Frame design question

[team1631]

We are having a debate about our frame design. Could someone give us some input. We are wanting to create a 3 inch lip on the front of the frame and then attache the bumper giving a total of six inches. The lip would not constrain the balls movement. I am saying the frame has to be flat on all sides but others say the design is ok because it does not constrain the balls movement and is inside the frame perimeter. Thanks for any insight.

[Vikesrock]

I am saying the frame has to be flat on all sides

Can you support this with a rule?

If the bumpers will be attached to the lip of the frame and the lipped part still fits within the 28x38 footprint I see no rules that would restrict such a configuration.

[BrendanB]

I would suggest that you continue the lower part of the frame all the way to the front of the robot and have an opening in the front to allow for balls to come in. That way balls won't slip out underneath the sides of your robot/bumper perimeter like you do now.

Good luck!

[Matt C]

The lip would not constrain the balls movement.

Why wouldn't you want it to help hold the ball?

And to lend you insight, read rule <R19> and the associated diagram. assuming your "lip" does not allow the ball more than 3" under the FRAME PERIMETER, I see no issues.

Be sure to understand the difference between FRAME PERIMETER and BUMPER PERIMETER.

Also, look at <G30> part A in regard to the "ball hitting device" mechanism.

[team1631]

We were interpreting the rules as no corralling or holding the ball. Maybe we are reading to much into the possession rule. It would be better if we could put sides on the frame to keep the ball from sliding out.

POSSESSION: Controlling the position and movement of a BALL. A BALL shall be considered in POSSESSION if, as the ROBOT moves or changes orientation (e.g. backs up or spins in place), the BALL remains in approximately the same position relative to the ROBOT.

[Matt C]

POSSESSION is legal. (albeit one ball at a time)

CARRYING is not.

CARRYING is POSSESSION not in contact with the field.

So as long as your are not lifting up the ball...

Refer to rules <G43> and <G44>

[team1631]

cool thanks.

[Al Skierkiewicz]

Team,
If your design is a way to massage the 3" intrusion rule consider that the attachment for the bumpers is the edge of the 3" rule. You can make the shape of the robot under the bumpers whatever way you want, but you will be called if in the opinion of the refs, a ball enters more than 3" beyond the frame perimeter. The drawings in the manual R19 are very specific.

[Zanfardino2892]

POSSESSION: Controlling the position and movement of a BALL. A BALL shall be considered in POSSESSION if, as the ROBOT moves or changes orientation (e.g. backs up or spins in place), the BALL remains in approximately the same position relative to the ROBOT.

So is having multiple free spinning balls in front of your robot with general control of position illegal or would it be considered possession of multiple balls? Or are you not even allowed to intentionally go after multiple balls?

[Vikesrock]

POSSESSION: Controlling the position and movement of a BALL. A BALL shall be considered in POSSESSION if, as the ROBOT moves or changes orientation (e.g. backs up or spins in place), the BALL remains in approximately the same position relative to the ROBOT.

So is having multiple free spinning balls in front of your robot with general control of position illegal or would it be considered possession of multiple balls? Or are you not even allowed to intentionally go after multiple balls?

If the balls are free spinning and not controlled by any mechanism on your robot they will not stay in the same position relative to the robot if you back up or turn your robot. When backing up the balls will stay in their same absolute position as your robot moves away, and when turning they will at there will be a relative movement across your robot sideways.

Based on this it would be legal to have multiple balls being pushed by your robot.

[Zanfardino2892]

what if the balls are3 only controlled or held by a light suction by either rollers or fans? then they'd still have a tendency to move with the robot but not truly held

[Vikesrock]

what if the balls are3 only controlled or held by a light suction by either rollers or fans? then they'd still have a tendency to move with the robot but not truly held

The definition of POSSESSION is spelled out pretty clearly in the rule you quoted. A ball is either possessed or not, it can't be lightly possessed or sort of possessed.

If you back up and/or turn with a roller or suction the ball will probably stay in the same position relative to the robot (otherwise what is the point of using the device?) so it would be considered POSSESSED. You could only possess one ball at a time in this manner without receiving a penalty.

[Zanfardino2892]

ok. so controlling the tendency of a ball to roll toward a robot without grabbing onto the ball is that considered possession?

[Matt C]

what if the balls are3 only controlled or held by a light suction by either rollers or fans? then they'd still have a tendency to move with the robot but not truly held

You can only control one ball:
If you have a ball magnet/suction/roller/dark matter/whatever device that "held" or "controlled" balls and more than one ball enters it or touches it, I can almost guarantee you'll get a penalty.

[Zanfardino2892]

Ok. That's what I thought, thank you. You wouldn't happen to be a member of the Robovikes would you?

[DonRotolo]

A ball is either possessed or not, it can't be lightly possessed or sort of possessed.
Poltergeists notwithstanding :rolleyes:

[Bill_B]

I was thinking the same thing, Don. Anyone offering to exorcise a possessed ball? Or is it cheaper just to replace it? #5s are too small to be exercise balls, right?

[RRLedford]

What if frame is seriously convex to the point where it is curves a pocket into itself, like an island atoll and having an opening on the wide side just larger than a ball? Would the bumper have to wrap both the outside and the inside "shore" of the "lagoon"? Could several balls be rolling around inside the lagoon area without being considered possessed, or having penetrated more than 3" into the frame zone? Would all the robot's H/W have to be built up ONLY within vertical space directly above the atoll shaped frame, or could some hardware protrude into the space above the lagoon? Why would there even need to be a bumper inside anyway, since no impact could ever happen there, and only "topologically" it is still the "outside" of the frame?
Kind of tricky getting a shooter concept to fit with this scheme for sure.

-RRLedford

[GaryVoshol]

What if frame is seriously convex to the point where it is curves a pocket into itself, like an island atoll and having an opening on the wide side just larger than a ball? Would the bumper have to wrap both the outside and the inside "shore" of the "lagoon"? Could several balls be rolling around inside the lagoon area without being considered possessed, or having penetrated more than 3" into the frame zone? Would all the robot's H/W have to be built up ONLY within vertical space directly above the atoll shaped frame, or could some hardware protrude into the space above the lagoon? Why would there even need to be a bumper inside anyway, since no impact could ever happen there, and only "topologically" it is still the "outside" of the frame?
Kind of tricky getting a shooter concept to fit with this scheme for sure.

-RRLedford

You would have to have a bridge across the mouth of the lagoon to attach your bumpers to, to meet <R07-M> and associated Fig 8.3. Note that the balls will still fit under the bumper attached to such a bridge. Therefore if the lagoon is more than 3" deep, you will violate <G46> and <R19>.

I would suggest spending a few more hours digesting the manual before you finalize your designs. You seem to have missed a few key rules.

[Zanfardino2892]

What if frame is seriously convex to the point where it is curves a pocket into itself, like an island atoll and having an opening on the wide side just larger than a ball? Would the bumper have to wrap both the outside and the inside "shore" of the "lagoon"? Could several balls be rolling around inside the lagoon area without being considered possessed, or having penetrated more than 3" into the frame zone? Would all the robot's H/W have to be built up ONLY within vertical space directly above the atoll shaped frame, or could some hardware protrude into the space above the lagoon? Why would there even need to be a bumper inside anyway, since no impact could ever happen there, and only "topologically" it is still the "outside" of the frame?
Kind of tricky getting a shooter concept to fit with this scheme for sure.

-RRLedford

Any convex part of the frame will not be considered as the frame perimeter, if you have a convex are you want the ball to sit in the ball may only go 3" past the line created by wrapping a string about the corners of your robot, that is what defines the frame perimeter

[Al Skierkiewicz]

From the definitions at the beginning of Section 8...

FRAME PERIMETER – the polygon defined by the outer-most set of exterior vertices on the ROBOT (without the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a piece of string around the ROBOT at the level of the BUMPER ZONE - the string describes this polygon.

The string in your scenario bridges the lagoon and crosses the island.

[RRLedford]

From the definitions at the beginning of Section 8...

FRAME PERIMETER – the polygon defined by the outer-most set of exterior vertices on the ROBOT (without the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a piece of string around the ROBOT at the level of the BUMPER ZONE - the string describes this polygon.

The string in your scenario bridges the lagoon and crosses the island.

Well, my curved "atoll" frame effectively has no vertexes (or ALL vertexes), so it is NOT a polygon. Perhaps, a topologically proper string "wrap" should enter and follow around the shore the lagoon? I guess not.
It appears that the rules clearly are meant to discourage curves in general, and all but the shallowest of concave perimeter shapes in particular.
-RRLedford

[EricH]

Well, my curved "atoll" frame effectively has no vertexes (or ALL vertexes), so it is NOT a polygon. Perhaps, a topologically proper string "wrap" should enter and follow around the shore the lagoon? I guess not.
It appears that the rules clearly are meant to discourage curves in general, and all but the shallowest of concave perimeter shapes in particular.
-RRLedford
As you're a rookie, be glad you're in this year's bumper debates instead of last year's. Last year's rules were almost the same, though with an allowed opening percentage, but the way they were written and a required piece of hardware (that had to be included in the opening percentage) practically forced a rectangular design. There was one case where a particularly tricky design to call had to be shown, Q&A by Q&A and rule by rule, where the interpretations of the GDC differed from the design. (Admittedly, this particular limitation had already been accepted by the team. Someone else was pressing the issue.) This year's are much easier, at least for those that were around last year.

And convex curves in general are not prohibited; see http://forums.usfirst.org/showthread.php?t=13723

As for concave perimeter shapes, the only place you can't have them is on the frame perimeter and anywhere you think a ball can get into the lower frame perimeter more than 3".

One thing I might suggest for next year's rules is the changing of the word "string" to either "stretched string" or "rubber band", as a number of people have thought the same thing.

[Al Skierkiewicz]

Dick,
Where in Chicago are you located? Perhaps we could meet or I can come over and explain some of the nuances of this years game to the team. Just PM me and we can see what we can set up.