It's fascinating for me to see this layout of the whole process, because I was involved with prototyping from day one. There was a team of a few students who only worked on the "chokehold" mechanism for all or most of build season. It was amazing being part of that team, and analyzing the geometry of the cans and landfill and robot and different materials we could use and different ways to bring the cans in afterwards.
My favorite part was designing the hooks themselves, in the early stages. One thing Mr. Harvey didn't show as much is how the hook design changed. When we were working on a 4-recon grabber, we had one design of the hooks that looked like this:
http://imgur.com/9si9wYw
http://imgur.com/ER59TsF
http://imgur.com/grvPWZZ
http://imgur.com/fwo7YVL
They would go into the center of the hole, and the two "fingers" would bend in and snap out because of torsional springs around a bolt at the pivot point. Those strings held the two fingers in tension against the spring, and in the final design with the bent sheet metal, there were pneumatic pistons that these strings were wrapped around. To release the cans, the pneumatic pistons would release, allowing the strings to fall and release the fingers, which would release the cans. We realized that we wanted a passive release system in case of a tug-of-war, so we experimented with looping a zip tie over the pistons, and tying the strings to the other end of the loop. If there was too much force, the zip ties would break without the pistons needing to release, and the strings would release. This was one of our final designs of the hooks for the 4-recon grabber. I think we did some CADing to make the design more sleek and lighter, but I don't think the mechanism changed beyond that.
I was not as involved with the 2-recon grabber, because I focused more on the chairman's presentation at that point in the season, but the hook design changed to something without any moving parts or active systems, which is what we used for CVR, Sac, and SVR, and Mr. Harvey talked about the Champs hook design!
There was indeed an incredible amount of work done on this by a majority of the mechanical subteam at one point or another, as well as Mr. Harvey and Mike! I learned so much about the engineering process, and I'm so glad I got to work on it because it made me really excited to see other teams' recon grabbers!