Team RANA: Team RANA Final Blog Post

At the start of the semester, our team decided that we wanted to create a machine that was capable of efficiently collecting the red balls from the upper ledge of the arena without having to travel up the obstacle-filled (golf tees) incline to do so. Thus, we quickly decided to manufacture a machine with a rotating arm that could "rake" the balls down from the incline so that we could collect them and deposit them into our own goal. The benefit of this strategy was that we wouldn't actually have to collect many balls to earn a large number of points, which would make our team difficult to defend against.
Initially, we made our machine as bulky as possible, with its largest components barely fitting inside the 12"x18"x24" guidelines. After making a solid model of our concept, however, we realized that maneuvering our machine around the tower would prove very difficult (and it would be impossible to move behind the tower if we wanted). Finalizing our then-concept of the machine on Solidworks and checking the mass properties, we also realized that the dimensions we had set would make our machine far too heavy for the motors that we were being provided with, so we spent some time during the following week making our machine more compact and using different materials (e.g. acrylic) where possible to make the machine lighter.
Our machine had two independently-driven wheels in the back, with two ball casters (one from our own kit, and one obtained from trading with another team) in the front. This allowed us to maneuver the machine easily with a very small turning radius. Our most critical module was our arm/trap door mechanism. We had a single planetary motor that controlled the angular motion of both the arm and the trap door. The idea was that, as we lowered the arm to rake in balls, we wanted the trap door to be open so that the balls could be collected in the machine "holding reservoir" (area behind the trap door within the main body of the machine); then, we wanted to somehow close the trap door so that we could move the machine around without losing any balls that we had collected (we saw that this was a major problem with previous years' machines and was something we wanted to avoid). The way we decided to do this was to introduce a series of four gears, one of which would be driven by the motor and which would drive the other gears to move the arm and trap door. In our final setup (as is apparent from the pictures), lowering our arm automatically raised the trap door, and raising the arm lowered the trap door.
When we finally manufactured and assembled our machine, we realized that we had to revise our strategy since the planetary motor could not drive our long arm. Thus, we made the decision to shorten the arm and go after the black balls on the incline. Once we shortened the arm, the planetary motor was easily able to control the motion of our arm, and our most critical module worked beautifully.