[Brian Leach] of the South East London Meccano Club has put an impressive amount of ingenuity into making his pinball machine almost entirely out of Meccano parts. He started in 2013 and we saw an earlier version of the table back in 2014, but it has finally been completed. It has all the trappings of proper pinball: score counter, score multiplier with timeout, standing targets, kickouts, pot bumpers, drop targets, and (of course) flippers and plunger.
The video (embedded below) is very well produced with excellent closeups of the different mechanisms as [Brian] gives a concise tour of the machine. Some elements are relatively straightforward, others required workarounds to get the right operation, but it’s all beautifully done. For example, look at the score counter below. Meccano electromagnets are too weak to drive the numbers directly, so a motor turns all numbers continuously with a friction drive and electromagnets are used to stop the rotation at specific points. Reset consists of letting the numbers spin freely to 9999 then doing a last little push for a clean rollover to zero.
[Mark Gibson] probably has nothing against silicon. He just knows that a lot that can be done with simple switches, relays, and solenoids and wants to share that knowledge with the world. This was made abundantly clear to me during repeat visits to his expansive booth at Denver Mini Maker Faire last weekend.
In the sunlight-filled atrium of the Museum of Nature and Science, [Mark] sat behind several long tables covered with his creations made from mid-century pinball machines. There are about two dozen pieces in his interactive exhibit, which made its debut at the first-ever Northern Colorado Maker Faire in 2013. [Mark] was motivated to build these boards because he wanted to get people interested in the way things work through interaction and discovery of pinball mechanisms.
Most of the pieces he has built are single units and simple systems from pinball machines—flippers, chime units, targets, bumpers, and so on—that he affixed to wooden boards so that people can explore them without breaking anything. All of the units are operated using large and inviting push buttons that have been screwed down tight. Each of the systems also has a display card with an engineering drawing of the mechanism and a short explanation of how it works.
[Mark] also brought some of the original games he has created by combining several systems from different machines, like a horse derby and a baseball game. Both of these were built with education in mind; all of the guts including the original fabric-wrapped wires are prominently displayed. The derby game wasn’t working, but I managed to load the bases and get a grand slam in the baseball game. Probably couldn’t do that again in a million summers.
There are lots of ways to build an encoder, and this is one we haven’t seen before. Not intended in any way to be a practical engineered solution, [HomoFaciens]’ build log and the video below document his approach. Using a rotating disc divided into segments by three, six or eight resistors, the encoder works by adding each resistor into a voltage divider as the disc is turned. An Arduino reads the output of the voltage divider and determines the direction of rotation by comparing the sequence of voltages. More resistors mean higher resolution but decreased maximum shaft speed due to the software debouncing of the wiped contacts. [HomoFaciens] has covered ground like this before with his tutorial on optical encoders, but this is a new twist – sort of a low-resolution continuous-rotation potentiometer. It’s a simple concept, a good review of voltage dividers, and a unique way to sense shaft rotation.
Is this all really basic stuff? Yep. Is it practical in any way? Probably not, although we’ll lay odds that these encoders find their way into a future [HomoFaciens] CNC build. Is it a well-executed, neat idea? Oh yeah.
We’ve heard it said that no one invented the old mechanical Teletype. One fell from the sky near Skokie, Illinois and people just duplicated them. It is true these old machines were similar to a modern terminal. They sent and received serial data using a printer instead of a screen. But inside, they were mechanical Rube Goldbergs, not full of the electronic circuits you’d think of today.
Teletype was the best-known name, but there were other mechanical monster terminals out there. [Carsten] recently took some pictures of his 99 pound Olivetti mechanical terminal. According to him, there’s only one electronic component within: a bistable solenoid that reads the data. Everything else is mechanical and driven with a motor that keeps everything at the right baud rate (110 baud).
Like the Teletype, it is a miracle these things were able to work as well as they did. Lacking a microcontroller, the terminals could respond to an identity request by spinning a little wheel that had teeth removed to indicate which letters to send (TeleType used a similar scheme). Things that are simple using today’s electronics (like preventing two keys pressed at once from being a problem) turned out to be massive design challenges for these old metal monsters.
Turns out that when [Carsten] last fired the terminal up, a capacitor finally gave up its magic smoke. He plans to fix it, though, and as long as it isn’t a mechanical problem, we bet he will.
After seeing an exhibit of an old relay-based computer as a kid, [Simon] was inspired to build a simple two-relay latching circuit. Since then, he’s been fascinated by how relays can function to do computation. He’s come quite a long way from that first latching circuit, however, and recently finished a huge five-year project which uses electromechanical relays to calculate square roots.
The frame of the square root calculator can hold up to 30 identical relay modules, each of which hold 16 relays on PCBs, for a total of 480 relays. The module-based setup makes repair and maintenance a breeze. Numbers are entered into the computer by a rotary dial from an old phone and stored in the calculator’s relay memory. A nixie tube display completes the bygone era-theme of the device and shows either the current number that’s being entered, or the square root of that number as it’s being calculated.
The real magic of this project is that each relay has an LED which illuminates whenever the relay is energized, which shows the user exactly where all of the bits of the machine are going. [Simon] worked on this project from 2009 and recently completed it in 2014, and it has been featured at the San Mateo Maker Faire and at Microsoft Research in Redmond, WA. We’ve seen smaller versions of this before, but never on this scale and never for one specific operation like square roots.
[Chris’] design inspiration came from some research into Victorian Era mechanical looms. He adjusted the concept to build a punch card reader, starting with a capacity of three holes and moving to this design which can read ten holes. It provides just enough bits to address all three of the counters pictured above. Program the computer by inserting a punch card that is the size of a business card and crank away. The video below shows the process from afar… hopefully he’ll post a follow-up video with closer views of each piece in action.
This mechanical version of Donkey Kong uses an Arduino stuffed into an old NES to control Mario jumping over ball bearing ‘barrels.’ The game starts with 12 of these barrels ready to be thrown by our favorite gorilla antagonist, which Mario carefully dodges with the help of a pair of servos.
This is only the first iteration of [Martin]’s mechanical version of Donkey Kong. The next version will keep the clever means of notifying the player if Mario is crushed by a barrel – a simple magnet glued to the back of the Mario piece – and will be shown at the UK Maker Faire next year.
Although [Martin]’s ideas for a mechanical version of Donkey Kong aren’t fully realized with this build, it’s already a build equal to electromechanical Pong.