ChiBall Fall 2008

Contest Date: 
Sun, 10/19/2008

ChiBall Rules

Audience: All Levels


This contest tests a builder's ability to construct a robot which can manipulate golf ball sized foam balls within a limited space and deliver said balls over a wall into another player’s area.

Course Construction

The ChiBall course consists of a hexagonal walled Playing Field divided into three equal sized Playing Areas by three inner walls, as shown below.


ChiBall Playing Field

The outer walls are constructed from ¼” thick MDF cut into 5” high by 47” long strips.   The inner walls, which divide the Playing Areas, are made of the same ¼” MDF cut into 3 ¾” high by 40 ¾” long strips.  Each of the inner walls attach to the midpoint of every other outer wall at a ninety degree angle.  The three inner walls meet in the center of the hexagon held together by a 3 ¾” high ¾” dowel rod painted green, as shown above.

The floor of the playing field consists of whatever surface the walls are sitting on. Normally this will be the standard Chibots line following table (MDF painted flat black as described in the Racing Line Following Rules). This means there may be white lines in some of the playing areas from the RLF track which is a permanent part of the table surface.

The outside of the hexagon is painted flat black. The interior walls of the three Playing Areas are painted a unique color (red, orange, or blue) at the bottom with a 1 ¾” white band at the top. This pattern is reversed on the interior of the outside walls with the unique color on the top and a 1 ¾” white band at the bottom inside surface of each outside wall. The color strip at the top of each wall extends onto the top edge said wall.

This opposite the color pattern and height difference between the inner wall and outer walls is intended to allow a robot to easily differentiate between the two.

This Playing Field arrangement provides three irregular pentagonal Playing Areas where each robot shall operate.


Robot Construction

Robots must be autonomous, but not necessarily mobile.  Each robot, in its starting orientation, must fit within a 77 cm diameter cylinder.  We will use a Mini Sumo ring and the Judge’s discretion to make this measurement.  There is no limitation on robot height.  The robot weight may not exceed 11 lb (~5 kg).  All other Chibots’ general robot guidelines apply.

The robot must be placed in the Playing Area as a single self supporting entity.  That is, the robot must hold itself together while being placing in the Playing Area, for example it may consist of several separate pieces on a platform.

Once the game begins, each robot wait for a five-second delay before beginning operation.  During operation the robot may expand in any dimension or disassemble itself into multiple pieces provided it does not exceed the bounds of its Playing Area.  At the end of the 3 minute playing time (excluding initial 5 second delay) each robot is required to automatically stop.  Failure to do so will result in the judge undoing whatever actions the robot took when the 3 minute time limit expired.

Contest Procedure

Each contest consists of one or more 3 minute matches.  The object during each match is for each robot to keep its playing area clear of balls.  The contest will begin when the judge says “start” at which point each builder must activate their robot either remotely or by pressing a button.  After the initial five second delay each robot will begin its task of removing all balls from its playing area.

Some basic rules are followed throughout each match as follows:

·        The judge(s) will ensure a clear 24” wide perimeter is maintained around the playing field during the course of a game.

·        At the start of each match four balls will be placed in the center of the longest outside wall of each Playing Area.

·        Each initial ball will be the same color as the interior walls of the playing area in which they are placed.  Ball color does not matter in the current version of ChiBall so different colors may be substituted if necessary.

·        Each robot must be placed in the approximate center of the Playing Area as per the Judge’s discretion.  The builder will make said placement and can put the robot in whatever orientation is desired.

·        A robot may not reach over any wall.

·        A robot may not attach itself to the walls or flooring, doing so results in immediate disqualification.

·        A robot may touch a wall but may not push with enough force to bend or distort the wall.  Robots that bend a wall will be given a warning.  After two such warnings, on the third bend, the robot will be disqualified.

·        A robot may look over walls and/or block incoming balls.

·        A robot must physically contact a ball to move it.  That is, each ball must be mechanically manipulated.  Suction is allowed, but “blowing” balls out of the robot’s playing area (akin to a leaf blower or giant fan) is not allowed.

·        Balls must not be ejected from the Playing Field (i.e. moved over the outer walls which form the hexagonal Playing Field).  Doing so will result in penalties for the robot which initiated the initial movement of said ball.

·        Any ball ejected from the Playing Field will be returned to the Playing Area of the robot that last touched the ball.

·        While balls may be tossed a short distance, they are not allowed to be used as projectiles nor “shot” at other robots or the Playing Field.

·        Spare balls will be kept to use as replacements for any ball knocked out of the Playing Field.  The ball knocked out can be collected after the replace ball is set in the middle of the longest outside wall of the Playing Area for later use.

·        At the end of a match any ball touching a robot is considered to be held by said robot.

·        If a ball is balanced on top of an outer wall of a Playing Area then the ball is to be considered inside said Playing Area.

·        If a ball is balanced on an inner wall of a Playing Area then said ball is considered to be in the Playing Area with the greater volume of the ball over hanging it.  If the ball is resting evenly between two or more Playing Areas then the penalty points are to be split evenly amongst said Playing Areas.


Robots will be scored based on their performance in a series of matches.  Depending on how many robots participate, the judges will decide between one of several ranking methodologies to determine the robots that will participate in each match.

The winner of each individual match is determined by the robot with the lowest score based on the table below.

Each robot’s score in a match is assessed as follows:

Scoring Possibilities

Points per ball

Ball on own Playing Area floor


Ball held by own robot


Ball ejected from Playing Field

Note, the ball is returned to the Playing Area where it was ejected]



To determine the overall contest winner, at the end of each match points are assigned, 6 points for 1st place, 4 points for 2nd place and 2 points for 3rd place.  Should a tie occur the tied robots will split the point total for the places involved.  For example if two robots tie for 1st place they will each get 5 points ( (6+4)/2 ).

The overall contest 1st, 2nd and 3rd place will be determined by total points accumulated.  Should a tie occur a tie breaking match will be played with the three top ranking robots.  Only the tied positions shall be determined.  Should multiple ties occur, the judges may decide the winner by selecting the robot with the smallest starting circumference.


This page is a rule set for this general contest: