How I 3D Printed My Own Lego-Compatible Train Bridges

March 16, 2026 by No comments

Lego train sets have been available for decades, now. The Danish manufacturer long ago realized the magic of combining its building block sets with motors and plastic rails to create real working railways for children and adults to enjoy. Over the years, Lego has innovated through several generations of trains, from classic metal-rail systems to the more modern IR and later Bluetooth-controlled versions. The only thing largely missing over all that time, though…? A bridge!

Yes, Lego has largely neglected to build any bridges for its mainstream train lineup. There are aftermarket solutions, and innovative hacks invented by the community, all with their own limitations and drawbacks. This glaring oversight, though, seemed like a perfect opportunity to me. It was time to fire up the 3D printer and churn out a fully-realized Lego rail bridge of my very own.

Bridges Are Hard

I’ve experimented with building Lego rail bridges before, using standard track and household objects like cardboard, books, and beer. Unfortunately, it can be very difficult to support the track evenly at the joints which occur every 150mm, and derailments are common. Credit: author

There’s actually a good reason Lego bridges aren’t a big thing in the company’s own product lineup, beyond a few obscure historical parts. This is probably because they aren’t very practical. Lego locomotives are not particularly strong haulers, nor do they have excellent grip on the rails, and this makes them very poor at climbing even mild grades. Any official Lego bridge would have to be very long with a shallow slope just to allow a train to climb high enough to clear a locomotive on a track below. This would end up being an expensive set that would probably prove unpopular with the casual Lego train builder, even if the diehard enthusiasts loved it. 

There are third-party options available out there. However, most rely on standard Lego track pieces and merely combine them with supports that hold them up at height. This can work in some cases, but it can be very difficult to do cool things like passing a Lego train under a bridge, for example. It can be hard to gain enough height, and the short length of Lego track pieces makes it hard to squeeze a locomotive between supports. Continue reading “How I 3D Printed My Own Lego-Compatible Train Bridges” →

LEGO Machine Plays Tic-Tac-Toe Without Electronics

March 16, 2026 by 2 Comments

Tic-Tac-Toe is a relatively simple game, and one of the few which has effectively been solved for perfect play. The nature of the game made it possible for [Joost van Velzen] to create a LEGO machine that can play the game properly in an entirely mechanical fashion.

The build features no electronics to speak of. Instead, it uses 52 mechanical logic gates and 204 bits of mechanical memory to understand and process the game state and respond with appropriate moves in turn. There are some limitations to the build, however—the game state always begins with the machine taking the center square. Furthermore, the initial move must always be played on one of two squares—given the nature of the game though, this doesn’t really make a difference.

It’s also worth heading over to the Flickr page for the project just to appreciate the aesthetics of the build. It’s styled in the fashion of an 18th-century automaton or similar. It’s also been shared on LEGO Ideas where it’s raised quite a profile.

If you’ve ever wanted to think about computing in a mechanical sense, this build is a great example of how it can be done. We often see some fun LEGO machines around these parts, from massive parts sorters to somewhat-functional typewriters.

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Ask Hackaday: Wired Or Wireless Headphones?

March 16, 2026 by 27 Comments

They say you should never throw out old clothes because they will come back in style one day. Maybe they are right. We noted in a recent BBC post that, apparently, wired headphones are making a comeback. Like many people, we were dismayed when Apple took the headphone jack out of the iPhone and, as [Thomas Germain] notes, even Google eventually ejected the normal headphone jack. (Although, in fairness, most of the Pixel phones we’ve seen come with a pair of USB-C earbuds.)

On the face of it, though, wireless seems to be a good idea. You can get cheap Bluetooth earbuds now, although maybe still not as cheap as wired buds. Sure, they sound terrible, but so do cheap buds. It is a pain to charge them, of course, but not having to untangle wires is a benefit. On the other hand, you never have to charge your wired headphones.

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The IPV4 We Didn’t Get

March 16, 2026 by 10 Comments

If you have ever read science fiction, you’ve probably seen “alternate history” stories. You know, where Europeans didn’t discover the New World until the 19th century, or the ancient Egyptians stumbled upon electricity. Maybe those things happened in an alternate universe. [BillPG] has an alternate history tale for us that imagines IPv6 was shot down and a protocol called IPv4x became prominent instead.

The key idea is that in 1993, the IP-Next-Generation working group could have decided that any solution that would break the existing network wouldn’t work. There is precedent. Stereo records play on mono players and vice versa. Color TV signals play on black and white sets just as well as black and white signals play on color TVs. It would have made perfect sense.

How could this be? The idea was to make everyone who “owns” an IPv4 address the stewards of a 96-bit sub-address block. IPv4x-aware equipment extracts the entire 128-bit address. IPv4-only equipment routes the packet to the controlling IPv4 address. Wasteful? Sure. Most people don’t need 79 octillion addresses. But if everyone has that many, then why not?

The fictional timeline has DNS and DHCP, along with dial-up stacks, changing to accommodate the new addresses. Again, you had to assume some parts of the network were still IPv4-only. DNS would return both addresses, and it was up to you to pick the IPv4x address if you understood it.

Your ISP would probably not offer you the entire extra space. A regional router could handle all traffic for your neighborhood and then direct it to your specific 128-bit address or your pool of addresses, if you have multiple devices. No need for NAT to hide your devices, nor strange router configurations to punch traffic through.

Of course, back in the real world, we have two incompatible systems: IPv4 and IPv6. IPv6 adoption has been slow and painful. We wondered why [BillPG] wrote about this future that never was. Turns out, he’s proposed a gateway that IPv6 hosts can provide to allow access from IPv4-only networks. Pretty sneaky, but we can admire it. If reading all this makes you wonder what happened to IPv5, we wondered that, too.

ATtiny85 Plays The Chrome Dinosaur Game

March 16, 2026 by No comments

If you’ve ever had your internet connection drop out while running Chrome, you’ve probably seen a little dinosaur pop up to tell you what’s going on. You might have then tapped a key and learned that it’s actually a little mini-game built into the browser where you have to hop your intrepid T-rex over a bunch of cactii. [Albert David] is well familiar with this little Easter egg, and set about building a system to automatically play the game for him.

The build uses an Digispark ATtiny85 microcontroller board to run the show. It’s set up to plug in to a PC and enumerate as a USB HID device, so it can spoof the required key presses to play the game. To sense the game state, the device uses a pair of LM393 light-dependent resistor comparator modules. The bottom sensor is used to detect cactus obstacles in the game, while the upper sensor detects flying bird obstacles. Armed with this information, the microcontroller can deliver keypresses at just the right time to jump over cactuses while dodging birds overhead.

[Albert] does a great job of explaining how the project came together in the write-up. There are also useful calibration instructions that indicate how to place the sensors and tweak their thresholds so they trigger reliably and help you net a suitably high score.

Interestingly enough, this isn’t the first time we’ve seen a microcontroller take Chrome’s hidden game for a spin. The game itself has become popular enough that we’ve also seen it ported to other platforms.
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Magnetic-Suspension Hoverboard Is Only 11 Years Late

March 15, 2026 by 17 Comments

Anyone who saw Back to the Future II was disappointed when 2015 rolled around with nary a hoverboard in sight. There have been various attempts to fake it, but none of them quite have the feel of floating about wherever you’d like to go that the movie conveys. The little-known YouTuber [Colin Furze] has a new take on the idea: use magnets. Really big magnets.

If you’re one of [Colin]’s handful of subscribers, then you probably saw his magnetic-suspension bike. We passed on that one, but we couldn’t resist the urge to cover the hoverboard version, regardless of how popular [Colin] might be on YouTube. It’s actually stupidly simple: the suspension is provided by the repulsive force between alarmingly large neodymium magnets. In this case, two are on the base plate that holds the skateboard ‘trucks’, and two are on the wooden ‘deck’ that [Colin] rides upon.

Of course magnetic repulsion is a very unstable equilibrium, so [Colin] had to reduce the degrees of freedom. In his first test, that was with a pair of rods and linear bearings. That way the deck could only move in the z-axis, providing the sensation of hovering without allowing the deck to slide off its magnetic perch. Unfortunately those pins transferred too much vibration from the ground into the deck, ruining the illusion of floating on air.

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Building A Rad Bluetooth Speaker That Didn’t Really Exist

March 15, 2026 by 11 Comments

[Nick] came across an awesome Bluetooth speaker online, only, there was a problem. It didn’t really exist—it was just a render of a device that would be nice to have. Of course, there was an obvious solution—[Nick] just had to build the device for real!

The key to the aesthetic of the build is the external case. [Nick] was able to recreate the rough design of the rendered device in SolidWorks, before having the components produced on a resin 3D printer which provided excellent surface finish. Internally, the Bluetooth audio receiver was cribbed from an old pair of wireless headphones. However, a little more oomph was needed to make the speaker really usable, so [Nick] hooked the audio output up to a small MAX98306 amplifier board and a pair of 3 W speakers. The tiny tactile buttons from the headphone PCB wouldn’t do, either. For a nicer feel, [Nick] hacked in a set of four hall effect keyboard switches to control the basic functions.

The result is a Bluetooth speaker that looks as rad as the rendered unit, only you can actually take it outside and bump some tunes! It recalls us of some fine up-cycling work we’ve seen done to vintage 80s radios in a similar vibe.

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