Design Project 2 was the biggest project for the quarter. We had to design a machine to wait, move, stop, wait, turn, move, and shoot a ball into a bucket. Please see the instuction sheet, especially page 2 for the diagrams.
We were in teams of 3 people that we got to pick, so I was with two of my close friends, which made it that much more fun! We had about a month to complete the project, and at the very beginning, we decided we were not going to be one of those groups pulling all-nighters the few days before it was due. We met to work on the project pretty much every available time, which was nearly every day. The good news was that the plan worked, and we were finished a day early! We started with lots of brainstorming and prototyping. My experiences with robotics were helpful, because I had a better sense of what might work. There were two main part of the project - the movement and the triggers. The trickiest part of this project were the triggers and getting all the different components to work together and trigger at the right times.
We began by trying to figure out the movement - it needed to move forward, stop, and then move to the left. We prototyped an idea of a turning wheel, but we quickly realized it was not going to work. We ended up using 3 different types of wheels: one pair that we made out of CDs, one pair of casters, and one pair of omni-wheels. Omni-wheels (which I knew about from robotics) are wheels with little rollers on them, which enable them to slide sideways in addition to rolling forward. The CD wheels and the omni wheels were powered by wound-up strings and falling weights, and their axles were mounted perpendicular to each other. The CD wheels powered the first movement (with the omni wheels sliding sideways) and were built into a hinged contraption we designed to lift the wheels off the floor once the string reached the end. Then a second weight fell, powering the omni wheels "forward", which was to the left of the original starting configuration. We had a catapult to shoot the ball into the bucket. Then we had to figure out the trigger system. We deided to go with golf ball mazes, so the golf ball would take time traveling through a small maze and then hit something to start the next action. We designed a trap door system to release the falling weights, so the golf balls hit levers which released trap doors. There were 3 golf balls, plus another lever system.
So, the sequence of events in the final machine was:
1) Pull up a piece holding the first golf ball in place, releasing it
2) Golf ball travels through maze for 5 seconds, then goes down ramp, hitting a lever that releases the trap door with the first weight and the golf ball falls into a bag to keep it contained.
3) The weight falls, unwinding the string around the CD wheel set, moving machine forward, and popping the wheels up when the string runs out.
4) The falling weight lands on a lever that hits more levers to release another golf ball down a maze, a ramp, and hits a second lever to release a trap door to release the second weight.
5) The second falling weight powers the omni wheels so the machine moves to the left.
6) The weight hits another lever that again triggers more levers to release the third golf ball.
7) That golf ball falls down a chute to hit the lever that pulls the pin out of the catapult, releasing it - catapult fires ping pong ball at the bucket!