[Black Beard Projects] sealed some pine cones in colored resin, then cut them in half and polished them up. The results look great, but what’s really good about this project is that it clearly demonstrates the necessary steps and techniques from beginning to end. He even employs some homemade equipment, to boot.
Briefly, the process is to first bake the pine cones to remove any moisture. Then they get coated in a heat-activated resin for stabilizing, which is a process that infuses and pre-seals the pine cones for better casting results. The prepped pine cones go into molds, clear resin is mixed with coloring and poured in. The resin cures inside a pressure chamber, which helps ensure that it gets into every nook and cranny while also causing any small air bubbles introduced during mixing and pouring to shrink so small that they can’t really be seen. After that is cutting, then sanding and polishing. It’s an excellent overview of the entire process.
The video (which is embedded below) also has an outstanding depth of information in the details section. Not only is there an overview of the process and links to related information, but there’s a complete time-coded index to every action taken in the entire video. Now that’s some attention to detail.
Late last year, artist [Steve Messam]’s project “Whistle” involved 16 steam engine whistles around Newcastle that would fire at different parts of the day over three months. The goal of the project was bring back the distinctive sound of the train whistles which used to be fixture of daily life, and to do so as authentically as possible. [Steve] has shared details on the construction and testing of the whistles, which as it turns out was a far more complex task than one might expect. The installation made use of modern technology like Raspberry Pi and cellular data networks, but when it came to manufacturing the whistles themselves the tried and true ways were best: casting in brass before machining on a lathe to finish.
The original whistles are a peek into a different era. The bell type whistle has three major components: a large bell at the top, a cup at the base, and a central column through which steam is piped. These whistles were usually made by apprentices, as they required a range of engineering and manufacturing skills to produce correctly, but were not themselves a critical mechanical component.
In the original whistle shown here, pressurized steam comes out from within the bottom cup and exits through the thin gap (barely visible in the image, it’s very narrow) between the cup and the flat shelf-like section of the central column. That ring-shaped column of air is split by the lip of the bell above it, and the sound is created. When it comes to getting the right performance, everything matters. The pressure of the air, the size of the gap, the sharpness of the bell’s lip, the spacing between the bell and the cup, and the shape of the bell itself all play a role. As a result, while the basic design and operation of the whistles were well-understood, there was a lot of work to be done to reproduce whistles that not only operated reliably in all types of weather using compressed air instead of steam, but did so while still producing an authentic re-creation of the original sound. As [Steve] points out, “with any project that’s not been done before, you really can’t do too much testing.”
Embedded below is one such test. It’s slow-motion footage of what happens when the whistle fires after filling with rainwater. You may want to turn your speakers down for this one: locomotive whistles really were not known for their lack of volume.
Knobs! Shiny candy-colored knobs! The last stand of skeuomorphism is smart light switches! Everyone loves knobs, but when you’re dealing with vintage equipment with a missing knob, the odds of replacing it are slim to none. That’s what happened to [Wesley Treat] when he picked up a vintage Philco tube tester. The tester looked great, but a single knob for a rotary switch was missing. What to do? Clone some knobs! You only need some resin and a little bit of silicone.
The process of copying little bits of plastic or bakelite is fairly standard and well-tread territory. Go to Michaels or Hobby Lobby, grab some silicone and resin, make a box, put your parts down, cover them in silicone, remove the parts, then put resin in. For simple parts, and parts with flat bottoms like knobs, this works great. However, there’s something weird about the knob on this old Philco tube tester. Firstly, it doesn’t fit a standard 1/4″ shaft — it’s a bit bigger. There’s also no set screw. Instead, this knob has a stamped spring aligning it with the flat part of the D-shaft in this rotary switch. This means a copy of this knob wouldn’t be useful to anyone else, and that no other knob would work with this tube tester.
However, a bit of clever engineering would make a copy of this knob fit the existing switch. Once the resin was cured, [Wesley] drilled out the hole, then sanded a dowel down to fit into the flat of the D-shaft. It took a little kergiggering, but the knob eventually fit onto one of the rotary switches. Not bad for a few bucks in silicone and resin.
Liquid two-part resins that cure into a solid are normally used for casting, and [Cuddleburrito] also found them useful to add strength and rigidity to 3D printed pillar supports. In this case, the supports are a frame for some arcade-style buttons, which must stand up to a lot of forceful mashing. Casting the part entirely out of a tough resin would require a mold, and it turns out that filling a 3D print with resin gets comparable benefits while making it easy to embed fastener hardware, if done right.
Filling the inside of an object with some kind of epoxy or resin to reinforce it isn’t a new idea, but [Cuddleburrito] learned how a few small design considerations can lead to less messy and more successful results. The first is that resin can be poured with screws in place without any worry of trapping the screws in the resin, if done correctly. As long as only the threads of the screw are in the resin, they can be backed out after the resin has cured. Embedding nuts into the resin to act as fasteners becomes a much easier task when one can simply pour resin with both nut and screw in place, and remove the screw afterwards. A thin layer of a lubricant on the threads to act as a release may help, but [Cuddleburrito] didn’t seem to need any.
The second thing learned was that, for a pillar that needs a cap and embedded nut on both ends, it can be tricky to fill the object’s void with the perfect amount of required resin before capping it off. On [Cuddleburrito]’s first attempt, he underfilled and there wasn’t enough resin to capture the nut on the top lid of the pillar he was making. The way around this was to offset the nut on a riser, and design in either a witness hole or an overflow relief. A small drain hole or a safe area for runoff allows for filling things right up without an uncontrolled mess in the case of overfilling.
Something worth keeping in mind when experimenting in this area is that in general the faster a resin cures, the more it heats up in the process. It may be tempting to use something like 5 minute epoxy in a pinch, but the heat released from any nontrivial amount of it risks deforming a thin-walled 3D print in the process. For cases where resin would be overkill and the fasteners are small, don’t forget we covered the best ways to add fasteners directly to 3D printed parts.
We sometimes get our inspirations from art. When [kodera2t] saw some Japanese art of fish drawings embedded in clear epoxy he just had to make his own. But while skilled in electronics, he wasn’t skilled at drawing. We’d still call him an artist, though, after seeing what he came up with in his electronics embedded in crystal clear epoxy.
His first works of electronic art were a couple of transistors and some ICs, including an 80386, encased in epoxy. But then he realized that he wanted the electronics to do something interesting. However, once encased in epoxy, how do you keep the electronics powered forever?
He tried a solar cell charging a battery which then powered an LED but he didn’t like the idea of chemical batteries encased in epoxy for a long time.
He then switched to wireless power transmission with a receiving coil in the base of epoxy pyramids. For one of them, the coil powers a BLE board with an attached LED which he can control from his phone. And his latest contains an ESP32-PICO with an OLED display. The code allows him to upload new firmware over the air but on his Hackaday.io page, he shows the difference between code which can brick the ESP32 versus code which won’t. But don’t take our word for it. Check out the video below to see his artistry for yourself.
[Tony]’s tale of woe begins innocently enough, and where it usually begins for wannabe metal casters: with [The King of Random]’s homemade foundry-in-a-bucket. It’s just a steel pail with a homebrew refractory lining poured in place, with a hole near the bottom to act as a nozzle for forced air, or tuyère. [Tony]’s build followed the plans pretty faithfully, but lacking the spent fire extinguisher [The King] used for a crucible in the original build, he improvised and used the bottom of an old propane cylinder. A test firing with barbecue charcoal sort of worked, but it was clear that more heat was needed. So [Tony] got hold of some fine Welsh anthracite coal, which is where the fun began. With the extra heat, the foundry became a mini-blast furnace that melted the thin steel crucible, dumping the molten aluminum into the raging coal fire. The video below shows the near catastrophe, and we hope that once [Tony] changed his pants, he hustled off to buy a cheap graphite or ceramic crucible for the next firing.
All kidding aside, this is a vivid reminder of the stakes when something unexpected (or entirely predictable) goes wrong, and the need to be prepared to deal with it. A bucket of dry sand to smother a fire might be a good idea, and protective clothing is a must. And it pays to manage your work area to minimize potential collateral damage, too — we doubt that patio will ever be the same again.
Creating 3D prints is great, but sometimes you need something more durable. [Myfordboy] printed a new 3D printer extruder in PLA and then used the lost PLA method to cast it in aluminum. You can see the results in the video below.
The same process has been used for many years with wax instead of PLA. The idea is to produce a model of what you want to make and surround it with a material called investment. Once the investment sets, heat melts the PLA (or wax) leaving a mold made of the investment material. Once you have the mold, you can place it in a frame and surround it with greensand. Another frame gets a half pipe placed and packed with greensand. The depression made by this pipe will provide a path for the metal to flow into the original mold. Another pipe will cut a feeder into the greensand over this pipe.