Mechanical Calculators

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The Elegance of Mechanical Calculators

A journey through time showcasing the engineering and design of mechanical calculators—devices that marked an era. This gallery features a curated selection of fascinating machines, from early 19th-century models to the more advanced examples of the 20th century. Each image highlights the intricate inner workings, the refinement of levers and gears, and the timeless charm of an age when calculation was a mechanical art. A tribute to human ingenuity that laid the foundation for modern computing.

Napier's Bones Napero's sticks were described in a work published in 1617. They consist of ten rods numbered at the top from 0 to 9 and another rod called a ruler. This is my 3D printed version.

To carry out, for example, the multiplication between 10 and 5, sticks 1, and 0 are placed alongside the ruler.

You then choose the line corresponding to the number 5 on the ruler. To find the result, add diagonally, possibly with a carry; in our case we have the 0 alone (right), then the 5 and the zero (center) and finally another 0 (left). The result, therefore, will be 50.

Now let's do an operation with the carry. Multiplication between 9 and 815

Let's take the row of 9, write 7 - 2+0 - 9+4 - 5

7 - 2 - 13 - 5

<- carryover

7 - 3 - 3 - 5 the carryover (1) is added to 2

Wikipedia Napier's Bones

Mechanical Calculator

Technical Features
Manufacturer: Otis King Year:1960-1962
Info: With a log-scale decade length of 66 inches, the Otis King calculator should be about a full digit more accurate than a 6-inch pocket slide rule. But due to inaccuracies in tic-mark placement, some portions of its scales will read off by more than they should. For example, a reading of 4.630 might represent an answer of 4.632, or almost one part in 2000 error, when it should be accurate to one part in 6000 (66"/6000 = 0.011" estimated interpolation accuracy).

The Geniac brand cylindrical slide rule sold by Oliver Garfield Company in New York was initially a relabelled Otis King; Garfield later made his own, probably unauthorized version of the Otis King (around 1959). The UK patents covering the mechanical device(s) would have expired in about 1941–1942 (i.e. 20 years after filing of the patent) but copyright in the drawings would typically only expire 70 years after the author's.

Mechanical Calculator

Technical Features
Manufacturer: Picket Model: N600-ES Date: 1958-1962
Scales: FRONT SIDE: LL1, LL01, A [B, ST, T, S, C] D, DI, K
REAR SIDE: LL2, LL02, DF [CF, Ln, L, CI, C] D, LL3, LL03
Material: Wood / Celluloid Cursor Metal / Glass
Info: A version of this slide rule is said to have gone to the moon with Buzz Aldrin on Apollo 11. Because of this, it's known sometimes as the "Apollo Rule."

This, of course, has made it very collectible, whereas it becomes hard to find a copy for less than $50...MUCH more if it comes with the original box, case, and documentation.

Mechanical Calculator

Technical Features
Manufacturer: Nestler
Model N ° 0232 Type Rietz Lenght (scales) cm. 25

Material Wood / Celluloid Cursor Metal / Glass

Info: Nestler's Model 23 was a Mannheim-style ruler very popular with professionals in Europe, and its rulers were used by notables such as Wernher von Braun, the Russian rocket pioneer and 'chief designer', Sergei P. Korolev and Albert Einstein.

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