So during our brainstorming sessions today the idea came up to build a pure defensive robot with a big wall that can expand out and in to block Frisbee’s as they are shot. The question we have is, are there goal tending rules. We cant find anything in the rule book that would not allow this as long as we where not using it to delay the movement of the game by blocking the whole field and not letting anyone through. Over what do you guys think of this possibly strategy.
Your robot size is limited to a 54" cylinder. If you are in a position to block shots, you may not be more than 60" tall.
I understand the 54in cylinder, this would follow those constraints. But I thought you could be at 84in tall after the start of the match.
With some exceptions.
3.2.5.1 G22
ROBOT height (as defined in relation to the ROBOT) must be restricted as follows during the MATCH:
A. If in contact with the carpet in its AUTO ZONE and/or its PYRAMID, ? 84 in.
B. Otherwise, ? 60 in.
So is the Autozone the middle of the field and you would be able to be 84in tall there. But if you are on either side of that zone you can only be 60in tall?
I believe for your robot to be 84" tall, it must be touching your alliance’s pyramid or on the platform surrounding it. I could be wrong though, so feel free to correct me.
3.2.5.1 G22
ROBOT height (as defined in relation to the ROBOT) must be restricted as follows during the MATCH:
A. If in contact with the carpet in its AUTO ZONE and/or its PYRAMID, ? 84 in.
B. Otherwise, ? 60 in.
The auto zone is the carpet behind the blue or red lines.
Your AUTOZONE is “an area on either end of the FIELD bounded by the ALLIANCE WALL, FEEDER STATIONS, LOW GOAL, GUARDRAILS, and the nearest AUTO LINE.”
so as long as you are on your side, you can be 84".
Please read the manual.
3.3.5 ROBOT Actions
G22 ROBOT height (as defined in relation to the ROBOT) must be restricted as follows during the MATCH:
A. If in contact with the carpet in its AUTO ZONE and/or its PYRAMID, ≤ 84 in.
B. Otherwise, ≤ 60 in.
Violation: FOUL. If continuous or repeated violations, TECHNICAL FOUL.AUTO ZONE: an area on either end of the FIELD bounded by the ALLIANCE WALL, FEEDER STATIONS, LOW GOAL, GUARDRAILS, and the nearest AUTO LINE.
AUTO LINE: a line, marked in Red or Blue gaffers tape, located 108 in. from and parallel to the CENTER LINE.
Your robot may only be in the 60" - 84" height range if part of your robot is A) within (i.e. contacting the carpet of) your side of the field, or B) in contact with your pyramid,
I agree that wall-bots may be very viable this year. Most shooter discussion I have seen has involved robots with a low profile meaning they will be shooting from less than 30" off the ground on a relatively straight line to their target. It will be very difficult to shoot over a 60" tall wall parked in front of them.
We actually thought of this, and we decided that as opposed to a wall, just make it hang down the same chains used on the goals like a curtain. Any shots will deflect, or just fall
A. If you’re in a position to block shots–that is to say, in your opponent’s Auto Zone–your opponent can be up to 84" tall, and you can only be up to 60" tall.
B. Many shooters won’t be 60" tall, and Frisbees shoot close to straight, so this will give you the impression that you can likely block a lot of shooters with a wall-bot. But you probably can’t, because…
C. If you get in front of them, they can likely shoot over you because they can use the pyramid for protection – they’ll tuck mostly under it, and if you move up close enough to their robot to block their shots, they can bump you while still in contact with the pyramid and then get penalty points for their alliance. This will force you to stay a reasonable distance back from them, allowing them to shoot right over your head into the 3 or 2 point goals.
FIRST games are hard, and strategies can often be maddening. When considering robot design, I think it’s a mistake not to hash out every strategic and tactical implication of any given design that you can possibly think of – and to do that, you need to have an iron grasp on the rules.
A good point on using the pyramid as a defensive object. In order for a goal tending strategy to work it will depend heavily on getting to the other robot before they reach their safe zones. The way I interpret the rules on pyramid penalties is in order to receive a penalty the other robot has to be in contact with its pyramid. So the distance you have to stay stay away is not that great.
G30 Regardless of who initiates the contact, a robot may not contact an opponent Robot
A. contacting its pyramid
B. touching the carpet in its loading zone.
You can only be 60" tall in the defensive zone
If our robot is 24" long (plus 3" of bumpers) and I’m parked so that the front of my robot is touching the leg of the pyramid, then you’d better stay at least 12-18" away (if not more) if you don’t want to get a penalty…
As for what 12-18" away (plus your own 3" bumpers) does for goal-tending strategies, I’ll leave that trigonometry up to all you students out there. 
I think it would be more strategically valuable to sit in your opponents protected feeding station and deny them access.
G30
Regardless of who initiates the contact, a robot may not contact an opponent Robot
A. contacting its pyramid
B. touching the carpet in its loading zone.
This rule basically states that as long as your opponent doesn’t touch the carpet in their zone, you can sit in their zone and block them by moving back and forth, unlike the lanes of 2012 and 2011, and you wouldn’t be breaking G25 as it is a robot-robot interaction and not multiple robots.
G25
ROBOTS on the same ALLIANCE may not blockade the FIELD in an attempt to stop the flow of the MATCH. This rule
has no effect on individual ROBOT-ROBOT interaction.
You may want to recheck exactly how much of the loading zone you’re able to block at one time–it’s quite a bit larger than your robot. 7 feet on the short base is a heck of a space for a 54" cylinder to block, especially when there’s a 20 point penalty on the other side.
Understand that the blockading rules has been substantively consistent since 2011 (2011’s G48-C and 2012’s G23), and 2012’s G28 is essentially 2013’s G30 for these purposes. This means that though the Loading Zone is much smaller than the Ally, do consider the way it played out last year. If you were trying this strategy against me, I’d take it on in almost any situation. Remember you’re betting 20 tech foul points against slowing them down and/or denying maybe 12 high goal points. Heck of a bet when the zone is well over a yard wider than you are.
I would agree that sitting in the zone is a bad, bad idea.
Pushing robots around as they try to get to the zone, or pinning them to walls outside the zone? Perfectly legitimate defense!
It is theoretically possible, through the use of proper geometric calculations and coaxial bevel gears/axles, to make a large OD fan on a robot that is very wide and very short (length-wise) – something on the order of 8" long x 48" wide – in order to create a massive amount of turbulence in front of any disc trajectory (and do a ‘fly-by’ of the refs :D). Of course, one would want to use wheelie bars to prevent tipping while driving.
The practical use of such a robot is up for conjecture though – there wouldn’t be much room to add manipulators that get a positive point differential for that robot if it were solo.
When the subject of fan equiped defensive robots came up during our strategy session one of our students asked “wouldn’t that count as actively trying to remove game objects from the field, which is against the rules?” As we are not planning on building such a robot we didn’t go far into the legality of such a design, it is certainly an interesting approach.