Retrotechtacular: The CURTA Mechanical Calculator

September 16, 2014 by Kristina Panos 39 Comments

The CURTA mechanical calculator literally saved its inventor’s life. [Curt Herzstark] had been working on the calculator in the 1930s until the Nazis forced him to focus on building other tools for the German army. He was taken by the Nazis in 1943 and ended up in Buchenwald concentration camp. There, he told the officers about his plans for the CURTA. They were impressed and interested enough to let him continue work on it so they could present it as a gift to the Führer.

This four-banger pepper mill can also perform square root calculation with some finessing. To add two numbers together, each must be entered on the digit setting sliders and sent to the result counter around the top by moving the crank clockwise for one full rotation. Subtraction is as easy as pulling out the crank until the red indicator appears. The CURTA performs subtraction using nine’s complement arithmetic. Multiplication and division are possible through successive additions and subtractions and use of the powers of ten carriage, which is the top knurled portion.

Operation of the CURTA is based on [Gottfried Leibniz]’s stepped cylinder design. A cylinder with cogs of increasing lengths drives a toothed gear up and down a shaft. [Herzstark]’s design interleaves a normal set of cogs for addition with a nine’s complement set. When the crank is pulled out to reveal the red subtraction indicator, the drum is switching between the two sets.

Several helper mechanisms are in place to enhance the interface. The user is prevented from ever turning the crank counter-clockwise. The crank mechanism provides tactile feedback at the end of each full rotation. There is also a lock that disallows switching between addition and subtraction while turning the crank—switching is only possible with the crank in the home position. There is a turns counter on the top which can be set to increment or decrement.

You may recall seeing Hackaday alum [Jeremy Cook]’s 2012 post about the CURTA which we linked to. A great deal of information about the CURTA and a couple of different simulators are available at curta.org. Make the jump to see an in-depth demonstration of the inner workings of a CURTA Type I using the YACS CURTA simulator.

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Hackaday Links May 9th 2012

May 9, 2012 by Jeremy Cook 18 Comments

Homecut – CNC Cutting Directory

So you have a CNC machine that you use as a hobby, but would like to do some actual work on the side? Or maybe you have an idea you’d like made. Homecut is a map directory where you can maybe hook up with the right person.

The Curta Mechanical Calculator

As [leehart] mentioned in our comments section, the Curta mechanical calculator is a truly ingenious piece of engineering. A quick Google search should find all kinds of information on it, but this article could be a good place to start for some mechanical hacking inspiration!

Luxman Amplifier DAC Upgrade

[R. Barrios] wasn’t happy with using the sound card for his HTPC setup, so decided to add a DAC module onto his reciever. The resulting audio quality was very good, and the build came out quite clean. Check it out if you’re thinking of a hack-upgrade to your stereo equipment.

3D Printable Tilt-Shift Adapter

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New 3D Printer on the Block

If you would like to take the plunge into 3D printing, but are looking for somewhere to get a parts kit, the [ORD Bot Hadron 3D Printer] may be worth a look. The build quality looks great, and the price for the mechanical components is quite reasonable at $399. You’ll need to provide the electronics and extruder. Thanks [comptechgeek]!