Spinning Up A Water Cooled 3D Printed Stirling Engine

March 31, 2021 by 7 Comments

The Stirling external combustion engine has fascinated gear heads since its inception, and while the technology has never enjoyed widespread commercialization, there’s a vibrant community of tinkerers who build and test their own takes on the idea. [Leo Fernekes] has been working on a small Stirling engine made from 3D printed parts and common hardware components, and in his latest video he walks viewers through the design and testing process.

We’ve seen Stirling engines with 3D printed parts before, but in most cases, they are just structural components. This time, [Leo] really wanted to push what could be done with plastic parts, so everything from the water jacket for the cold side of the cylinder to the gears and connecting rods of the rhombic drive has been printed. Beyond the bearings and rods, the most notable non-printed component is the stainless steel spice shaker that’s being used as the cylinder.

The piston is made of constrained steel wool.

Mating the hot metal cylinder to the 3D printed parts naturally introduced some problems. The solution [Leo] came up with was to design a toothed collar to hold the cylinder, which reduces the surface area that’s in direct contact. He then used a piece of empty SMD component feed tape as a insulator between the two components, and covered the whole joint in high-temperature silicone.

Like many homebrew Stirling engines, this one isn’t perfect. It vibrates too much, some of the internal components have a tendency to melt during extended runs, and in general, it needs some fine tuning. But it runs, and in the end, that’s really the most important thing with a project like this. Improvements will come with time, especially once [Leo] finishes building the dynamometer he hopes will give him some solid data on how the engine’s overall performance is impacted as he makes changes.

If you’ve got a glass test tube laying around, putting together a basic Stirling engine demonstration is probably a lot easier than you might think. Commercial kits are also available if you’re looking for something more substantial, but even those can benefit from some aftermarket modifications. With a little effort, you’ll have a power plant ready for the surface of Mars in no time.

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Direct Memory Access: Data Transfer Without Micro-Management

March 31, 2021 by 16 Comments

In the most simple computer system architecture, all control lies with the CPU (Central Processing Unit). This means not only the execution of commands that affect the CPU’s internal register or cache state, but also the transferring of any bytes from memory to to devices, such as storage and interfaces like serial, USB or Ethernet ports. This approach is called ‘Programmed Input/Output’, or PIO, and was used extensively into the early 1990s for for example PATA storage devices, including ATA-1, ATA-2 and CompactFlash.

Obviously, if the CPU has to handle each memory transfer, this begins to impact system performance significantly. For each memory transfer request, the CPU has to interrupt other work it was doing, set up the transfer and execute it, and restore its previous state before it can continue. As storage and external interfaces began to get faster and faster, this became less acceptable. Instead of PIO taking up a few percent of the CPU’s cycles, a big transfer could take up most cycles, making the system grind to a halt until the transfer completed.

DMA (Direct Memory Access) frees the CPU from these menial tasks. With DMA, peripheral devices do not have to ask the CPU to fetch some data for them, but can do it themselves. Unfortunately, this means multiple systems vying for the same memory pool’s content, which can cause problems. So let’s look at how DMA works, with an eye to figuring out how it can work for us.
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Scanimate Analog Video Synths Produced Oceans Of Motion Graphics

March 31, 2021 by 21 Comments

Why doesn’t this kind of stuff ever happen to us? One lucky day back in high school, [Dave Sieg] stumbled upon a room full of new equipment and a guy standing there scratching his head. [Dave]’s curiosity about this fledgling television studio was rewarded when that guy asked [Dave] if he wanted to help set it up. From that point on, [Dave] had the video bug. The rest is analog television history.

Today, [Dave] is the proud owner and maintainer of two Scanimate machines — the first R&D prototype, and the last one of only eight ever produced. The Scanimate is essentially an analog synthesizer for video signals, and they made it possible to move words and pictures around on a screen much more easily than ever before. Any animated logo or graphics seen on TV from the mid-1970s to the mid-80s was likely done with one of these huge machines, and we would jump quite high at the chance to fiddle with one of them.

Analog television signals were continuously variable, and much like an analog music synthesizer, the changes imposed on the signal are immediately discernible. In the first video below, [Dave] introduces the Scanimate and plays around with the Viceland logo a bit.

Stick around for the second and third videos where he superimposes the Scanimate’s output on to the video he’s making, all the while twiddling knobs to add oscillators and thoroughly explaining what’s going on. If you’ve ever played around with Lissajous patterns on an oscilloscope, you’ll really have a feel for what’s happening here. In the fourth video, [Dave] dives deeper and dissects the analog circuits that make up this fantastic piece of equipment.

Here’s another way to play with scan lines: delay the output to some of them and you have a simple scrambler.

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The Difference Between 4WD And AWD

March 31, 2021 by 102 Comments

Car manufacturers will often tout a vehicle’s features to appeal to the market, and this often leads to advertisements featuring a cacophony of acronyms and buzzwords to dazzle and confuse the prospective buyer. This can be particularly obvious when looking at drivelines. The terms four-wheel drive, all-wheel drive, and full-time and part-time are bandied about, but what do they actually mean? Are they all the same, meaning all wheels are driven or is there more to it? Let’s dive into the technology and find out.

Part-Time 4WD

Part-time four-wheel drive is the simplest system, most commonly found on older off-road vehicles like Jeeps, Land Cruisers and Land Rovers up to the early 1990s, as well as pickup trucks and other heavy duty applications. In these vehicles, the engine sends its power to a transfer case, which sends an equal amount of torque to the front and rear differentials, and essentially ties their input shafts together. This is good for slippery off-road situations, as some torque is provided to both axles at all times. However, this system has the drawback that it can’t be driven in four-wheel drive mode at all times. With the front and rear differentials rotating together, any difference in rotational speed between the front and rear wheels — such as from turning a corner or uneven tyre wear — would cause a problem. The drive shaft going to one differential would want to turn further than the other, a problem known as wind-up.

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Web Tool Cranks Up The Power On DJI’s FPV Drone

March 31, 2021 by 22 Comments

Apparently, if the GPS on your shiny new DJI FPV Drone detects that it’s not in the United States, it will turn down its transmitter power so as not to run afoul of the more restrictive radio limits elsewhere around the globe. So while all the countries that have put boots on the Moon get to enjoy the full 1,412 mW of power the hardware is capable of, the drone’s software limits everyone else to a paltry 25 mW. As you can imagine, that leads to a considerable performance penalty in terms of range.

But not anymore. A web-based tool called B3YOND promises to reinstate the full power of your DJI FPV Drone no matter where you live by tricking it into believing it’s in the USA. Developed by the team at [D3VL], the unlocking tool uses the new Web Serial API to send the appropriate “FCC Mode” command to the drone’s FPV goggles over USB. Everything is automated, so this hack is available to anyone who’s running a recent version of Chrome or Edge and can click a button a few times.

There’s no source code available yet, though the page does mention they will be putting up a GitHub repository soon. In the meantime, [D3VL] have documented the command packet that needs to be sent to the drone over its MODBUS-like serial protocol for others who might want to roll their own solution. There’s currently an offline Windows-only tool up for download as well, and it sounds like stand-alone versions for Mac and Android are also in the works.

It should probably go without saying that if you need to use this tool, you’ll potentially be violating some laws. In many European countries, 25 mW is the maximum unlicensed transmitter power allowed for UAVs, so that’s certainly something to keep in mind before you flip the switch. Hackaday isn’t in the business of dispensing legal advice, but that said, we wouldn’t want to be caught transmitting at nearly 60 times the legal limit.

Even if you’re not interested in fiddling with drone radios, it’s interesting to see another practical application of the Web Serial API. From impromptu oscilloscopes to communicating with development boards and conference badges, clever developers are already finding ways to make hardware hacking easier with this new capability.

[Thanks to Jules for the tip.]

Boston Dynamics Stretch Robot Trades Lab Coat For Work Uniform

March 31, 2021 by 30 Comments

Boston Dynamics has always built robots with agility few others could match. While great for attention-getting demos, from outside the company it hasn’t been clear how they’ll translate acrobatic skills into revenue. Now we’re getting a peek at a plan in an interview with IEEE Spectrum about their new robot Stretch.

Most Boston Dynamics robots have been research projects, too expensive and not designed for mass production. The closest we got to date was Spot, which was offered for sale and picked up a few high profile jobs like inspecting SpaceX test sites. But Spot was still pretty experimental without an explicit application. In contrast, Stretch has a laser-sharp focus made clear by its official product page: this robot will be looking for warehouse jobs. Specifically, Stretch is designed to handle boxes up to 50 lbs (23 kg). Loading and unloading them, to and from pallets, conveyer belts, trucks, or shipping containers. These jobs are repetitive and tedious back-breaking work with a high injury rate, a perfect opportunity for robots.

But warehouse logistics aren’t as tightly structured as factory automation, demanding more adaptability than typical industrial robots can offer. A niche Boston Dynamics learned it can fill after releasing an earlier demo video showing their research robot Atlas moving some boxes around: they started receiving inquiries into how much that would cost. Atlas is not a product, but wheels were set in motion leading to their Handle robot. Learning from what Handle did well (and not well) in a warehouse environment, the designed evolved to today’s Stretch. The ostrich-like Handle prototype is now relegated to further research into wheeled-legged robots and the occasional fun dance video.

The Stretch preproduction prototypes visible in these videos lacks acrobatic flair of its predecessors, but they still have the perception and planning smarts that made those robots possible. Those skills are just being applied to a narrower problem scope. Once production models are on the job, we look forward to reading some work performance reviews.

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Sawblade Turned Beyblade Looks Painful To Tangle With

March 30, 2021 by 14 Comments

Beyblades were a huge craze quite some years back. Children battled with spinning tops in small plastic arenas, or, if their local toy stores were poorly merchandised, in salad bowls and old pie dishes. The toys were safe enough, despite their destructive ethos, by virtue of being relatively small and lightweight. This “Beyblade” from [i did a thing] is anything but, however. 

The build begins with a circular saw blade over 1 foot in diameter, replete with many angry cutting teeth that alone portend danger for any individual unlucky enough to cross its path. Saw blades tend to cut slowly and surely however, so to allow the illicit Bey to deal more traumatic blows, a pair of steel scraps are welded on to deliver striking blows as well. This has the added benefit of adding more mass to the outside of the ‘blade, increasing the energy stored as it spins.

With the terrifying contraption spun up to great RPM by a chainsaw reeling in string, it’s able to demolish cheap wood and bone with little resistance. Shrapnel is thrown in many directions as the spinner attacks various objects, from a melon to an old CRT TV. We’d love to see the concept taken further, with an even deadlier design spun up to even higher speeds, ideally with a different tip that creates a more aggressive motion across the floor.

As aggressive as this saw blade looks in action, not all are so scary. Even paper can do the job under the right conditions. Video after the break.

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