An aluminium top is shown spinning on a plastic disk in front of a tablet showing the text "2:07:49.5"

Self-Powered Top Spins For Hours

January 20, 2026 by Aaron Beckendorf 17 Comments

The meaning of Inception’s ending famously revolves around a top which spins forever in dreams, but in real life comes to a stop like any other top. Any other top, that is, except for [Aaed Musa]’s self-spinning top, which can continuously spin for about two hours before coming to a stop.

The one constraint was that every functional component had to be contained within the top’s shell, and [Aaed]’s first approach was to build a reaction wheel into the top. When a motor accelerates a weighted wheel, conservation of angular momentum applies an equal and opposite torque to the motor. The problem is that motors eventually reach a top speed and stop accelerating, which puts an end to the torque. This is known as saturation, and the only way to desaturate a reaction wheel is to slow it down, which counteracts the originally generated torque. [Aaed] originally planned to mount the motor in a one-way bearing, which would let it bleed off speed without producing torque against the rest of the top, but it was rather choppy in practice.

The solution occurred to [Aaed] while watching the aforementioned final scene, when it occurred to him that the wobbling of a top could actually generate rotation. A prototype proved that an off-center weight rotating at a constant speed did successfully spin the top by rotating the center of mass, and after that, it was a matter of incremental testing and improvement. A higher moment of inertia worked better, as did a lower center of gravity and a tip made from a hard, low-friction silicon nitride ball bearing. He made housings out of both 3D-printed plastic and CNC-milled aluminium, which each contained a tiny brushless motor, an electric speed controller, a microcontroller, and a small rechargeable lithium battery.

If you allow for external power, you can make the top itself the rotor of a motor, and drive it from a base. Alternatively, if you levitate your top in a vacuum, it could spin for longer than recorded history.

Dad Makes Kid’s Balance Bike Into Electric Snow Trike Like A Boss

January 14, 2026 by Tyler August 2 Comments

The balance bikes toddlers are rocking these days look like great fun, but not so great in the snow. Rather than see his kid’s favourite toy relegated to shed until spring, [John Boss] added electric power, and an extra wheel to make one fun-looking snow trike. Like a boss, you might say.

Physically, the trike is a delta configuration: two rear wheels and one front, though as you can see the front wheel has been turned into a ski. That’s not the most stable configuration, but by shifting the foot pegs to the front wheel and keeping the electronics down low, [John] is able to maintain a safe center of gravity. He’s also limiting the throttle so kiddo can’t go dangerously fast– indeed, the throttle control is in the rear electronics component. The kid just has a big green “go” button.

Bit-banging the throttle, combined with the weight of the kiddo up front, creates a strong tendency towards wheel-spin, but [John] fixes that with a some cleverly printed TPU paddles zip-tied to the harbor-freight wheels and tires he’s hacked into use. Those wheels are fixed to a solid axle that’s mounted to flat plate [John] had made up to attach to the bike frame. It’s all surprisingly solid, given that [John] is able to demonstrate the safety factor by going for a spin of his own. We would have done the same.

We particularly like the use of a tool battery for hot-swappable power. This isn’t the first time we’ve seen a kid’s toy get the tool battery treatment, but you aren’t limited to mobile uses. We’ve seen the ubiquitous 18V power packs in everything from fume extractors to a portable powerpack that can even charge a Tesla.

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The best-practice wind tunnel (above) vs a compact version (below)

Optimizing A Desktop, 3D Printed Wind Tunnel

January 12, 2026 by Tyler August 2 Comments

You’ve heard of wind tunnels– get some airflow going over a thingy, put some some smoke on, and voila! Flow visualization. How hard could it be? Well, as always, the devil is in the details and [toast] is down in there with him with this Hot-Wheels sized wind tunnel video.

To get good, laminar flow inside of a wind tunnel, there are important ratios to be followed– the inlet and outlet diameters must relate to the interior size to get the correct slope on the contraction and exhaust cones. You need a flow straightener on both ends. All of it can be easily 3D printed, as [toast] shows, but you have to know those design rules and pay attention to, which [toast] does… this time. One of his “don’t do this” examples in this video is previous build of his where he did not follow all the rules, and the difference is clear.

Now, unless you’re hooked on flow visualizations —guilty— or are a Hot-Wheels aficionado, since that’s what this wind tunnel is sized for, you probably won’t rush to gumroad to buy [toast]’s STLs. On the other hand, if you pay attention to the lessons [toast] has learned in this video you can apply them to wind tunnels of whatever size and construction technique you need, be it cardboard or junk box plastic and get a more stable result.

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Reverse-Engineering The Tamagotchi IR Connection

January 10, 2026 by Maya Posch 7 Comments

The Tamagotchi Connection is a series of Tamagotchi toys that took the original portable pet concept and mixed things up with a wireless connection, which allowed you to interact with the pets of other proud Tamagotchi owners. This wireless connection is implemented using an infrared transceiver, somewhat like IrDA, but as [Zach Resmer] discovered while reverse-engineering this connection, it’s actually what is called ‘Nearly NEC’ by [Natalie Silvanovich], who has a GitHub repository full of related Tamagotchi hacking tools and ROM dumps.

With the protocol figured out, creating a transceiver for low-bitrate infrared communication isn’t particularly hard. In this case, it was implemented using an RP2040 MCU and an appropriate IR LED and receiver pair. This Tamagometer project was also implemented as an app for the Flipper Zero, and a custom PCB called the Pico TamaBadge by [Daniel Weidman].

There’s a web application associated with [Zach]’s project using a Web Serial-enabled browser (i.e. Chrome). The serial protocol is somewhat documented in the patent for the device’s connection feature, which makes it relatively easy to implement yourself.

Making The Fastest LEGO Technic Air-Powered Engine

January 1, 2026 by Maya Posch 1 Comment

Just because LEGO Technic is technically a toy doesn’t mean that you cannot do solid engineering with it, like building air-powered engines. After first building a simple air-powered piston engine, this time around [Jamie’s Brick Jams] sought to not only optimize the engine, but also build a clutch and something to power with said engine.

The four-piston design in radial configuration. (Credit: Jamie's Brick Jams, YouTube) — The four-piston design in radial configuration.

The piston head is one of the handful of 3D printed parts, with the new design featuring twin rubber o-rings as a seal instead of a single big one as in the old design. This incidentally matches the multiple seal rings on an internal combustion engine’s pistons, probably for similar blow-by related reasons. The air hose diameter was also increased from 2 to 3 mm to give the engine a larger volume of air to work with, which along with a new flywheel gave a lot more torque. Next the piston rod length was optimized.

The final radial 4-piston engine turns out to work pretty well, with the clutch engaging smoothly. This was used to drive a DIY generator that turned out to produce about 3 Watt of usable power in its final configuration at 6 V, though it’s admittedly a rather crude generator that could be further optimized. When trying a twin-piston configuration with the highest air pressure before air hoses began to pop off, it hit a dizzying 14,600 RPM.

These aren’t half bad results for some LEGO Technic together with some 3D printed bits, rubber o-rings and some lube.

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All Projections Suck, So Play Risk On A Globe Instead

December 30, 2025 by Tyler August 11 Comments

The worst thing about the getting people together is when everyone starts fighting over their favourite map projection– maybe you like the Watterman Butterfly, but your cousin really digs Gall-Peters, and that one Uncle who insists on defending Mercator after a couple of beers. Over on Instructables [madkins9] has an answer to that problem that will still let you play a rousing game of Risk– which will surely not drag on into the night and cause further drama– skip the projection, and put the game on a globe.

The pieces are from a 1960s version. The abstract tokens have a certain charm the modern ones lack.

Most globes, being cardboard, aren’t amenable to having game pieces cling to them. [madkins9] thus fabricates a steel globe from a pair of pre-purchased hemispheres. Magnets firmly affixed to the bases of all game pieces allow them to stick firmly to the spherical play surface. In a “learn from my mistakes” moment, [madkins] suggests that if you use two pre-made hemispheres, as he did, you make sure they balance before welding and painting them.

While those of us with less artistic flair might be tempted to try something like a giant eggbot, [madkins] was able to transfer the Risk world map onto his globe by hand. Many coats of urethane mean it should be well protected from the clicking or sliding magnet pieces, no matter how long the game lasts. In another teachable moment, he suggests not using that sealer over sharpie. Good to know.

Once gameplay is finished, the wooden globe stand doubles as a handsome base to hold all the cards and pieces until the next time you want to end friendships over imaginary world domination. Perhaps try a friendly game of Settlers of Catan instead.

An HO Model Power Bogie For Not A Lot

December 22, 2025 by Jenny List 8 Comments

For people who build their own model trains there are a range of manufacturers from whom a power bogie containing the motor and drive can be sourced. But as [Le petit train du Berry] shows us in a video, it’s possible to make one yourself and it’s easier than you might think (French language video with truly awful YouTube auto-translation).

At the heart of the design is a coreless motor driving a worm gear at each end that engages with a gear on each axle. The wheelsets and power pickups are off-the-shelf items. The chassis meanwhile is 3D printed, and since this is an ongoing project we see two versions in the video. The V5 model adds a bearing, which its predecessor lacked.

The result is a pretty good power bogie, but it’s not without its faults. The gear ratio used is on the high side in order to save height under a model train body, and in the version without a bearing a hard-wearing filament is required because PLA will wear easily. We’re guessing this isn’t the last we’ll see of this project, so we hope those are addressed in future versions.

We like this project and we think you will too after you’ve watched the video below the break. For more home-made model railway power, how about a linear motor?

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