# This POV Clock Combines A Nixie With A Pendulum

Talk about your mixed timekeeping metaphors: there are clocks, and pendulum clocks, and there are Nixie clocks, and persistence of vision clocks. But this is a Nixie pendulum POV clock, and we think it’s pretty cool.

We first spied this on Twitter and were subsequently pleased to learn that [Jayzon Oeve] has posted a more detailed build log over on Hackaday.io. Rather than a moving array of dots to create the characters to display, this uses a single IN-12b Nixie tube at the end of a pendulum. The pendulum is kept moving by a small nudge created by a pulse through a fixed hard drive voice coil acting on a magnet affixed to the bottom of the pendulum — we’ve seen a similar approach used before.

Pretty much all of the electronics are mounted on the pendulum arm, including a Nano, an RTC, and an accelerometer to figure out where in the swing the bob is and when to flash a number on the display. There’s a video below that shows it at work both at full speed and in slow-motion; as always with POV clocks, these things probably look better in person than on video. And while swinging Nixies around like that seems a little dicey, we like the way this turned out.

# The Fine Structure Constant In A Blink

Electronics is really an applied branch of physics, so it isn’t surprising that if you are serious about your electronics, you probably know a little physics, too. If you’ve ever heard the term “fine structure constant” and weren’t entirely sure what it means, [Parth G] wants to explain it to you in about a minute. His video explanation appears below.

You may know that the constant, often represented by α, is approximately 1/137, but what does that mean? The answer relates to the orbit of electrons. You might remember from school that electrons orbit in shells around the nucleus.  That is, an atom might have some electrons in the innermost shell, and more electrons in an outer shell.

# K’nex Pinball Machine Is A Playable Work Of Art

It’s really a wonder that we missed this one, what with all the extra time in front of a computer we’ve had over the last year or so. But better late than never, we always say, so behold, (a little at a time, because there’s quite a lot to look at), [Tyler Bower]’s pinball machine built entirely from K’nex.

Where do we even start? This is a full-size pinball machine, as in 7′ tall, 5′ long, and 3′ wide. [Tyler] estimates that it’s made from about 16,000 pieces, or around 73 pounds of plastic, much of which was obtained locally and is secondhand. Many of those pieces make up the ten drill motor-driven chain lifts in the back — these move the ball through the machine after it goes through one of the track triggers and return it to the playfield in various delightful ways.

Speaking of ways to score, there are nine of them total, and some are harder to get to than others. They all involve some really amazing K’nex movement, and each one uses aluminum foil switches to trigger scoring through a MaKey MaKey.

Of course there’s a multi-ball mode, but our favorite has to be the trap door in the playfield that gets you to the mini pinball game in the upper left, because only the best pinball games have some kind of mini game. Either that, or our favorite is the rotating arm that swings around gracefully and drops the ball on a track. Anyway, all nine elements are explored in the video after the break, which frankly we could watch on repeat. If you’re hungry for more details, there’s quite a bit of info in the description.

The only thing this machine is missing is a tilt switch, but as you’ll see in the video, it would probably get triggered quite often. Is this somehow not cool enough for you? Here’s a slightly bigger K’nex ball machine that doesn’t seem to move as much, but also isn’t a full freaking pinball machine complete with meta game.

# A Trip Down The Vacuum Clamping Rabbit Hole

We all know how easy it is to fall down the rabbit hole,  something that turns a seemingly simple job into an accidental journey of experimentation and discovery. And perhaps nobody is more prone to rabbit-holing than [Matthias Wandel], at least judging by his recent foray into quantitating different techniques for vacuum clamping in the woodshop. (Video, embedded below.)

To understand where this all came from, you’ll have to dial back to [Matthias]’s first video, where he was just trying to make a simple corkboard. In an effort to get even pressure over the whole surface of the board, he came up with a shop-expedient vacuum clamp, made from a sheet of thick plastic, some scraps of wood and clamps, and a couple of vacuums. With the workpiece sandwiched between a smooth, flat table and the plastic sheet, he was able to suck the air out and apply a tremendous amount of force to the corkboard.

The comments to the first video led to the one linked below, wherein [Matthias] aimed to explore some of the criticisms of his approach. Using a quartet of BMP280 pressure sensor breakout boards and a Raspberry Pi, he was able to nicely chart the pressure inside his clamping jig. He found that not only did the sensors make it easy to find and fix leaks, they also proved that adding a porous layer between the workpiece and the vacuum bag wouldn’t likely improve clamping. He was also able to show which of his collection of vacuums worked best — unsurprisingly, the Miele sucked the hardest, although he found that it wasn’t suitable for continuous clamping duty.

We can see a lot of uses for a jig like this, and we really like it when trips down the rabbit hole yield such interesting results. Especially quantitative results; remember [Matthias]’s exploration of basement humidity?

As the channel name implies, [Workshop From Scratch] is building a growing list of tools and machines from scratch. His latest edition is a heavy-duty metal band saw.

As with all his tools, the frame consists of thick welded steel components. The blade runs on a pair of modified belt pulleys and is driven by a motor with a worm gearbox. The blade tension is adjustable, and so are the pair of blade guides. To slowly lower the blade while cutting, [Workshop From Scratch] added a hydraulic piston with an adjustable valve to limit the lowering speed. When it reaches the bottom, a limit switch turns off the motor. The saw is mounted on a heavy steel table and can rotate at the base to cut at different angles. A heavy-duty vise, also built from scratch holds the workpieces securely in place.

Judging by the amount of steel he cuts for his projects, we imagine this saw will be a welcome addition to the shop. It’s impressive what he is able to build with just a drill, angle grinder, and welder. Many of the other tools used in the video, like the magnetic drill press and hydraulic vise are also his handiwork. Continue reading “Homemade Metal Band Saw”

# How To Build A Turbo Car The Cheap, 90s Way

If you want to coax more power out of your car’s engine, a turbocharger is a great way to go about it. Taking waste energy from the exhaust and using it to cram more air into the engine, they’re one of the best value ways to make big gains in horsepower.

However, unlike simpler mods like a bigger exhaust or a mild cam swap, a turbocharger install on a naturally aspirated, fuel-injected engine often requires a complete replacement of the engine management system, particularly on older cars. This isn’t cheap, leaving many to stick to turbocharging cars with factory tuneable ECUs, or to give up altogether. In the 1990s, aftermarket ECUs were even more expensive, leading many to avoid them altogether. Instead, enthusiasts used creative hacks to make their turbo builds a reality on the cheap, and there’s little stopping you from doing the very same today.

# Hackaday Podcast 117: Chiptunes In An RCA Plug, An Arduino Floppy Drive, \$50 CNC, And Wireless Switches

Hackaday editors Mike Szczys and Elliot Williams discuss the latest hacks from around the Internet. 3D-Printed linear rails don’t sound like a recipe for a functional CNC machine but there was one this week that really surprised us. We were delighted by the procedurally generated music from a \$0.03 microcontroller inside of an RCA plug (the clever flexible PCB may be the coolest part of that one). There’s an interesting trick to reverse engineering Bluetooth comms of Android apps by running in a VM and echoing to WireShark. And we look at what the buzz is all about with genetically engineered mosquito experiments taking place down in the Florida Keys.

New this week is a game of “What’s that sound?”. Use the form link on the show notes below to send in your answer, one winner will receive a podcast T-shirt.