-4 high strength motors on the base(geared for torque)
-4 normal strength motors on the arm(geared 12t to 36t, then 12t to 60t)
-Intake mechanism is a tube through the middle with intake rollers on the outside
The base is a 4 high strength motor cantilevered X type holonomic, with the high strength motors geared for torque. Each wheel has a quadrature encoder attached directly to the shaft. This base allows us to move in any direction, with enough torque to easily push goals around. The disadvantage of the cantilevered X base is that rings can very easily impede movement, but this problem can be solved by placing a suitable guard on the outside of the wheel. The frame in the middle of the base consists of 5 hole wide C channel attached together to make an X that is 35 holes long in each direction. The reasoning behind making the X base as wide as this, which is basically as wide as is practical within the 18" size limit, was to increase stability and prevent it from being tipped over easily, as would have been the problem with a smaller holonomic base. The disadvantage of this is that the size of the mechanism is restricted more than would have been the case with a smaller base.
The tower is made again of 5 hole C channel, and is 25 holes high. It is attached to a 35x5 piece of C channel via more C channel which attach the sides of the tower to the lip of the 35x5 C channel, and is extremely rigid in this configuration. However, a piece of rail across the rear reduces the twist which could occur. The 35x5 C channel is connected to the X base by 4 standoffs, which were a real pain to force into the holes due to the 45 degree offset. The tower is a total of 25 holes wide, with two pieces of 25x5 C channel spaced 5 holes apart on each side, to form supports for the gearing and the arms. In the middle are all of the electronics, with the Cortex mounted by 4 rubber links to absorb sudden shocks to the chassis.
The arm consists of two 35x2 rails per side, each attached to a 60t high strength gear via two screws. The 60t gets its power from a 12t gear, which is in turn connected to a 36t gear, which is fed power by two 12t gears, each being driven by a normal strength motor. The reasoning behind having each rail attached to a gear is to help spread the load across the system, rather than having it all placed on one gear, which can cause issues with the gear skipping if you try and hang with it. Having the gears connected in the way that they are results in a 25:1 gear ratio. The robot can easily lift itself up, and could have easily hung. We decided not to hang due to the minimal swing in points from one robot hanging on an alliance. The robot is built well enough to handle the stresses of hanging, as it has survived falling off a 3’ high desk twice ><
The mechanism consists of a basic upside down U frame which is attached to the end of the 4 rails from the arm. On each side of the U frame at the bottom is an intake roller constructed from modified parts from the tank tread upgrade kit, wrapped around a 6t gear. Another 6t gear is opposite this, which receives power via high strength chain from a motor mounted above it, due to the X chassis preventing directly driving the intake roller.
In the middle of the U frame is a tube constructed from polycarbonate, which is held together using wire sewn through a series of holes. This tube allows us to pick up rings much like the well loved needle design, but also allows us to descore by pushing the tube down over a goalpost. It has a total capacity of 6 rings, which is a disadvantage when descoring.
Feel free to ask questions.
More photos at: