In one of the most unique DIY projects, Reddit user PickentCode has created what can be described as a completely off-the-grid "heat engine computing device." Instead of relying on solar panels or a battery pack, the creator went in a completely different direction, building a custom steampunk-inspired microcomputer which features a miniature Stirling engine to power the hand-crafted wooden console.

Originally patented in 1816 by the Scottish minister and inventor Robert Stirling, a Stirling engine converts heat directly into mechanical energy. By applying a flame to one end of a sealed cylinder, the temperature difference forces the air inside to expand and contract. This cycle pushes a piston that spins the flywheel, which can be used to power a simple generator that converts the mechanical rotation into usable electricity.

"The entire project took about a month to design, build, and program," PickentCode told Tom's Hardware. They first conceptualized a 3D layout using Blender before constructing the physical case out of wood. They even went ahead and utilized a DIY laser engraver to etch a portrait of Robert Stirling and his original 1816 engine patent sketch directly onto the wooden side panels. For the smaller structural elements, the electronic housings and the keycaps were custom 3D printed, while the decorative pipes winding across the frame were made from old shower tubing and some gold paint.

The brains of the system are an ESP32 C3 microcontroller paired with a 2.42-inch monochrome OLED display with a 128x64 resolution, alongside a 16-key keypad. The electrical output of the generator is stabilized using small capacitors wired into the circuit. One can also actively monitor the voltage output using the analog voltmeter, which is wired in parallel, and the two toggle switches mounted on the front panel can be used to turn on the main circuit and the voltmeter.

Running an electronic device, in this case a microcomputer, purely on fire comes with obvious energy limitations. The model Stirling engine can produce only 150 milliwatts of power, and to stay within this tiny power budget, the creator implemented certain hardware and software optimizations. For instance, Wi-Fi and Bluetooth were completely disabled, and the screen brightness was kept low to conserve every milliwatt. PickentCode also tuned the ESP32's CPU frequency, reducing it down to just 80 MHz when updating the screen or interpreting opcodes, going all the way down to just 10 MHz while sitting idle in the main loop.

Despite the limitations, the computer is fully functional. It runs a custom CHIP-8 virtual machine preloaded with classic gaming ROMs like Tetris, Snake, and Pong. Impressively, it also features a built-in code editor, allowing users to type in CHIP-8 opcodes directly to write and execute their own custom programs on the fly.

Stirling engines are not exactly new to the world of computing. Earlier this year, we covered a project by Windows development guru Dave Plummer who showcased a cooling solution that used a small Stirling engine to convert waste heat from an AMD Threadripper system into mechanical energy, which was used to spin the engine's flywheel. While it isn’t an actual solution to an overheating chipset, it is claimed that the flywheel can spin up to about 200 RPM in a 20C/68F environment.

Noctua is known for making high-end, high-quality fans and air coolers, which it has been doing for over 20 years, recently expanding into AIOs. However, it appears that there were a few questions regarding its PC case compatibility database, which some PC DIYers say don’t match the data from the manufacturer’s website. The company cleared this up in a blog post, saying that it has undertaken its own measurements and it has determined that 56 of the more than 100 cases it has tested showed significant deviation from the details officially listed online.

The company gave two diverging situations of inaccurate official measurements. The first one is when the case is larger than what is actually written, which would allow PC builders to attach a larger cooler. Noctua said that the deviations aren’t minor, either. For example, the NZXT H2 Flow case is listed as being compatible with a maximum 75mm CPU cooler height, but the actual case can accommodate an air cooler up to 79mm. There’s also the Thermaltake TR100, which is 2.7mm larger than what the Thermaltake website says, and the Corsair Frame 4000D, which gives you 10mm of extra clearance.

This is a good thing, as any cooler you bought based on their website’s measurement means that it will definitely fit, but Noctua said that this is a missed opportunity. That’s because you could’ve bought a larger cooler that delivered more performance in the same case.

On the flip side, the company warned that there were also some cases that were actually smaller versus the numbers in their specifications. It cited two examples — the Asus Prime AP201 and the Lian Li B4-mATX. The former is 1.7mm shorter while the latter is 3.5mm shorter than what’s listed on their specific product pages.

This could to be a major issue, especially if you bought items that fitted the available space exactly, based on the manufacturer’s measurements. It would mean that these parts would either be touching the case panels, or worse, not allow them to close at all. If that’s the case, you’ll have to spend extra effort to return either the part or the case and get something that fits better.

The safest solution to this is for you to buy the PC case before you shop for the remaining parts of your build. This is especially true if you’re looking at the best mini-ITX cases, as the tight tolerances mean that you don’t have much margin if the numbers aren’t accurate. But by having the case physically available and measuring it yourself, you’re at least confident that what you’re buying will fit. Alternatively, you can check out Noctua’s compatibility search page, with the clearances of the cases in its database verified by its team.

This compatibility tool will give you peace of mind when shopping for the best cooler and is useful for confirming measurements even if you end up buying from another brand. But this begs the question — are the variations between official and actual measurements limited to the air coolers? Or are the numbers for other components, like the GPU, PSU, and other key components also inaccurate? Noctua’s website only covers coolers, so you’ll have to rely on other pages (or your own measurements) if you want some confirmation of a case’s specifications and clearances for other parts like GPUs and PSUs.