measurement clarification at match time

We have been told (and I saw this at 2009 World Champs) that a driver may ask for a size clarification of an opposing robot that has been placed in the field of play, befor autonomous starts. The referee “quickly” uses the official 18" box to measure the robot in question.

My following questions assume that the robot in question is placed in the field of play in its starting configuration within 18", and that its overall size measurement was verified with tolerances of 1/32" inside of 18".

My first question is, Do the rules permit this clarification by a driver or coach, of an opposing robot.

It has also been told to me by New Zealand VEX officials that in this instance, the game referee is able to quicly place the measuring box over the robot in question, and if DURING PLACEMENT OF THE BOX over the robot it touches the robot, then the referee is entitled to summarily remove the robot from the field WITHOUT RIGHT of rebuttal by a CAREFUL placement of the robot in the box to prove compliance.

Considering our robot is in the order of 1/16" to 1/32" within the 18" size, our robot wold be bound to touch the sides of the measuring box during any quick placement of the box. Settling of the box over the robot to determine compiance is not able to be achieved by a “quick” placement. It would require extreme CARE.

My second question is. Is a referee boud to give a robot in question a “fair” measurement in the manner in which it was originally measured.

Third Question. If a robot is exactly 18" which is LEGAL according to the rules, how would you verify size compliance if a team challenges size at the match before autonomous. Surely the rule that the robot must not touch the sides of the measurement box is a conflict with the allowable robot size .

Fourth Question. Does placing the polycarbonate covered metal measuring boxbox OVER a robot, block the vision of a referee to see DOWN the iINSIDE of the box to accurately establish compliance inside 18".

Piratech once had a robot that had to fit in the box diagonal. No one ever challenges us to a sizing box nor have I ever seen a team demand a robot be sized. This is not to say that it doesn’t happen, but it’s rare. Even when a referee “quickly” checks your size he will still have to carefully drop the sizing cube over your robot. The biggest size issue I have seen is tie-wraps that touch the box, these kind of violations are usually caught at inspection.

I am not affiliated with Vex Robotics Inc. but I would say that if your robot does truely fit inside of the 18" cube, you should be fine. I do NOT recommend pushing those limits too much nor do I recommend building a robot that is actually exactly 18", if you notice even the longest Vex metal is 17.5", that’s done for a reason.


This is not in the rules. The sizing rule states:

The addition you stated above that the box must not touch the robot when placing the box over the robot (or the robot into the box) is not part of <R4>.

Generally speaking, it is up to the referee to make sure teams follow the rules. All robots will have passed sizing during inspections, but teams tend to tinker during events and it is not impossible that a robot that passed inspection may have “grown” and require reinspection. A team that is on the ball will have voluntarily taken their robot back to the inspectors if they have changed the size of their robot. If a robot shows up at the field looking like it might be over 18x18x18, it is well within the referee’s right to call in an inspector or to check the robot personally. Just because a team in the opposing alliance asks for a sizing check does not mean that a referee is obligated to do so, but a referee has considerable latitude to make sure the rules are followed.

Since the rules say nothing about the sizing box touching a robot while it is being placed, that would be outside my understanding of what is right. If the robot cannot be placed so that it does not touch the box, it is in violation of sizing rules.

I have immense respect for the New Zealand adult leaders I met at Worlds last year. Is it possible that you misunderstood what you were told in the heat of the moment?

On your third question, the maximum size of a robot is not really 18x18x18 – it is “To pass inspection, a robot must fit within the box without
touching the box walls or ceiling.” This is clearly in <R4> and I do not see that any confusion is possible.

On your fourth question, when I inspect robots, sometimes it’s easier to set the box on its side and slide the robot in, and sometimes it’s easier to set the robot on the table and drop the box over it. In all cases, it is MUCH easier to measure a robot that leaves a generous 1/8" or more gap. I tell my students to shoot for 17-1/2" which leaves room for screw heads to stick out. Building a robot that is only 1/32" small (less than 1mm) is just asking for trouble. I’ve built a lot of robots in the last six years and there is nothing that you are attempting that so desperately needs that last 2 or 3mm. Good luck this season.