Ask Hackaday: Solutions, Or Distractions?

The “Long Dark” is upon us, at least for those who live north of the equator, and while it’s all pre-holiday bustle, pretty lights, and the magical first snow of the season now, soon the harsh reality of slushy feet, filthy cars, and not seeing the sun for weeks on end will set in. And when it does, it pays to have something to occupy idle mind and hands alike, a project that’s complicated enough to make completing even part of it feel like an accomplishment.

But this time of year, when daylight lasts barely as long as a good night’s sleep, you’ve got to pick your projects carefully, lest your winter project remain incomplete when the weather finally warms and thoughts turn to other matters. For me, at least, that means being realistic about inevitabilities such as competition from the day job, family stuff, and the dreaded “scope creep.”

It’s that last one that I’m particularly concerned with this year, because it has the greatest potential to delay this project into spring or even — forbid it! — summer. And that means I need to be on the ball about what the project actually is, and to avoid the temptation to fall into any rabbit holes that, while potentially interesting and perhaps even profitable, will only make it harder to get things done.

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Failed 3D Printed Part Brings Down Small Plane

Back in March, a small aircraft in the UK lost engine power while coming in for a landing and crashed. The aircraft was a total loss, but thankfully, the pilot suffered only minor injuries. According to the recently released report by the Air Accidents Investigation Branch, we now know a failed 3D printed part is to blame.

The part in question is a plastic air induction elbow — a curved duct that forms part of the engine’s air intake system. The collapsed part you see in the image above had an air filter attached to its front (towards the left in the image), which had detached and fallen off. Heat from the engine caused the part to soften and collapse, which in turn greatly reduced intake airflow, and therefore available power.

Serious injury was avoided, but the aircraft was destroyed.

While the cause of the incident is evident enough, there are still some unknowns regarding the part itself. The fact that it was 3D printed isn’t an issue. Additive manufacturing is used effectively in the aviation industry all the time, and it seems the owner of the aircraft purchased the part at an airshow in the USA with no reason to believe anything was awry. So what happened?

The part in question is normally made from laminated fiberglass and epoxy, with a glass transition of 84° C. Glass transition is the temperature at which a material begins to soften, and is usually far below the material’s actual melting point.

When a part is heated at or beyond its glass transition, it doesn’t melt but is no longer “solid” in the normal sense, and may not even be able to support its own weight. It’s the reason some folks pack parts in powdered salt to support them before annealing.

The printed part the owner purchased and installed was understood to be made from CF-ABS, or ABS with carbon fiber. ABS has a glass transition of around 100° C, which should have been plenty for this application. However, the investigation tested two samples taken from the failed part and measured the glass temperature at 52.8°C and 54.0°C, respectively. That’s a far cry from what was expected, and led to part failure from the heat of the engine.

The actual composition of the part in question has not been confirmed, but it sure seems likely that whatever it was made from, it wasn’t ABS. The Light Aircraft Association (LAA) plans to circulate an alert to inspectors regarding 3D printed parts, and the possibility they aren’t made from what they claim to be.

A Musically-Reactive LED Christmas Tree

Regular Christmas trees don’t emit light, nor do they react to music. If you want both things in a holiday decoration, consider this build from [dbmaking]. 

An ESP32-D1 mini runs the show here. It’s hooked up to a strip of WS2812B addressable LEDs. The LED strip is placed on a wooden frame resembling the shape of a traditional Christmas tree. Ping-pong balls are then stacked inside the wooden frame such that they act as a light diffuser for the LEDs behind. The microcontroller is also hooked up to an INMP441 omnidirectional MEMS microphone module. This allows the ESP32 to detect sound and flash the LEDs in time, creating a colorful display that reacts to music. This is achieved by using the WLED web installer to set the display up in a sound reactive mode.

It’s a fun build, and we’d love to tinker around with coding more advanced visualizer effects for a build like this. We’ve seen builds that go the other way, too, by toning down excessive blinkiness in Christmas decorations.

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