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Oct 16, 2026, 11:00 PMSimplifying Slide Rule Calculations with Trig
https://hackaday.com/2026/10/16/simplifying-slide-rule-calculations-with-trig/
Replies
Bill RickerBRicker@fosstodon.orgOct 19, 2026, 12:27 AMc=√(a²+b²) is seemingly hard with a sliderule that won't add, but if we convert it to c=a√(1²+(b/a)²) , adding ONE in the head and sliding the cursor to that location is one slide setting, one cursor setting, done. With a very particular placement of the trig scales (below B, in lieu of C; or aligned fore-and-aft), one can also read angle for simultaneous rect-to-polar, faster than a calculator. (I used this for Traveller ...)
Oct 19, 2026, 12:42 AMThat sounds like it would make a great nomogram. With the advantage that it would have no moving parts, and one can print out a copy for each player.
- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 1:11 AM
Nomograms are great. As are specialist slides.
But the moving part there is turning pages until you find the right monogram.(Ditto specialist slider rules, except rummaging in a drawer.)
Coast Artillery ran on large interconnected wooden slides & nomograms until the cams&gears analog fire control computers described* by Heinlein are fielded (classified, so not in contemporary writings; ditto RADAR tracking & spotting).
- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 1:15 AM
- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 1:21 AM
The great advantage of general purpose computers (slide rules, Hollerith plugboard accounting, Marchant mechanical calculators, Whirlwind, ...) is they can switch from one calculation to another quickly.
But it takes skill and knowledge for the operator to be equally flexible. The specialist sliderules and nomograms provide instructions at point of use for a specific family of calculations, neatly simplifying training at the cost of flexibility.
- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 1:31 AM
@nyrath
When we played Scarp/8Worlds Variant Traveller with 3D starmaps, we could read the first diagonal off the graph paper with an draughtsman's 🔺️📏 scale, and the old EE rect↔️polar trick could add the +-Z to the in-plane radius to get the true* hypoteneuse quicker than entering the numbers into a calculator, as quick as lining the ruler 📏 on a nomogram. Which i may have had, could've made, but finding my sliderules was quicker. - Bill RickerBRicker@fosstodon.orgOct 19, 2026, 1:32 AM
*[ true Jump hypoteneuse *provided* the map was correct that a star system was actually where it was last reported ... which in a post-Imperium return-to-space lower TL campaign wasn't a guarantee!]
FredKiesche 🇺🇦FredKiesche@dice.campOct 19, 2026, 10:52 AM- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 2:11 PM
@FredKiesche @nyrath
"sounds like work" was my opinion of the dirigible campaign which required players to plan & track ballast use instead of a skill roll. (Overlapping cast of players, GMs.)
"Wing it" was probably what GM who drew the map probably expected, he had! (The other GM likely had calculated what he plotted.) But for me, i enjoyed a chance to use my esoteric tool and knowledge. And it was quick. - Bill RickerBRicker@fosstodon.orgOct 19, 2026, 2:15 PM
(Since Jump range was fairly crisp, @nyrath 's suggestion of a nomogram or even a simple chart would have been quite sufficient; what is the max +-Z [1..29] in-range for r [1..29]. The draughtsman's scale 🔺️📏 direct reading the in-plane r greatly facilitated matters either method; Book Traveler suggested leaving it at that, ignoring Z, and inking-in the known feasible Jumps. )
- Bill RickerBRicker@fosstodon.orgOct 19, 2026, 2:19 PM
@FredKiesche @nyrath
Having a central star with jumps in-plane but also up & down, none of which are mutually in-range, makes for a critical nexus. The 'truck stop' planet. Connects the known space sector map with the north and south exploratory maps. - Bill RickerBRicker@fosstodon.orgOct 19, 2026, 3:12 PM
In an exploratory sector (South, Rimward, *and*Trailing, iirc, so far from the beaten-path, an unrecovered sector), we had centuries-old (pre-collapse) Imperial Scout Service notes on the 3 possible intermediate-jump systems; Scout was apparently not impressed, their notes were one word only each:
Water.
Sand.
Ice.
For refueling purposes, we picked Water, as we didn't fancy chopping or melting ice; may have missed discovering the Spice planet? ;-)