Torsion Onager 175+ Yards

     I am a 8th grader and I built this onager for my science fair project.  All the metal was laser cut at my dad's work.  It took about two weeks to build, just because of all the trips we made.  This compact machine launches a golf ball over 175 yards.  I am working on a better trigger system now and looking for a crank so we can go over 40 pounds of force. I am hoping to get a video up soon.

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    7 Discussions

    rjnerd- The sling i used is 2 feet long. the rope is 3/8 in. diameter. the rope was tightened by turning a nut with a ratchet on the small gear.


    6 years ago on Introduction

    Looks great! What range of sling lengths have you tried? What diameter and material are you using in the bundle? Did you pre-tension the bundle when you laid it up?