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Perpetual Motion Machine in Red Oak

Cut from solid Red Oak!


(Note: these photos are of the white-wood version. For an example of what red oak looks like, see our href=/10902 target=redoak>Onager or Ballista models.)

The overbalanced wheel is the oldest type of perpetual motion device in history. The oldest known
description of one is from 8th century India - a wheel with vials of mercury arranged in such a way that as
the wheel rotates, the mercury sloshes away from the center on one side, but towards it on the other.
However, mercury is expensive, very heavy and (we now know) dangerous. In later years, the mercury was
replaced with shifting mallets, but the operating principle is the same.

The oldest surviving drawing of a perpetual motion machine was made by the French architect Villiard De
Honnecourt in about 1235. He wrote:
Many a time have skillful workmen tried to contrive a
wheel that should turn of itself; here is a way to make such a one, by means of an uneven number of
mallets.
-- Villiard De Honnecourt, 1235 AD
Leonardo DaVinci studied the concept
in depth, and he also constructed several models - the models have not survived the ages, but dozens of
his drawings have survived. Ultimately, he concluded that perpetual motion was indeed, impossible, and
he abandoned the idea completely.

This particular model is a kit. When assembled, it is an historically accurate representation of the concept,
complete with a crank-arm for "starting" it. We consider it to be a kinetic sculpture, inspired by the work
and the genius of the ancients. It makes a fabulous conversation piece, and when treated with a finishing
wax or hand-rubbed with fine oils, is suitable for prominent display in any museum.

The kit is manufactured from 100% solid hardwood. The finished model is 22 inches tall, 6 inches wide
and 18 inches long. All parts are computer manufactured for guaranteed fit and accuracy. Everything you
need to construct this kit is included except for a few simple tools. All you need to supply are scissors, a
utility knife, sandpaper (to smooth any rough edges), some wood glue, a ruler and some rubber bands (or
small clamps) to hold parts together while the glue dries. It takes about three to six hours to assemble,
depending on how much attention to detail you put into it.

It's a fascinating piece of engineering history. A concept more than a thousand years old, that failed in its
design goal, yet still manages to capture the imaginations of people generation after generation.

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    Price: $199.95
    Minimum age: 8
    Availability: out of stock

    Item code: 14102

Notes:
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.


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Villiard de Honnecourt's original drawing, circa 1235 AD.

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How it's supposed to work:

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On one side of the wheel the hammers extend straight out, making a longer lever arm (the distance from the center of the wheel to the hammer's head). On the opposite side of the wheel, the hammers lay close and make a short lever arm. Since the lever ratio is greater where the hammers stick out, it's unbalanced and makes the system want to tip, and thus the wheel to rotate. As it rotates around, the next hammer falls into place continuing the motion "perpetually". Of course, we now know that such a device will never actually work, but the subtle reasons why it won't work can be elusive.

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Kids love it!

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