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Custom-Built Knife-Throwing Robot
FARM SHOW reader Austin Elliott suggested we check out a knife-throwing machine on his YouTube channel. It introduced us to an engineer with a knack for explaining complex projects.
    Quint is an engineer with 20 years of experience, a lifetime of curiosity, and a desire to share knowledge. His website provides links to more projects, all designed to educate, inform and interest kids and adults alike.
    The knife-throwing video provides overviews of the building process. It also includes challenges and mistakes, including frying a $150 LiDAR sensor.
    Quint built the knife-throwing machine to better understand the physics behind the process, something he didn’t understand when he started. He also enlisted the aid of his teenage son to program the electronics and learn alongside him.
    The goals were to stick 10 consecutive knives, make it mobile and cordless, and weigh less than 20 lbs. They achieved the first two but overshot the third by 50 percent.
    The video starts with the metal framework Quint built to hold the various components. It covers their choice of high-performance servo motors to power two double-sided timing belts that provide propulsion and their use of 3D printing and machining of parts.
    Quint’s son wrote code for a computer processor to control the servo motors and other electronics. High-speed starts and stops were needed, as was a way to hold, rotate and release knives on command.
    Quint designed a toothed carriage to travel between the belts with an electromagnet to hold and release knives. He outfitted it with electric motor brushes to power the magnet and a solenoid with a custom-designed plunger to help keep the knife in place until release.
    A LiDAR sensor provided distance data to the controller, which then adjusted the targeting laser for the trajectory of the knife. Soon the father/son team was able to stick five knives in each of two targets at different distances. The process took about 8 mos., starting with a spreadsheet of calculations on things like the mass of the knife and the force needed to achieve velocity.
    Quint gives a lot of credit to an online learning platform called Brilliant. He noted that their lesson on axe throwing taught him engineering concepts his 20 years of work experience had not provided. The website uses hands-on, interactive problem-solving (like ax throwing) to teach math and science fundamentals.
    A final set of videos will be of value to anyone engineering their own projects. Quint is one of only five people in his home state of Oregon and about 500 around the world to hold a senior-level certificate in Geometric Dimensioning and Tolerance (GD&T). This is the engineering standard governing mechanical fit of parts. Those videos can be found on his channel Quint GD&T and are well worth a visit.
    Contact: FARM SHOW Followup, Build2Learn, 16055 SW Walker Rd. #202, Beaverton, Ore. 97006 (quintbuilds@gmail.com; www.quintbuilds.com).

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2023 - Volume #47, Issue #3