Hi I'm new to the forum, I'm a mechanical engineering student at Drexel University. My younger brother and I are designing a catapult for his school competition, naturally I've decided to use it as an opportunity to show him that engineering is fun, especially with projectiles. Our design is simple, a metal frame with mounted ball bearings holding either side of the rotating shaft. In the middle of the shaft is a tee holding the catapult arm, which is a golf club shaft in our case. So right now we have a great low friction, light-weight rotating arm, now we have to come up with a launching mechanism. Does anyone have any ideas on the best way to do this? We're considering torsion or linear springs or possible elastic bands or a combination of methods. For scale the shaft axis is 16" and the launching arm is 36"