When you create logic circuits using ICs or FPGAs, you can’t easily visualize their operation without special tools. But if you’ve ever seen a mechanical computer (like the Computer History Museum’s Babbage engine) operate, you know you don’t have that problem. Just like it is fascinating to watch a 3D printer or CNC machine, watching mechanical logic gates work can be addictive.
[Anthony] wanted to build some mechanical logic gates and set out designing them using Inkscape. Unlike some common mechanical gate schemes, [Anthony’s] gates use gears to implement the logic operations. He sent the designs off to a laser cutter service and got back parts cut from 3mm acrylic.
Continue reading “Laser Cut Mechanical Logic Gates”
I collect slide rules. You probably know a slide rule is a mechanical calculator of sorts. They usually look like a ruler (hence the name) and have a sliding part (hence the name) and by using logarithms you can multiply and divide easily by doing number line addition and subtraction (among other things).
It is easy to dismiss old technology like that out of hand as being antiquated, but mechanical computing may be making a comeback. It may seem ancient, but mechanical adding machines, cash registers, and even weapon control computers were all mechanical devices a few decades ago and there were some pretty sophisticated techniques developed to make them work. Perhaps the most sophisticated of all was Babbage’s difference engine, even though he didn’t have the technology to make one that actually functioned (the Computer History Museum did though; you should see it operating in person, but this is good too).
Continue reading “Rod Logic and Graphene: Elusive Molecule-Scale Computers”
The world’s leading expert on mechanical computers wasn’t [Charles Babbage]; sure, he could design stuff, but eventually you need to actually build something. We are now graced with the expertise of [Chris Fenton]. He’s built mechanical calculators, a mechanical digital computer, and now a mechanical display inspired by the Jacquard loom.
[Chris] calls his creation the PixelWeaver, and the name isn’t far from the truth; it’s a 32-hook Jacquard style punch card reader that could be mounted over a small loom. Instead of weaving rugs and fabric, the PixelWeaver controls a 6×5 black and white display.
The PixelWeaver is built out of t-slot aluminum, 3D printed parts, and a web of thread to transfer motion from rotating cams to ratchets and pixels. The display itself is heavily inspired by a Lego mechanical display, and the cards that store the data for the display are laser-cut plywood. Interestingly, there’s nothing in this machine that couldn’t have been made 150 years ago; it’s the same technology used to weave rugs, although the necessity of a bitmap display in the Victorian era is a bit questionable.
You can see a few videos of the PixelWeaver below. If you’re wondering what else has come out of [Chris]’ mechanical computing lab, check out his digital computer and Fibonacci calculating set of gears. For a real treat, here’s a machine that will calculate all primes under 1000 in 30 years.
Continue reading “Jacquard Loom Becomes A Display”
Here is a two-part Navy training film from 1953 that describes the inner workings of mechanical fire control computers. It covers seven mechanisms: shafts, gears, cams, differentials, component solvers, integrators, and multipliers, and does so in the well-executed fashion typical of the era.
Fire control systems depend on many factors that occur simultaneously, not the least of which are own ship’s speed and course, distance to a target, bearing, the target’s speed and course if not stationary, initial shell velocity, and wind speed and direction.
The mechanisms are introduced with a rack and pinion demonstration in two dimensions. Principally speaking, a shaft carries a value based on revolutions. From this, a system can be geared at different ratios.
Cams take this idea further, transferring a regular motion such as rotation to an irregular motion. They do so using a working surface as input and a follower as output. We are shown how cams change rotary motion to linear motion. While the simplest example is limited to a single revolution, additional revolutions can be obtained by extending the working surface. This is usually done with a ball in a groove.
Continue reading “Retrotechtacular: Fire Control Computers in Navy Ships”
Back in the 70’s when computers were fairly expensive and out of reach for most people, [David Hagelbarger] of Bell Laboratories designed CARDIAC: CARDboard Illustrative Aid to Computation. CARDIAC was designed as an educational tool to give people without access to computers the ability to learn how computers work.
The CARDIAC computer is a single-accumulator single-address machine, which means that instructions operate on the accumulator alone, or on the accumulator and a memory location. The machine implements 10 instructions, each of which is assigned a 3-digit decimal opcode. The instruction set architecture includes instructions common to simple Von Neumann processors, such as load, store, add/subtract, and conditional branch.
Operating the computer is fairly simple–the cardboard slides guide you through the operation of the ALU and instruction decoder, and the flow chart shows you which stage to go to next. The program counter is represented by a cardboard ladybug which is manually moved through the program memory after each instruction completes.
Even though the CARDIAC is dated and very simplistic, it is still a useful tool to teach how microprocessors work. Although modern processors include multi-stage pipelines, finely-tuned branch predictors, and numerous other improvements, the basic principles of operation remain the same.
Feeling adventurous? Print out your own CARDIAC clone and try writing your first cardboard computer program.
The device that these seamen are standing around is a US Navy targeting computer. It doesn’t use electricity, but relies on mechanical computing to adjust trajectories of the ship’s guns. Setting up to twenty-five different attributes by turning cranks and other input mechanisms lets the computer automatically calculate the gun settings necessary to hit a target. These parameters include speed and heading of both the ship and it’s target, wind speed and bearing, and the location of the target in relation to this ship. It boggles the mind to think of the complexity that went into this computer.
The first of this seven part series can be seen after the break. The collection covers shafts, gears, cams, and differentials. Sounds like it would be quite boring to sit through, huh? But as we’ve come to expect from this style and vintage of training film it packs a remarkable number of simple demonstrations into the footage.
Continue reading “Retrotechtacular: Mechanical targeting computers”