Talk:Slide rule

This is the talk page for discussing improvements to the Slide rule article.
This is not a forum for general discussion of the article's subject.

Put new text under old text. Click here to start a new topic.
New to Wikipedia? Welcome! Learn to edit; get help.

Article policies

Find sources: Google (books · news · scholar · free images · WP refs) · FENS · JSTOR · TWL

Archives: 1, 2: 12 months

Slide rule was nominated as a Engineering and technology good article, but it did not meet the good article criteria at the time (July 27, 2013). There are suggestions on the review page for improving the article. If you can improve it, please do; it may then be renominated.

Computing Mid‑importance

	This article is within the scope of WikiProject Computing, a collaborative effort to improve the coverage of computers, computing, and information technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.ComputingWikipedia:WikiProject ComputingTemplate:WikiProject ComputingComputing
Mid	This article has been rated as Mid-importance on the project's importance scale.

Technology

This article is within the scope of WikiProject Technology, a collaborative effort to improve the coverage of technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.TechnologyWikipedia:WikiProject TechnologyTemplate:WikiProject TechnologyTechnology

Mathematics High‑priority

	Mathematics portal This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.MathematicsWikipedia:WikiProject MathematicsTemplate:WikiProject Mathematicsmathematics
High	This article has been rated as High-priority on the project's priority scale.

Popular Culture

♥ In Season 4 of The Avengers, John Steed uses a slide rule... But now I can't figure out which episode! I should have written it down. Damn.

♠ In Season 2 Episode 2 of The Wire, at 31m35s, a slide rule is used by the coroner's assistant to calculate how long 13 murdered girls were able to breathe in a closed shipping container.

Duplex

The entire section "Multiplication" has not one reference, and thus I must assume that it is forbidden "original research". I will post a reference as soon as the original document arrives on my doorstep in a few days. I was taught to use a slide rule in the eighth grade. I used it until my junior year in college, a total of seven years. I was surrounded by classmates, all with slide rules. I every slide rule I ever saw was duplex, as in the image I uploaded. Therefore all of the discussion of "going of scale" is deeply in error. I challenge someone to produce an actual non-duplex slide rule made before 1970. It must be a straight engineering slide rule, not a special purpose one. It must not contain the duplex A and B rules, but only contain the C and D rules. I do not think such a slide rule exists. Nick Beeson (talk) 17:46, 10 August 2022 (UTC)[reply]

Thanks for your observation. The use of "duplex" in that section was incorrect and I have removed the term. As the article states elsewhere, duplex means the slide rule has scales on both sides. You are correct that the inclusion of the A/B scales was pretty much universal. I believe double scales go back to the earliest days. Single sided slide rules ("simplex") were common at the low end of the price range. See e.g. https://www.sphere.bc.ca/test/cheap.html The Multiplication section is somewhat misleading. Proper use of a slide rule to multiply e.g. 2 X 7 does not require using he A/B scales, only the C/D scales would normally be used and that should be explained. Using the A/B scales for this needlessly sacrifices accuracy. And yes, a reference would be helpful.--agr (talk) 19:15, 10 August 2022 (UTC)[reply]

Slide rule scale has a bit to say about this. Thincat (talk) 19:32, 10 August 2022 (UTC)[reply]

Entirely an aside, but I did want to note that in the early days of Wikipedia, there was little attention paid to adding sources and citations. In fact, the 'citation needed' template didn't exist before 2005 - and this article was started in 2001. So I think it's less a matter of 'original research' (even though yes, it is) and more a matter of inertia, so to speak...cheers! Anastrophe (talk) 22:17, 10 August 2022 (UTC)[reply]

Walter Shawlee

Walter Shawlee is described in a February 2024 obit in the NYT as being responsible for a resurgence of interest in slide rules. Maybe someone with access to the article (around 9 Feb.) can see if he is worth mentioning. 02:26, 10 February 2024 (UTC) Kdammers (talk) 02:26, 10 February 2024 (UTC)[reply]

Sub-optimal multiplication example

The 7x2 example is done in a suboptimal way that would have lead to a failing mark in my school in the 1960s. The two-decade scale should only be used when squares are involved. Using it for multiplication leaves you with a suboptimal result (half accuracy resolution vs single decade scale). The correct way to do the multiplication is to use the single decade scale as follows. On the single-decade scale you'll notice that setting top left number 1 on top of bottom number 2 would lead top number 7 to be out of range. So instead we'll set *right* number 1 on top of bottom number 2 and read the result 1.4 from where top number 7 now lands. Using right number 1 on top has a multiplier of 10, so the result is 1.4*10 is approximately 14.0 (any result you get on a slide rule is *always* an approximation; you always need to have a mental image on how many calculations you have in a cascade and how accurate your result is supposed to be). Using the single decade scale gives twice as accurate results as using the two-decade scale. 79.134.103.35 (talk) 11:04, 13 March 2025 (UTC)[reply]

Oh, and the same goes for the 88x20 example, it has exactly the same mistake. This is *not* what the double-decade scale was meant for and it also goes against what was shown in the first example 2x3 where the correct single-decade scale was used. Whoever did these examples obviously did their own research but didn't do it properly. Looking at *any* slide rule instruction manual would have sufficed. A random example: https://www.sliderule.ca/k12-prep-p6-7.jpg says of multiplication: "To multiply two factors, set the index of the C scale (either the left or right end) so that it is directly above one of the factors on the D scale." Note the "left or right end" part, and that C and D scales are single decade scales. 79.134.103.35 (talk) 11:14, 13 March 2025 (UTC)[reply]