Weekly Update: Competition and Final Update

Figure1: View Of Cad of Final Machine



Figure 2: Our Machine In Competition

Our final machine ended up placing fourth overall in the “slot-bots” competition this past Thursday. For those that could not see our machine, it involves a cart module allowing us to drive back and forth, with an arm that travels vertically via acetal gear and nylon rack allowing us to reach the hard to get ping pong balls. The end of our arm, there was a rotating scoop driven by a motor in the cart that turned a stainless steel shaft with bevel gears rotating the scoop. On the front of our cart module we had our defensive module which was a wall that helped constrain the vertically moving arm. As the arm travelled downwards a switch on our wall released the wall flaps made from delrin and mesh, where two torsion springs expanded our wall outwards. The final rear defensive module was a very basic wall made from wood, used to protect our rear container.

Figure 3: CAD Model of Machine Showing Shaft Module

During the competition, out team decided not to use the wall flaps (zip tied together) or the rear defensive module, so that we could have a larger initial offensive move without violating the rules of the competition (No defensive moves first). We used a large amount of aluminum on our cart and welded a significant portion of our machine while using very high torque motors. This combination allowed us to push nearly every machine out of our way to score ping pong balls. Despite having technical trouble (A stripped Set screw in the motor) during the first round of competition, we came back and achieved a fourth place finish.



Our final design of our machine did not vary a great deal from our initial design. The biggest variation was the attachment of the torsion springs to the wall. In our CAD model, our torsion springs were just sitting between the wall and wall flaps. During the final week, we determined how to attach the torsion springs using extended hinge rod, and turned out to be successful. One other component we had trouble with was the timing belt we used as treads. The timing belts turned out to be very taught, and we had to manufacture new, offset bushings for the rear axle to accommodate the timing belt properly. It worked out well for us, providing extra traction on the arena.

Figure 4: CAD Model Showing Hiden Lines (Shows Timing Belt Pulleys, shafts, Acetal Gears)

The wall module seen below was modified slightly in the manufacturing process as well. Originally made from aluminum, we decided to save weight, and not make our cart as front heavy, so used a combination of delrin, acrylic and mesh. Finally, the last modification we made, that has been talked about in previous posts was the bushings. Originally planning on using delrin bushing, we sought something with less friction to use, and turned to Teflon. The Teflon bushing worked very well for our purposes letting our shafts turn well and being very low friction.

Figure 5: Wall Module Made from Delrin, Mesh and Acrylic

Overall, the competition was fun and we are happy with our finish. Despite some big and small problems arising throughout the semester, we pushed through and had a working machine for the competition, pulling out a top five finish.

Figure 6: Read Defensive Module that was not used in Competition