Tetra Manipulators

okay, this is personally my biggest concern. Designing an Appendage witch is Gracefully Powerful and proficient in handling the tetrahedrons. From the grabber mechanism to the arm Assembly or tentacle or whatever. What are your thoughts?

I’ve been giving it some pretty heavy thinking(seeing as its the only field element) and i think tetra grabbers are not going to be anything fancy. To lift one all you really need is a swinging pole with maybe a hook on the end and a stopper to stop the tetra from falling too far back down the pole. Thats about as simple as you can get, but even the best shouldn’t be too much more complicated. I’m thinking something akin to a fork lift with no powered grabber, just the up and down motion of the fork lift prongs. Anybody any ideas that more clever than that? (not that its particularly clever or anything)

YAY! people who did OCCRA this year just might have a bit of an advantage! tubies and tetras heh. close enough lol.
well stacking them on a goal is pretty simple once you figure a way to grab and lift that high. because the tetras can be placed with any side facing down… well except the vision ones im guessing?
well anyways. if you can think of a strong reliable way to actually grip the pvc securly. maybe a simple claw. but i dunno.
is flinging these tetras against the rules? im not sure… because if you can make a backboardish thing, flinging these wouldnt be too hard… dangerous yes. so if you can get a consistent arc with no spin, youre a winner.
ok ignore me.

here’s a place to look for ideas-

in 1997 the playing pieces were inner tubes hung on a rack or topping a pyramidal goal. The grabbers from that year would be very similar-

look for the designs from Toroid Terror

WC :cool:

yes, it is. i can’t quote you the section in the rules yet, but i remember it was one of the questions during the “quiz show” at the end of the webcast. you were correct, it’s just far too dangerous to send those objects flying.
i agree with you Ian, simple ideas do sound good right about now!

just to second that it was said multiple times that flinging, throwing and tosing of the tetras is not allowed… so basically no projectiles.

well man, from what i can tell the actual construction of an appendage to lift the tetrahedrons, but rather the effect that having such a long endefector, or the power necessary to power a platform or forklift type object for lifting and stacking the tetrahedron will have on the 'bot’s center of gravity.

Uhhh, if u make a ski-like design with a pole about 2 ft down, u can keep the tetra from sliding down the pole and the ski-ended part will keep the tetra on and allow it 2 b easily unloaded onto the large stationary tetra.

   _______L_____¸,.  <---Ski

Obviously the problem with the arm isn’t going to be grabbing the tetras, parsay, but getting them up high enough. It would be pretty sad to get to a match where every robot was only designed to just put one tetra on top. Imagine how much fun that would be for the one robot that could stack higher…

As stated before, it throwing the tetras is not allowed. The rule is G23


In addition to getting the tetras high enough, there’s half a million ways to get a little bit of extra height out of your arm component but The arms can only get so high.

I think grabbers than can get a little extra height with the tetras are going to come through in the end of matches to get some final rows in where grabbers that are simple and work quickly might not. Where and how you grab the tetra has a big effect on wether or not you can put on the highest tetra.

Howabout a forklift that had an arm extending out with a ball jointed grabber hanging on it to grab tetras? Kind of like one of those stuffed animal claw machines.

the problem with that is that then you have to get your arm on top of the tetra. Something that can hold the tetra flat (like it would rest on a flat surface) by one of the bottom corners, or pvc pipes is going to work best as far as height.

Or pick the tetra up from the bottom PVCs and hold it tilted at an angle towards the robot. That way, you wouldn’t have to get the tetra as high up as the goal, just almost… and then tilt it away from the robot, lower the tetra however low it must go, and then move away.

At least… in theory, that works. I’m working with 6 unsharpened pencils, put together like a tetra with scotch tape … and two other, separate pencils with a part of an unused row of small staples taped to them to test out my grabber ideas :stuck_out_tongue:

If I learned anything from a late-night 1257 brainstorming session, it’s that straws and tape work best.

right. so if you get a small (Well doesnt have to be small) grabber that will grip one side of the tetra tightly enough so it wont slip or spin, then you can use a 4 bar or anything w/e to lift it vertically … and then have a bit of or wait a second… since the sides of these tetas are uhhh 60 degrees?or a bit less i think… since its not a pyramid. dont feel like looking up geometry dimensions now… well anyways, if you get a grab on this at one side from a 120?60?(where am i measuring from?) angle,

(o is the arm axis)

and then rotate the arm up so itll look like

then you will have a 'holding as if it were flat on the ground" even though the
arm has rotated… makeing full use of the tetrahedral shape… little problem with the vision ones tho im thinkin…

Thats what i was thinking. If you don’t drive into the large tetra stacks (over the pvc bars and such) your robot will have to reach about 2 feet in to get it over the top of the stack. But after that just lower your arm/forklift/whatchamacallit down and i’m pretty sure the tetra will sort itself into a nice position.

I guess the question is, are other teams going to be knocking tetras from your grasp. Without an actuating grabber your tetras could easily go flying.

i thought that it would be a good idea to have an arm the has a 60 or so dergee angle on it so you can hold two of the base sides for a better hold then have it clamp down on the pvc, and lift it up like a fork lift
___ <-- fork lift type structure
|| <- arm

  /\ &lt;--tetra, with out the third side

imagine it from looking down at it, also imagine that the arm has about a 60 degree angle on it because if i remember right tetras have 60 degree angles. then have it drive up to it get it with in the arm angles and then with the two grabbers on each end clamp down and use the fork lift mechanism to lift it up and cap the goal

Exactly how tight is that? Maybe it might be easier to handle a tetra if you grab it from a vertex, or from two edges.

But I do like the idea of taking advantage of the tetrahedron’s rotational symmetry.

Well, looking at one of the posts, I noticed this: “And one other thing about the tetras that may or may not be addressedsoon…holding some of them, a loose nut in one piece of the pipe will cause that part to spin around. Know that if you’re planning on building a one-pole grabber.” This could be another problem similar to somwhat deflated blass and deformed balls at competition in '04. It wouldn’t surprise me if this was considered part of the challenge. If in fact though the edges can spin, then any height advantage gained by grabbing an edge would be lost. (your arm has to extend to a little less than 9 feet, if you’re doing an arm that pivots at the base of the robot)