Claw ideas (particularly materials and such)

[All Bones]

Alright, I've done most of the conceptual designs for the claw of our bot to grab the tubes this year and I've figured out a few things.

1. Optimal space in between the claw should be about 6.25 inches
2. The bottom part of the claw only has to be as long as the height of the tube(s)
3. Being able to hook under the tube then rotate the claw at the point where it meets the arm until it is above the tube and perpendicular to the tube will make it arguably easy(ier) to pick up tubes. Or you could just keep the claw pointed down as you drive but that would be boring.

And
4. Rubber bands and wood can easily grab the tubes by themselves if used with the 6.25" gap and step 2, so obviously not much power is needed

However we can't build a functional claw (well maybe functional but probably not practical) out of wood for the competition. What I was thinking was, where the two parts of the claw meet, it would be optimal to keep the bottom most part non-movable and put some kind of gear teeth on the inside edge of the top part, still where the claw meets the arm. Then just use a servo to spin a gear that will close the top part of the claw. We were also considering adding extra space to the top part in order to put in a kind of roller to manipulate the tubes vertically. Other then all that though, I'm not sure how to build it. Like what materials to use or how to attach it to the arm (which is not fully designed yet so please don't ask anything regarding that). Any suggestions would be appreciated.