How the Curta Calculator, Intended as a Gift For Hitler, Kept its Inventor Alive During WWII

By Bulent Yusuf on at

Before the arrival of the microchip in the 1970s, a maths boffin didn’t have the luxury of a portable electronic calculator. They carried an abacus, a blackboard, and a bit of chalk on their person at all times. But wait, we stand corrected – for a brief spell in the second half of the twentieth century, there was an alternative, an ingenious device known as the Curta

A gleaming black cylinder with a crank at one end, the Curta is the approximate size and shape of a pepper mill. It's not much use for garnishing a plate of steak and chips, but it is amazing for crunching numbers, and not a single battery is required to power it. This stunning piece of engineering is a mechanical calculator, a stepped drum mechanism containing 605 intricate parts and capable of addition, subtraction, multiplication, division, and even square roots.

To use it is simplicity itself. Numbers are selected from the sliders along the side, and each turn of the crank – which emits a signature purring noise as it goes about its business – will multiply those numbers. Further settings allow more complicated calculations, for example, increasing the power of an individual crank turn so that a single turn multiplies the number value by two, or four, or ten.

Whilst modern technology has rendered the Curta obsolete, they remain highly-sought after as collectible items by mathematicians and connoisseurs of good design – especially those models where the serial number also happens to be a prime number. It’s a maths thing.


A Work of Wartime Genius

The Curta was first conceived by Curt Herzstark in Vienna, Austria in 1938, where he was a technical manager in his father's company. He filed a patent, describing how the device would work in theory, but further work on the design was interrupted when Austria was annexed by Germany that same year. The Nazis forced Herzstark's factory to manufacture measuring devices and distance gauges for the German Army.

This continued until 1943 when Herzstark, the son of a Catholic mother but Jewish father, was himself taken into custody and interned at the Buchenwald concentration camp. His health suffered terribly, and his chances of survival were remote. Then the Nazis learned about his intriguing design for a portable mechanical calculator; they placed him in a workshop with better conditions, and instructed him to make detailed drawings of the device. The intention was to build the Curta and present it to Hitler as a gift.

By the time the camp was liberated in 1945, however, Herzstark was still working on the Curta. There's no doubt the project was critical in keeping him alive through to the end of the war. He hadn't yet managed to take the Curta from a concept to an actual working prototype, but he was now able to draw the plans from memory.

Following the end of World War II, Herzstark finally completed the design of the Curta. With financial backing from the Prince of Liechtenstein, the first models began rolling off the production line in 1948. They were made in Liechtenstein by Contina AG Mauren, and for twenty-five years they were widely considered the best portable calculators available.

Two models were produced. The original Type I Curta had 8 digits of slides, a 6-digit revolution counter, and an 11-digit result counter. The larger Type II Curta, introduced in 1954, had 11 digits of slides, an 8-digit revolution counter, and a 15-digit result counter. An estimated 140,000 Curta calculators were made in total, with 80,000 Type I and only 60,000 of the Type II. The last Curta was manufactured in November 1970.


Cranking out the Answers

During the 1960s, 1970s and even into the 1980s, the Curta was very popular amongst participants in sports car rallies. Whilst it is a delicate piece of machinery, it was much sturdier than the early electronic calculators, and hence better suited to the constant movement and bounces of rally car racing. The Curta was used in time-speed-distance rallies to help calculate the times to checkpoints and distances off-course and the like.

According to the Rallyist’s Guide for the Use and Operation of a Curta Calculator, the Curta enables a driving team to run an entire rally using only one watch and to negotiate any number of speed changes without resetting their odometer. “Completely flexible, the Curta allows you to calculate ahead, and, if the need should arise, to reconstruct all or part of your previous computations. If, for example, you discover that you have changed speed at the wrong point, you can make the necessary corrections in a few seconds.”

Beyond that, the Curta is now largely forgotten. There’s the occasional bidding war on eBay, whenever they surface, or the occasional pop-culture reference on TV or in print. In William Gibson's Pattern Recognition from 2002, there's a chapter entitled 'Math Grenades', where a character mistakes the Curta for a hand grenade when they first see them.

Curta Herzstark died on 27th October 1988. His invention didn’t make him rich; the microchip and the march of progress put paid to that. But more importantly, the Curta saved his life in extremely difficult circumstances. And perhaps also, it represents the last, beautiful gasp of the mechanical age.

Image Credit: redcam

This feature was originally published in October 2011.

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