YouTube engineer builds an insanely accurate knife-throwing gun

Cal Jeffrey

Posts: 3,581   +1,075
Staff member
In context: Throwing a knife and sticking it blade-first into a target is not as easy as Hollywood makes it seem. Navy Seal Casey Ryback, played by Steven Seagal in the movie Under Siege, is an expert in landing a blade right where it counts. But doing this in real life takes a lot of mental mathematics, as this YouTuber points out with his latest project — a knife-throwing gun.

The concept of blade-throwing guns is not something new. The Ripper from Unreal Tournament and the Ripjack from Unreal Championship 2 come to mind. Other video games have had similar weapons too. However, finding a real-life version is challenging.

YouTuber Quint is an engineer who has done numerous crazy projects on his channel Quint BUILDs — BUILD stands for "Better Understanding Involves Learning and Doing." His latest is a knife-throwing machine (above). It was partly inspired by Ryback's skill in Under Seige and partly because of Quint's desire to figure out the mechanics of it all.

From an engineering standpoint, this thing is nuts. It uses a laser pointer for aiming while a LiDAR sensor measures the distance for the computer algorithms. The laser pointer even adjusts to compensate for varying distances. It is so accurate that as long as your aim with the laser is halfway decent, you can stick a knife precisely in the same spot as a previous throw. With a 10+ blade magazine, Quint had to aim away from previously fired shots to ensure a stick. You could say his target was hosting a regular knife party.

Quint had three goals in building his machine. First, it had to be able to stick 10 knives consecutively from varying distances. Second, it had to be mobile, so not wires attached. Lastly, since it had to be portable enough to carry it around, it had to be light. He was shooting for 20 pounds or less but ended up being over 30.

It all sounds relatively straightforward, but there were tons of calculations and mechanical hurdles to overcome. While Quint did most of the math on paper, his adolescent son programmed all the computer algorithms. It also took quite a bit of machining. Other than the motors and servos, Quint custom machined all the steel parts, including the knives, and 3D printed the necessary plastic parts.

After some misstarts and at least two catastrophic failures, the father and son team had a bazooka-like gun that landed knives wherever aimed. On his final test run, the machine stuck ten consecutive hits at two different distances, completing one of his goals. There was one more knife in the magazine, so he fired it off, and that one ricocheted to the ground.

If you're interested in the layman's synopsis, watch Quint's video in the masthead. For those more technical-minded, we've included the more detailed engineering video above. However, as cool as it is, please don't try this at home.

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RudyBob

Posts: 712   +675
As a kid we often took family trips to Mackinaw Island where I could buy pretty decent throwing knives. I never put anyone on a balloon wheel but I got pretty good with those things. My parents FREAKED when they saw my bedroom door.
 

mbk34

Posts: 358   +260
I wonder if they'd of done better with a pneumatic throwing arm rather than high power motors and batteries. It would be lighter and could perhaps have longer range as it could then throw a knife at 45 degrees. If it could carefully monitor the speed of the arm then it could calculate when to release so the rest of the "gun" wouldn't have to be so precise. It would probably need a balancing arm to stop the throwing motion moving the gun too much.
 

p51d007

Posts: 3,310   +2,919
Oh no! I can here the anti-gun people screaming that we need to now ban
semi-automatic knife throwing machines LOL
 

Nobina

Posts: 3,882   +4,392
Even though things like these are pointless it's interesting to see what a man can build if he's determined. An average person won't give a **** unless it's something mass produced and sold. Every man should build something.