RCA’s Clear Plastic TV Wowed Crowds In 1939

In the United States in 1939, television sets still had a long way to go before they pretty much sold themselves. Efforts to do just that are what led to RCA’s Lucite Phantom Telereceiver, which aimed to show people a new way to receive broadcast media.

Created for the 1939 World’s Fair, the TRK-12 Lucite Phantom Telereceiver introduced people to the concept of television. Production models were housed in contemporary wood cabinets, but the clear acrylic (itself also a relatively new thing) units allowed curious potential customers to gaze within, and see what was inside these devices.

One interesting feature is the vertically-mounted cathode ray tube, which reflects off a mirror in the top cover of the cabinet for viewing. This meant that much of the bulk of the TRK-12 could be vertical instead of horizontal. Important, because the TRK-12 was just over a meter tall and weighed 91 kilograms (or just over 200 lbs.)

Clearly a luxury item, the TRK-12 sold for $600 which was an eye-watering sum for the time. But it was a glimpse of the future, and as usual, the future is made available a few ticks early to those who can afford the cost.

Want to see one in person? You might be in luck, because an original resides at the MZTV Museum of Television in Toronto, Canada.

Directing Ambient Light For Some Extra Glow

[Yuichiro Morimoto] wanted to create a decorative lamp, one that wasn’t burdened with batteries or wires, but used just the ambient light in the room to create a directed glow effect. Using a coloured circular acrylic sheet, with a special coating (not specified) ambient light impinging on the surface is diffused toward the edge. This centre sheet is embedded in an opalescent sheet, which scatters the light from the center sheet, giving a pleasant glow, kind of akin to a solar corona. An additional diffuser cover sheet on the front covers over the edge to hide it, and further enhance the glow effect.

Details of the ‘special coating’ are scarce, with the coloured sheet described as a condenser plate. This clearly isn’t the same as diffuser plastic, as that cannot be seen through as clearly as some of the photographs show. So we’re a little stumped on this one! Please answer in the comments if you can, ahem, shed some light on this one!

When talking about ambient light, many people will think more along the lines of active lighting, for example, adaptive ambient light around a TV like this hack.

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The Physics Behind The Collapse Of A Huge Aquarium

At the end of last week Aquadom, the world’s largest cylindrical aquarium, unexpectedly shattered and caused an emergency as it flooded both the Berlin hotel that housed it and the surrounding streets. From an engineering perspective it’s a fascinating story, because its construction was such that this shouldn’t have happened. We have an analysis of what might have gone wrong from [Luis Batalha] (Nitter), and from it we can learn a little about the properties of the plastic used.

The aquarium was made of an acrylic polymer which has an interesting property — at a certain temperature it transitions between a glass-like state and a rubber-like one. Even at room temperature the acrylic is well below the transition temperature, but as the temperature drops the acrylic becomes exponentially more brittle. When the outside temperature dropped to well below zero the temperature also dropped in the foyer, and the high water pressure became enough to shatter the acrylic.

Sadly few of the fish from the aquarium survived, but fortunately nobody was killed in the incident. News coverage shows how the force of the water destroyed the doors and brought wreckage into the street, and we’re guessing that it will be a while before any other hotel considers such a project as an attraction. Meanwhile we’ve gained a little bit of knowledge about the properties of acrylic, which might come in handy some day.

Header: Chrissie Sternschuppe, CC BY-SA 2.0.

Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required

Casting parts in silicone is great, and 3D printing in resin is fantastic for making clean shapes, so it’s natural for an enterprising hacker to want to put the two together: 3D print the mold, pour in the silicone, receive parts! But silicone’s curing process can be inhibited by impurities. What’s cure inhibition? It’s a gross mess as shown in the image above, that’s what it is. Sadly, SLA-printed resin molds are notorious for causing exactly that. What’s a hacker to do?

Firstly: there are tin-cure and platinum-cure silicones, and for the most part tin-cure silicone works just fine in resin-printed molds. Platinum-cure silicones have better properties, but are much more susceptible to cure inhibition. Most workarounds rely on adding some kind of barrier coating to molds, but [Jan Mrázek] has a cheap and scalable method of avoiding this issue that we haven’t seen before. Continue reading “Stop Silicone Cure Inhibition, No Fancy Or Expensive Products Required”

laser cut acrylic coaster with rgb leds inside

Your Mug Will Like This Glowy Coaster

[Charlyn] wanted to highlight their friends beautiful mug collection, so the Glowy Coaster was born.

The coaster is made up of six layers of laser cut acrylic. The top and bottom layer are cut out of clear acrylic, providing a flat surface for the coaster. A top pattern layer made of pearl acrylic has a thin piece of vellum put underneath it to provide diffusion for the LED strip sandwiched inside. The middle layers are made of peach acrylic and have their centers hollowed out to provide room for the electronics inside. The top pearl acrylic layer gives the coaster, as [Charlyn] writes, a “subtle touch of elegance”. The coaster itself is screwed together by an M3 screw at each point of the hexagon that feed through to heat-set inserts.

inside of glowy coaster with electronics exposed

The electronics consist of a short NeoPixel strip, cut to include 12 LEDs pointed in towards the center of the coaster. The LEDs are driven by a Trinket M0 microcontroller with a LiPo “backpack” to provide power, attachment points for the exposed power switch and recharging capability to the 110 mAh 3.7 V battery. The code is a slightly modified NeoPixel “rainbow” wheel loop (source available as a gist). The design files are available through Thingiverse.

Creations like these highlight how much care and work goes into a project with minimal beauty, where decisions, like the opacity and thickness of the acrylic or countersinking the M3 screws, can have huge consequences for the overall aesthetic. [Charlyn] has an attention to detail that brings an extra touch of professionalism and polish to the project.

Coasters are a favorite for laser cutting and we’ve covered many different types, including
coaster bots, coaster engravers and even a color changing, drink sensing coasters.

Continue reading “Your Mug Will Like This Glowy Coaster”

DIY Retrograde Clock Is 3D Printed

Retrograde clocks are unique, in that they eschew the normal fully-circular movement for the hands. Instead, the hands merely sweep out a segment of a circular arc, before jumping back to their start position to begin again. They’re pretty rare to find, but [Jamie Matthews] decided he had to have one. Thusly, he elected to build his own!

For his build, [Jamie] started with a regular off-the-shelf clock movement you might find in any hobbyist clock build. From there, he affixed his own witches’ brew of racks and gears to the output in order to create the desired semi-circular mechanism. The arcane mechanism enables the clock to tell time over roughly a 180-degree arc.

It’s relatively simple to make one of your own, too. The parts are all readily 3D printable, with [Jamie] reporting it took less than 8 meters of filament to produce the geartrain for his build. You can even print the clock face if you don’t want to CNC cut it out of acrylic.

Overall, it’s a fun look at an often-forgotten part of our horological history. Desktop 3D printing really does enable the creation of some exciting, different clock designs. Video after the break.

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Hackaday Prize 2022: Upcycling Acrylic Scraps

Living and working in a remote rain forest may sound idyllic to those currently stuck in bland suburbia, and to be sure it does have plenty of perks. One of the downsides, though, is getting new materials and equipment to that remote location. For that reason, [Digital Naturalism Laboratories], also known as [Dinalab], has to reuse or recycle as much as they can, including their scraps of acrylic leftover from their laser cutter.

The process might seem straightforward, but getting it to actually work and not burn the acrylic took more than a few tries. Acrylic isn’t as thermoplastic as other plastics so it is much harder to work with, and it took some refining of the process. But once the details were ironed out, essentially the acrylic scraps are gently heated between two steel plates (they use a sandwich press) and then squeezed with a jack until they stick back together in one cohesive sheet. The key to this process is to heat it and press it for a long time, typically a half hour or more.

With this process finally sorted, [Dinalab] can make much more use of their available resources thanks to recycling a material that most of us would end up tossing out. It also helps to keep waste out of the landfill that would otherwise exist in the environment indefinitely. And, if this seems familiar to you, it’s because this same lab has already perfected methods to recycle other types of plastic as well.

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