In the middle 1870s, the Swedish machinist Johan Fredrik Hellström devised räknemaskin (calculating machine), an interesting rounded adding device, similar to the earlier calculators of Braun, Leupold, and Hahn. The invention was announced in the Swedish press (e.g. in the newspaper Wermlands Läns Tidning on 21 June 1878). The calculating machine of Hellström was patented in 1879 (patent X4593, 1879-07-10, for 9 years, for å räknemaskin af framstäld beskaffenhet). The machine was presented at the Exposition Universelle 1878 in France and was awarded, as the inventor was appointed as a member of the Académie Nationale Agricole, Manufacturiere et Commerciale in Paris.
The calculating machine (räknemaskin) of Hellström (see the nearby photo) was made of brass and walnut. Dimensions: diameter 16.5 cm, height 6.5 cm. Weight: 1.1 kg.
The machine is a decimal and 5-positional device, suitable for the addition of up to 5-digit figures (1–99999). It has tens carry mechanism, so required ten transfers are performed automatically.
The machine has a cylindrical wooden case and outer brass ring with 100 holes (marked with 1 on the nearby image), used to set the one- and ten-decades. A window (2) shows the figures in the outer ring mechanism. (3) is a stop pin and (4) is a stop plate, used to stop the rotation of the ring. (5), (6), and (7) are square shafts, used to set the hundred-decade, thousands-decade, and tens-of-thousands-decade respectively, with pointers (used during the entering of a digit) and windows (to show the result) above the shaft to show the figures.
The outer ring and the square shafts may only be turned clockwise to prevent damage to the inner mechanism.
The square shafts with pointers (5), (6), and (7) can be rotated to the max value of 9, before being stopped by an internal hard stop. After adjustment, the shaft rotates by springs back until the pointer arrives at the original position. (0 or 1)
The adjusted figure remains in the display, transferred by an internal ratchet mechanism.
Let’s make a simple addition, for example, 34367+29435=63802, using the machine.
First, we have to enter the first addend:
1. Set figure 67 in the display window of the one- and ten-decade by putting the stop pin into the hole next to the number 67 and turning the outer ring (1) clockwise, until it stops (stop pin arrives at the stop plate’s groove).
2. Set on the hundreds-decade figure 3 in the display window by turning the square shaft (5) clockwise.
3. Set on the thousands-decade figure 4 in the same way.
4. Set on the tens of thousands-decade the figure 3.
Next, we have to enter the second addend:
1. Put the stop pin in the hole next to the number 35 and turn the outer ring clockwise until it stops. The one and ten decades are added.
2. Add in the hundreds-decade by turning the square shaft (5) clockwise the figure 4. The figure is visible on the pointer.
3. Add in the thousands-decade and tens of thousands-decade in the same way—the numbers 9 and 2.
Now, in the windows, the final result (63802) will be displayed.
Biography of Johan Hellström
Little is known about the inventor of this calculating machine. Johan Fredrik Hellström was born on 3 November 1832, in Helgona, a village nearby Nyköping, Sweden. He was the son of Carl Hellström and his second wife Anna Catharina Hellström (Malmberg). In 1857 Johan Hellström moved to Nyköping, where he lived until his death on 19 May 1921. He spent also some time in Stockholm. Hellström’s occupation was listed as machinist and fabricant.