Wright State University
8th Annual Trebuchet Competition

Complete Rules

Design Rules

1. The contest is open to all high school students. Any number of students from a school may work on a single team. Participating schools are encouraged to submit multiple teams. Only one trebuchet may be submitted by any one student.
2. The counterweight (see mass m1) is two un-opened 12 oz. soda pop cans. The cans must be either: a) dangling throughout the entire throwing motion (makes no contact with other parts of the trebuchet lever arm: L2+L5 in the figure) OR b) must be rigidly attached to the arm (can't slide, jiggle...). If the cans are rigidly attached to the arm, it will be included in measurements of the arms length. Rigid is defined as anything other than dangling. Click here for a clarification.
3. The top pivoting lever must not be longer than 12 feet. The length includes the hook (see the hook rule).
4. The top pivoting lever (length L2+L5 on the example figure) must be balanced toward the projectile end ( see L5) throughout the entire range of motion. It may not be collapsible. The arm cannot be locked in place while testing it for balance (including friction, which should remain negligible - in operational condition). Testing is performed by removing the counterweights, lifting the projectile end all the way to within 1 inch of the vertical, and releasing. It should fall to the ground, back to the cocked position (see avi movie or quicktime movie), and in contact with the ground. If it fails to fall (without being pushed!) all the way to contacting the ground, it is not in compliance.
   We use the "pencil test". With the arm in the cocked position, with neither the counterweight or projectile loaded, raise them arm as shown (Quicktime format, avi format) with a pencil. The trebuchet fails the balance test if it leaves contact with the pencil when raising it to vertical (Quicktime format, avi format).
   • The top pivoting lever may not be less than 1/4" thick.
5. In order to satisfy the balance rule, the counterweights (pop cans) must be removable from their holder.
6. The height H of the center of the axle must be less than or equal to 1 feet 9 inches from the ground.
7. You must be able to remove the cans, and only the cans, from your trebuchet leaving all other connecting hardware in place.
8. Any fastening devices/holders/brackets to be used during the competition will be included as part of the arm during testing for balance. We really, really mean it. This comes up every year. We will not allow you to augment your counterweights with excessive tape, wire, washers, or wood. If you think you have beaten this rule, you have violated it. We will have scales. Allowance will be given for up to 30" of duct tape and 30" of light string.
9. The hook (the little thing that your sling goes onto at the projectile end of the arm; this is the point where L5 and L3 meet in the figure) is counted as part of the arm length!
10. No catapults or catapult/trebuchet hybrids are allowed. No energy can be stored in deformation of components. That means no springs, rubber bands or flexible arms. No pulleys can be used. The counterweight must be attached, not looped over, the end of the arm (or in close proximity).
11. The trebuchets will be inspected for safety. Any parts that are unnecessarily loose must be tightened. No parts of the trebuchet other than the projectile are allowed to become completely disconnected from the trebuchet (A partial disconnect is necessary in order to release the projectile). Any trebuchet deemed to be unsafe will be disqualified.
12. Counterweights must not come free during competition. If a counterweight falls off, the trebuchet operator must operate with the remaining counterweights. If the trebuchet becomes inoperable due to a loss of any counterweights, it must be declared lost and removed from the playing field.
13. Trebuchets must not have protruding parts that may damage the floor (no metal may protrude below a wooden or other softer material).
14. Recoiling trebuchets (with wheels) must be on a platform (board) that contains them.
15. Each trebuchet must be outfitted (i.e. come to the tournament ready) with one plastic 1 gallon milk jug target mounted on the side of the trebuchet in a clearly exposed area. The milk jug is to have the bottom 1" cut off and be inverted. The target opening must be no less than 1.5 feet from the ground, and no more than 2.5 feet from the ground. It must be forward facing, and on the front most pillar or support of the trebuchet. It can be mounted at a decline to the direction of fire of up to 45 degrees (pointing forward and up) if necessary (i.e. so that it is even more exposed). This is what the other teams will shoot at. It must not be placed where the operator might block the target during operation (this is also covered in the operator rules). If you do not understand these rules, the simple explanation is "put it where everyone can easily hit it". Trebuchets with inadequate targets will not be allowed to participate.
16. The projectiles will be regulation soft squash balls of a variety of sizes. They can be bought at some local sporting goods stores, however you can also order them online. One place to look is Squash.net.
17. Firing of the trebuchet will be performed by release of the projectile and/or its sling. No other moving part of the trebuchet may be touched during firing.

NOTE: Each trebuchet must be accompanied by a check sheet. The sheet must be filled out in advance of the competition and brought to the judges for qualification. If the check sheet is not filled out in advance (i.e. you are not "pre-qualified") you will be assesed penalty shots; that is, your first opponent will be given free shots at your team on the playing field before you are allowed to return fire. See Matches for details

A well performing trebuchet can be made from household materials. Very effective trebuchets can be built from cardboard, some Elmers glue, and an Exacto knife, so don't feel that you need a workshop.

Trebuchet Figure

Counterweights

Milk Jug Trebuchet Target

The pictures below 1) show a half-gallon jug and 2) don't have any newspaper at the bottom of the jug. Note, however, that the target is a single 1 gallon milk jug with one full sheet of newspaper wadded in the bottom.

	This is the top view looking down.
Here's a view from the side.
	Here's a view from in the front, slightly off toward the other side.

Note that in the rules, there is nothing that says the target has to be on the same side as the operator (as it is in these photos). Keep in mind, however, that if you do put the target on the same side as the operator, you must be careful not to block the target.

Check Sheet

The Teams

1. A team consists of 6 positions: a captain, an assistant, and up to 4 trebuchets, with one operator per trebuchet.  The advisors may fill the roles of captain and assistant only.
2. The team is defined by the group of trebuchets. A team may have more than 6 persons, but only 6 may participate in any match. Those 6 persons may change from one match to the next.
3. Teams of up to 4 trebuchets (one per trebuchet operator, and only one operator per trebuchet) will compete in a head to head competition. Individuals not belonging to any team will be assigned to other teams at the competition (or ahead of time if possible) for the duration of the competition.
4. Each trebuchet must be operated by only one person. The operator may not move away from their trebuchet. If the trebuchet is left unattended, it is considered to be captured by the opposing team. Subsequently the trebuchet will be considered destroyed by the "enemy saboteurs" and will be removed from the playing field.
5. Each team will have a single captain. The captain is in charge of commanding his/her forces in match. The captain may not enter the playing field. Good strategy is an important part of winning the match.
6. Each team will have a captain's assistant (team assistant). The assistant may enter the playing field. The assistant's primary responsibility is maintaining the arsenal by retrieving spent munitions for reuse. Assistants may not interfere with the opposing team in any way, and may not go to the opposing side of the playing field.
7. Teams must each supply 10 squash balls for their matches. They must collect them after each match. Teams are responsible for marking and recovering squash balls.
8. Each person who will be on the playing field must have safety goggles or glasses that will protect the eye. This is 5 per team. If you have 4 teams, you need 20 goggles.
9. All judge decisions are final. Under no circumstances shall a video replay of an event be used to reverse a decision.

Captains

You are in command of an team. Making and implementing a strategy is of paramount importance to your role. However, observance of the rules is even more important. The rules that pertain to your individual actions are as follows:

1. You may NOT enter the playing field.
2. You may not throw projectiles. You may roll them.
3. You may take the role of the assistant, should it be necessary. In that case, you may NOT act as the captain once you have entered the playing field.
4. You are responsible for placement of your "castle" at the beginning of the match. You may position it anywhere on the battlefield on your side of the neutral zone.
5. You may change the roles of team members as desired before each match. You may chose different operators for each match, and you may desire to rotate out the assistants as needed. However only one assistant may be on the playing field at a time.
6. Your team's objective is to destroy the enemy "castle". However, if all opposing team trebuchets are destroyed, your team is victorious by default.
7. It is the responsibility of the captain to assure that the eye protection rules are followed. If a second warning is given to your team, they will be disqualified from the tournament.
8. It is the responsibility of the captain to stay in the staging area at all times when not participating in a match, or until the team is disqualified. If you are not ready for an assigned match, you will forfeit. We don't have time to chase you around the Nutter Center.
9. The director and assistant directors know the rules. The director wrote them with the assistant director of rules. If we say a rule is in here, it is. We will not debate you, and we will not look up rules for you. Learning the rules is your problem, we don't have time to tutor you.
10. Note that this is our tournament and we can change the rules any time we see fit. This won't be done without good cause. However, that means if the director says something, it is the rule because he said it. You are a guest. Please respect that your invitation, and that of your school, can be temporarily or permanently revoked.
11. There is no higher authority for the tournament than the director. There is no recourse if you disagree with the director at the tournament.

Strategy (some suggestions)

1. Pick targets based on strategic value and opportunity, and direct your team appropriately.
2. Be aware of the strengths and weaknesses of the members of your team. Proper use of their talents is essential.
3. Listen to your team. They may have insight about their capabilities that you lack.
4. Concentrate fire on targets of immediate concern. If the opposing team has one long range trebuchet, it may be prudent to concentrate on it instead of the opposing team's "castle". If an opposing team's trebuchet is getting close to hitting your "castle", take it out.
5. Moving your trebuchets will require them to re-acquire their targets. Moving may be inadvisable under those circumstances.

Assistants

You are the assistant to the Captain. You are the official Spy and Go-For.

Preceeding the Match

1. Proceed to the end of the playing field that your team will be shooting at.
2. Act as a spy. Inspect enemy weapons.
3. Inspect enemy targets. Report any potential violations to the attending judge for correction.

During the Match

1. You may enter the playing field, but must stay on the side of the playing field on which YOUR "castle" resides.
2. You may not throw projectiles. You MAY roll them.
3. You may take the role of the captain, should it be necessary. As captains aren't allowed to enter the battlefield, you may only act as the captain from off the battefield.
4. You are responsible for assisting the Captain. This may mean observing projectile landings.
5. You may not obstruct a projectile from hitting a target or your "castle". If a judge believes that you might have acted as an obstruction, then that target/"castle" will be considered destroyed. (TIP: Don't stand in front of any targets or "castles").
6. You may not hoard ammunition. You must return ammunition that your team is not using. If your team at any time has 75% or more of the projectiles you must send 10 back to the other side. If the opposing team runs low on ammunition on account of hoarding, hits by your team will be disqualified.

Operators

You are the trebuchet operators. You are at the command of your general, but you will need to take initiatives to win.

Moving

1. You may not leave the playing field.
2. You may not leave arm's reach of your trebuchet. This will result in capture of the trebuchet. There will be no mercy by the judges for violations of this rule.
3. A clock judge will be responsible for timing advancement on the match field. At the clock judge's determination, trebuchets may advance or retreat one section of the battlefield at a time.
4. Only 10 seconds will be allowed for the move.
5. Both teams will move during the 10 second period, and no firing can take place.
6. There will be only two moves in the entire match.
7. Trebuchets may not screen one another, or be positioned to screen their team's "castle".
8. You may not advance your trebuchet outside of the playing field.
9. Trebuches may be pivoted (rotated) for aiming.
10. Trebuchets may not pivot for the purpose of dodging a projectile.
11. No match will be given more than 20 minutes, including setup time. If a match ends by decree, then the judges will vote for a winner.
12. You may take the role of the captain, should it be necessary. You may only act as the captain from the Captain's Area. Your trebuchet will be forfeited and must be removed from the playing field.

Tasks/Goals

1. You will need to follow the targeting information from your assistants and the captain.
2. You may not hit a target with anything other than the projectile.
3. You may not obstruct a projectile from hitting a target or the "castle". If a judge believes that you might have acted as an obstruction, then that target will be considered destroyed. (TIP: Don't stand in front of any targets or "castles"). This has, in previous years, cost a team a match, and who knows, maybe the war.
4. You may not hoard ammunition. You must return ammunition that your team is not using. If your team, at any time, has 75% of the projectiles, you must send at least 10 back to the other side. If the opposing team runs out of ammunition on account of hoarding, your hits will be disqualified.
5. Your team's objective is to destroy the enemy "castle". However, if all opposing team trebuchets are destroyed, your team is victorious by default.
6. If your trebuchet's target is hit, you must leave the playing field immediately, along with your trebuchet. Be careful not to obstruct any projectiles.

Safety

1. You may not throw projectiles. You MAY roll them to other operators or to the assistants.
2. Your trebuchet must always be safe to operate, with no loose pieces, and may not swing in such a way as to potentially harm any participant.
3. You must wear safety goggles at all times. Your trebuchet will be declared destroyed if corrective action is not taken after the first warning.

Trebuchet Maintenance

1. Your trebuchet must conform to the trebuchet design guidelines.
2. You must maintain your target during the match. Correction must be made immediately when notified during a match. You will only be warned once about illegal targets. The second notice will be removal of the trebuchet from the match.
3. If your target is found to be undersized, you may not participate in a match.
4. If, after a match, the opposing team contests that your targets were undersized, and the claim is substantiated, then your team will be disqualified, and the opposing team will advance.
5. Intentional modification of the target to reduce it's effective size will result in immediate expulsion from the match, and from your team.
6. No part of the trebuchet may interfere with an opponents projectile. If a projectile hits a part of a trebuchet that shades the target (either the trebuchet's target or the "castle"), the target will be considered to have been hit. Advice: after firing, get the arm back out of the way
7. Operators may make minor repairs, such as fixing a broken sling, during a match. This does not include re-attaching fallen counterweights; see the trebuchet design rules concerning counterweight loss during match. Further clarification of the definition of a "minor repair" falls to the judges of the match, who have the final say whether or not a trebuchet must leave the playing field.

Matches

Penalty Barrages

1. Teams will be subject to 1 barrage per incomplete pre-qualification sheet per match. (Please come prequalified).
2. Individual trebuchets will be subject to 1 barrage for a qualification failure in the first round only.e.g. if trebuchet A failed to qualify on the first try, the other team gets 1 barrage (typically 4 shots), before the match starts, at that trebuchet.

The Playing Field

1. The matches will take place in the Main Arena of the WSU Nutter Center.
2. Captains will have 5 minutes to position their target and trebuchets.
3. Trebuchets may be positioned any place on your side of the playing field, outside of the Neutral zone.
4. To start the match, all but one trebuchet will be positioned by the captain on or behind the "Long Line". The remaining trebuchet must be positioned between the Short Line and the Long Line.
5. At each end of the playing field, there will be a single target representing the opposing team's "castle". In order to win, a team must either knock out (hit) the opposing team's target or eliminate all opposing trebuchets. The pole/base is not considered to be part of the target. The size of the "castle" target may be changed between matches (in order to expedite matches), but will always be equal for both sides during any given match.
6. The boundaries of the playing field will be marked.

Firing

1. The match will start at the sound of a horn. Trebuchets fire-at-will once the match starts. Trebuchets that aren't ready are valid targets for the opposing team. Trebuchets that aren't set up as targets when the match begins may not enter the playing field during the match.
2. Trebuchets are destroyed by hitting their targets. See graphic.
3. Trebuchets eliminated from competition are eliminated for the remainder of the match. They may be "rebuilt" to "fight another day".
4. Friendly fire may destroy a trebuchet by going in to the trebuchet's target.
5. Trebuchets may not destroy an enemy target using anything other than a projectile.
6. Projectiles are NOT considered harmless once they have struck the ground. That is, getting a ball into the target off a bounce counts.

Moving

1. A clock judge will be responsible for timing advancement on the match field. At the clock judge's determination, trebuchets may advance one line (i.e. from the Long Line to the Short Line, or from the Short Line to the Neutral Zone Line) or retreat.
2. Only 10 seconds will be allowed for the move.
3. Both teams will move during the 10 second period, and no firing can take place.
4. There will be only two moves in the entire match.
5. Trebuchets may not screen one another, or be positioned to screen their target.
6. You may not advance your trebuchet outside of the playing field.
7. Trebuches may be pivoted (rotated) for aiming.
8. Trebuchets may not pivot for the purpose of dodging a projectile.
9. No match will be given more than 20 minutes, including setup time. If a match ends by decree, then the judges will vote for a winner.

Miscellaneous

1. Operators must not interfere with in-flight projectiles. Operators who are considered to have potentially protected one of their targets by interfering, intentionally or not, with their bodies or other trebuchets will have that target removed. Hint, don't stand in front of the target. You become the target to hit if the judge thinks you are in the way.
2. No part of the trebuchet may interfere with an opponents projectile. If a projectile hits a part of a trebuchet that shades the target (the trebuchets target, or the "castle" target), the trebuchet is considered to have been hit. Advice: after firing, get the arm back out of the way.
3. You may not hoard ammunition. You must return ammunition that your team is not using. If your team at any time has 75% or more of the projectiles (there will be a total of 20 or more), the assistant must send (by rolling) no less than 10 projectiles to the opposing team. Targets hit while the opposing team is low an ammunition will be considered undamaged.
4. All judge decisions are final. Under no circumstances shall a video replay of an event be used to reverse a decision.

Playing Field

The Tournament

1. The tournament will be conducted as a set of single elimination matches.
2. Trebuchets destroyed in preceding matches are considered repaired for subsequent competitions.
3. Trebuchets may not be re-used from a previous year.
4. Byes may be used to facilitate the tournament. When granted, priority will be given to teams with the fewest trebuchets, teams who register earliest, schools with the fewest students (entered), and finally by arbitrary decision by the judge. A team will not receive more than one bye per tournament. If in a given round two remaining teams have previously received byes, they will be forced into match.
5. Priority for scheduling matches: Teams from the same school will be pitted against one another early in the process. Nearby schools will then be pitted against one another. Remaining teams with fewer wins will always be pitted against each other.
6. Expect to be ready to compete as soon as your team arrives. There is no guaranteed practice time or place.
7. In the case of a final match between teams with an unequal number of wins: The team with more wins will win the tournament with one victory. The team with fewer wins will have to win two matches in a row to win the tournament.
8. The final match will be allotted extra time. Other matches will be allotted 20 minutes or less, at the discretion of the director.
9. The schedule for the tournament may be altered up to the day of the tournament. If you or your team/s have special needs (like a late start time, please contact the director directly by email.
10. All judge decisions are final. Under no circumstances shall a video replay of an event be used to reverse a decision.