YouTubers make laser-sighted, fully automatic, knife-throwing machine gun

Don't try this at home.
Loukia Papadopoulos
Knife throwing machine.
Knife throwing machine.

Quint Builds/ YouTube 

YouTube channel Quint Builds, the father and son duo, conceived of a weapon that's bound to blow your mind. Showcased in their most recent video published in August, the pair developed a laser-sighted, fully automatic, knife-throwing machine gun.

Inspired by a movie

The video says the YouTubers were inspired by the movie Under Siege where a navy seal throws knives at his enemies. “In theory it’s simple,” says the YouTuber in his clip.

“Match the knives’ rotation to the distance so the tip hits the target. But in practice it’s hard. There are so many other ways the knife can hit the board and I've found all of them.”

The YouTuber proceeds to demonstrate this fact with a board that gets hit from all sides by incoming knives. He then adds that even if he gets some success with a specific distance, changing this distance requires him to start the process all over again.

“Cutting edge technology should do this easily if we can keep it from destroying itself,” warns the YouTuber.

What are the YouTuber’s goals for this project?

They want a machine that can stick throwing knives consecutively from distances of three to five meters and that has no wires tethering it to an external power source or a computer. And lastly, they want a device that is light enough to carry, so less than 20lbs (or 9kg).

The YouTubers start by measuring the speed of a thrown knife. It is about 10 meters per second. The next step is figuring out a device that can launch the knife at a similar speed and rotation.

This device will make up the main part of the new weapon and consists of motors and pulleys.

Power motors

“I don’t know if we can find motors powerful and fast enough to throw like a human,” warns the YouTuber. Will he achieve this difficult task?

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The solution is found in high performance servo motors. The resulting machine requires some pretty powerful batteries but the YouTubers do manage to test it.

Unfortunately there is still not enough torque to accelerate the knife’s mass enough for it to be thrown at human speeds. The YouTuber then decides to use two of these devices side by side, doubling the power and running one faster than the other to spin the knife any way they want.

“Think about it like one of those helicopter toys. It’s tricky but you can spin it and throw it at the same time,” says the YouTuber.

Linking two motors together requires a very sturdy base. That’s why the YouTubers choose metal for their base and effectively cut it up into all the necessary parts.

For the teeth of the weapon, they use a powerful 3D printer since every part the motors move need to be as light as possible. Once all the parts have been produced, the pair put together their formidable weapon and proceed to test it out.

Low and behold, it works wonderfully. We would not suggest you try this at home although the experiment is replicable.

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