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ReCurta: Our goal is to build the first Curta calculator since 1972 (github.com/daeken)
80 points by 0xdada on Dec 31, 2017 | hide | past | favorite | 26 comments

Marcus Wu designed, 3D-printed, and assembled a 3x scale working Curta calculator. He shared his models and progress on Thingverse at https://www.thingiverse.com/thing:1943171

His YouTube channel includes many videos of the development, assembly, and operation of his calculator. Watch a short demonstration at https://youtu.be/ShFkJgck6Pw

Adam Savage commissioned Marcus to build a copy. Adam unboxes his 3D-printed Curta on YouTube at https://youtu.be/j9uRckJLqLk

I wonder if Adam ever envisioned he would get such a following when he agreed to co-host Mythbusters.

I agree that Mythbusters was important to Adam's progression, but perhaps not just because of the exposure of being a co-host of a popular show. It gave him "fuck you" money and let him know just how many people at large are interested in doing what he does.

Ultimately, Adam has done much more to put him in his current spot than just co-host Mythbusters. He has gone to maker events, cons, and works hard to encourage others to take up the making hobby. He makes tutorials on how to create props freely available. He actively participates in the community, and makes people feel good about themselves - such as unboxing and praising creative efforts.

IMO, Adam is the quintessential example of what is possible when someone no longer has to worry about providing for food and shelter, and can do what they want. Maybe he's the 1% in that regard, but the value provided by his 1% is worth the other 99%.

Well, this is a surprise! ReCurta had been in a bit of a holding period for a while; we did all the drawing translations and the conversions to Solidworks, but then hit a wall when it came to finding a way to actually make the thing.

Last month, I bought a lathe and mill and started teaching myself machining, with the goal of making it myself. It's going to take a long time, but it's pretty amazing making brand new Curta parts.

You may want to look into etching as a method of manufacture of flat pieces of metal as well.

Per https://en.m.wikipedia.org/wiki/Curta “The Curta is a small mechanical calculator”

My grandma has an old Felix artithmometer. AFAIK these are capable of the same things as the Curta but with a less elegant and convenient form factor. It really shows why Curtas are so valuable.

Last time I visited her I used it to estimate sqrt(2) to 3 digits precision. (Result is on the left side https://imgur.com/a/CoEuC)

Also interesting to see previous mentions on HN


such as "Old Calculator Web Museum" | https://news.ycombinator.com/item?id=15821248

Also that Wikipedia page mentions that someone had made a Curta using a 3D printer but because it the low tolerance they had to make very big pieces.

Yes! There's a video on Tested (YouTube) where Adam receives his

The Curta-Test: A 3D-printer to be able to print a functioning Curta in original dimensions

Can anybody estimate how far from that are modern 3D printers in terms of precision?

Current SLA printers could probably do it, they have much better resolution than the typical FDM machines. SLA machines have gotten a lot cheaper in the past few years but the consumables (resin) remain expensive. And FDM printers will probably never really get significantly better than the current state of the art, there's only so much refinement you can make to squirting melted plastic out of a nozzle.

I have a cheap 300USD FDM printer and even on that you can put a 0.2mm nozzle on and use 0.04mm layer height. These sizes however are already not very practical, in addition to being excruciatingly slow to print it does a very poor job of handling any geometry with overhangs in the printed object.

Even the cheaper SLA models (i.e. Wanhao D7 is ~500USD shipped from china and a kickstarter model called SparkMaker is supposedly going to be 250USD) are capable of fantastic levels of detail.

The "original Curta Type I engineering diagrams" can be found here: http://www.vcalc.net/curta_1_engineering_drawings.zip (warning: large file)

Everything produced as part of this project is being released into the public domain. Everyone should be able to inspect, visualize, or even build their own Curta calculator; it shouldn't be fated to forever be an expensive relic on eBay.

Interesting. I wonder if the Chinese might take off with the plans and start making clones, the same way you can now find surprisingly good mechanical watches on AliExpress.

A nice video explaining how they work:


Awesome! I’ve got a great mint condition Curta and it’s simply an amazing piece of engineering. Love to see renewed interest in the design.

Long-shot, but if there's any chance you're in the Bay Area, do you think I could buy you coffee or lunch to check it out some time? I really want to see a Curta in-person.

They have one at the Compute History Museum, although it’s behind glass. It’s worth going here for everything else they have too - try to go when they have an IBM 1401 demo going.

Sorry in LA. Open offer if you're in the area!

Oh man, I've been wanting to buy my dad a curta for years (he started his career in electronics, repairing calculators in the 70s/80s). If something like this pans out might make it affordable.

Did you try and drag it into fictiv to see what they would qoute you for making it :)?


> 2 years ago

Would be worth updating the title to (2015) or (2016)

Why wouldn't you 3d print it?

For the same reason you will not be printing a mechanical watch: the device parts have a resolution that is measured in 1/100ths of a mm, no 3D printer that is even close to affordable can make parts like that. Besides that you will want your parts to be made out of metal powder to be sintered rather than plastic filament which is the material of choice for budget 3D printers.

It's been done, but you run into problems immediately. For one the tolerances on 3D printing are not as tight as you'd like for a device like a Curta, which is why the example I'm aware of printed a replica at a much larger scale. Additionally, 3D printed plastics are typically not very strong, and they change shape over time. This means that the usable lifetime of a 3D printed Curta is typically not very high.

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