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

March 16, 2026 by Lewin Day 3 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” →

Toy Train Joins The Internet Of Things

September 30, 2025 by Lewin Day 1 Comment

[Zoltan] was developing a workshop on Matter for DEF CON, and wanted to whip up a fun IoT project to go with it. His idea was simple—take a simple toy train, and put it on the Internet of Things.

Speed and low cost were the goals here, with a budget of around $40 and a timeline of one week. The train set sourced for the build was a 43 piece set with a locomotive, one carriage, and a simple oval track, retailing for $25. The toy train got a new brain in the form of an ESP32-C3 DevKitM-1, with the goal of commanding the device over Wi-Fi for ease of use. The microcontroller was set up to control the train’s brushed DC motor with an IRL540 MOSFET. A USB battery bank was initially employed to power the rig, which sat neatly on the train’s solitary carriage. This was later swapped out for a CR123A battery, which did the job for the train’s short duration in service.

Code for the project was simple enough. The ESP32 simply listens for commands via Matter protocol, and turns the train on and off as instructed. [Zoltan] demos the simple interoperability of the Matter protocol by switching the train on and off with Google Home voice commands, and it works perfectly well.

Toy trains aren’t something we typically see included in smart homes, but maybe they should be. If you’re cooking up your own oddball IoT hacks, be sure to let us know on the tipsline!

A Second Chance For The Single Wheel Monorail?

August 16, 2025 by Heidi Ulrich 28 Comments

Lately, this peculiar little single wheel monorail came to our attention. Built by [extraglide1976], all from Meccano. His build started with modest tests: one gyro obviously flopped. Two gyros geared together ran slightly better. But when he adds active gimbal control, things suddenly come to life – the model shudders, catches itself, and carries on. The final green-roofed locomotive, with LEDs signalling ‘system go’, trundles smoothly along a single rail on [extraglide1976]’s deck.

To be fair, it houses a lot of mechanics and engineering which we don’t find in the monorails of today. We do have quite a few monorails in our world, but none of them balance on a single wheel like this one. So, where did this invention derail?

Outside of theme parks, Japan is one of the few countries where monorails are still used as serious urban transport: though Germany’s century-old Wuppertal Schwebebahn, the lesser-known C-Bahn, China’s sprawling Chongqing and Shanghai systems, Malaysia’s Kuala Lumpur line, Brazil’s São Paulo network, the US links in Seattle and Las Vegas, and India’s Mumbai Monorail prove the idea has quietly taken root elsewhere.

The thing you’ll see in nearly all these monorails is how the carriages are designed to clamp onto the tracks. This is of course the most safe option, but it loses out on speed to the ones that sit on top of the tracks, balancing on one wheel. Such a train was actually invented, in 1910, by Louis Brennan. His original monorail promised faster, cheaper transport, even using existing rails. The carriages leaned into turns like a motorbike, without any intervention from the driver. Two counter-rotating gyroscopes kept the carriage upright, cancelling precession forces like a mechanical Jedi trick.

Back then, it failed commercially, but today? With cheap sensors, brushless motors, and microcontrollers, and intelligent software, why not let it make a comeback? It could carry freight through narrow urban tunnels. With high-speed single-rail pods?

Investors killed Brennan’s idea, but we live in a different time now. You could start out with a gimmicky ‘snacks and beer’ highline from your fridge to your garage. Share your take on it in the comments!

Continue reading “A Second Chance For The Single Wheel Monorail?” →

Track Your Circuits: A Locomotive PCB Badge

April 18, 2025 by Matt Varian 7 Comments

This fun PCB from [Nick Brown] features a miniature railroad implemented with 0805-sized LEDs. With an eye towards designing his own fun interactive PCB badge, the Light-Rail began its journey. He thoroughly documented his process, from shunting various late-night ideas together to tracking down discrepancies between the documentation of a part and the received part.

Continue reading “Track Your Circuits: A Locomotive PCB Badge” →

Push Your Toy Train No More, With This Locomotive!

February 11, 2025 by Jenny List 8 Comments

One of the most popular evergreen toys is also one of the simplest, wooden track with push-along trains. We all know the brand name, and savvy parents know to pick up the much cheaper knock-off because the kid won’t know the difference. But a really cool kid shouldn’t have to push their train around by hand, and thus [Lauri] has given the wooden track a real, powered, locomotive.

In the 3D printed chassis goes a small geared motor driving one axle, with an ESP32 and a motor driver taking care of the smarts. Power comes from an 18650 cell, which almost looks like the right scale for a fake steam boiler. The surprise with this train comes in the front axle, this machine has steering. We’re curious, because isn’t the whole point of a train that the track directs it where it needs to go? Or perhaps a little help is required in the absence of a child’s guidance when it comes to points. Either way, with remote control we guess there would be few kids who wouldn’t want one. We certainly do.

The London Underground Is Too Hot, But It’s Not An Easy Fix

December 4, 2024 by Lewin Day 92 Comments

The London Underground is an iconic piece of Victorian era engineering. What started in 1863 quickly became a core piece of infrastructure that would define the modern character of the British capital. It’s grown and changed immensely in the many years that have passed. Sadly, increasing patronage and more trains have created problems that the original designers never envisaged.

Deep in those London tunnels lies an engineering challenge. The Tube is literally cooking itself. Every day, millions of commuters descend into a network of tunnels that have been absorbing heat since the reign of Queen Victoria. Those clay-lined tubes have been soaking up excess thermal energy like a giant underground radiator, and now they’re giving it back with interest. The tunnels are simply too hot, and cooling them down is inordinately difficult.

The Perfect Storm of Thermal Chaos

The Tube’s heat problem isn’t just about one thing gone wrong – it’s about everything gone wrong at once. When Victorian engineers designed these tunnels, cooling wasn’t a major consideration. The tight, compact tunnels were built deep, nestled in the clay beneath London. In the early days, temperatures in the Underground were considered comfortably low.

“The Underground’s the only spot for comfort when the days are hot; it is cooler below.” – London Underground poster, 1926

Originally, the clay surrounding the tunnels sat at around 14°C, acting as a heat sink for the network. However, over the years, with more trains coming and going and more heat pouring in, the temperature has risen. It now typically sits anywhere from 19° to 26 °C. That’s just the earth around the tunnels, though. Air temperatures are worse—hitting as high as 47°C during a 2006 heatwave. The problem has been a continual bugbear of the beloved Tube, with concerns that future heatwaves could see temperatures rise ever higher. Continue reading “The London Underground Is Too Hot, But It’s Not An Easy Fix” →

Train Speed Signaling Adapted For Car

September 11, 2024 by Bryan Cockfield 33 Comments

One major flaw of designing societies around cars is the sheer amount of signage that drivers are expected to recognize, read, and react to. It’s a highly complex system that requires constant vigilance to a relatively boring task with high stakes, which is not something humans are particularly well adapted for. Modern GPS equipment can solve a few of these attention problems, with some able to at least show the current speed limit and perhaps an ongoing information feed of the current driving conditions., Trains, on the other hand, solved a lot of these problems long ago. [Philo] and [Tris], two train aficionados, were recently able to get an old speed indicator from a train and get it working in a similar way in their own car.

The speed indicator itself came from a train on the Red Line of the T, Boston’s subway system run by the Massachusetts Bay Transportation Authority (MBTA). Trains have a few unique ways of making sure they go the correct speed for whatever track they’re on as well as avoid colliding with other trains, and this speed indicator is part of that system. [Philo] and [Tris] found out through some reverse engineering that most of the parts were off-the-shelf components, and were able to repair a few things as well as eventually power everything up. With the help of an Arduino, an I/O expander, and some transistors to handle the 28V requirement for the speed indicator, the pair set off in their car to do some real-world testing.

This did take a few tries to get right, as there were some issues with the power supply as well as some bugs to work out in order to interface with the vehicle’s OBD-II port. They also tried to use GPS for approximating speed as well, and after a few runs around Boston they were successful in getting this speed indicator working as a speedometer for their car. It’s an impressive bit of reverse engineering as well as interfacing newer technology with old. For some other bits of train technology reproduced in the modern world you might also want to look at this recreation of a train whistle.

Continue reading “Train Speed Signaling Adapted For Car” →