8 Bit Mechanical Computer Built From Knex

Long before electricity was a common household utility, humanity had been building machines to do many tasks that we’d now just strap a motor or set of batteries onto and think nothing of it. Transportation, manufacturing, agriculture, and essentially everything had non-electric analogs, and perhaps surprisingly, there were mechanical computers as well. Electronics-based computers are far superior in essentially every way, but the aesthetics of a mechanical computer are still unmatched, like this 8-bit machine built from K’nex.

More after the break…

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An image of a light grey graphing calculator with a dark grey screen and key surround. The text on the monochrome LCD screen shows "Input: ENEB Result 1: BEEN Confidence 1: 14% [##] Result 2: Good Confidence 2: 12% [#] Press ENTER key..."

A Neural Net For A Graphing Calculator?

Machine learning and neural nets can be pretty handy, and people continue to push the envelope of what they can do both in high end server farms as well as slower systems. At the extreme end of the spectrum is [ExploratoryStudios]’s Hermes Optimus Neural Net for a TI-84 Plus Silver Edition.

This neural net is setup as an autocorrect system that can take four character inputs and match them to a library of twelve words. That’s not a lot, but we’re talking about a device with 24 kB of RAM, so the little machine is doing its best. Perhaps more interesting than any practical output is the puzzle solving involved in getting this to work within the memory constraints.

The neural net “employs a feedforward neural network with a precisely calibrated 4-60-12 architecture and sigmoid activation functions.” This leads to an approximate 85% accuracy being able to identify and correct the given target words. We appreciate the readout of the net’s confidence as well which is something that seems to have gone out the window with many newer “AI” systems.

We’ve seen another TI-84 neural net for handwriting recognition, but is the current crop of AI still headed in the wrong direction?

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Repairing Vintage Sony Luggable Calculators

You might wonder why you’d repair a calculator when you can pick up a new one for a buck. [Tech Tangents] though has some old Sony calculators that used Nixie tubes, including one from the 1960s. Two of his recent finds of Sony SOBAX calculators need repair, and we think you’ll agree that restoring these historical calculators is well worth the effort. Does your calculator have a carrying handle? We didn’t think so. Check out the video below to see what that looks like.

The devices don’t even use modern ICs. Inside, there are modules of discrete parts encapsulated in epoxy. There isn’t even RAM inside, but there is a delay line memory, although it is marked “unrepairable.”

There is some interesting history about this line of calculators, and the video covers that. Apparently, the whole line of early calculators grew out of an engineer’s personal project to use transistors that were scrapped because they didn’t meet the specifications for whatever application that used them.

The handle isn’t just cosmetic. You could get an external battery pack if you really wanted a very heavy — about 14 pounds (6.3 kilograms) — and large portable calculator. We are sure the $1,000 retail price tag didn’t include a battery.

These machines are beautiful, and it is fun to see the construction of these old devices. You might think our favorite calculator is based on Star Trek. As much as we do like that, we still think the HP-41C might be the best calculator ever made, even in emulation.

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Soviet Calculator Teardown Reveals Similarities And Differences

Tearing down hardware from different parts of the world can be revealing, showing unique parts, techniques, and tricks employed by engineers living in a very different world from our own. To that end, [msylvain59] has been kind enough to give us a look inside the Elektronika MK-26—a calculator built in the former Soviet Union.

There’s lots of interesting stuff to see from the get-go. The oddball button pad is covered in Cyrillic symbols, quite alien to those of us more accustomed to the Latin character set. It’s also constructed somewhat unlike more familiar models from Western-aligned companies like Casio or Commodore. It also rattles when shaken, which doesn’t inspire confidence. Inside, it’s got old-school brown PCBs without the usual green solder mask, a chunky IC in a weird package, and display is via a power-hungry VFD.

It doesn’t look so totally alien inside; much of the construction is pretty typical of the mid-1970s, wherever you went around the world. The most striking differences are more in the graphics and visual design than anything else.

Ultimately, there are reasons why manufacturers around the world tend to converge on similar techniques. Generally, it’s because it’s more economical or easier to do things a certain way. And yet, we still see regional variances because conditions, technologies, and parts availability varies around the world. This teardown highlights that quite clearly.

If you’re just getting a taste for Soviet hardware teardowns, you’ll love this video diving inside a real Soyuz clock.

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Trekulator: A Reproduction Of The 1977 Star Trek Themed Calculator

A recent project over on Hackaday.io from [Michael Gardi] is Trekulator – Where No Maker Has Gone Before.

This is a fun build and [Michael] has done a very good job of emulating the original device. [Michael] used the Hackaday.io logging feature to log his progress. Starting in September 2024 he modeled the case, got his original hardware working, got the 7-segment display working, added support for sound, got the keypad working and mounted it, added the TFT display and mounted it, wired up the breadboard implementation, designed and implemented the PCBs, added some finishing touches, installed improved keys, and added a power socket back in March.

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Casio Calculator Gets New Keyboard

What do you do with a circa 1985 Casio FX-451 calculator with a bad keyboard? Well, if you are [Poking Technology], you transplant the inside of the calculator to a new custom keyboard. There are two videos that cover the process in detail, which you can watch below.

The calculator has a unique design. It looks like a simple calculator in a wallet. But the wallet opens to reveal an extended keyboard with all the scientific features onboard. Unsurprisingly, the membrane keys didn’t survive over four decades. Disassembling the unit was a challenge. Soldering wires to the keyboard lines was further complicated by the fact that some of the lines are on the back of the PCB and pass through to the top under the main IC.

The new keyboard is quite a bit larger than the original, making this more of a desk calculator, but that also means you can use high-quality keys. We’d love to see a 3D printed case to wrap it all up, but the bare PCB look has its charms, too.

If you can’t understand how [Poking] can love a calculator so much, you probably never owned an HP-41C, either. Of course, our retro calculator dreams also include Star Trek.

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A Mechanical Calculator For The Modern Age

There was a brief period through the 1960s into the 1970s when the last word in electronics was the calculator. New models sold for hundreds of dollars, and owning one made you very special indeed. Then the price of the integrated circuit at their heart fell to the point at which anyone could afford one, and a new generation of microcomputers stole their novelty for ever. But these machines were by no means the first calculators, and [What Will Makes] shows us in detail the workings of a mechanical calculator.

His machine is beautifully made with gears hand-cut from plywood, and follows a decimal design in which the rotation of a gear with ten teeth represents the numbers 0 to 9. We’re taken through the mechanical processes behind addition, subtraction, multiplication, and division, showing us such intricacies as the carry lever or a sliding display mechanism to implement a decimal equivalent of a bitwise shift multiplication.

We have to admit to be particularly impressed by the quality of the work, more so because these gears are hand made. To get such a complex assembly to work smoothly requires close attention to tolerance, easy with a laser cutter but difficult by hand. We heartily recommend watching the video, which we’ve placed below the break.

Meanwhile if you’d like more mechanical calculators, take a look at one of the final generation of commercial models.

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