Full-Auto Crossbow Rocks and Rolls on Rubber Bands and Electric Drill

You’ve got to enjoy any project where the hacker clearly loves what he or she is doing. And when the project is as cool as a motor-driven, rubber band powered, fully automatic crossbow, it’s hard not to laugh along.

A full-auto crossbow is no mean feat, and it took a man with a love for rubber-powered firearms to get it right. [JoergSprave]’s design is based on a rack-and-pinion system and executed mainly in plywood. The main pinion gear is a composite of aluminum and wood, in a bid to increase the life of the mechanism and to properly deal with the forces involved. The pinion, turned by a powerful electric drill, drives the rack back and locks the carrier under the 30-bolt magazine. A rubber-powered follower forces a bolt down and a cam on the pinion trips the sear, the bolt is fired and the cycle continues.

We slowed the video down a bit and it looked to us like the cyclical rate of fire was about 7 rounds per second, or a respectable 420 rounds per minute. Pretty powerful, too, and the accuracy isn’t bad either.

We’ve seen [Joerg]’s inventions before, like this soda bottle Gatling arrow launcher, or his ridiculous machete launcher. We hope he keeps having fun and letting us watch.

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Your Fingers Will Never Leave Your Hands with This Firecracker Launcher

Who doesn’t like to ring in the New Year with explosives? But speaking from personal experience – I can neither confirm not deny nearly blowing my hand off once with a small dry-ice grenade – a hands-off way to launch your fireworks can be a plus, in which case you might want to check out this automatic firecracker launcher.

[Valentin]’s build has all the earmarks of an inspired afternoon of hasty hacking. Mostly built of wood and hot glue, there’s a feed ramp for fresh ammo and an elastic-powered sled on a ramp. Fireworks are metered onto the sled with one turn of a small gear motor, the fuse is light by a butane torch, and another gear motor pulls the sled back and launches the firecracker. The launch is somewhat anemic – perhaps some stouter rubber bands or latex tubing would provide a little more oomph. But it’s still a fun build with plenty of potential for improvement – perhaps something along the lines of this automated beer catapult?
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Custom Machined Triple Threat Slingshot

Time was when a lad in need of a ranged weapon would hack a slingshot together out of a forked tree branch and a strip of inner tube. Slingshot design has progressed considerably since [Dennis the Menace]’s day, but few commercially available slingshots can match up to the beauty and functionality of this magnificently machined multipurpose handheld weapon system.

Making it clear in his very detailed build log that this is but a prototype for a design he’s working on, [Gord] has spared little effort to come up with a unique form factor that’s not only functional as a slingshot, but also provides a few surprises: a magazine that holds nine rounds of ammo with magnets; knuckle protection on the hand grip that would deal a devastating left hook; and an interchangeable base that provides a hang loop or allows mounting a viciously sharp broadhead hunting arrow tip for somewhat mysterious purposes. There’s plenty to admire in the build process as well – lots and lots of 6061 billet aluminum chips from milling machine and lathe alike. All told, a nice piece of craftsmanship.

For a more traditional slingshot design with a twist, check out this USB-equipped slingshot that talks to Angry Birds. And when your taste in slingshots run more toward the ridiculously lethal, [Jörg Sprave]’s machete launcher never disappoints.

[Thanks Leslie!]

Tennis Ball Launcher Has Puppies Running the 100m Dash

Launching Tennis Balls with Ease

[Brian] from 24 Hour Engineer has a friend with arthritis who can’t easily play ball with his new puppy — so [Brian] stepped in and built him this awesome tennis ball launcher.

You see, most tennis ball launchers require a solid flick of the wrist, and since just plain old throwing it is out of the question too, [Brian] had to make him something powerful and easy to use. After sketching out some designs he came up with the basic concept that eventually became what is pictured above.

The frame is made of 2″ PVC pipe, which serves two purposes, support, and safety. The bungee cord launching system is actually contained within the pipe, keeping it out of the way, and free from catching on anything during firing. A pair of pulleys mounted at the cord opening ensure the cord doesn’t wear out.

What we really like is the trigger mechanism [Brian] made out of some carefully cut wood,  a steel corner brace and a few nuts and bolts. It’s a simple mechanism that provides leverage and an easy way to release the bungee cord.  Continue reading “Tennis Ball Launcher Has Puppies Running the 100m Dash”

Hackaday Links: February 2, 2014

hackaday-links-chain

[Michel] was in need of a 9V battery connector, and in a brilliant bit of insight realized 9V batteries will plug directly into other 9V batteries (just… don’t do that. ever.) Taking a dead 9V, he tore it open, was disappointed by the lack of AAAA cells, and soldered some wires onto the connector.

Sometimes a project starts off as a reasonable endeavour, but quickly becomes something much more awesome. [Wallyman] started off building a hammock stand and ended up making a giant slingshot. We’re not one to argue with something that just became a million times more fun.

We’ve seen solder stencils made out of laser-cut metal, photoetched metal, plastic cut on a vinyl cutter, laser-cut plastic, and now finally one made on a 3D printer. It’s a pretty simple process – get the tCream layer into a .DXF file, then subtract it from a plastic plate in OpenSCAD.

Apple loves their proprietary screws, and when [Jim] tried to open his Macbook Air with the pentalobe screwdriver that came with an iPhone repair kit, he found it was too large. No problem, then: just grind it down. Now if only someone could tell us why a laptop uses smaller screws than a phone…

[Victor] has been playing around with an RTLSDR USB TV tuner dongle for a few months now. It’s a great tool, but the USB thumb drive form factor wasn’t sitting well with him. To fix that, he stuck everything into a classy painted Hammond 1590A enclosure. It looks much cooler, and now [Victor] can waterproof his toy and add a ferrite to clean things up.

GoPro Slingshot

Want to try out aerial photography, but can’t afford a quadcopter? [Jeremy] rigged up a low cost GoPro Slingshot and took some pretty nice flyover shots of the lake.

The slingshot itself is meant for water balloons, but easily has enough power to fire the camera. In order to get good video, some stabilization was needed. [Jeremy] made a stabilizing fin out of packaging foam, and used an eye bolt to connect it to the GoPro’s threaded tripod mount. The simple tail fin made of out foam and zip ties actually did a good job of stabilizing the camera.

This looks like a fun experiment to try when you’re at the lake, since you can probably build it with stuff lying around the house. For [Jeremy], it also proved to be a way to keep his dog entertained since she retrieved the camera after each shot. After the break, check out the video footage from the GoPro slinging rig.

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USB slingshot controller is for the birds

This USB slingshot controller really brought a smile to our faces. Part of it is the delightfully silly promo video you’ll find after the break. [Simon Ford] combined nature and technology to bring this USB-enabled slingshot into existence.

The frame itself is from a branch he found in the Epping Forrest of London. He whittled away the bark, and hollowed out an opening in at the base of the ‘Y’ to receive an accelerometer board. It has a pair of female pin headers to interface with the mbed seen in the image above. But the real hack here is the code he wrote to translate accelerometer data into appropriate mouse movements. His success in the area makes this translate the virtual world of Angry Birds in a visceral experience of killing things with a slingshot.

We’re suckers for this type of project. Two examples that pop into mind are these musical instrument hacks for Rock Band 2.

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