[bobdahaxor]

when you decide what you want to do, think about the weight of the ball. The ball is 10 pounds and 40 inches in diameter. that is quite heavy. If I were you,I would make a list of the pro's and con's of each type and then make a list of what you want your arm to do. Then compare the pro's and con's list to the list of what you want the robot to do. Besides that, I want to warn you that scissor lifts are extremely hard to properly manufacture. I also did the math for the spring (gotta love physics 201 and oscillation's and elasticity) and pushing or punching the ball is out of the question. There is not enough of an impulse to do so. I have a hint though (or for what I think is a good idea). That 8020 you got in the KOP is more than likely just sitting there. It can easily be used as more than just a square tube.