A Stirling Engine is a heat engine, powered by the expansion and contraction of a working fluid (such as air) which is heated and cooled in a cycle. In the video [Tom] begins by demonstrating the Stirling Engine with some model engines and explains the role of the displacer piston. His target power output for his bike engine is 150 watts (about 0.2 horsepower) which is enough power to cycle at about 15 mph (about 24 km/h). After considering a CPU heatsink as the cooling system he decided on water cooling instead.
Do you feel nostalgia for a childhood novelty toy that had potential but ultimately fell short of its promise? Do you now have the skills to go make a better version of that toy to satisfy your long-held craving? [ExpensivePlasticCrap] does and has set off on a mission to make a better jumping bean.
Jumping beans, the phenomenon on which the novelty of [ExpensivePlasticCrap]’s childhood is based, are technically not beans, and their movement is arguably not a jump — a small hop at best. The trick is that the each not-a-bean has become the home to moth larvae that twitches and rolls on the ground as the larvae thrash about, trying to move their protective shells out of the hot sun.
The novelty bean was a small plastic pill-like capsule with a ball bearing inside what would cause the “bean” to move in unexpected ways as it rolled around. [ExpensivePlasticCrap]’s goal is to make a jumping bean that lives up to its name.
Various solenoids and motors were considered for the motion component of this new and improved bean. Ultimately, it was a small sealed vibrating motor that would be selected to move the bean without getting tangled in what was to become a compact bundle of components.
An ATtiny microcontroller won out over discrete components for the job of switching the motor on and off (once per second), for ease of implementation. Add this along with a MOSFET, battery and charging board for power into a plastic capsule, and the 1 Hz jumping bean was complete.
[ExpensivePlasticCrap] offers some thoughts on how to get more jump out of the design by reducing the weight of the build and giving it a more powerful source of motion.
On this date in 1975, a Soviet and an American shook hands. Even for the time period, this wouldn’t have been a big deal if it wasn’t for the fact that it happened approximately 220 kilometers (136 miles) over the surface of the Earth.
Crew of the Apollo–Soyuz Test Project
Although their spacecraft actually launched a few days earlier on the 15th, today marks 50 years since American astronauts Thomas Stafford, Vance Brand, and Donald “Deke” Slayton docked their Apollo spacecraft to a specifically modified Soyuz crewed by Cosmonauts Alexei Leonov and Valery Kubasov. The two craft were connected for nearly two days, during which time the combined crew was able to freely move between them. The conducted scientific experiments, exchanged flags, and ate shared meals together.
Politically, this very public display of goodwill between the Soviet Union and the United States helped ease geopolitical tensions. On a technical level, it not only demonstrated a number of firsts, but marked a new era of international cooperation in space. While the Space Race saw the two counties approach spaceflight as a competition, from this point on, it would largely be treated as a collaborative endeavour.
The Apollo–Soyuz Test Project lead directly to the Shuttle–Mir missions of the 1990s, which in turn was a stepping stone towards the International Space Station. Not just because that handshake back in 1975 helped establish a spirit of cooperation between the two space-fairing nations, but because it introduced a piece of equipment that’s still being used five decades later — the Androgynous Peripheral Attach System (APAS) docking system.
Feeling nostalgic? Weren’t around in the 90s but wonder what it was like? ProtoWeb has you covered! Over on his YouTube channel [RetroTech Chris] shows you how to browse the web like it’s 1995.
The service that [RetroTech Chris] introduces is on the web over here: protoweb.org. The way it works is that you configure your browser to use the service’s proxy server, then the service will be able to intercept your browsing activity and serve you old content from its cache. Also, for some supported sites, you will see present-day content but presented in the format you would have seen in the 90s. Once you have configured your browser to use the ProtoWeb proxy you can navigate to http://www.inode.com/ where you will find a directory listing of sites which have been archived or emulated within the service.
In his video [RetroTech Chris] actually demos some of the old web browsers running on old hardware, which is a very good recreation of what things were like. If you want the most realistic experience you can even configure ProtoWeb to slow down your network connection to the speed of a 56k dial-up modem. There are some things from the 90s that we miss, but waiting for websites to load isn’t one of them!
We had a look in our own archive to see how far back we here at Hackaday could go, and we found our first post, from September 2004: Radioshack Phone Dialer – Red Box. A red box! Spicy.
So far in the “Field Guide” series, we’ve mainly looked at critical infrastructure systems that, while often blending into the scenery, are easily observable once you know where to look. From the substations, transmission lines, and local distribution systems that make up the electrical grid to cell towers and even weigh stations, most of what we’ve covered so far are mega-scale engineering projects that are critical to modern life, each of which you can get a good look at while you’re tooling down the road in a car.
This time around, though, we’re going to switch things up a bit and discuss a less-obvious but vitally important infrastructure system: the cold chain. While you might never have heard the term, you’ve certainly seen most of the major components at one time or another, and if you’ve ever enjoyed fresh fruit in the dead of winter or microwaved a frozen burrito for dinner, you’ve taken advantage of a globe-spanning system that makes sure environmentally sensitive products can be safely stored and transported.
3D printing is arguably over-used in the maker community. It’s just so easy to run off a quick prototype and then… well, it’s good enough, right? Choosing the right plastic can go a long way to making sure your “good enough” prototype really is good enough for long term use. If you’re producing anything with gearing, you might want to cast your eyes to a study by [Mert Safak Tunalioglu] and [Bekir Volkan Agca] titled: Wear and Service Life of 3-D Printed Polymeric Gears.
No spin doctoring here, spinning gears.
The authors printed simple test gears in ABS, PLA, and PETG, and built a test rig to run them at 900 rpm with a load of 1.5 Nm against a steel drive gear. The gears were pulled off and weighed every 10,000 rotations, and allowed to run to destruction, which occurred in the hundreds-of-thousands of rotations in each case. The verdict? Well, as you can tell from the image, it’s to use PETG.
The authors think that this is down to PETG’s ductility, so we would have liked to see a hard TPU added to the mix, to say nothing of the engineering filaments. On the other hand, this study was aimed at the most common plastics in the 3D printing world and also verified a theoretical model that can be applied to other polymers.
This tip was sent in by [Benjamin], who came across it as part of the research to build his first telescope, which we look forward to seeing. As he points out, it’s quite lucky for the rest of us that the U.S. government provides funding to make such basic research available, in a way his nation of France does not. All politics aside, we’re grateful both to receive your tips and for the generosity of the US taxpayer.
We’ve seen similar tests done by the community — like this one using worm gears — but it’s also neat to see how institutional science approaches the same problem. If you need oodles of cycles but not a lot of torque, maybe skip the spurs and print a magnetic gearbox. Alternatively you break out the grog and the sea shanties and print yourself a capstan.
Machine learning and neural nets can be pretty handy, and people continue to push the envelope of what they can do both in high end server farms as well as slower systems. At the extreme end of the spectrum is [ExploratoryStudios]’s Hermes Optimus Neural Net for a TI-84 Plus Silver Edition.
This neural net is setup as an autocorrect system that can take four character inputs and match them to a library of twelve words. That’s not a lot, but we’re talking about a device with 24 kB of RAM, so the little machine is doing its best. Perhaps more interesting than any practical output is the puzzle solving involved in getting this to work within the memory constraints.
The neural net “employs a feedforward neural network with a precisely calibrated 4-60-12 architecture and sigmoid activation functions.” This leads to an approximate 85% accuracy being able to identify and correct the given target words. We appreciate the readout of the net’s confidence as well which is something that seems to have gone out the window with many newer “AI” systems.
![An image of a light grey graphing calculator with a dark grey screen and key surround. The text on the monochrome LCD screen shows "Input: ENEB Result 1: BEEN Confidence 1: 14% [##] Result 2: Good Confidence 2: 12% [#] Press ENTER key..."](https://hackaday.com/wp-content/uploads/2025/07/Hermes-Optimus-TI-84-Plus-Silver-Edition-Neural-Network-YouTube-0-0-52.jpeg?w=600&h=450)
