Larger bore actuation speed

[ollien]

My team has been trying to use a pneumatic launching mechanism and we hit a brick wall today when we realized that it didn't shoot high enough. At the practice field we were at, another team's mentor mentioned that we should use a higher bore size than we are using. We presently use a 7" stroke and 3/4" bore. I know that increasing the bore size would increase the force, given F = PA but wouldn't it also decrease the speed of the pistons, given Av = k, thus lowering the initial speed of the boulder and decreasing the effectiveness of our catapult? Am I missing something?