Final Testing of the Rov Arm

My Rov arm, which was mounted upon Team Decepticons Rov, competed in the 2008 New England Regional MATES competition. The arm was required to grab simulated rock crabs, where it could attain a maximum of five for 20 points each. Each rock crab was made from a 1 and ½” ABS. Attached to this were eight pipe cleaners for legs, and two bent pipe cleaners for antennas. For every crab lifted off the pool bottom ten points were awarded by the competition. For every crab brought to the surface an additional 10 points were awarded. The arm was also required to be maneuvered into a simulated hydrothermal vent where the temperature gauge mounted to its side could obtain a reading. A maximum of 100 points were awarded if the temperature readout is within 2 degrees Celsius. Lesser amounts were given for lower accuracy. The vent was a ½” PVC pipe mounted vertically at the bottom of the pool.
Initial testing was done in the small pool in the systems lab, as well as out of water. A shortened tether was attached to the arm and all functions of the arm were tested. At this point everything worked as planned. The arm was able to pick up five pounds of weight and hold it with no issues.
After the Rov was completely assembled the final tether was filled and attached to the arm. The arm was then submerged in the pool. With the new tether attached the arm opened and closed much slower, but with the same force. The arm was able to grip a rock underwater and hold onto it as it was pulled out of the pool. The arm was also able to grab onto small waffle balls with weights inside that were close in size to the rock crabs. Further testing was done after minor modifications were made to the design. After boring out the syringe holes to a larger diameter the system operated at nearly twice the speed.
While obtaining the temperature, a readout of 54 degrees Celsius was shown. This was within 2 degrees Celsius of the actual temperature and 100 points were awarded to our team. The thermometer setup had a quick response time and showed the temperature within one second of being placed over the vent. When grabbing the rock crabs one crab was obtained and brought to the surface for 20 points. Five points were later deducted for pulling on the tether. Pulling on the tether had nothing to do with the arm and was necessary as the craft was not moving due to the propulsion system. On the second attempt to capture a rock crab the hydraulic control syringe at the top of the pool broke. Too much pressure was applied while lifting the first crab and the arm locked into place. When trying to reset the arm the rubber seal separated from the plastic plunger, breaking the vacuum seal of the system. This prevented our team from capturing another crab, although we only had two minutes left at this point.
Our team ended up placing 6th out of 14 teams. The total score can be seen on the attached sheet. Shown below in Figure 1 is our Rov completing a task during the competition.