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We decided to go with under the bumper for the packaging benefits. It would allow us to have a lot more space for other mechanisms, while protecting our intake at the expense of a small amount of reach. Due to the large plate, we then integrated the intake plate with our amp mechanism. The top of the plate is pocketed for weight savings, while lower portion of the plate is pocketed for strength purposes.
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The active indexer allows us to quickly center game pieces. The polycarbonate intake without any grip tape allows the note to slide sideways which prevents rip.
To prevent “stick” we utilized 0.09 and 0.125 thick aluminum plates as they’re stiffer and lighter than polycarbonate, as well as polycarbonate having higher friction with the note (plates transparent for viewing).
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Inspired by 3255’s and 6328’s shooter, we made a new shooter which utilized spin and decreased the compression of the game piece.
We also switched to 3 inch flywheels and added another row of wheels to increase shot consistency.
Both sides are decoupled which allows us to run speed differentials to add spin to the note, allowing us to have a significantly more consistent shot.
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This light but strong amp mechanism allows for low mass movement when scoring to an optimal location, allowing for extremely fast yet safe scoring and the allow for flexibility when slamming into the amp.
We chose to decouple amp from our shooter as it keeps the reliability of both mechanisms separate. If shooter breaks, we can still amp, and if amp breaks, we can still shoot. It also allows us to optimize our amp and have a more optimal scoring position.
Early on, we calculated that we needed at least 2lbs of wheels for a shot with 40ft/s projectile speed which was the minimum to consistently shoot from wing. Over-under vs side-side wheels was a huge question for us and the answer was mainly chosen due to questions about spin, which projectile modeling didn’t account for. Videos from teams such as 95, 6328, 5026, and 8033 helped influence our decision. The concept of shooter rip, or shot inconsistency resulting from the note dragging along surfaces moving slower, meant that we needed a separate kicker/feeder to minimize shot deflection as well as separate our game piece storage from our pivot in order to improve cycle time. Our shooter pivot needed to have sub degree accuracy for accurate modeling so we followed 2910 and 4414’s lead and used shim tape in the gearbox combined with an inline tensioner and current zeroing to remove the need for an absolute encoder.
During Revision 1, we finalized pivot location but we used a MAXPlanetary for our pivot and we had no spin on our shot which meant we could shoot from the podium at the most.
In Revision 2, we switched from a MAXPlanetary to a custom gearbox as MAXPlanetaries were out of stock as well as custom gearboxes allowing us to significantly decrease our backlash through shimming and tensioning.
In Revision 3, we decided to mechanically link both sides of the flywheels together to increase system consistency, before switching to our final revision detailed later.
Our final shooter revision mixes the concepts we learned, while adding the idea of spin. Spin is incredibly important, it helps shot consistency and allows you to shoot from significantly farther distances, decreasing our cycle time.
By splitting the two sides of the flywheel and making them separately powered, we can control how much spin we want in the note, creating a fast, but smooth trajectory.
We also emphasized contact time. Unlike a lot of other teams, we use a second row of rollers in order to contact the note for longer. This allows for longer energy transfer to the note, meaning a more consistent shot, as well as needing less power. We still utilize an upduction for additional speed to hit a more ideal spot on our motor curve, but the 3 inch wheels compared to the traditional 4 inch flywheels compensates for the decrease in torque.
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We had two different styles of intakes we considered, over the bumper and under the bumper.
We initially started with an over the bumper intake due to simplicity reasons and because we had designed one previously in our “Robot in 24 Hours” CAD. An over the bumper intake would have more reach due to less packaging concerns but would also take up more space on the bot due to the pivot location. Packaging was a huge issue once you considered “shooter rip” The intake took up half of the robot, and if the intake was contacting the shooter at the same time, the game piece would “rip” which would damage the game piece and mess with shot consistency. We had more experience with this type of intake but it was also fragile and polycarbonate and 7075 aluminum can only take so much force, and we don’t have the resources to constantly do swaps and make multiple intakes..
A under the bumper intake would be more durable and allow us to win the center line auto race without concern of our intake breaking as well as allow us to drive more aggressively while intaking, reducing the need to care about defense. However, packaging was an issue as the gap between our swerve module was only 14”, the exact width of the note which wouldn’t allow us to package an intake in between them, which we resolved in our final version.
In a future revision, we eventually switched to a 1.65 solid leading roller, which helped with our compression issues and allowed for a more consistent intake. Additionally, we added nut strips and added superstructure triangle supports (as seen on the physical robot) to increase the intake’s stability, reduce the cantilever, and ensure there is enough compression.