# This Minibike Will Land You In Hot Water

The minibike is an American phenomenon which fascinates those of us from countries in which such contraptions are illegal on the road; they seem to deliver bucketloads of low-octane fun in which we are unable to participate. [HowToLou] has one, and as it’s something for use in the Great Outdoors it naturally requires some means of fixing a brew. His solution to the need for a mug of boiling water in out-of-the-way places? A gravity-fed heat exchanger for the exhaust pipe, fed from a reservoir made using an upturned bottle.

As can be seen in the video below the break it’s a simple enough piece of work but surprisingly effective. A piece of small-bore copper tube is passed through a cork into the bottle, then wrapped round a piece of pipe which forms an exhaust The resulting heat exchanger is insulated, the engine started, and the cork loosened just enough to cause a bit of water to flow. The result – a good flow of hot water for that morning coffee.

It may not be the most practical of water heaters, but it’s certainly a bit of fun even if it might not work with all the minibikes we’ve covered.

# Complicated Calculated Solution To 3D-Printed Puzzle

3D printers have made a lot of things possible that were either extremely difficult or downright impossible with traditional tooling. Certain shapes lend themselves to 3D printing, and materials and tooling costs are also generally greatly reduced as well. One thing that may not be touched on as often, though, is their ability to rapidly prototype solutions to complex mathematical problems, in this case taking the form of a 3D printed maze, known as a dodecahedral holonomy maze, with an interesting solution.

The puzzle presents itself as a sphere composed of various inlaid hexagons which form a track for the puzzle piece, or “rook”. The tracks create the maze for the rook to travel, as some paths are blocked when the rook is oriented in certain ways. To solve the puzzle, the player must rotate the rook by moving it around the hexagons in such a way that its path isn’t physically blocked by any of the pegs in order to successfully reach the exit. This might seem like a fun toy to have on its surface, but the impressive thing about this is that the solutions are designed to reduce the likelihood of solving the puzzle with any “brute force” methods while at the same time having more than one path that will reach the exit as well as several bottlenecks that the puzzle solver must traverse as well.

There are actually many possible puzzles that can be produced in this size and shape, and all have predetermined solutions with cleverly chosen paths. This might seem like a lot but when you realize that the entire build from concept to 3D modeling to implementation was done by [Henry Segerman] and a group of other mathematicians at Oklahoma State University it starts to become more clear how the puzzle was so well-designed. In fact, we’ve featured some of his other mathematically-modeled builds in the past as well.

Thanks to [Inne] for the tip!

If you need evidence that our outwardly peaceful little neck of the solar system is actually a dangerous place, look no further than the 40 newly launched Starlink satellites that were just clobbered out of orbit. It seems that the SpaceX launch on February 3 was ill-timed, as it coincided with the arrival of energetic plasma from a solar storm that occurred a few days before. The coronal mass ejection followed an M-class flare on the Sun, which was aimed just right to hit just as the 49-satellite addition to the Starlink constellation was being released. This resulted in an expansion of the upper atmosphere sufficient to increase drag on the newborn satellites — up to 50% more drag than previous launches had encountered. Operators put the satellites into safe mode, but it appears that 40 of them have already met a fiery demise, or soon will. Space is a tough place to make a living.

# No LEDs Required For This Servo-Controlled Larson Scanner

All things considered, it’s pretty easy to get one LED is a strip to light up sequentially, and have it bounce back and forth. Turning that simple animation into a real Larson scanner, with smooth transitions and controlled fade-out, is another thing entirely. And forgetting the LEDs altogether and making a servo-operated Larson scanner is — well, let’s just call it an interesting lesson in hardware abstraction.

The Larson scanner, named after famed TV producer Glen A. Larson for his penchant for incorporating it into shows like Battlestar Galactica and Knight Rider, is actually hard to execute in hardware thanks to the fading tail that follows the lead pixel as it dances back and forth across the display. [Eric Gunnerson] decided to make this and other animation effects easier to achieve with Fade, a custom framework for LED animations that runs on an ESP32.

LED animations are fine, but what about servos? Could Fade be modified to support them? This turned out to be a fairly easy mod thanks to Fade’s architecture and [Eric]’s existing support for non-addressable LEDs via PWM signals. And it was even possible to support more than the 16 PWM channels on an ESP32by adding a UDP connection that puts multiple ESP32s under the control of a central microcontroller.

The video below shows [Eric]’s demo of servo support, with an eight-channel electromechanical Larson scanner. Each “pixel” is a painted ping pong ball swinging back and forth on a hobby servo, and the whole thing sounds just about as awful as you’d expect it to. If you squint just right, the effect looks pretty convincing, but that’s hardly the point. The real story here is [Eric]’s thoughtful architecture, which made the mods easier than starting from scratch.

# Pump Up The Resin

Sometimes the best ideas are simple and seem obvious after you’ve heard them. [Danny] showed us a great idea that fits that description. He uses a peristaltic pump to move resin in and out of his print bed. (Video, embedded below.) Normally, you remove the tank and pour the resin out into a container. With the pump, you can leave the tank where it is and simply pull the resin through a tube. The process is slower than pouring, but not as messy and doesn’t risk damage to your FEP film.

You can also use the pump like a vacuum to clean up resin. According to [Danny], the biggest value is when working with very large printers. He shows a Peopoly Phenom which has a huge tank compared to the other printers he shows in the video.

# Weather Station Predicts Air Quality

Measuring air quality at any particular location isn’t too complicated. Just a sensor or two and a small microcontroller is generally all that’s needed. Predicting the upcoming air quality is a little more complicated, though, since so many factors determine how safe it will be to breathe the air outside. Luckily, though, we don’t need to know all of these factors and their complex interactions in order to predict air quality. We can train a computer to do that for us as [kutluhan_aktar] demonstrates with a machine learning-capable air quality meter.

The build is based around an Arduino Nano 33 BLE which is connected to a small weather station outside. It specifically monitors ozone concentration as a benchmark for overall air quality but also uses an anemometer and a BMP180 precision pressure and temperature sensor to assist in training the algorithm. The weather data is sent over Bluetooth to a Raspberry Pi which is running TensorFlow. Once the neural network was trained, the model was sent back to the Arduino which is now capable of using it to make much more accurate predictions of future air quality.

The build goes into quite a bit of detail on setting up the models, training them, and then using them on the Arduino. It’s an impressive build capped off with a fun 3D-printed case that resembles an old windmill. Using machine learning to help predict the weather is starting to become more commonplace as well, as we have seen before with this weather station that can predict rainfall intensity.

# 3D Printing Rainbows

[The Action Lab] had a very serious technical problem. His daughter wanted to 3D print sparkly unicorns. But how do you make a 3D print sparkly? Turns out, he had used a diffraction grating before to make rainbow-enhanced chocolate.

The method turns out to be surprisingly simple. Using a diffraction grating as a print bed, puts the pattern on the bottom of the 3D print and — thanks to how a diffraction grating works — the 3D print now works like a grating, too.