Was there life before computer?

calculating instruments before the digital era


The amazing Astacalcolo

Download the printable template and the instructions


in the 50 's the eclectic Italian engineer Aldo Nanni invented this peculiar cal- culator, calling it "Astacalcolo, regolo calcolatore semplificato" (en. simplified calculating ruler).

The original Astacalcolo: its layout does not works!

The plan was to market a popular instrument without slide and cursor, but the Astacalcolo, not easy to use, was never patented and never went into produc- tion. Only a few prototypes were built and, as far as I know, this is the only one survived. Was designed as the first in a series of simplified calculating tools, called "Strumentario", that was never produced either.

Purpose: general computing, other models for specialist calculations were projected but never built. Its peculiarity is to operate with a mix of logarithmic and metric measurements.

Dimensions: 170 mm; 25 mm; 1 mm.

Material: transparent acrylic, it was also planned a metallic model.

Layout and scales:

  • Above: metric scale of 15 centimetres;
  • In the middle: three sets of numbers, used to determine how many digits are to assign to the results of the operations;
  • Below: double log scale.

I think this is one of the first prototypes: the scales are badly misaligned and does not works! I made some corrections on both scales and below you can see it as described in the instructions booklet.

The Astacalcolo corrected

Designer: Ing. Aldo Nanni, born in Bologna, professor of Applied Mechanics at the Ferdinando II University (Naples) in the 50's. I haven't found any other information.

Manufacturer: Aennotecnica. No information are available about this brand, that was never officially registered in Italy.

Remarks: the instruction booklet is full of errors and widely corrected with a red pen.

Use: in spite of its name, calculate with Astacalcolo is difficult. I think the in- ventor's idea was to eliminate the estimating problems that people have with a slide rule through an even more difficult process.

The Astacalcolo has to be used with a sheet of paper and a pencil, these are the steps needed to multiply two numbers:

  1. trace a line on the paper, marking a point in correspondence of the index (the left 1) of the log scale;
  2. identify the two factors on the log scale and mark their position on the line;
  3. turn the ruler upside down and measure the two distances on the metric scale;
  4. sum the two distances an divide the result by 75;
  5. turn upside down and mark the remainder of the division on the line, using the log scale;
  6. turn upside down and measure the remainder on the metric scale: this is the result of the operation.

We got it, but isn't finished yet. Now we have to determine the numbers of digits to assign:

  1. count the total digits of the factors and subtract one;
  2. sum the quotient of the division done before: this is the required result.

There is also a so called "rapid system" to do it using the numbers that are in the middle of the ruler, but it seem to be more complicated. An example, from the amazing booklet that declare "the instructions are written in a simple way in order to be understood by all, you will learn to use it in a few minutes":

Conclusions: during the 50's in Italy only the happy few could use a slide rule, regarded as too difficult from the public. Ing. Nanni tried to make an easier instrument, but his Astacalcolo was unnecessarily complicated to come into production. There was no real need of it: the popular calculators in my country were the nomograms, easier to use. In the magazines of that years was possi- ble found a lot of them, for any imaginable purpose.



Nicola Marras 2008

      

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