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Floating Arm Trebuchet
- Hobbyist Version


The F.A.T. 3000, Guillotine-Style Catapult


Designed and made in the USA for
better quality, better performance!

This new and improved 21st century version of the trebuchet uses a modern understanding of physics and engineering principles for incredible power and range!

Also available in a
lower-cost competition version!
(click for info)




This version of our most popular kit incorporates several improvements over the old model, including our new "gap-hop" architecture - now the wheels gently hop over the gap in the tracks instead of pounding over them, eliminating the destructive "thump-bump" of the old model. This enables us to use positive tracking wheels - no more frame-strikes! The wheels are locked-in to a track system that prevents them from drifting off-course during firing. We've also added a turnbuckle based pin angle tuning mechanism, for non-slip ultra-fine tuning of the pin angle. The virtually indestructible steel counterweight boxes are included too! All major improvements for accuracy and repeatability in this one-of-a-kind machine!

Engineered using modern mechanical principles and computer aided design, this mini-powerhouse can hurl a golf ball over 200 feet. It uses guillotine action and a plunging beam to maximize potential energy and a floating arm to convert that energy into projectile motion. Precision crafted of high quality hardwood, the kit contains everything you need to build a working model.*

The trebuchet is essentially a gravity powered energy conversion machine, turning potential energy into kinetic energy and using it to throw a ball. It's a great way to see classical mechanics in action!

Similar to the forty-foot tall, 25 ton behemoth "T-Wrecks" we built on the TV show "In The Name Of Science" (2004, The Discovery Channel), except this model is only 34 inches tall, 18 inches long and 7 inches wide (12 inches wide including the steel boxes) but it hurls more than five times as far as T-Wrecks in scaled distance.

A common complaint from engineering professors is that "Students today have a great understanding of computers, but fewer and fewer of them have any real hands-on, real-world understanding of physics and mechanics." Our kits are designed and intended to spark an interest in real-world science and engineering, and maybe even a bit of history too!

The detailed instructions (14 pages!) are complete with diagrams, photos, tuning tips, equations for calculating the machine's efficiency and more! All parts are pre-cut, pre-drilled and can be assembled to a finished model in one evening (plus glue drying time).

We've put a lot of time and effort into making this kit as easy and complete as possible. It's a fun way to learn about physics and engineering!

FAT, F.A.T. and Floating Arm Trebuchet are trademarks of RLT Industries, inc.


Tools required:
Scissors, Glue, Ruler, a utility knife, small wrenches (for one 1/4" bolt and one 3/8" bolt). Sandpaper is optional.

Assembly time:
For a Master carpenter doing a sloppy job: about 2 hours.
A person with no kit building experience being extremely meticulous: two or three days.
The model in these photos was built by Ron Toms in about four hours.

Assembled Size:
- Height: 34"
- Length: 18"
- Width: 7" (frame) 12" (with counterweights attached)

Additional Counterweight Required: 10 to 15 lbs.
(Loose nuts and bolts, coins, rocks, anything that
can fit into the 4" x 2" x 6" counterweight boxes.)

Range:
- Golf balls, up to 200 feet
- Tennis balls, about 100 feet.
(Optimal range assumes a well tuned machine)

Shipping weight: 14 lbs.
Box dimensions: 36" x 12" x 4"



Quantity pricing info:
0 to 4 kits, standard price.
5 to 9 kits, 10% off
10 or more kits, 15% off


Orders of $200 or more qualify for FREE ground shipping!

WARNING! This is a functional model intended for educational demonstrations of physics. It contains a fast moving arm and projectile that can cause injury if you make contact when firing. Use only under strict, competent adult supervision.

* You'll need to supply the counterweight material. Anything from nuts and bolts, BBs, coins, sand or a good fist full of pebbles will do!

* Can throw 200 feet when properly constructed and tuned with sufficient counterweights. Your performance may vary.

* FAT, F.A.T. and Floating Arm Trebuchet are trademarks of RLT Industries.


If you are buying this model for the Science Olympiad:


There is a rule which requires the trebuchet arm to remain stationary when the counterweights are removed and the trigger is pulled. The original intent of this rule was to disqualify springs and bungee cords from the trebuchet competition.

Since the FAT does not contain any springs or bungee cords, it does not violate the intent of the rule, even though it does violate the letter of the rule. Keep this in mind if you ever become a lawmaker - good wording is difficult and extremely important in order to keep the intent, without doing harm or injustice to innocence.

If you want to use the FAT for your competition, there are options. First, I'd recommend negotiating with your instructor or judges, let them know about the problem and the intent of the rule, and see if you can get an exemption from it. This has worked for other folks in the past, but not always. It depends on how reasonable your judges are.

If that fails, here's another strategy that has worked. The rule states that the arm cannot move when the counterweights are removed and the trigger is open (unset). In this model, the arm is part of the counterweight system. Its center of gravity falls as part of the launch sequence and the arm's weight (including the wheels and wheel carriage) contributes to the total energy transferred to the projectile. You should be allowed to remove the whole arm and weight-box assembly to satisfy the "no motion" rule. In fact, since the arm is part of the counterweight, if you are not allowed to remove the arm during this test, then your judges ARE violating the letter of the rule in regards to this test!

Once the arm is removed and set aside, it will not move when the trigger is pulled, and the test is passed.

Of course, the decision whether to accept these lines of reasoning are entirely up to the judges of your competition. It would be wise to check with them first before purchasing this kit. If they will not allow it, then the SPECK or the TK3 are your next best options, although nothing performs better than our FAT!


More info about SciOly and the FAT can be found here


Good luck with the competition!


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    Price: $195.00
    Minimum age: 14
    Availability: out of stock

    Item code: 10101

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Interesting Notes

Some Trebuchet History:


From the 13th century writing: "Itinerarium Peregrinorum et Gesta Regis Ricardi"

In June and July of 1191, Richard the Lionheart (the Duke of Normandy) laid siege to the city of Acre as part of the medieval Crusades.

The Duke concentrated on constructing siege machines and placing trebuchets [petrariae - literally, stone hurler] in suitable places. He arranged for these to shoot continually day and night. He had one excellent one which he called "Bad Neighbor" [Malvoisine]. Its continual bombardment partly destroyed the main city wall and shattered the Cursed Tower. On one side the Templars' trebuchet wreaked impressive devastation, while the Hospitallers trebuchet also never ceased hurling, to the terror of the Turks.

Besides these, there was a trebuchet that had been constructed at general expense, which they called "God's Stone-Thrower". A priest, a man of great probity, always stood next to it preaching and collecting money for its continual repair and for hiring people to gather the stones for its ammunition. This machine at last demolished the wall next to the Cursed Tower for around two perches' Length [11 yards or 10 meters].

The count of Flanders had had a choice trebuchet, which King Richard had after his death, as well as another trebuchet which was not so good. These two constantly bombarded the tower next to a gate which the Turks frequently used, until the tower was half-demolished. Besides these, King Richard had two new ones made with remarkable workmanship and material which would hit the intended target no matter how far off it was. . . . He also had two mangonels [traction trebuchets] prepared. One of these was so swift and violent that its shots reached the inner streets of the city meat market.

King Richard's trebuchets hurled constantly by day and night. It can be firmly stated that one of them killed twelve men with a single stone. That stone was sent for Saladin to see, with messengers who said that the diabolical king of England had brought from Messina, a city he had captured, sea flint and the smoothest stones to punish the Saracens. Nothing could withstand their blows; everything was crushed or reduced to dust.