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.
Continue reading “Full-Auto Crossbow Rocks and Rolls on Rubber Bands and Electric Drill”
There’s an old saying that the only two things that are certain are death and taxes. However, unless you live in a nudist colony, there’s probably also laundry. [Darpan Bajaj] and some friends were at a hackathon and decided to put their washing machine on the Internet.
Most of us here at Hackaday — and many Hackaday readers, judging by the comments — are a little suspicious about how much we really need everything attached to the Internet. However, a washing machine is probably not a bad idea: you use it often, you need to know when it is done, and you probably don’t want to just sit and watch it spin. Besides, the intended installation is in a hostel where there are multiple machines and many potential users.
Continue reading “Death, Taxes, and Laundry”
There’s a variety of ways to add threaded holes to 3D printed objects. You can tap a hole, but the plastic isn’t always strong enough. Nut traps work, but aren’t very attractive and can be difficult to get exactly the right size. If you try to enclose them, you have to add a manual step to your printing process, too. You can buy threaded inserts (see video below) but that means some other piece of hardware to have to stock in your shop.
[PeterM13] had a different idea: Cut a piece of threaded stock, put nuts on the end and heat it up to let the nuts reform the plastic. This way the nut traps wind up the perfect size by definition. He used two nuts aligned and secured with thread locker. Then he used a hot air gun to only heat the metal (so as to reduce the chance of deforming the actual part). Once it was hot (about 15 seconds) he pulled the nuts into the open hole, where it melted the plastic which grips the nuts once cooled again.
Continue reading “Custom Threaded Inserts for 3D Printing”
[Shawn] wrote in to tell us about his extremely simple method he used for mounting a webcam on a tripod. His article explains it better, but the basic premise is to glue a 1/4 – 20 nut onto the bottom of it. The hack-worthiness of this could be in question, but the technique could come in handy at some point.
After seeing this tip, I was reminded of a slightly crazier, if effective mount that I made for my
state of the art Env2 phone. Referenced in a links post in March, it was made of a 2×4 with a 1/2 inch slot milled in it. After some thought, it was drilled and tapped for a 1/4 – 20 bolt in the other side to mount it on a tripod. So this could be an option in very limited circumstances.
On the other hand, if you want something a bit more hack-worthy, why not check out this motorized camera rig that we featured in July. Sure, it’s more complicated than gluing a nut onto a webcam, but at least it still uses 2 x 4s in it’s mounting hardware!
If you’ve ever been caught in the situation of needing to drill a clean straight hole down the center of a bolt or rod, you’ve probably tried and ended up with a broken bit or tilted hole, and a ton of cursing to boot.
[Vik] let us know about this nifty trick for drilling ‘down the middle’ using a simple hobby drill press and vice. He claims it’s ‘physics guiding the bit’ but in reality its just crafty use of a chuck. Either way the quick trick works, and will hopefully save a lot of hackers some headaches in the future.
Let us know in the comments if you have any simple quick tips that you use when you’re out in the shop.