100-Year Old Wagon Wheel Becomes Dynamometer

October 30, 2025 by Lewin Day 8 Comments

If you want to dyno test your tuner car, you can probably find a couple of good facilities in any nearby major city. If you want to do similar testing at a smaller scale, though, you might find it’s easier to build your own rig, like [Lou] did.

[Lou’s] dynamometer is every bit a DIY project, relying on a 100-year-old wagon wheel as the flywheel installed in a simple frame cobbled together from 6×6 timber beams. As you might imagine, a rusty old wagon wheel probably wouldn’t be in great condition, and that was entirely true here. [Lou] put in the work to balance it up with some added weights, before measuring its inertia with a simple falling weight test. The wheel is driven via a chain with a 7:1 gear reduction to avoid spinning it too quickly. Logging the data is a unit from BlackBoxDyno, which uses hall effect sensors to measure engine RPM and flywheel RPM. With this data and a simple calibration, it’s possible to calculate the torque and horsepower of a small engine hooked up to the flywheel.

Few of us are bench testing our lawnmowers for the ultimate performance, but if you are, a build like this could really come in handy. We’ve seen other dyno builds before, too. Video after the break.

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Keep An Eye On Your Air-Cooled Engine

October 23, 2025 by Bryan Cockfield 23 Comments

There was a time, long ago, when passenger vehicles used to be much simpler than they are today. There were many downsides of this era, safety chief among them, but there were some perks as well. They were in general cheaper to own and maintain, and plenty could be worked on with simple tools. There’s perhaps no easier car to work on than an air-cooled Volkswagen, either, but for all its simplicity there are a number of modern features owners add to help them with these antiques. [Pegor] has created his own custom engine head temperature monitor for these vehicles.

As one could imagine with an air-cooled engine, keeping an eye on the engine temperature is critical to ensuring their longevity but the original designs omitted this feature. There are some off-the-shelf aftermarket solutions but this custom version has a few extra features that others don’t. It’s based on a ATMega32u4 microcontroller and will work with any K-type thermocouple, and thanks to its open nature can use a wide array of displays. [Pegor] chose one to blend in with the rest of the instrumentation on this classic VW. The largest issue that needed to be sorted out was around grounding, but a DC-DC converter created an isolated power supply for the microcontroller, allowing the thermocouple to be bonded to the grounded engine without disrupting operation of the microcontroller.

The finished product looks excellent and does indeed blend in to the dashboard more than the off-the-shelf temperature monitor that was in use before. The only thing that is planned for future versions is a way to automatically dim the display when the headlights are on, as [Pegor] finds it a little bright at night. We also enjoy seeing anything that helps these antiques stay on the road more reliably as their modern descendants don’t have any of the charm or engineering of these classics.

Dog Plays Chess On ESP32

December 22, 2024 by Bryan Cockfield 10 Comments

The ESP32 is s remarkably powerful microcontroller, where its dual-core processor and relatively high clock speed can do some impressive work. But getting this microcontroller designed for embedded systems to do tasks that would generally be given to a much more powerful PC-type computer takes a little bit more willpower. Inspired by his dog, [Folkert] decided to program an ESP32 to play chess, a famously challenging task for computer scientists in the past. He calls this ESP32 chess system Dog.

One of the other major limitations of this platform for a task like this is memory. The ESP32 [Folkert] is using only has 320 kB of RAM, so things like the transposition table have to fit in even less space than that. With modern desktop computers often having 32 or 64 GB, this is a fairly significant challenge, especially for a memory-intensive task like a chess engine. But with the engine running on the microcontroller it’s ready to play, either in text mode or with something that can use the Universal Chess Interface (UCI). A set of LEDs on the board lets the user know what’s going on while gameplay is taking place.

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Retrotechtacular: Making Enough Merlins To Win A War

October 25, 2024 by Dan Maloney 16 Comments

From the earliest days of warfare, it’s never been enough to be able to build a deadlier weapon than your enemy can. Making a sharper spear, an arrow that flies farther and straighter, or a more accurate rifle are all important, but if you can’t make a lot of those spears, arrows, or guns, their quality doesn’t matter. As the saying goes, quantity has a quality of its own.

That was the problem faced by Britain in the run-up to World War II. In the 1930s, Rolls-Royce had developed one of the finest pieces of engineering ever conceived: the Merlin engine. Planners knew they had something special in the supercharged V-12 engine, which would go on to power fighters such as the Supermarine Spitfire, and bombers like the Avro Lancaster and Hawker Hurricane. But, the engine would be needed in such numbers that an entire system would need to be built to produce enough of them to make a difference.

“Contribution to Victory,” a film that appears to date from the early 1950s, documents the expansive efforts of the Rolls-Royce corporation to ramp up Merlin engine production for World War II. Compiled from footage shot during the mid to late 1930s, the film details not just the exquisite mechanical engineering of the Merlin but how a web of enterprises was brought together under one vast, vertically integrated umbrella. Designing the engine and the infrastructure to produce it in massive numbers took place in parallel, which must have represented a huge gamble for Rolls-Royce and the Air Ministry. To manage that risk, Rolls-Royce designers made wooden scale models on the Merlin, to test fitment and look for potential interference problems before any castings were made or metal was cut. They also set up an experimental shop dedicated to looking at the processes of making each part, and how human factors could be streamlined to make it easier to manufacture the engines.

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A Wobble Disk Air Motor With One Moving Part

October 22, 2024 by Dan Maloney 17 Comments

In general, the simpler a thing is, the better. That doesn’t appear to apply to engines, though, at least not how we’ve been building them. Pistons, cranks, valves, and seals, all operating in a synchronized mechanical ballet to extract useful work out of some fossilized plankton.

It doesn’t have to be that way, though, if the clever engineering behind this wobbling disk air engine is any indication. [Retsetman] built the engine as a proof-of-concept, and the design seems well suited to 3D printing. The driven element of the engine is a disk attached to the equator of a sphere — think of a model of Saturn — with a shaft running through its axis. The shaft is tilted from the vertical by 20° and attached to arms at the top and bottom, forming a Z shape. The whole assembly lives inside a block with intake and exhaust ports. In operation, compressed air enters the block and pushes down on the upper surface of the disk. This rotates the disc and shaft until the disc moves above the inlet port, at which point the compressed air pushes on the underside of the disc to continue rotation.

[Resetman] went through several iterations before getting everything to work. The main problems were getting proper seals between the disc and the block, and overcoming the friction of all-plastic construction. In addition to the FDM block he also had one printed from clear resin; as you can see in the video below, this gives a nice look at the engine’s innards in motion. We’d imagine a version made from aluminum or steel would work even better.

If [Resetman]’s style seems familiar, it’s with good reason. We’ve featured plenty of his clever mechanisms, like this pericyclic gearbox and his toothless magnetic gearboxes.

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This Go-Kart Rides On A Pallet

April 17, 2024 by Bryan Cockfield 16 Comments

Many beginner woodworkers, looking to offset the introductory costs of starting a hobby, will source their wood from pallets. Generally they’re easily found and can be low or no cost, but typically require a bit of work before they’re usable in a project. [Garage Avenger] is looking to do something a little outside of the box with his pallet project, though. He’s using raw pallets as a chassis for a four-speed go-kart, partially for the challenge and excitement and also to one-up a Pinterest post.

Almost immediately, though, the other major downside of working with pallets arose which is that they’re generally built out of low-grade pine which is soft and flexible. Flexibility is generally not a good thing to have in a vehicle frame so plenty of the important parts of this build were strengthened with steel tubing including the rear axle, steering mounts, and a few longitudinal supports to strengthen the overall frame. After working out some kinks with ordering a few of the wrong parts, and mounting the steering box backwards, it was time to test out the four-speed engine (and brakes) on the the go-kart, making it nearly ready for the road.

To complete the build, some tidying of wiring and fuel lines was done, along with improving some of the non-critical parts of the build like the bucket seat. Of course, adding pallet spoilers and body kit puts the finishing touches on the build and the go-kart is finally ready to tear up the local go-kart track and the less-inspiring Pinterest projects. [Garage Avenger] is no stranger to strange vehicle builds, either. Although it’s a bit out of season for most of our northern hemisphere readers now, his jet-powered street sled is still worth a view.

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Retrotechtacular: The Free Piston Engine

March 4, 2024 by Jenny List 20 Comments

We all know how a conventional internal combustion engine works, with a piston and a crankshaft. But that’s by no means the only way to make an engine, and one of the slightly more unusual alternatives comes to us courtesy of a vintage Shell Film Unit film, The Free Piston Engine, which we’ve placed below the break. It’s a beautiful period piece of mid-century animation and jazz, but it’s also an introduction to these fascinating machines.

We’re introduced to the traditional two-stroke diesel engine as thermally efficient but not smooth-running, and then the gas turbine as smooth but much more inefficient. The free piston engine, a design with opposed pistons working against compressed air springs and combining both compression and firing strokes in a single axis, doesn’t turn anything in itself, but instead works as a continuous supplier of high pressure combustion gasses. The clever part of this arrangement is that these gasses can then turn the power turbine from a gas turbine engine, achieving a smooth engine without compromising efficiency.

This sounds like a promising design for an engine, and we’re introduced to a rosy picture of railway locomotives, ships, factories, and power stations all driven by free piston engines. Why then, here in 2024 do we not see them everywhere? A quick Google search reveals an inordinately high number of scientific review papers about them but not so many real-world examples. In that they’re not alone, for alternative engine designs are one of those technologies for which if we had a dollar for every one we’d seen that didn’t make it, as the saying goes, we’d be rich.

It seems that the problem with these engines is that they don’t offer the control over their timing that we’re used to from more conventional designs, and thus the speed of their operation also can’t be controlled. The British firm Libertine claim to have solved this with their line of linear electrical generators, but perhaps understandably for commercial reasons they are a little coy about the details. Their focus is on free piston engines as power sources for hybrid electric vehicles, something which due to their small size they seem ideally suited for.

Perhaps the free piston engine has faced its biggest problem not in the matter of technology but in inertia. There’s an old saying in the computer industry: “Nobody ever got fired for buying IBM“, meaning that the conventional conservative choice always wins, and it’s fair to guess that the same applies anywhere a large engine has been needed. A conventional diesel engine may be a complex device with many moving parts, but it’s a well-understood machine that whoever wields the cheque book feels comfortable with. That’s a huge obstacle for any new technology to climb. Meanwhile though it offers obvious benefits in terms of efficiency, at the moment its time could have come due to environmental concerns, any internal combustion engine has fallen out of fashion. It’s possible that it could find a life as an engine running on an alternative fuel such as hydrogen or ammonia, but we’re not so sure. If new free piston engines do take off though, we’ll be more pleased than anyone to eat our words.

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