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Courtesy of FRC Team 118: The Robonauts
FRC Team 118 stands among the most accomplished and respected organizations in the history of the FIRST Robotics Competition, fielding competition robots engineered for peak performance and consistency.
This robot utilizes an 8 wheel west coast drivebase, with the wheels being large pneumatic wheels. The reason for this was because one of the defenses teams needed to be able to cross to score points was the Rough Terrain, where the pneumatic wheels were clearly the best option. Pneumatic wheels and a the raised front wheels of a west coast drivebase also helped when crossing other obstacles such as the Rock Wall, Ramparts, and Moat.
A multi axis arm is used to deal with the Drawbridge, Portcullis, and Cheval de Frise. There is a very wide large pivot arm made of plastic. The left sheet of the large pivot arm has a 2nd pivot at the end, making a double jointed multi axis arm. This 2nd pivot arm is driven by a belt to keep the weight of the the motor that drives it in the base of the robot. An additional separate pivot arm in conjunction with the multi axis arm is used to bypass with the Sally Port defense specifically.
This robot is a shooting type robot, though unlike most robots, it opted to use an adjustable shot catapult instead of some type of flywheel. This is likely so that the robot can simply drive through the Low Bar defense as it is a very short robot. While it is possible to make a low profile flywheel robot for Stronghold, the naturally ball flow through the robot would require the robot to turn around while crossing the field, which is less efficient than just moving forward.
Diag. R23.1: Ball Flow of Short Single Vertical Flywheel vs. Catapult
To support this adjustable catapult, the robot uses an through bumper intake with mecanum wheels to help filter Boulders towards the robot's catapult.
Unfortunately, this website does not include descriptions for any other Stronghold Robots. Another design worth checking out would be Team 254's design.
* Further explanation of the various mechanisms in FRC Handbook Volume 1.