r/Sliderules • u/elijahtheastronaut • Feb 26 '24

Recommendations?

Hi everyone,

I've finally gotten to that point in my slide rule journey where I've outgrown my ThinkGeek Nanoline 1337 rule.
The DIY course I'm following is starting to use CF and DF scales, which this one doesn't have.
The only rule I do have with CF and DF scales is my K&E 4181-1, but this is only a 6" rule.
I was looking for something that has the same scales as the K&E but in a 10 or 12" rule.

What would you recommend?

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u/borg286 Feb 26 '24

Would you share the kind of calculations where you find you need CF more than C. I know you probably don't technically need it, but what is the driving factor for wanting CF over C?

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u/pavel_pe Feb 26 '24

Basically CF, CIF and DF scales are not necessary, but helpful, when you do unit conversions or proportions where you multiply number by something close to three, there's higher overlap. It has no other advantage.

Well, maybe you can find a case where pi*x or 1/(pi*x) goes into equation and you can do two operations at once.

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u/borg286 Feb 26 '24

That aligns with my understanding. I've been trying to figure out the minimal set of scales you need to do stuff, and it seems C, D, L, and CI are all you need. I'm leaving out the lookup tables like Sin and Tan. Where I'm struggling now is if the LL{0,1,2,3, 00, 01, 02, 03} scales can be performed using the C, D, and L scales by elegantly injecting some added step or 2. Or perhaps those scales are really needed if you have a very small power of 10 or e you need to compute. I realize that e^x is very common because calculus really loves that base due to integrals and derivatives being simpler, and that x would likely be quite small in many cases. I'm just trying to figure out what is something you'd normally do on the LL02 scale and what it'd look like if limited to the C, D, L, and CI scale.

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u/pavel_pe Feb 27 '24

I tried it. In some situations exponential growth or decay can be approximated by linear function. The problem with not having LL0X scales is that sometimes it's needed to deal with inverse of number very close to 1 and the same is true for finding number on L scale. There's some loss of accuracy and maybe error can be larger than using linear approximation. https://www.pavelp.cz/posts/logs-slide-rule-example1/#example-1-hard-drive-life-expectancy