Hello folks, I have very little robotic experience, so would like to start my knowledge accumulation here at PhysicsForums. I am trying to design and build a launching mechanism to launch a 400 gram projectile. I was hoping to get a bit of guidance in what devices I should be looking into; motors, actuators, so forth. How are robotic arms constructed? What drives them? (As I write this, I'm almost preparing for someone to throw me a website of some sort for elementary questions such as this. That's fine.) Typical energy stored launching devices such as trebuchets or catapults are something I'm not looking into. In addition, pneumatic and hydraulic systems are also undesirable. I want to be able to control the mechanism with an ECU. This is something I have experience in doing, but don't have enough knowledge of mechanical components out there. Thanks for the help in advance.