Rules

Vermont Pumpkin Chuckin' Festival
Official Rules and Divisions, revision #6*

Five divisions for trebuchets.
  1. Lightweight Division: Age 10 and below
    Max. total weight of trebuchet is 20 lbs.
    Max height = 41"
    Projectile weight = 3 ounce tomato
  2.  
  3. Middleweight Junior Division: Age 17 and below
    Max. total weight of trebuchet is 100 lbs.
    Max height = 70"
    projectile weight = 1 pound pumpkin
  4.  
  5. Middleweight Open Division: Open to all ages
    Max. total weight of trebuchet is 100 lbs.
    Max. height = 70"
    projectile = 1 pound pumpkin
  6.  
  7. Heavyweight Division: Open to all ages
    Max. total weight of trebuchet is 500 lbs.
    Max. height is 10 feet
    projectile = 5 pound pumpkin
  8.  
  9. Unlimited Division (Throw for Show)
    Age: Open to all ages
    Max Trebuchet Weight: No limit
    Max Trebuchet height: No limit
    Min pumpkin weight: No limit, whatever the captain wants to throw
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Eligibility

Who can participate in the Pumpkin Chuckin' Contest?

Open to anyone to compete. One person or a team of up to 8 people. We are hoping to get kids of all ages, cub scouts, boy scouts, brownies, girl scouts, universities, companies, etc. to enter the competition.

In the lightweight and middleweight junior divisions the participants must take part in the construction of their trebuchet; an adult mentor is permitted to assist in the construction of the trebuchet only when and if necessary.
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General Rules for Trebuchets

Total weight of trebuchet including counterweight (not including projectile) may not exceed limit. See table above for weight limits for the 4 competitive divisions. There are no limits for the Unlimited (Throw for Show) Division, all hurlers are welcome.

Two exceptions; a cocking mechanism may be used without counting towards the total weight.  This mechanism can also exceed the height limit.  This exception was added for safety reasons.  Also a trailer may be used without counting toward the total weight or height, although there is a small penalty listed below.

Height of trebuchet including throwing arm fully extended (the un-cocked height, straight up in the air) may not exceed limit. The sling is not included in the height limit, so the sling may exceed the limit.  Also as state above, a cocking mechanism can also exceed the height limit.

Another exception; the trebuchet may be mounted or assembled on a trailer, for convenience.  The height of the trebuchet will be measured from the floor of the trailer.  This does give a slight advantage so to compensate, the height of the trailer will be subtracted from the distance of the throw.  For example, if someone uses a 3 foot trailer and throw 100 feet, they get credit for only 97 feet.

No digging into the ground is allowed (like a pit for the counterweight to fall further). You may use the ground to stake the trebuchet to prevent rocking.  Ropes, wires or straps are also allowed and are not included in the total weight.  This is encouraged again for safety reasons.

Winches or other electrical motors are allowed to cock a trebuchet. This is for safety reasons.  The winch or motor will not count towards the total weight.  If these devices are electrical they must be battery operated since there will be no access to AC power in the field.

All trebuchets must be only gravity powered. No springs or pneumatics or other power sources.  The air cannon will not compete against the trebuchets.
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New rules:
  1. A loading or firing structure CAN go over the height limit with no penalty. This is to ensure safety in loading and firing the trebuchets. The height limit refers to the top of the throwing arm (at its highest point during the throwing motion) and the top of the counterweight at its highest point. Neither the top of the throwing arm or the counterweight can go below ground. This is to ensure that all the contestant have the same amount of potential energy to use.
  2. A loading or firing structure is NOT counted towards the total weight of the trebuchet. The weight limit is meant to ensure that all contestants have the same potential energy, and the loading or firing structure does not contribute to that potential energy.
  3. Staking the trebuchet to the ground is also permitted, as well as adding sand bags to the frame, etc. This will NOT be counted towards the total weight of the trebuchet.
  4. Teams must get their trebuchets weighed and measured before they are
    staked down, to get a fair weight.
  5. A more severe penalty will be charged for trebuchets which are over weight. Before 2011 the height and weight penalties were based strictly on percentage. If you were 10% taller or heavier than allowed, you were penalized roughly 10%. It was pointed out to me that this is not quite fair (for weight) because the counterweight is not the total weight of the trebuchet. Therefore, overweight trebuchets will be penalized roughly 15% for being 10% overweight.
  6. Here is an example of the 2010 rules versus the 2011 rules for a middleweight trebuchet which is 10 pounds over the 100 pound limit:

    2010 rules: a 110 pound trebuchet that threw 100 feet would get credit
    for 100*100/110 = 90.9 feet.

    2011 rules and after: a 110 pound trebuchet that threw 100 feet would get credit
    for 100*100/115 = 86.9 feet.

    In other words, the 10 pounds over is multiplied by 1.5 so it is
    considered 15 pounds over.
  7. A prop or firing device may fall over the firing line, as long as the arm or main structure of the trebuchet stays behind the firing line.

  8. No physical pushing or shoving of the counterweight will be allowed. Trebuchets must be gravity-only powered, not gravity-plus-a-shove. This rule will be strictly enforced starting in 2015. Breaking this rule will result in disqualification of the throw.
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This is a clarification of how trebuchets are measured for classification in the different weight divisions: lightweight, middleweight, and heavyweight.

The height of the trebuchet is the difference between the top and bottom.

The top is the highest point reached by the arm (including the finger) or the counterweight (CW) during firing. The bottom is the lowest point of the arm or counterweight during firing.

For a King Arthur trebuchet two measurements are made when the trebuchet is at rest; the highest point of the finger and the lowest point of the counterweight. Two measurements are made when the treb is loaded; the highest point of the counterweight and the lowest point of the finger. See figures 1 and 2.

King Arthur trebuchet two measurements are made when the trebuchet is at rest;

King Arthur trebuchet two measurements are made when the trebuchet is loaded

All four measurements are made from a convenient fixed level; the ground is a good level or the lowest point of the trebuchet.

The four measurements are:
  1. Highest point of finger at rest
  2. Lowest point of CW at rest
  3. Lowest point of finger when loaded
  4. Highest point of CW when loaded
The top is the highest of all four points and the bottom is the lowest of all four points. So the height of the trebuchet is simply the distance between the highest top and the lowest bottom.

See figures 3 and 4 for a floating point trebuchet measurements.

Floating Arm trebuchet two measurements are made when the trebuchet is at rest

Floating Arm trebuchet two measurements are made when the trebuchet is loaded

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BYOP

Bring your own pumpkin (or tomato, or whatever you want to hurl). We may have some rotten vegetables donated or for sale on site, but there is no guarantee. We suggest you have 3 prime pumpkins at exactly the right weight for the contest, and several other for practice and free-for-all at the end. Water balloons are an easy projectile. Be sure the projectile is AT LEAST the required weight.

Projectile must weigh at least the limit or more.  Lightweight = 3 ounces, Middleweight = 1 pound, Heavyweight = 5 pounds.

Density of projective:  It was my original intention to have all the trebuchets throw pumpkins, so all projectiles would be roughly the same density.  This may not be practical since the lightweight category is throwing a 3 ounce projectile.  I looked up the average density of an apple (.9), potatoe (1.6) and a pumpkin (.22).  If we allow potatos, this gives a big advantage because they are 8 times as dense as a pumpkin and will go through the air with much less air resistance.  I'm inclined to allow only projectiles that float, which would require a density less than 1.0.  Any suggestions are welcome.

Judges will weigh trebuchet and projectile and measure height before firing. Total weight of the trebuchet (including counterweight) must be UNDER the limit, or subject to a small penalty. Weight of projectile must be OVER the limit. Height must be UNDER the limit, or subject to small penalty. No part of the trebuchet may go over the line during firing, except the sling.

If any of the trebuchet weights or heights are above of the specified range, a small penalty will added by the judging committe. For example, if a heavyweight trebuchet weighs 525 pounds and throws 100 feet, they will be penalized by a percentage.  For example, they would get credit for 100*500/525 = 95 feet.

There is no advantage given to trebuchets that are under weight or under height.

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"Best Design" Prize

All trebuchet divisions/classes are competing for the overall "Best Design" prize.

The overall "Best Design" winner is determined by computing the scaled distance for each division/class winner and the one with the greatest value wins.

Scaling: Trebuchets "scale" very well. All things being equal, a trebuchet that is twice as tall will throw twice as far. However, it will weight 8 times more and throw a projectile that weighs eights times more. The reason is that something twice as big, is twice as wide and twice as deep so the volume and weight increase by a factor of eight.

With this in mind, each division is 5 times heavier than the division below it. Doing the math, this scales to 1.71 taller (cube root of 5). So each division is 1.71 times taller than the division below it so they can be compared against each other to award an overall "Best Design" prize. The lightweight division distance will be multiplied by 2.924 and the middleweight divisions will be multiplied by 1.71 to accurately compare against the heavyweight division. For example, if a lightweight trebuchet throws 50 feet and a heavyweight trebuchet throws 145 feet, the lightweight trebuchet is scaled up to 146 (50*2.924) feet which beats the heavyweight trebuchet. This scaling will be used to award the overall "Best Design" prize. Each division will also have a best distance prize.

This gives the younger divisions a real chance to walk off with the most prestigious prize, no fancy metal working or wood working shop required, just brains and persistence.
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Safety

All trebuchets must have a safety device (like a C-clamp) to stop the throwing arm from firing prematurely during loading of the projectile. Another excellent safety device is a support which can be placed directly under the counterweight, preventing it from falling.  The safety committe will determine if the trebuchet is safe.  If the trebuchet is deemed not safe, the safety committe will make every effort to help the team make it safe, time permitting.

Once the counterweight is lifted, the trebuchet is dangerous (even the small ones). Be careful not to put hands, feet or any body part in the potential path of the throwing arm or counterweight. Put the safety on immediately after the counterweight is lifted (before loading the sling, etc)!

All trebuchets will be inspected before firing and must pass the inspection to fire.
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All hurlers welcome

Other catapults, trebuchets, and hurling machines may "throw for show."
Other trebuchets, or catapults, or air cannons not in the above categories are encouraged to come and "throw for show" along with the other contestants. However, if they do not meet the division specs., they will not be part of the official competition.
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How to Enter

To enter the trebuchet contest, email the following information to Dave Jordan at DJordan@gmavt.net:
  • Name of Captain
  • Team members (optional)
  • Representing (optional)
  • Division (Lightweight, Middlweight Junior, Middleweight Open, Heavyweight)
  • Name of Trebuchet (optional)
  • Phone: (optional)

Cost is $5 for all competitors and spectators, collected the day of the event.
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Notes:
revision #7, Aug. 26 2016 -- Added trebuchet measurement clarification and diagrams.
* revision #6, Oct. 2014 -- Added new rule #7 that trebuchets must only be gravity powered. No physical pushing or shoving of the counterweight will be allowed. Hurls that break this rule will be disqualified.
revision #5, Sept. 2014 -- changed "How to Enter," money now collected day of the event, dropped requirement to bring flags to mark throws.
revision #4, October 2012 -- formally added unlimited weight category (throw-for-show)
revision #3, August 26, 2012 -- New rule #6 was added.
revision #2, Summer 2011 -- new rules 1-5 were added.