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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Mercy Me, Thanks For The Heals

Sometimes, you have to call in the experts. [CorSec Props], builders of fine props, costumes and more, were commissioned to replicate Mercy’s healing staff from the game Overwatch. Sounds simple, but the customer — right as they always are — requested that it spin and light up just like the original.

To get a look at the electronics, the rotating head slides off after removing a screw. Inside, the rechargeable 18650 lithium-ion 3.7V battery — via a DC to DC converter — is bumped up to 5.5V in order to run a 12V, 120rpm motor. At full voltage the staff’s head rotates too fast, and so it’s deliberately under-powered for a more replica-appropriate speed.

A ring of RGB LEDs as well as a pair pointed at the tip of the staff toggle between yellow and blue hues. To switch between these different lighting modes, a double-pole, triple throw switch was modified to function like a more-suited-to-the-task-than-what-we-had-in-the-shop three position, double-pole, double-throw switch.

On the motor shaft, pair of studs slot into a piece of acrylic at the tip of the staff. This stops it from slipping, but also allows the LED glow to diffuse out the top as well as the portholes on the side of the staff. Check out the build after the break!

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Thermite Creates A Sword

Thermite can cut cars in half but [TheBackyardScientist] relies on its ability to create rather than destroy. In fact, thermite was the key component when he casts a solid metal sword. The casting doesn’t require a furnace since the heat is produced by the thermite itself.

In case it wasn’t abundantly clear: this procedure is not without risk.

[TheBackyardScientist] compares two types of iron oxide, red and black, then judges their usability based on the post-ignition mass. His goal is to get the most metal from a single reaction. He also adds some stainless steel beads to improve the quality of the casting and to utilize some of the excess heat.

With encouragement from his neighbors and a couple of trials with fire bricks, buckets, and sand, [TheBackyardScientist] is successful. The resulting sword is treated, given a handle, sharpened, then scientifically tested with a variety of things found in a regular kitchen.

If you look in the background of [TheBackyardScientist]’s workshop, you may notice his molten PEWter gun. This steel sword is an upgrade from his recycled pewter sword a few years ago.

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Semi-Automatic Rail Gun Is A Laptop Killer

It’s huge, it’s unwieldy, and it takes 45 seconds to shoot all three rounds in its magazine. But it’s a legitimate semi-automatic railgun, and it’s pretty awesome.

Yes, it has its limits, but every new technology does, especially totally home-brew builds like this. The aptly named [NSA_listbot] has been putting a lot of work into his railgun, and this is but the most recent product of an iterative design cycle.

The principle is similar to other railguns we’ve featured before, which accelerate projectiles using rapidly pulsed electromagnets. The features list in the video below reads like a spec for a top-secret military project: field-augmented circular bore, 4.5kJ capacitor bank, and a custom Arduino Nano that’s hardened against the huge electromagnetic pulse (EMP) generated by the coils. But the interesting bits are in the mechanical design, which had to depart from standard firearms designs to handle the caseless 6 mm projectiles. The resulting receiver and magazines are entirely 3D printed. Although it packs a wallop, its cyclic rate of fire is painfully slow. We expect that’ll improve as battery and capacitor technology catches up, though.

Want to check out some more railgun builds? We’ve got them in spades — from one with $50,000 worth of caps to a wrist-mounted web-slinger.

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Propane-Powered Plasma Rifle

It may not be a “phased plasma rifle in the 40-watt range,” and it doesn’t even use plasma in the strict definition, but it’s pretty cool nonetheless. It’s a propane-powered bottle-launching rifle, and it looks like a lot of fun.

[NighthawkInLight] sure likes things that go pop, like his watermelon-wasting air-powered cannon and cheesy-poof pop gun. This one has a little more oomph to it, powered as it is by a propane torch. The principle is simple: fill a soda bottle with propane, ignite the gas, fun ensues. The details are a little more subtle, though, and allowances need to be made to keep back pressure from preventing the projectile from filling with fuel. [NighthawkInLight] overcomes this with some clever machining of the barrel. The final production version in the video below is needlessly but delightfully complex, with a wooden stock and a coil of clear vinyl tubing helical plasma accumulator before the barrel; the last bit is just for show, and we have to admit that it looks pretty good.

Unless you count the pro tip on using CPVC pipe to make custom fittings, this one is nothing but fun. But we don’t have a problem with that.

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A Lightsaber, With Rave Mode

How often after being exposed to Star Wars did you dream of having your own working lightsaber? These days — well, we don’t quite have the technology to build crystal-based weapons, but tailor-made lightsabers like redditor [interweber]’s are very much real.

Piggybacking off the Korbanth Graflex 2.0 kit — a sort of bare-bones lightsaber ready to personalize — [interweber] is using a Teensy 3.5 to handle things under the hilt. Instead of taking the easy route and cramming everything into said handle, a 3D printed a cradle for the electronics and speaker keep things secure. The blade is made up of two meters of APA102 LEDs.

As well as all the sound effects appropriate to ‘an elegant weapon for a more civilized age’, a cluster of buttons handle the various functions; , playing and cycling through music(more on that in a second), changing the color of the lightsaber — Jedi today, Sith tomorrow — enabling a flickering effect that mimics Kylo Ren’s lightsaber, color cycling, and a…. rave mode?

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Wield The Power Of Molten Metal

[TheBackyardScientist] at it again with another super villain-esque demonstration of gadgetry: a liquid metal squirt gun.

The squirt gun has a compressed air tank like most others — more on that later — but to fire its primary ammunition, a nozzle that connects directly to an air compressor is needed. Again, like most guns of this nature, air is forced into the gun’s reservoir, displacing the pewter and expelling it out the gun’s barrel. Yes, pewter.

Working around the heat tolerances of thread seal tape, pewter has a low enough melting point that an airtight system is preserved — plus it’s really cool to fire a stream of liquid metal. The ammunition is made from pewter ware melted down and cast into pucks. These pucks are stacked into the gun’s magazine, melted with a propane torch and carefully loaded into the gun.

The built-in compressed air tank lacks the oomph to push out the pewter — hence the air compressor, but any lighter liquids or condiments are fair game for rapid-fire exercises. Yes, condiments.

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