Pretty much the topic. I’m interested in how the good teams did it. Does anyone have any?
Here is a picture of the goal grabber that Team 228 used in 2002. The general mechanism was somewhat overengineered, but it worked flawlessly. The two steel grabbers would squeeze between the bars of the mobile goal, and when the piston fired they would be pushed apart into the bars.
This is the best picture that I could find of Team 340’s 2002 robot. The grabber consisted of two claws that would open with a pneumatic cylinder. Each claw consisted of a limit switch. This made for a cool program. If one limit switch was in contact with the goal, the robot would automatically turn until the other switch was enabled. Then the claws would close simultaneously. The robot also had a lowering system. After the robot latched onto the goal, the entire frame would lower to the ground. This gave us better traction and a better center of gravity.
Best pic of Sparky 3.0’s system…
Basically, three T shaped hooks held perpendicular to the playing field could be tripped by a mechanism once the goals get inside the Ts. Then, they would rotate to be parallel to the playing field, and locked the goals in.
The Bobcats (Team 177) used a very slick statically operated latch. It was based off a similar design from Team 38’s goal grabber in 2001, and refined by (then student) Tom Schindler. Simply put, as the goals’ vertical pipes slid into the latch, a spoked gate would turn against a spring-loaded ratchet/cam. At this point, the goal was locked and could only be released by pulling the cam out of the way. We used two of these latches, spaced about 30" apart to secure the goal. We had zero problems with the latch, and never lost a goal once we had it.
Below are a couple pictures. One is a close-up, showing the rotating gate and the spring-loaded cam. The other is a top view, showing the placement of the two latches. The entire mechanism was extended horizontally on 8020 bearings.
Feel free to ask if you have any questions.
Here’s one that I had a hand in, 188’s 2002 robot, Blizzard 3. It worked very well indeed. (On each side, a piston for extension, a piston for locking, and a pivoted, spring-loaded head that allowed it to attach while imperfectly lined up.)
There are many more here in the galleries of the Waterloo Regional website.
Here’s 696’s 2002 bot. It has a quite unique worm gear driven set of arms. I don’t think there was any other like it. Worked quite well.