Why Opposed Piston Internal Combustion Engines Are Great

May 6, 2026 by Maya Posch 67 Comments

Converting the ignition of a fuel-air mixture into usable mechanical energy lies at the core of a dizzying number of internal combustion engines developed over the course of more than century. Although typical piston engines with a cylinder head and valve-train are the most common by far, and even rotary engines are quite well-known, the opposed-piston engine design is significantly more obscure. In a recent video by [driving 4 answers], this type of engine is covered and why it’s actually a pretty nifty ICE design with many benefits.

Achates opposed-piston design. (Source: driving 4 answers, YouTube)

Above all, the design is mechanically far more simple, as it omits all the valves and timing-related hardware of the typical four-stroke ICE. Each ignition event pushes against two pistons at the same time, allowing for more of the kinetic energy to be converted into usable power, as well as enabling largely vibration-free operation in a more compact package, especially in the case of the Asender design that eliminates the second crankshaft of the Achates design. This makes the Asender rather similar to the 1914 Simpson’s design.

Despite these many advantages, opposed-piston engines have mostly led a quiet life in industrial and military applications, including tanks, submarines and airplanes. This is where the video also sees their continued use, but as a 2021 article in Autoweek suggests, we might be seeing more of these engines in everywhere from trucks to cars as well. Even if it’s only in hybrid cars where it would be in a generator role, there are many reasons why this ICE design would fit right into certain roles.

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A Tractor From A Small Town Might Just Be The Catalyst For Ousting Machinery DRM

April 30, 2026 by Jenny List 82 Comments

Odd things sometimes pop up in the feed of a Hackaday scribe, not hacks as such, but stories with a meaning in our community. One such that’s come our way from a variety of sources over the last week features Ursa Ag, a small machinery manufacturer based in Alberta, Canada. The reason they’re in the news is because they have gained bulging order books by taking on the likes of John Deere with a tractor more like the one their customers’ parents bought back in the ’80s or ’90s. It’s a basic machine without much in the way of electronics, and certainly without all the DRM lockdown that has made those big manufacturers so unpopular.

It’s clear that Hackaday isn’t in the business of shilling Canadian tractors, but it should be of interest to readers because it represents an alternative route to challenge the DRM lockdowns than the legal and consumer routes we’ve previously reported on. The Ursa Ag tractor may be as niche Albertan as a Corb Lund CD, but it’s not the tractor itself but the idea which matters. We doubt much sweat will be shed by John Deere execs over a tiny company out on the prairies making a basic spec tractor, but given that Ursa Ag customers are reported as buying them because they have no DRM, the prospect of larger upstart competitors taking note and offering machines without it may cause them some sleep loss. The free market is held up to outsiders as perhaps the most American of ideals, and for it to eventually prove to be the means by which something intended to limit it might be defeated, is sweet justice indeed.

We’ve reported extensively on the Deere tractor saga over the years, but perhaps the best illustration of the self-inflicted damage the brand has suffered through DRM comes in their older products being worth considerably more than their newer ones.

A Sail And Oar Skiff Built From Common Lumber

April 26, 2026 by Bryan Cockfield 13 Comments

For those first venturing into sailing, it can be overwhelming since the experience is thick with jargon and skills that don’t often show up in life ashore. With endless choices, including monohulls versus catamarans, fiberglass versus wood, fractional versus masthead rigs, and sloops versus ketches, a new sailor risks doing something like single-handing a staysail schooner when they should have started on a Bermuda-rigged dinghy without a spinnaker. Luckily, there are some shortcuts to picking up the hobby, like the venerable Sunfish or Hobie ships. It’s also possible to build a simple sailing vessel completely out of materials from a local hardware store, as [Cumberland Rover] has been demonstrating.

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Quirky Electric Car Rides The Rails

April 19, 2026 by Bryan Cockfield 22 Comments

We wouldn’t be surprised if you’d never seen the Spira before. The lightweight three-wheel vehicle is closer to a go-kart than a traditional car, and that’s before you even get to the foam body panels. But even the most niche of products enjoys a certain fandom, and [Matt Spears] certainly seems to love working on his Spira. His latest video documents the new modifications he’s made to the car in an effort to ride it on abandoned railroad tracks in the western United States.

His first attempt at riding the rails worked pretty well but he hit an obstruction at high speed which destroyed his front axle and damaged a few other parts on the vehicle, which gave him a perfect excuse to make some upgrades. He swapped the old rear axle out with one from a go-kart, complete with custom wheels and a new braking system. The drivetrain received an upgrade with a 5 kW electric motor, and although [Matt] planned on casting new wheels for the higher speeds, the chemicals he needed didn’t arrive in time. So, to test the new vehicle he repurposed some old wheels just to get the Spria back out on the tracks.

The test run went so well that [Matt] ended up pushing the vehicle farther than he had ever been on this abandoned rail, including over a questionable trestle and far out into the wilderness. Hopefully we’ll see more videos of [Matt] taking this car to explore even more remote places. In the meantime, take a look at some simpler, non-electric vehicles that are often used to explore abandoned rail lines in California.

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A Better Jogging Stroller

April 1, 2026 by Bryan Cockfield 13 Comments

Although the jogging stroller is a fixture of suburban life, allowing parents the opportunity to get some exercise while letting their young children a chance for some fresh air, it would seem like the designers of these strollers have never actually gone for a jog. Requiring a runner to hold their hands at fixed positions can be incredibly uncomfortable and disrupts most people’s strides and cadence — so [John] attempted to solve the problem after finding one of these strollers on the secondhand market.

While there are some purpose-built strollers that attempt to address these issues, they can be pricey. Rather than shell out for a top-dollar model, [John] got to work with his 3D printer and created a prototype device that allows him to attach the stroller at his waist while leaving his hands free. There were a few problems to overcome here, the first of which would cause the device to buckle under certain loading situations. This was solved with some small pieces of rope which act as flexible bump stops, keeping the hinge mechanism from binding up. Another needed to be solved with practice, which was that it took some time to be able to steer the stroller without using one’s hands.

As an added bonus, [John] also included a system that tracks the distance the stroller has traveled. Using a hall effect sensor and a magnet attached to the wheel, a small microcontroller is able to quickly calculate distance and display it on a tiny screen mounted near the handlebars. Although smartphones are handy, their GPS systems can be surprisingly inaccurate, so a system like this can be a better indicator since it’s being directly measured. All in all, not a bad few upgrades to a secondhand stroller.

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Looking At A Bike Built For The Apocalypse

March 26, 2026 by Fenix Guthrie 17 Comments

So-called bug out cars are a rather silly venture that serve little purpose more than snagging your jumper. The odds of a car working well through a nuclear winter are rather minimal. But what about a bicycle? On paper it’s a better choice, with extreme efficiency, reliability, and runs off whatever sustenance you can find in the barren landscape of a collapsed society. But [Seth] over at Berm Peak proved an apocalypse bike is at least as silly as a bug out car.

While a utilitarian bike fit for a cross-country trek across a nuclear wasteland can certainly be a reasonable venture, this particular bicycle is not that. This three wheeled monstrosity of a bicycle (is it still a bicycle if it has three wheels?) was built by [TOMO] for the Bespoked bike show’s apocalypse buildoff. It placed second among a number of strange bikes with features ranging from pedal driven circular saws to beer keg grills. But this particular example of apocalypse bike is easily the strangest example of the lot.

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Electric Motorcycles Don’t Have To Be Security Nightmares, But This One Was

March 25, 2026 by Tyler August 31 Comments

Once upon a time, they told us we wouldn’t download a car, and they were wrong. Later, Zero Motorcycles stated in their FAQ that you cannot hack an electric motorcycle, a statement which [Persephone Karnstein] and collaborator [Mitchell Marasch] evidently took issue with. Not only can you hack an electric motorcycle, it is — in [Persephone]’s words — a security nightmare.

You should absolutely go over to [Persephone]’s website and check out the whole write-up, which is adapted from a talk given at BSides Seattle 2026. There’s simply way more detail than we can get into here. Everything from “what horridly toxic solvents would I need to unpot this PCB?” to the scripts used in de-compiling and understanding code, it’s all there, and in a lively and readable style to boot. Even if you have no interest in security, or electric motorcycles, you should check it out.

The upshot is that not only were Zero Motorcycles wrong when they said their electric motorcycles could not be hacked, they were hilariously wrong. The problem isn’t the motorcycle alone: it has an app that talks to the electronics on the bike, which take over-the-air (OTA) updates. What about the code linked to the VIN alluded to in that screenshot? Well, it turns out you just need a code structured like a VIN, not an actual number. Oops. By the end of it, [Persephone] and [Mitchell] have taken absolute control of the bike’s firmware, an so have them full control over all its systems.

Why cut the brake lines when you can perform an OTA update that will do the same thing invisibly? And don’t think you can just reset the bike to factory settings to fix it: they thought of this, and the purely-conceptual, never-deployed malware has enough access to prevent that. Or they could just set the battery on fire. That was an option, too, because the battery management system gets OTA updates as well.

To be clear, we don’t have any problem with a motorcycle that’s dependent on electronics to operate. After all, we’ve seen many projects that would meet that definition over the years. But the difference is none of those projects fumbled the execution this badly. Even this 3 kW unicycle, which has a computer for balance control, doesn’t see the need to expose itself. It’s horribly unsafe in very different ways.