprised me with it after I mastered a ten-inch polyphase. We ate potato soup that week—but Dad says you should always budget luxuries first. I knew where it was. Home on my desk. Robert A. Heinlein, Have Space Suit—Will Travel (1958)