Junkyard Crossbow Aims to be a Car Killer

[James], aka [Turbo Conquering Mega Eagle], is not your typical Hackaday poster boy. Most of his builds have a  “Junkyard Wars” vibe, and he’d clearly be a good man to have around in a zombie apocalypse. Especially if the undead start driving tanks around, for which purpose his current anti-tank compound crossbow is apparently being developed.

At its present prototype phase, [James]’ weapon o’ doom looks more fearsome than it actually is. But that’s OK — we’re all about iterative development here. Using leaf springs from a Toyota Hi-Lux truck, this crossbow can store a lot of energy, which is amplified by ludicrously large aluminum cams. [James] put a lot of effort into designing a stock that can deal with these forces, ending up with a composite design of laminated wood and metal. He put a lot of care into the trigger mechanism too, and the receiver sports not only a custom pistol grip cast from aluminum from his fire extinguisher foundry, but a hand-made Picatinny rail for mounting optics. Test shots near the end of the video below give a hint at the power this fully armed and operational crossbow will eventually have. The goal is to disable a running car by penetrating the engine block, and we’re looking forward to that snuff film.

If rubber band-powered crossbows are more your speed, take you pick — fully automatic, 3D-printed, or human-launching.

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The Fine Art of Heating And Cooling Your Beans

They say that if something is worth doing, it’s worth doing right. Those are good words to live by, but here at Hackaday we occasionally like to adhere to a slight variation of that saying: “If it’s worth doing, it’s worth overdoing”. So when we saw the incredible amount of work and careful research [Rob Linnaeus] was doing just to roast coffee beans, we knew he was onto something.

The heart of his coffee roaster is a vortex chamber with an opening on the side for a standard heat gun, and an aperture in the top where an eight cup flour sifter is to be placed. [Rob] modeled the chamber in Fusion 360 and verified its characteristics using RealFlow’s fluid simulation. He then created a negative of the chamber and printed it out on his Monoprice Maker Select 3D printer.

He filled the mold with a 1:1 mix of refractory cement and perlite, and used the back of a reciprocating saw to vibrate the mold as it set so any air bubbles would rise up to the surface. After curing for a day, [Rob] then removed the mold by heating it and peeling it away. Over the next several hours, the cast piece was fired in the oven at increasingly higher temperatures, from 200 °F all the way up to 500 °F. This part is critical, as trapped water could otherwise turn to steam and cause an explosion if the part was immediately subjected to high temperatures. If this sounds a lot like the process for making a small forge, that’s because it basically is. Continue reading “The Fine Art of Heating And Cooling Your Beans”

Enresoning An iPhone 8 Ring

The iPhone 8 was just released last week, and that means some people were standing in line in front of an Apple store for hours waiting to get their hands on the latest and greatest glowing rectangle. [Patrick Adair] had a better idea: he would stand in front of an Apple store for four hours, then do something productive with his new smartphone. With the help of a waterjet, some resin, a lathe, and some very fine grades of sandpaper, he created the Apple Ring.

Setting aside the whole process of actually acquiring an iPhone 8 on launch day, the process of turning an iPhone into a ring is more or less what you would expect. First, the iPhone was cut into ring-shaped pieces on a waterjet cutter. Special care was taken to avoid the battery, and in the end [Patrick] was able to get a nice chunk ‘o phone that included the camera lens.

This ring piece was then embedded in clear resin. For this, [Patrick] used Alumilite epoxy, a pressure pot, and a toaster oven to cure the resin. Once the phone parts were firmly encased for the rest of eternity, the ring blank moved over to the lathe. The center of the ring was bored out, and the process of sanding, polishing and gluing in all the tiny parts that fell out during the process commenced. The end result actually looks pretty great, and even though it’s probably a little too bulky, it is a remarkable demonstration of the craft of turning.

You can check out [Patrick]’s video below, along with a video from the Waterjet Channel showing the deconstruction of a glowing rectangle.

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A Thoughtful Variety of Projects and Failures

Our friends at [The Thought Emporium] have been bringing us delightful projects but not all of them warrant a full-fledged video. What does anyone with a bevy of small but worthy projects do? They put them all together like so many mismatched LEGO blocks. Grab Bag #1 is the start of a semi-monthly video series which presents the smaller projects happening behind the scenes of [The Thought Emporium]’s usual video presentations.

Solar eclipse? There are two because the first was only enough to whet [The Thought Emporium]’s appetite. Ionic lifters? Learn about the favorite transformer around the shop and see what happens when high voltage wires get too close. TEA lasers? Use that transformer to make a legitimate laser with stuff around your house. Bismuth casting? Pet supply stores may have what you need to step up your casting game and it’s a total hack. Failures? We got them too.

We first covered ionocraft (lifters) awhile back. TEA lasers have been covered before. Casting is no stranger to hackaday but [The Thought Emporium] went outside the mold with their technique.

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Hackaday Prize Entry: An Open Source Kiln

For his Hackaday Prize entry, [Matt] is building a small kiln for melting metals and firing clay.  He’s making this kiln out of materials anyone can acquire — dirt and a bit of nichrome wire.

Most kiln builds you’ll find on the Internet use fancy refractory bricks and other materials you may not have in your back yard. [Matt]’s project is entirely DIY, and starts with a large pile of dirt and rocks. Aftter shaking off the sifted dirt, washing the rocks, straining off the gravel, getting rid of the sand, and siphoning off the water, [Matt] has a big bag of wet clay. This clay is mixed with perlite, an insulating, refractory material, molded into bricks, and fired. The result is a brick that looks good enough to be made into a kiln.

[Matt] has already put a lot of work into the calculations required to figure out the heat transfer of this kiln. At best, this kiln is going to take 14 hours to get up to temperature. That’s incredibly slow, but then again, this kiln will be electric, and will only use 1500 Watts. That’s nothing compared to a commercial electric kiln, but it is a build [Matt] designed himself without any outside help, using only parts he can easily acquire. In any event, this is an excellent project for the Hackaday Prize.

Casting Metal Directly Into 3D Printed Molds

Casting metal and 3D printing go together like nuts and gum, and there are no shortage techniques that use the two together. Lost PLA casting is common, and sculptors are getting turned on to creating their works in plastic first before sending it off to the foundry. Now the folks at FormLabs have turned the whole ‘casting metal and 3D printer’ thing on its head: they’re printing sacrificial molds to cast pewter.

There are two techniques demonstrated in this tutorial, but the real winner here is printing a complete sacrificial mold for pewter miniatures. While this technique requires a little bit of work including washing, curing, and a bit of post-processing, you would have to do that anyway with anything coming out of a resin printer.

The material of choice for these molds is a high temp resin with a heat deflection temperature of 289 °C. Using a pewter alloy that melts at 260 °C, casting a metal miniature is as simple as pouring molten metal into a mold. Demolding might be a little finicky, but with a small screwdriver used as a chisel, it’s possible to get the cast newly parts out.

We’ve seen pewter casting with PLA, but the quality available from the Form resin printers is truly amazing and produces some great looking miniatures.

Harvesting Copper from Microwave Ovens

Obsolete appliances were once a gold mine of parts, free for the taking with a few snips of your diagonal cutters. Times have changed, though, and most devices yield only a paltry supply of parts, so much so that only by harvesting raw materials can you get much value out of them. And so we have this example of reclaiming copper from used microwave ovens.

The primary source of copper in most microwaves is the transformer, which we usually see re-tasked for everything from spot welders to material handling electromagnets. But the transformer is not the only source of the red metal; [eWaste Ben] also harvests it from relay coils and the main coil and shading coils of the fan motor.  The bounty is melted down in an electric foundry and cast in a graphite mold into a lovely ingot.

Unless you’re into repeatedly casting copper trinkets, a large bar of reclaimed copper might not be something you have a burning need to possess. But bearing in mind that copper can go for about $2.50 a pound at the scrap yard, there’s some money to be made, especially with dead microwaves essentially free for the taking. As [Ben] points out, taking the extra step to melt and cast the copper harvested from microwaves makes no sense if all you’re going to do is sell the scrap, but it’s nice to know how to do it just the same.

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