Question on 3 inch perimeter rule

[EricH]

Originally Posted by Sixis

The frame perimeter is defined as such: "FRAME PERIMETER – the polygon defined by the outer-most set of exterior vertices on the ROBOT". While it does go on to talk about the string, they give an exact definition for each, which further convinces me that the string is no more than a concept. I am not interesting in starting a fight, however this seems like a debatable point which is of interest to me.

Yep, and because it is "exterior vertices", the inner U is not part of the frame perimeter, because it has 4 vertices: 2 are exterior (at the front of the robot) and 2 are interior (the inner side of the U).

One method that we've been using to describe this is instead of string, use a rubber band. Wrap it around the robot (in your mind--that's a huge rubber band!) in the bumper zone. Follow the rubber band; that's your frame perimeter.

As for the string being able to be pulled into the U, I believe they meant to say, "wrap a string tightly around the robot at the level of the bumper zone".


As you guys are rookies, you probably don't know about the massive debates we had last year about what was and wasn't a legal bumper configuration. It was so bad that at one point someone posted a legal configuration and the comment was made that they couldn't do that because then we'd have nothing to talk about. Look it up and see just how discussed it was--it'll be informative at worst and enlightening at best.

[Sixis]

Originally Posted by EricH

Yep, and because it is "exterior vertices", the inner U is not part of the frame perimeter, because it has 4 vertices: 2 are exterior (at the front of the robot) and 2 are interior (the inner side of the U).

One method that we've been using to describe this is instead of string, use a rubber band. Wrap it around the robot (in your mind--that's a huge rubber band!) in the bumper zone. Follow the rubber band; that's your frame perimeter.

As for the string being able to be pulled into the U, I believe they meant to say, "wrap a string tightly around the robot at the level of the bumper zone".


As you guys are rookies, you probably don't know about the massive debates we had last year about what was and wasn't a legal bumper configuration. It was so bad that at one point someone posted a legal configuration and the comment was made that they couldn't do that because then we'd have nothing to talk about. Look it up and see just how discussed it was--it'll be informative at worst and enlightening at best.

ahh, thanks to both of you for clearing that up (before we had to debate it on the team). You would think the perimeter would be the geometric perimeter but I guess this is one of many things we'll have to learn. Cheers for the advice!

[T3_1565]

no problem... I remember how much trouble the "perimeter" was last year... would hate to start it up again

[bookman101]

thanks for the help! have a great FRC season!

[GaryVoshol]

All of this is really academic. It doesn't matter. The FRAME PERIMETER is defined at the BUMPER ZONE height, 10 to 16 inches off the ground. That's above the ball. If you want an indent below the BUMPER ZONE to channel the ball, it's perfectly legal. The ball will fit under your bumper.

[Leav]

Originally Posted by GaryVoshol

All of this is really academic. It doesn't matter. The FRAME PERIMETER is defined at the BUMPER ZONE height, 10 to 16 inches off the ground. That's above the ball. If you want an indent below the BUMPER ZONE to channel the ball, it's perfectly legal. The ball will fit under your bumper.

If I understand you correctly I think you are mistaken.
step 1) define frame perimeter (e.g. using the string method)
step 2) ball may not enter more than 3" into frame perimeter, when viewed from the top. (i.e. may not enter more than 3" into the projection of the frame perimeter to any surface parallel to the floor)

[GaryVoshol]

Originally Posted by Leav

step 2) ball may not enter more than 3" into frame perimeter, when viewed from the top. (i.e. may not enter more than 3" into the projection of the frame perimeter to any surface parallel to the floor)

<R19> ROBOTS must be designed so that in normal operation BALLS cannot extend more than 3 inches inside the FRAME PERIMETER below the level of the BUMPER ZONE.

(emphasis mine)

But

<G46> BALL Penetration Restriction – The BALL must not extend more than 3 inches inside the FRAME PERIMETER as defined in Rule <R19>. Violation: PENALTY for a basic infraction, plus a YELLOW CARD if no immediate attempt to remedy.

They really should have repeated "below the BUMPER ZONE" here, instead of just referencing <R19>.

Nevertheless, this is the way it has to be interpreted. Else, whenever an airborne ball went above your robot, you'd be in violation.

[Leav]

Yup. thanks for the correction!

[engunneer]

The frame perimeter also projects downward onto the floor. This is the boundary which is used for both the 3" incursion rule and the 2 second 'kicker zone' rule.