Today we built our first prototype catapult (that actually worked!!!), which can be seen in this video. After figuring out the shape of the "flinger" was the problem, we changed from the bent chair legs to just a piece of conduit bent twice. Both "flingers" can be seen in the video, the conduit mounted on the cart being used and the chair legs sitting on the bottom of the cart. The biggest problem was the general geometry. The flinger has a constant angular acceleration, but that translates to linear acceleration based on how far away the ball is from the pivot point. Because the chair legs are bent at half the length, the end of the chair legs prevent the ball from getting to the back of the chair legs, which would be the same as using a straight "flinger" that is half the length, meaning half the linear acceleration. This is the main reason why the conduit works so well, since the ball can get to the back of the conduit, meaning larger linear acceleration for the ball since it is further away from the pivot point.
This was found after an increase in tension with the chair legs had no significant affect on the ball's flight. This change made the ball go from being shot 3' high and 5' far to 7' high and 25' far, with the same amount of tension. This was now a proven design, although we did want to see whether or not an air powered launcher/puncher would work better or be more compact.
It is safe to say this design of the shooter has now moved out of the conceptual design and is in the middle of preliminary design. We have now shown the concept works and works well, and are in prototyping phases and have made basic CAD models and other drawings.
Intake
Today the intake group looked at ways to build an intake, and have now decided to use information we found from the Robot in 3 Days groups, and past intakes we have built. As expected, roller intakes appeared to work, so the intake team began building a roller intake as a prototype, powered by a drill motor. This was much more desirable than a claw due to the speed of the intake and outake.
Drivetrain
Today we began to get the drivetrain working, but it was primarily modifying software, rather than making hardware changes.
Catcher
Today I created a CAD model for a potential catcher, as we came up with an idea to use a funnel. Since robots have to start within their own frame perimeter, but can expand outward after the start of the match. The catcher is similar to a cardboard box with 40" flaps that extend 20" outward.
We had two ideas for actuation (moving the stuff), either directly controlling the sides using pistons, or make the edges like levers, and actuate the levers with either pistons or motors. After discussing both, we made prototypes of each, the first actually using a cardboard box, and the second using PVC pipe.
Now, most individual mechanisms were out of the conceptual design phase, and into the preliminary design phase.
Approximate times of working: 3:30 PM -7:30 PM
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