david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

Solving 2×2=4 is the for any slide rule with the basic D and C scales, including the :

  1. Adjust the wheels (or slide) to put 2 above 1
  2. Keeping the alignment, read 4 over 2.

Not so hard, was it? There's a lot of unnecessary mystification around , but they're simple tools at heart.

You can also try this with the online simulator at https://cardboard-computer.org

Closeup of a homemade circular slide rule showing 4 on the outer D scale above 2 on the inner C scale.

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

I tried a prototype of the with paper glued onto thick, corrugated box cardbord. It's easy to use, but looks messy.

https://cardboard-computer.org

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

prototype no. 2 (advanced version) solving the problem 5×25=75.

I cut the plastic cursor out of some stiff plastic "clamshell" packaging I pulled from the recycling bin.

Lessons from this iteration:

  1. Be more careful drawing the hairline on the cursor next time.
  2. Precise wheel alignment is very important, and I need to cover that more in the DiY instructions.

I'm going to glue these onto cardboard backings.

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

What's a Thursday without more news? 🙂

  1. There is now a home page with a virtual version that you can drag around manually to solve problems.
  2. The basic and advanced exercise pages now have help deeplinks directly to the relevant sections in the guide.

(I learned a bit making touch events work with SVG on mobile devices.)

https://cardboard-computer.org

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

The is looking spiffy with the @creativecommons CC0 Public Domain Mark attached.

https://cardboard-computer.org

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

First working prototype of the , calculating the Answer to Life, the Universe, and Everything.

https://cardboard-computer.org

david_megginson,
@david_megginson@mstdn.ca avatar

The printable templates for the are available now at

https://cardboard-computer.org/templates.html

(There are also PDFs in A4 and US Letter sizes, in case your browser doesn't print properly.)

david_megginson,
@david_megginson@mstdn.ca avatar

There is also a detailed guide, including a very short Quick Start for addition and multiplication:

https://cardboard-computer.org/guide.html#quick-start

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

My DIY circular slide rule side project — an excuse to improve my knowledge of CSS3 transitions and SVG — progresseth apace.

There is now a simple version (just multiplication and subtraction) and an advanced version (square and cube roots). It will also animate the solutions to random basic problems on either.

Coming soon:

  • advanced problems
  • DIY printables and instructions for assembling your own
  • detailed instructions

https://davidmegginson.github.io/cardboard-computer/

electropict, to Futurology
@electropict@mastodon.scot avatar

Continuing the excavation...

I knew this was there, and have been thinking it should go back on a wall for the last year or so.

This is probably (1950s?) the oldest device in the house. (With feadan for scale.) No batteries required.

Formerly used at lews.uhi.ac.uk to teach their use, until these electric things came by.

enobacon, to Sliderules
@enobacon@urbanists.social avatar

Did you get a $15k quote for swap from your central furnace? Are heat load calculators really still this hard to use or are sales bros just not doing the work? We had cardboard that did it in the 80's. LMAO just wait for the coldest day and measure it @TechConnectify 🤣

https://www.youtube.com/watch?v=_hAuKtoRxJI

david_megginson, to Sliderules
@david_megginson@mstdn.ca avatar

Airplane altimeters over-read in colder-than-normal temperatures. If you were on a plane before the digital age and it had to clear a ridge, this is how the flight crew decided whether they were actually high enough to make it.

You don't need to have an E6B analogue flight computer (though it's fun); just hit any key to see the complex steps — one really hoped the navigator hadn't skipped their morning tea or coffee. 🙂

https://e6b.org/calc.html#true_altitude

david_megginson, to analog
@david_megginson@mstdn.ca avatar

Among my hobbies, probably the weirdest one is circular slide rules. I was introduced to them 22 years ago when I started flying lessons, and have since branched out from the E6B to non-aviation circular rules. I like them because

  1. they're analogue, and
  2. they remind us of the correct level of precision.

Additionally, they make great fidget toys.

(See also my little website https://e6b.org/ )

david_megginson,
@david_megginson@mstdn.ca avatar

@nyrath The DC-3 (designed exclusively using ) has never crashed due to a design defect, according to people I talked to at McDonnell-Douglas in the late 1990s. You can't say the same for Boeing's latest aircraft. I suspect there are two reasons for that:

  1. GIGO: People trust the output of computers and skip common-sense sanity checks.
  2. The DC-3 was overbuilt (to be on the safe side), while modern CAD allows companies to cut things closer to the margins for extra $$$.

Name-Not-Applicable, to Sliderules
Name-Not-Applicable avatar

My Pickett N1006-ES. A handy pocket rule!

Name-Not-Applicable, to Sliderules in If you could only have one Slide Rule, which one would it be?
Name-Not-Applicable avatar

True, the space factor is a cool part of Pickett's history.

I have had a pretty close look at that picture at https://tothemoon.ser.asu.edu/gallery/Gemini/12/Hasselblad%20Super-Wide%20Camera%2070%20mm#S66-62984_G12-S

I think that one is a 1006 rather than a 600. I have attached a comparison picture, with an N600, an N1006, and Aldrin's slide rule with its contrast turned up a bit.

It looks like we are looking at the side without the logo, and it looks like the near end of the slide has "Pickett All Metal Slide Rules", which the 600 does not have. And the slide looks like it has CF, CIF, CI, and C scales, and the bottom rail has D and L.

I'm not saying Aldrin didn't take a 600 to the moon. I just don't think that's a 600 in the Gemini XII picture. What do you think?

Image Credits: NASA and International Slide Rule Museum. I used the ISRM pictures because they are clearer than my pictures of my own 600 and 1006.

Name-Not-Applicable, to Sliderules
Name-Not-Applicable avatar

Another of my favorite slide rules, the Aristo No. 867U System Darmstadt. This rule has a pleasant graphical design, and it's a very legible pocket rule. I like that it includes log-log scales, and the P scale is an interesting feature you don't see on a lot of rules. Having the trig scales on the body of the rule adds a wrinkle to using trig scales on a slide rule. You also don't see a BI (1/x²) scale on a lot of rules. This is also me experimenting with Kbin's Microblogging.

Cthululemon, to random

I sure love slide rules. Endless things to relearn about logarithms. Beautiful to behold, pleasing to use and play with. Fun to collect. My favorite more modern one has to be the venerable Pickett N600-ES (it’s been to the moon! Kind of!), which I keep on me much of the time. Here it’s telling me that my voltage regulator was dissipating 5.6 watts before it died.

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