[Rick TYler]

Originally Posted by BurningQuestion

We use a simple hook to grap the tetra by the apex.
(...) The drawback to this type of tetra grabber is that we have less control over the tetra, and it tends to swing around a little bit. We are planning on adding a horizontal beam to the hook that will keep it from sliding down the arm too easily, and to hopefully steady it a bit. Non-actuating hooks work well, but only if you design them right.

The most efficient tetra manipulator we developed in mock-up used a skewer with a cross bar behind and slightly below the arm beam. We also found that the skewer worked better when tilted 5-10 degrees upward. So far, I've seen lots of skewers with crossbars -- some powered at the wrist and some fixed -- but only a couple that include that tilt.

Ironically, our team voted on a different manipulator in part because the fixed skewer was too simple. Some teammates wanted to be able to flip the tetra over and carry it over the body of our 'bot, others thought it the skewer would require too much reduction in the arm lifter, and, more importantly, it would have made the pneumatics team unemployed.