Gas-Tight FDM 3D Printing Is Within Your Grasp

June 8, 2024 by Jenny List 65 Comments

The widespread availability of inexpensive 3D printers has brought about a revolution in what can be easily made at home. However these creations aren’t perfect, particularly when it comes to the adhesion between their layers. Aside from structural failures along the layer lines there is also the question of those joins being permeable, limiting the possibility for waterproof or gas proof prints. It’s something [German Engineer] has tackled in a new video, in which he’s looking at the design and preparation of small propane tanks.

A blurry image of a red 3d-printed part exploding — This is the frame at which the 3D printed tank explodes

The attraction of propane as a fuel is that it liquefies easily on compression, so a propane cylinder or tank will be an equilibrium of liquid propane with pressurized gas above it, whose pressure depends on the ambient temperature. This means that any tank must be expected to have a working pressure somewhere between 150 and 200 PSI, with of course a design pressure far exceeding that for safety reasons.

Filling a 3D printed tank immediately results in the propane escaping, as he demonstrates by putting one of his prints under water. He solves this with a sealant, Diamant Dichtol, which is intended to polymerize in the gaps between layers and create a gas-tight tank. A range of three tanks of different thicknesses are treated this way, and while the 1 mm thick variety bursts, the thicker ones survive.

It’s clear that this technique successfully creates gas-tight prints, and we can see the attraction of a small and lightweight fuel tank. But we can’t help worrying slightly about the safety, for even when the material is a lightweight 3D print, high pressure equipment is not to be trifled with. Tanks do burst, and when that happens anyone unfortunate enough to be close by sustains nasty, even life-threatening injuries. Use the technique, but maybe don’t hit it with high pressures.

Continue reading “Gas-Tight FDM 3D Printing Is Within Your Grasp” →

Retrotechtacular: TVO

June 6, 2024 by Jenny List 18 Comments

Hardware hackers come from a variety of backgrounds, but among us there remains a significant number whose taste for making things was forged through growing up in a farm environment. If that’s you then like me it’s probable that you’ll melt a little at the sight of an older tractor, and remember pretending to drive one like it at pre-school age, and then proudly driving it for real a few years later before you were smart enough to realise you’d been given the tedious job of repeatedly traversing a field at a slow speed in the blazing sun. For me those machines were Ford Majors and 5000s, Nuffields, the ubiquitous red Fergusons, and usually relegated to yard duty by the 1970s, the small grey Ferguson TE20s that are in many ways the ancestor of all modern tractors.

The Black Art Of Mixing Your Own Fuel

There was something odd about some of those grey Fergies in the 1970s, they didn’t run on diesel like their newer bretheren, nor did they run on petrol or gasoline like the family Austin. Instead they ran on an unexpected mixture of petrol and heating oil, which as far as a youthful me could figure out, was something of a black art to get right. I’d had my first encounter with Tractor Vapour Oil, or TVO, a curious interlude in the history of agricultural engineering. It brings together an obscure product of the petrochemical industry, a moment when diesel engine technology hadn’t quite caught up with the on-farm requirement, and a governmental lust for a lower-tax tractor fuel that couldn’t be illicitly used in a car.

TVO is a fuel with a low octane rating, where the octane rating is the resistance to ignition through compression alone. In chemical terms octane rating a product of how many volatile aromatic hydrocarbons are in the fuel, and to illustrate it your petrol/gasoline has an octane rating in the high 90s, diesel fuel has one close to zero, and TVO has a figure in the 50s. In practice this was achieved at the refinery by taking paraffin, or kerosene for Americans, a heavier fraction than petrol/gasoline, and adding some of those aromatic hydrocarbons to it. The result was a fuel on which a standard car engine wouldn’t run, but which would run on a specially low-compression engine with a normal spark ignition. This made it the perfect tax exempt fuel for farmers because it could only be used in tractors equipped with these engines, and thus in the years after WW2 a significant proportion of those Fergies and other tractors were equipped to run on it. Continue reading “Retrotechtacular: TVO” →

Tarzan, Lost Since 1983, Swings Back Onto The Atari 2600

June 6, 2024 by Jenny List 12 Comments

Computer gaming history is littered with tales of fabled lost hardware and software. Some of them are very famous such as the E.T. cartridges buried in a desert landfill or the few prototype SNES/CD-ROM hybrid that Nintendo was developing with Sony before the introduction of the PlayStation, but others have faded somewhat into obscurity. Among these is Tarzan for the Atari 2600, a game which was never released due to the 1983 console crash, and which the [Video Game History Foundation] have a report on its rediscovery and preservation.

The game was to be published by Coleco for their ColecoVision console as well as the 2600. The ColecoVision version was released and was apparently even fairly well reviewed, but the Atari port was canceled and its very existence eventually faded into obscurity.

Continue reading “Tarzan, Lost Since 1983, Swings Back Onto The Atari 2600″ →

The Pi Pico, An SDR Receiver Front End

June 5, 2024 by Jenny List 22 Comments

Making a software defined radio (SDR) receiver is a relatively straightforward process, given the right radio front end electronics and analogue-to-digital converters. Two separate data streams are generated using clocks at a 90 degree phase shift, and these are passed to the software signal processing for demodulation. But what happens if you lack a pair of radio front ends and a suitable clock generator? Along comes [Mordae] with an SDR using only the hardware on a Raspberry Pi Pico. The result is a fascinating piece of lateral thinking, extracting something from the hardware that it was never designed to do.

The onboard RP2040 ADC is of course far too slow for the task, so instead an input is used, with a negative feedback arrangement from another GPIO to form a crude 1-bit ADC. A PIO peripheral is then used to perform the quadrature mixing, resulting in the requisite pair of data streams. At this point these are sent over USB to GNU Radio for demodulating, mainly for convenience rather than necessarily because the microcontroller lacks the power.

The result is a working SDR front end, demonstrated pulling in an FM broadcast station. The Pico has to be overclocked to reach that frequency and it’s more than a little noisy, but we’re extremely impressed with how much has been done with so little. Oddly it isn’t the first Pico SDR we’ve seen, but the previous one was a much more conventional and lower-frequency affair for the European Long Wave band.

The Amiga We All Wanted In 1993

June 4, 2024 by Jenny List 51 Comments

To be an Amiga fan during the dying days of the hardware platform back in the mid 1990s was to have a bleak existence indeed. Commodore had squandered what was to us the best computer ever with dismal marketing and a series of machines that were essentially just repackaged versions of the original. Where was a PCI Amiga with fast processors, we cried!

Now, thirty years too late, here’s [Jason Neus] with just the machine we wanted, in the shape of an ATX form factor Amiga motherboard with those all-important PCI slots and USB for keyboard and mouse.

What would have been unthinkable in the ’90s comes courtesy of an original or ECS Amiga chipset for the Amiga functions, and an FPGA and microcontroller for PCI and USB respectively. Meanwhile there’s also a PC floppy drive controller, based on work from [Ian Steadman]. The processor and RAM lives on a daughter card, and both 68040 and 68060 processors are supported.

Here in 2024 of course this is still a 1990s spec board, and misty-eyed speculation about what might have happened aside, it’s unlikely to become your daily driver. But that may not be the point, instead we should evaluate it for what it is. Implementing a PCI bus, even a 1990s one, is not without its challenges, and we’re impressed with the achievement.

If you’re interested in Amiga post-mortems, here’s a slightly different take.

Pasteurisation: Probably Why You Survived Childhood

June 4, 2024 by Jenny List 124 Comments

There’s an oft-quoted maxim that youngsters growing up on farms have a much stronger immune system than those growing up in cities. The idea is that they are exposed to far more dirt and eat food much closer to the field than their urban cousins. Without the help of a handy microbiologist or epidemiologist it’s difficult to judge its veracity, but personal experience suggests that the bit about dirt may be true at least.

It’s Dangerous To Idealise The Past.

It’s likely that the idea of rural kids seeing more bugs may come from the idea that those in the cities consume sterile processed food from the supermarket, it plays into a notion of an idealised past in which a somehow purer diet came more directly from its source. Somehow so the story goes, by only eating pasteurised and preserved foods, city dwellers are eating something inferior, stripped of its goodness. There’s a yearning for a purer alternative, something supermarkets are only too happy to address by offering premium products at elevated prices. So, was the diet of the past somehow more wholesome, and are those kids having their future health ruined by Big Food? Perhaps it’s time to turn back the clock a little to find out.

A mostly black cow in a field of green grass — Even clean cows have bugs. Carolyn Parsons, CC BY-SA 4.0.

It’s likely everyone knows that food spoils if left unattended for long enough. Some foods, such as grain, can last a long time if kept dry, while others such as milk will go bad quite quickly. Milk in particular goes bad for two reasons; firstly because it’s an excellent bacterial growth medium, and secondly because it contains plenty of bacteria by its very nature. Even very clean cows have bugs.

If you lived in most large cities in the nineteenth century, the Industrial Revolution had likely placed you far enough from the nearest cow that your milk had a significant journey to make to reach you even with up-to-date rail transport. Without refrigeration, during that journey it had become a bacterial soup to the extent that even though it might not yet have gone sour, it had certainly become a bacterial brew. It was thus responsible for significant numbers of infections, and had become a major health hazard. So much for the purer diet consumed by city kids of the past. Continue reading “Pasteurisation: Probably Why You Survived Childhood” →

A Human-Sized Strowger Telephone Exchange

June 3, 2024 by Jenny List 3 Comments

A large hacker camp such as EMF 2024 always brings unexpected delights, and one of those could be found in the Null Sector cyberpunk zone: a fully functional Strowger mechanical telephone exchange. Better still, this wasn’t the huge array of racks we’ve come to expect from a mechanical exchange, but a single human-sized unit, maybe on a similar scale to a large refrigerator. [LBPK]’s PAX, or Private Automatic Exchange, is a private telephone network, 1950s style.

It stood at the back of the container, with a row of four telephones in front of it. We particularly liked the angular “Trimphone”, the height of 1960s and 70s chic. You could dial the other phones in the network with a two digit number, and watch the exchange clicking in the background as you did so. Some of the sounds weren’t quite the same as the full-sized equivalents, with the various tones being replaced by vibrating reeds.

This exchange has an interesting history, being built in 1956 by “Automatic Telephone & Electric” for the Midlands Electricity Board, power generator for much of central England, where it served its commercial life. On decommissioning it went to the Ffestiniog narrow gauge railway, in Wales. He was lucky enough to learn of its existence when the Ffestiniog had no further use for it, and snapped it up.

We have to admit, we want one of these, however he makes clear that it’s an unwieldy machine that requires quite some attention so a Hackaday mechanical exchange will have to remain a dream for now.