The largest commercial cylindrical slide rule has a scale length of 24m

I love slide rules. The amount of functionality stuffed into such a simple device is beautiful. Also, turning multiplication/division into addition/subtraction with logarithmic scales felt like a genius level hack when I first learned about it, like the fast inverse square.

On a mildly related note, does anyone know if it's possible to construct a logarithmic scale from simple tools? A demonstration I've always wanted to try is building a slide rule "from scratch"

EDIT: by "simple tools" I mean no computers. Pen and paper, compass and straight edge, that sort of thing. I would assume in real life it was made via trial and error on a very large scale and shrunk down optically for a screen print, but I wonder if there's a "precise" way

Re: The largest commercial cylindrical slide rule has a scale length of 24m

#6

Post by eternauta3k » Mon, Nov 16, 2020, 1:43 PM UTC

jedimastert wrote: post #5

I love slide rules. The amount of functionality stuffed into such a simple device is beautiful. Also, turning multiplication/division into addition/subtraction with logarithmic scales felt like a genius level hack when I first learned about it, like the fast inverse square. On a mildly related note, does anyone know if it's possible to construct a logarithmic scale from simple tools? A demonstration I've always wante…

You can plot the lines using matplotlib, then print it and stick it on a piece of wood. There are also slide rule PDFs online.

Re: The largest commercial cylindrical slide rule has a scale length of 24m

#7

Post by jedimastert » Mon, Nov 16, 2020, 1:47 PM UTC

eternauta3k wrote: post #6

jedimastert wrote: post #5

I love slide rules. The amount of functionality stuffed into such a simple device is beautiful. Also, turning multiplication/division into addition/subtraction with logarithmic scales felt like a genius level hack when I first learned about it, like the fast inverse square. On a mildly related note, does anyone know if it's possible to construct a logarithmic scale from simple tools? A demonstration I've always wante…

You can plot the lines using matplotlib, then print it and stick it on a piece of wood. There are also slide rule PDFs online.

Sorry, I meant "from scratch" meaning no computers. Pen and paper, compass and straight edge, that kind of thing.

Re: The largest commercial cylindrical slide rule has a scale length of 24m

#8

Post by Something1234 » Mon, Nov 16, 2020, 2:06 PM UTC

It would help if there was something to show the scale of the slide rule in the pictures.

Re: The largest commercial cylindrical slide rule has a scale length of 24m

#9

Post by Robotbeat » Mon, Nov 16, 2020, 2:13 PM UTC

jedimastert wrote: post #7

eternauta3k wrote: post #6

Earlier quoted context omitted.

You can plot the lines using matplotlib, then print it and stick it on a piece of wood. There are also slide rule PDFs online.

Sorry, I meant "from scratch" meaning no computers. Pen and paper, compass and straight edge, that kind of thing.

Yes. You can calculate logarithms by hand using pen and paper. Then, you can make divisions using the compass and a straight edge until you have a finely divided ruler and then mark logarithms on that ruler based on what you calculated.

After all, the slide rule was invented hundreds of years before the computer.

Re: The largest commercial cylindrical slide rule has a scale length of 24m

#10

Post by jerf » Mon, Nov 16, 2020, 2:33 PM UTC

jedimastert wrote: post #7

eternauta3k wrote: post #6

Earlier quoted context omitted.

You can plot the lines using matplotlib, then print it and stick it on a piece of wood. There are also slide rule PDFs online.

Sorry, I meant "from scratch" meaning no computers. Pen and paper, compass and straight edge, that kind of thing.

"Pen and paper, compass and straight edge,"

Compass and straight edges compute what are called the constructible numbers [1], which have 0, 1, and anything obtainable via addition, subtraction, multiplication, multiplicative inverse, and square roots of positive numbers.

These will not allow you to get to logarithms. You can't avoid having to calculate them numerically; from there you may also create approximations to construct them but you might as well just use a ruler at that point.

You can compute logarithms by hand but they're notoriously tedious even by 19th century standards (and they had a great deal more tolerance for that sort of thing than we do today, for obvious reasons), which is why you could buy books full of them, and that's generally what people used.

[1]: https://en.wikipedia.org/wiki/Constructible_number#Algebraic...