Ancient Engineering SeriesCatapult Kits
Have you hurled today?

Floating Arm Trebuchet ™
- Competition Machine

The new, stronger F.A.T. Guillotine-Style Catapult

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

This version of our 21st century trebuchet is manufactured from top-quality solid oak non-toxic formaldehyde-free domestic plywood. Plywood is more dimensionally stable, a lot stronger, and a lot less expensive than natural hardwood. This makes for a more cost effective trebuchet for teachers and students.

The F.A.T. is an updated version of the ancient trebuchet, designed from a modern understanding of physics and engineering principles for incredible power and range!

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. All major improvements for accuracy and repeatability in this one-of-a-kind machine! Just fill the counterweight boxes with anything from coins, nuts and bolts, BBs or anything heavy enough to give you five to seven pounds per box. The box dimensions are 2" wide, 5.75" long and 4.25" deep, for a whopping 48.8 cubic inches of volume.

Engineered using modern mechanical principles and computer aided design, this mini-powerhouse can hurl a golf ball over 250 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 top-quality engineered plywood, 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, 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!

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 18 lbs.
(Loose nuts and bolts, coins, rocks, anything that
can fit into the included plywood boxes.)

- Golf balls, up to 250 feet
- Tennis balls, up to about 120 feet.
(Optimal range assumes a well tuned machine)

Shipping weight: 12 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 250 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 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: $175.00
    Minimum age: 14
    Availability: out of stock

    Item code: 10102

Why should a kid
build a catapult?

Because the world needs good engineers and scientists, and because the kids who will grow up to become engineers and scientists need a way to get hands-on experience with physics, math and engineering.

In this age of 200-plus channels of TV, the Internet and computer games, kids are also spending far less time building tree houses, tinkering with engines, or designing downhill racers. We believe those are important skills to have. They help form the basis for good problem solving skills and an innate understanding of the real, physical world that you just can't get from a computer game, no matter how good its physics simulation software is.

Ballistic motion was one of the key players in the development of the science of physics. The word "engineer" even originated as the builders and designer of Siege Engines

Why is a budding engineering student expected to take a year or two of calculus in high school, but she isn't expected to have any real-world experience in building or working with machines and materials? Pencil and paper (or computer screens) are only one part of the learning experience. Where will she apply all of the stuff she learned in geometry and trig? Without physical projects to touch, feel and see, the lessons become abstract, their utility questionable.

A catapult project gives students a chance to see that science and engineering really can be fun, and it's a lot more than just numbers on paper. The real payoff for an engineer is in the field, where she can see and enjoy the results of her ingenuity. And it may seem counterintuitive, but engineering projects not only help kids learn math and science, they are also great at getting kids back outdoors, away from the massive over-exposure to video games, TV and the Internet.

Why all this interest in getting kids to study science and engineering? Because it's important to our society, and it's great mental cross training regardless of what field of work the kids eventually go into. Most people develop a sense for what they want to do in life while they are still in high school or even earlier. A catapult project is fun and interesting enough to inspire some kids to study the science behind how they work, and then go on to become the engineers and scientists of tomorrow.

(Click images to enlarge)
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Cocked and ready to fire!

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The new plywood boxes are incredibly strong and much larger than the old boxes. You can stuff a lot of counterweight into these!

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The release pin is fine-tunable to get the exact angle of release you want for optimal trajectories.

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The positive tracking wheels and gap-hop architecture make this one of the smoothest, most repeatable trebuchets in existence. And unlike traditional hanging counterweight trebuchets, the counterweight bucket doesn't flail around after the throw. That's because this one doesn't leave a lot of residual energy in the system. It's much more efficent!

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