2018-2019 Rover Ruckus Design Iterations
Design Iteration #1: Drawer slide arm with 40:1 NeveRest motor
We started out with mecanum drive and continued to use it our whole season. We started out using 3.7:1 motors, but changed to 40:1 for better torque and strafing. Then we used a drawer slide for latching. There is a hook on the drawer slide that attaches to the lander to pull ourselves up. Then a set of grabbers on the bottom that would grab minerals from the side, and gets extended up to be put in the lander. Soon we found that it would not extend far enough to put the minerals in the lander, and with the space limitations we would not have both on the same lift. We also realized that if we had both on the same system, we wouldn’t be able to be properly latched on at the beginning of autonomous, and we wouldn’t get the points for it, which are crucial. We decided to have one lifter for hooking on and another one for the grabber to pick up minerals. The hook was a tight fit, so the time we worked with it told us we had to change it. It was hard for us to accomplish this task so early in the season, especially with a tournament earlier than when we would normally do. As a team, we decided that we needed to move to a different type of mineral intake because we were running out of time to make the grabbers work.
Design Iteration #2: Drawer slide arm with spool, pulleys and string
Next, the string would not stay on the pulleys, and the string would not stay on the spool. To fix this we changed the string to kevlar string. We changed the string because the Actobotics string didn’t have enough strength to pull us up and hold us up on the lander. Next we changed to 3D printed two-way spool and pulleys. The spool is a two sided system, one side to lift the arm and the other side to lower the arm. The advantage of this design is that the string stays on the spool and the pulleys because they have higher side walls than the other ones we were using.
Design Iteration #3: Mineral sweeper and box
Because we were not sure about the grabber design for collecting minerals, we changed to a box mechanism with a sweeper. The sweeper is made with zip ties and the box is designed in CAD and 3D printed by Katie. The idea behind it is to use the sweeper to collect the minerals, and the box would hold them before we would release them into the lander for the points. We came to a few issues, the major one being that the box didn’t have enough of a fillet on the bottom of it to effectively function the way we wanted it to. The next issue that we had was a few of our servo mounts were not sturdy enough to hold the weight and tension, and they broke off. The box also does not fit properly at the front of the robot with the wheel motors in the way. We tried moving our front wheels back to accommodate, but the wheel base became way too short.
Design Iteration #4: New hook for the lander
We found an issue with our lander hook, and we had to change it. Before we were using half a piece of c-channel that was bent, but when we were testing it out, it bent out of place, and our robot almost fell to the floor. We used a different piece of c-channel, a thicker flat piece that was bent to be our hook. After testing it numerous times, we found out that this was a lot stronger and was better for holding up the robot because it had more support in the bend of the hook, instead of having a weak spot because of the holes in it, like our original hook design.
Design Iteration #5: Drawer slide arm w/mechanism to deposit marker
The latest iteration that we have is with the drawer slide lift arm with a hook for latching to the lander, and with two c-channel guide posts on either side to keep the robot straight as it lands. We have the 3D printed two-way spool and 3D printed pulleys on the lift arm with kevlar string to lift and lower the robot on the lander. We have mecanum wheels with 40:1 NeveRest motors for better torque and for strafing to more easily and quickly hook onto the lander. Because we had complications with the mineral collection box design, we decided not to worry about that for our tournament, and instead, we added on a simple way to drop the marker in the depot during autonomous. A servo is attached to an arm that knocks off the marker carefully into the depot, to claim it. We also have a plow on the front of the robot made with flat c-channel pieces, cardboard and duct tape to push minerals into the depot during the driver-controlled period.