3D Printed Axial Compressor Is On A Mission To Inflate Balloons

[Let’s Print] has been fascinated with creating a 3D printed axial compressor that can do meaningful work, and his latest iteration mixes FDM and SLA printed parts to successfully inflate (and pop) a latex glove, so that’s progress!

Originally, the unit couldn’t manage even that until he modified the number and type of fan blades on the compressor stages. There were other design challenges as well. For example, one regular issue was a coupling between the motor and the rest of the unit breaking repeatedly. At the speeds the compressor runs at, weak points tend to surface fairly quickly. That’s not stopping [Let’s Print], however. He plans to explore other compressor designs in his quest for an effective unit.

Attaching motor shafts to 3D printed devices can be tricky, and in the past we’ve seen a clever solution that is worth keeping in mind: half of a spider coupling (or jaw coupling) can be an economical and effective way to attach 3D printed things to a shaft.

While blowing up a regular party balloon is still asking too much of [Let’s Print]’s compressor as it stands, it certainly inflates (and pops) a latex glove like nobody’s business.

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Unbricking Trains, Uncovering Shady Behavior

The first clue was that a number of locomotives started malfunctioning with exactly 1,000,000 km on the odometer. And when the company with the contract for servicing them couldn’t figure out why, they typed “Polish hackers” into a search engine, and found our heroes [Redford], [q3k], and [MrTick]. What follows is a story of industrial skullduggery, CAN bus sniffing, obscure reverse engineering, and heavy rolling stock, and a fantastically entertaining talk.

Cutting straight to the punchline, the manufacturer of the engines in question apparently also makes a lot of money on the service contracts, and included logic bombs in the firmware that would ensure that revenue stream while thwarting independent repair shops. They also included “cheat codes” that simply unlocked the conditions, which the Polish hackers uncovered as well. Perhaps the most blatant evidence of malfeasance, though, was that there were actually checks in some versions of the firmware that geofenced out the competitors’ repair shops.

We shouldn’t spoil too much more of the talk, and there’s active investigation and legal action pending, but the smoking guns are incredibly smoky. The theme of this year’s Chaos Communication Congress is “Unlocked”, and you couldn’t ask for a better demonstration of why it’s absolutely in the public interest that hackers gotta hack. Of course, [Daniel Lange] and [Felix Domke]’s reverse engineering of the VW Dieselgate ECU shenanigans, another all-time favorite, also comes to mind.

Machining A Reciprocating Solenoid Engine

The reciprocating engine has been all the rage for at least three centuries. The first widely adopted engine of this type was the steam engine with a piston translating linear motion into rotational motion, but the much more common version today is found in the internal combustion engine. Heat engines aren’t the only ways of performing this translation, though. While there are few practical reasons for building them, solenoid engines can still do this job as well and, like this design from [Maciej Nowak Projects], are worth building just for the aesthetics alone.

The solenoid engine is built almost completely from metal stock shaped in a machine shop, including the solenoids themselves. The build starts by making them out of aluminum rod and then winding them with the help of a drill. The next step is making the frame to hold the solenoids and the bearings for the crankshaft. To handle engine timing a custom brass shutter mechanism was made to allow a set of infrared emitter/detector pairs to send signals that control each of the solenoids. With this in place on the crankshaft and the connecting rods attached the engine is ready to run.

Even though this solenoid engine is more of a project made for its own sake, solenoid engines are quite capable of doing useful work like this engine fitted into a small car. We’ve seen some other impressive solenoid engine builds as well like this V8 from [Emiel] that was the final iteration of a series of builds from him that progressively added more solenoid pistons to an original design.

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3D Printed Engine Gets Carburetor

3D printed materials have come a long way in the last decade or so as printers have become more and more mainstream. Printers can use all kinds of different plastics with varying physical characteristics, and there are even printers now for other materials like concrete and metal. But even staying within the realm of the plastic printer can do a lot of jobs you might not expect. [Camden Bowen] recently 3D printed a single-piston engine which nearly worked, and is back with some improvements to it thanks to a small carburetor.

The carburetor itself isn’t 3D printed (although not from lack of trying) — it’s on loan from a weed eater, and is helping to solve a problem with the fuel-air mixture of his original design. Switching from butane to a liquid fuel also solved some problems as well, and using starter fluid also helped to kick off the ignition. Although it ran for a short period of time over several starts, the valve train suffered some damage with the exhaust valves melting in place to the head. This is actually a problem common to any internal combustion engine like this, especially if the fuel-air mixture is too lean, there’s incomplete combustion, the valves aren’t adjusted properly, or any number of other problems. In this case it seems to have been caused by improper engine timing.

It’s actually noteworthy though that the intake valves weren’t burned, meaning that if the engine can be tuned to allow for complete combustion before the exhaust gasses leave the combustion chamber, the plastic 3D printed head and valve train will likely survive much longer operational periods. We’ll certainly look forward to the next iteration of this engine build to see if that’s the case. If 3D printed piston engines aren’t your speed, though, take a look at this jet engine which uses a 3D printed compressor.

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Two Pots On Your Moped

The fastest motorcycle in the world is not some elite racer piloted across the salt flats at crazy speeds, instead it’s your first bike. Even if it’s a 50 cc moped, no other motorcycle you will own afterwards will give you that same hit as the first time you sit astride it and open the throttle. It has to be admitted though, that 50 cc mopeds are slow if it’s not your first ever ride. Really slow. How can they be made faster? Perhaps an extra cylinder will do the trick. In the video below the break, [LeDan] takes a single cylinder Simson moped engine and turns it into a 2-cylinder model.

The build has something of the machining porn about it, but who doesn’t like to sit down and watch as rough metal is transformed into a machined finish? A second Simson engine is used as a donor, and from it another crankcase section is fabricated. In that foes a newly enlarged crankshaft which we’re supprised not to see being balanced, and on the end of the whole assembly goes the Simson end casting. Two cylinders and their blocks the bolt on top, and the engine is complete. It’s a twin-carb model, and we have to admit curiosity as to whether small two-strokes need their carbs balancing. The result seems to work, though we don’t see it on a bike or at high revs. The kid with this engine really would have the fastest motorcycle in the world — compared to his mates.

As you might expect, this isn’t the first small engine build we’ve seen.

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What Makes Wedge Coils Better Than Round For PCB Motors?

PCB motors are useful things. With coils printed right on the board, you don’t need to worry about fussy winding jobs, and it’s possible to make very compact, self contained motors. [atomic14] has been doing some work in this area, and decided to explore why wedge coils perform better than round coils in PCB motor designs.

[atomic14]’s designs use four-layer PCBs which allow for more magnetic strength out of the coils made with traces. While they’ve tried a variety of designs, like most in this area, they used wedge-shaped coils to get the most torque out of their motors. As the video explains, the wedge layout allows a much greater packing efficiency, allowing the construction of coils with more turns in the same space. However, diving deeper, [atomic14] also uses Python code to simulate the field generated by the different-shaped coils. Most notably, it shows that the wedge design provides a significant increase in field strength in the relevant direction to make torque, which scales positively on motors with higher numbers of coils.

This kind of simulation and optimization is typical in industry. It’s great to see an explainer on real engineering methods on YouTube for everyone to enjoy. Video after the break.

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Jet Engine Powers Tea Kettle

While there are plenty of places around the world to get a great cup of tea, no one has quite burned it into their culture like those in the United Kingdom. While they don’t have the climate to grow the plants themselves, they at least have figured out the art of heating water extremely rapidly in purpose-built electric kettles while the rest of us wait to heat water on our stoves and microwaves. But that’s still not fast enough for some, like [Finlay Shellard], who just completed this jet-powered tea kettle.

[Finlay] took some inspiration cues and parts from another jet engine he had on hand that was powering his toaster. This is a pulse jet design, which is welded together from laser-cut pieces of sheet metal with guides welded in place to allow water to flow around the combustion chamber and exhaust. Pressurized water sits in a reservoir at the top of the engine, and when it is up to temperature, a valve allows it to flow to the engine to heat up. When it has passed the jet engine section, it passes a tea bag holder and then out of a spout at the end of the engine.

A few tests at 100 PSI had the hot tea exiting the engine in a non-linear fashion, so the pressure was reduced. The device now makes tea at incredibly fast speeds, with the only downsides being access to some sort of jet fuel, and also the need for a protective hearing device of some sort. For anyone attempting to do this themselves, take a look at this build which includes a turbocharger design for improved efficiency of the pulse jet itself.

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