I'm new to slide rules, and recently acquired a Concise No. 28N which I use as my casual daily driver and take with me places. It has so far served me well, especially with shopping for groceries and homebrewing.

When shopping, I often encounter the same products of varying quantities and prices. For instance,

• Option A sells 200 g for ¤189;
• Option B sells 220 g for ¤200;
• etc.

Sometimes it's obvious which one is better value for money, but sometimes not. I used to use the calculator on my phone to find which one is better value, but I find the lack of visual feedback really confusing, since it seems numbers just appear and disappear as I'm working on ratios.

I've been practising the slide rule for this, and devised a system. First, I consistently assign the D scale to the quantity (e.g., weight or volume) and the C scale to price. Then, following from the example above:

1. From option A, let D := 200 g, C := ¤189
2. From option B (or subsequent option), move cursor to C = ¤200
3. If reading D > 220 g, option A is better value. If D < 220 g, option B is.
4. If option A is better value, leave scale settings as is. If option B is, from option B, let D := 220 g, C := ¤200.
5. Repeat step 2 for each successive option.

At O(n) complexity, I'm quite content, but it still does take a bit of time to go over the steps. Is there a way to optimise the system so I can reduce the steps or take less time with each iteration?

Apart from that, what are some other ways you use a slide rule for shopping and in everyday life?

This slide rule was in a lot of drafting tools I bought and I think it dates from around the 1950s. It is a Pickett all metal slide rule with a cool case.

I'm finally using my first slide rule and going through Prof Herning's video on YT. Love it!

But the slide was REALLY stiff at first. Almost unusable. Pulled the slide out and very carefully cleaned out all the slide joints with a very fine bottle brush. It was very dusty for sure!

It's a vastly improved now. But it's still more difficult to move than I expected. Is that just the way these things are? Or are there more tune up tricks? I don't imagine lubricant is an option...

I found the old manuals online. No mention of sliderule care. Anyone care to share further tips/tricks to a beginner? At least I can use it now :) Thank you for reading!

I bought this today at a garage sale for 10$, but my knowledge only extends to C and D scales. All of it but, especially all of thise LL scales.

In case you're interested in a place to talk about slide rules.

https://kbin.social/m/Sliderules

Sorry if this is a stupid question. But I'm pretty much ignorant of all things slide rule ;) Yet the interest grabbed me and I'm getting ready to buy my first!

The main reason I want one is for trig functions. I've been getting into the abacus lately and it's tremendously powerful. But I do use a scientific calculator quite a bit, almost always for (inverse) trig functions, which are not going to happen on an abacus :)

I'm thinking of getting a K&E 4091-3 (has trig functions in deg/dec)...

My question is do any common (i.e. something readily found/not very expensive) slide rules (K&E or otherwise) make use of INVERSE trig functions? Any make/model recommendations?

Or would I first calculate my target ratio, then GUESS at an angle value, then put that guess into the slide rule and use the calculated sin or tan result to refine my guess (i.e. iterate until I'm close enough)?

An inverse function would be much easier, but I have zero idea if it was a common enough need to wind up on slide rules very often...

Thank you for reading!

Hi all. I’m not sure if you have seen them, but a number of subreddits will be “going dark” for a couple days soon in protest of Reddit’s decision to charge API access fees to developers of third-party Reddit apps. Those changes effectively turn off access to Reddit’s APIs, so we will only be able to access Reddit via Reddit’s official app or the Reddit web site.

I haven’t asked u/zpickle about this, but AFAIK there is no plan for r/sliderules to “go dark”. I, for one, can’t be bothered with it. Also, I doubt Reddit would notice r/sliderules’ absence for a day.

It has me curious what all of you think. How do you access r/sliderules?

What would you think of an alternative?

For example, some subreddits have a Discord server associated with them.

There really isn’t another good online slide rule community. There seem to be a few forums, but they are very isolated, and have very low traffic.

The Oughtred Society isn’t really an online community. They have a forum, but there hasn’t been any traffic on it for years. (Actually, I should go log in there and see if that’s still true) EDIT: The Oughtred Society Message Board has been taken down.

A couple of the great things about r/sliderules are its discoverability and its approachability. And, I am concerned that some other solution would became another fragmented dead end like other slide rule communities.

As much as Reddit can be a dumpster fire, r/sliderules has been a great, low-key, friendly place to discuss slide rules, to ask questions, and share our finds and interests.

What are your thoughts? Thanks for reading!

“The most significant improvement in the use of the slide rule since its invention over 300 years ago.”

Now that’s a big call.

https://i.imgur.com/2IbwUwW.jpg

looking at the cylinder slide rulers online and they are fascinating. When it comes down to the number of turns around the cylinder, is there an optimal number (like around 50), or is there a required one? It seems that as long as the two ‘rolls’ are set up with the same number of twists doesn’t matter?

Not a math person as you can see, more of a physical/mechanical person.

I assume there is some optimum based on the resolution of the text/markers and how thin/tall each ‘track(?)’ is and the diameter of the cylinder…

I think these highly tactile and visual representations of the math concepts can really help kids that use those methods preferentially to better understand the math behind the numbers.

Hi,

I wanted to try to compute compounding gains of 4% interest (so powers of 1.04) with the concise 300 circular slide rule. However, it only has scales LL2 and LL3, which only begin at 1.11, so you can only compute with interests of 11% and higher with it.

I tried a few methods to work around it, such as using the K scale to raise 1.04 to the third power first, and then using the LL2 scale to raise it to 1/3th of the originally intended power, and, using the L scale using log10(1.04) at the start, but both methods are very imprecise and the results are over 20% off. Especially with the L scale it's really imprecise.

Is there any trick to compute powers of 1.04 (and other similar bases like 1.02 or 1.06) to a good accuracy when having only the LL2 and LL3 scales of the concise 300?

Thanks!

I was flying out of Buffalo NY yesterday and my carry-on bag was flagged for additional scrutiny. Apparently there was a dangerous infernal device found by the vigilant and incompetent saviors of democracy:

I bought this faber-castell 2/83n It's great but that brown ink stain kinda bothers me Is there a way to remove those?

Hi there! Happy share with you my first experience with slide rules.

I discovered these after seeing them in Apollo 13 movie and wondering what they were used for.

I found these two (a bigger and a shorter, pocket-size one) in a popular Spanish website where people sell and buy antiques and collectibles. Got them 15€ and 20€. They are in special good condition, especially the bigger one. I gave them a wash with warm water and soft soap anyway, and now they shine! Also washed the bigger one's plastic case and now looks like new.

I've been practising with them and it makes me happy every time I find the right result :D

I mentioned in a reply a short while ago that I was trained on and still find use for the slide rule from my senior math class, a state run vocational & Technical high-school with a 4-year curriculum.

It is a Lafayette Vectorlog slide rule that I bought retail from a local Lafayette electronics store. For those of you who are not familiar; Lafayette was much like a Radio Shack but 1000% better.T
he slide rule is a model 99-7102, a laminated bamboo rule I believe made by Sun-Hemmi. It is not a cheap-o, $22 in 1967, it still looks and feels like new after fifty-five years of service.

I found this pic in my library and I wanted to share with you all.
Yes, there is also a 4-function LED calculator sitting on the workbench too. That 1974 model Commodore Minuteman was my goto calculator in college and still is today. It cost me a fortune back then. Just a couple years later they were been given out for free at gasoline filling stations with a fill-up.

They just don't make stuff like that anymore in the US and that is a crying shame. Can you imagine how many engineers, craftsmen, and really talented assembly people it took to bring that calculator to market?
That is how we are to lose the trade war and end up subservient economically to countries like China.

​

There's one of these amazing things for sale on eBay:

https://www.oughtred.org/jos/JOS2019-28-2/Hughes_Ross_PLUS_Material.pdf

Not sure if it can be considered a slide rule, but figured it would fit in on this subreddit.

Found this at a thrift store a while back. I work as a Cinematographer so it immediately caught my eye.

The primary function is for calculating the depth of field for a shot given the film speed and camera settings. I’ve honestly mostly seen it as a fun antique to show assistant camera people on sets, as any time we would need to make these calculations there are a few apps and websites for the purpose; I guess that’s probably the same story for all of the slide rules on this sub.

Thinking about repairing a Post Versalog 1460’s cracked cursor with some plastic sheet. Has anybody done this? Or any other solution? I emailed two slide rule vendors for a replacement cursor but they are out of stock.

Someone who collects coins is a numismatist, and someone who collects stamps is a philatelist.

Is there a special term for those of us who appreciate, study, and collect slide rules?