DIVISUMMA 24

INSIGHTS

This machine has represented a great development within the economy and the market of electromechanical calculators. Despite the complicated mechanisms inside, it is a machine with which it is easy to interact. It is a simplified and less expensive version of the complete basic project, namely the Tetractys. Thanks to the good price-performance ratio, it was the most sold model by Olivetti (about 6 million units), guaranteeing a considerable diffusion of electronic calculators within the Italian market and international markets.
The Divisumma 24 calculator is part, together with the Elettrosumma 22, the Elettrosumma 24, the Multisumma 24 and the Tetractys, of a series of automatic electric calculators called MC-24. In particular, this series is equipped with a dynamic memory and integrated print register.
The Divisumma consists of a cast iron base, obtained by casting and milling, which gives rigidity to the structure and on which 4 sheet metal flanges are screwed, which act as a support to the main shaft and to the other shafts present. Instead the mechanisms and kinematic mechanisms are in iron and steel, and are mainly made up of levers and moved by cams in synthesized material, whose sliding area is tempered. The assembly was mostly done with screws.
In addition, the Divisumma 24 is equipped with a keyboard reduced to multiple zeros and print of each step of the calculation on a roll of paper through an inked ribbon with a blue and red band. The printing speed, that is the complete rotation of 360 degrees of the main shaft, was brought to 250 accredited cycles per minute and this made it possible to carry out a greater quantity of calculations and in a more rapid manner. The serial number (serial number) of the machine was manually engraved with a pantograph on the lower side of the base.
Il moto è affidato a un motore elettrico di 70 Watt il cui pignone a vite senza fine aziona una corona dentata in tela bachelizzata dotata di frizione, calettata sull’albero principale (diametro di 10 mm), lungo quanto tutta la larghezza della macchina, supportato da 4 boccole in bronzo; su questo, tramite coppie di viti temperate poste a 90 gradi, una mordente e una perforante, sono fissate le varie camme a profilo multiplo in materiale sinterizzato, azionanti a loro volta gli innumerevoli leveraggi. Gli unici cuscinetti sono la coppia di supporto dell’albero motore. La lubrificazione a vita è affidata a 4 tipi di lubrificanti, ognuno ottimizzato per il genere di attrito generato nel punto specifico: olio denso, grasso
a bassa viscosità, grasso infusibile e grasso al bisolfuro di molibdeno Molykote. Per il movimento del carrello delle CR, viene sfruttato il lato opposto dell’albero motore, sul quale è ricavato un secondo pignone azionante una ruota dentata frizionata, coassiale col tamburo tabulatore. La programmazione delle distanze di tabulazione del carrello viene fatta inserendo opportuni fermi metallici nelle asole ricavate.
In 1957 the Divisumma 24 was sold at the price of 325,000 lire. It therefore represented an important investment for a company, considering that the average salary of an employee was around 60000 Lire, and that the cost of a FIAT 500 car was 465.000 Lire.

Technical Data