1. Home /
2. Mechanical Calculators /
3. EOS

EOS

The EOS Calculator

The EOS calculator is used in a similar way to a standard pinwheel machine, except that the carriage contains the input register instead of the main register and counter. So instead of moving the output register to the right you move the input register to the left. It uses an oscillating segment mechanism.

It has a capacity of 9 digits of input, an 8-digit counter, and a 13-digit register. The counter does not have a carry mechanism, and displays red digits for subtraction/division. On the right hand side of the machine are a main crank, a small clearing crank for the counter, a clearing knob for the main register (the knob replaces the original small clearing crank), and a knob for selecting whether to clear the input automatically for addition. Note that the automatic clearing should not be used with subtraction as it clears the input before the subtraction can be executed.

The serial numbers for the EOS started at 20000, and my machine has serial number 20994. There seem to be no machines with a higher number so this is one of the last ones ever made, no more than about 1000 were produced.

The oscillating segment mechanism is controlled via various cams on the main axle that is turned by the crank. During an addition, the following steps are performed:

1. The main register shifts forward. This disconnects it from the carry mechanism, resetting any of the carry switches that were tripped during a previous turn of the crank. The main register becomes connected to the input register.
2. The input pins are pushed up to their zero position, causing their toothed segments to rotate the number wheels by the amount they were set to. Any number wheel that rolls over from 9 to 0 will trip a carry switch.
3. The register is shifts backwards, disengaging from the input, and engaging with the carry mechanism.
4. If any carry switch has been tripped, a bulge on the rotating carry drum pushes up against the switch which in turn moves up a toothed segment that rotates the next number wheel, executing the carry. The carry drum has a helical arrangement of these bulges so that carries are performed in right to left order.
5. The input pins are moved back to their original positions.

During subtraction the crank is turned in the opposite direction so most of the steps above are performed in reverse and in opposite order, except that the carries are performed at a different moment through a different set up bulges on the carry drum.

1. The input pins are pushed up to zero.
2. The main register shifts forward. This disconnects it from the carry mechanism, resetting any of the carry switches that were tripped during a previous turn of the crank. The main register becomes connected to the input register.
3. The input pins are pushed down to their original positions, causing their toothed segments to rotate the number wheels backwards by the amount they were set to. Any number wheel that rolls over from 0 to 9 will trip a carry switch.
4. The register is shifts backwards, disengaging from the input, and engaging with the carry mechanism.
5. If any carry switch has been tripped, a bulge on the rotating carry drum pushes down against the switch which in turn moves down a toothed segment that rotates the next number wheel, executing the carry. The carry drum has a helical arrangement of these bulges so that carries are performed in right to left order.

If automatic input clearing is active, the input will be cleared in step 1 so that step 3 then has no effect. The automatic input clearing should therefore never be used with subtraction.

Videos

In this video I demonstrate the EOS calculator.

In this video I show the mechanism of the EOS calculator.

History

Most of the information in this section was taken from an article written and researched by Martin Reese, that was reprinted in his 2002 book "Neue Blicke auf alte Maschinen". That article is available at Rechenmaschinen-illustrated (PDF, 2MB).

Hannovera

Albert Schubode worked at Grimme Natalis on Brunsviga calculators. He left in 1922 and moved to Peine, a town halfway between Brunswick and Hannover. There he co-founded "Hannovera-Rechenmaschinenfabrik, Oventrop, Heutelbeck und Co.". The other founders had experience in manufacturing, metalwork, and marketing, while Schubode was the designer. Production of pinwheel machines started in 1923.

The model A was a standard sized pinwheel machine, capacity 9×8×13, with a carry mechanism in the revolution counter. Model AK was the same but without carry in the counter. The B and BK models were machines with and extra large capacity, namely 20×12×20.

Grimme Natalis aggressively enforced their patent rights, especially relating to the carry mechanism in the counter. This together with the worsening inflationary economy soon made production of pinwheel machines very difficult. To overcome these troubles, Schubode designed a new mechanism that was easier to make. Most parts were stamped metal or cast iron rather than machined parts, and the toothed segment mechanism did not violate the Grimme Natalis patents. This was commercially released in 1926 as the models C and CK.

The model CK did not ease the financial difficulties of the Hannovera company, so further avenues had to be explored. The model CK was used as the basis for a cash register, a till. Despite the moderate success of this cash register, the company was still in financial trouble and ceased trading after about 1929.

Emil Bauer, who sold the Hannovera cash registers in North Germany, bought the remains of the Hannovera company, and set up a new production line in Berlin. From 1933 till 1971 he manufactured Hannovera cash registers, making about 16600 units in that time.

The EOS calculator

The EOS calculator was made by the EOS-Genossenschaft für Fabrikation und Vertrieb von Rechenmaschinen, based in Zürich at Albisstraße 2. Not much is known about this company. The EOS was virtually identical to the Hannovera CK, except that the case has an EOS logo. As with the CK, two carriage shifting mechanisms were available, a simple crank or a more complicated mechanism with a knob. The EOS was made purely for the Swiss market.

Martin Reese speculated that the EOS was made from a batch of Hannovera CK parts that was bought when Hannovera folded in 1929. This cannot be true however since the advertisements for the EOS calculator already appeared in 1927, and the company was present at the Schweizer Mustermesse in 1926. It therefore seems more likely that the EOS was a licensed version of the CK. It is not clear whether any Hannovera parts were used, especially at first, or whether it was completely manufactured by EOS. The case of the calculator states that it was manufactured in Switzerland so at least some of it was made there.

The EOS was manufactured until at least 1929, and probably for a few years after that. In 1934 the company was bought by H.W. Egli AG in order to expand the production capacity for the MADAS Portable calculator.

Overview

Here is a list of all the EOS machines I have been able to find online. Those that use a crank for the carriage shift are marked with an asterisk.
20011; 20185; 20080*; 20662*; 20772; 20994; 20???*.

Articles and Advertisements

The 1925 book Die Rechenmaschinen by Ernst Martin describes the Hannovera machines, including an early version of the model CK that had not been released yet at that time.

The 1930 book Organisations-Lexikon by Walter le Coutre and Walter Thoms has an entry for the EOS calculator.

Here are some adverts for the Hannovera CK and the EOS that I found in various online newspaper archives.

Patents

Here are some other patents relating to the Hannovera.

Links

• Rechner Lexicon has pages about the Hannovera CK and the EOS.
• Rechenmaschinen-Illustrated has pictures of Hannovera calculators and the EOS. It also has the Martin Reese article (2MB pdf).
• Cris Vande Velde has a nice Hannovera CK.
• Rechnen Ohne Strom has an EOS calculator.
• The Arithmeum has a Hannovera CK and an EOS.
• Milestones in Analog and Digital Computing by Herbert E. Bruderer shows that the EOS Genossenschaft was present at the Schweizer Mustermesse from 1926 to 1928.

© Copyright 2021 Jaap Scherphuis, mechcalc a t jaapsch d o t net.