The Compound Gear Train

Ancient Engineering SeriesCatapult Kits

Have you hurled today?

The Compound Gear Train

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

This Gear-Train model kit is a great way to demonstrate how compound gear ratios can reduce or increase torque and the effects that has on power and speed.

A gear train is a set or system of gears arranged to transfer rotational torque from one part of a mechanical system to another. Gear trains consists of driving gears, intermediate or "idler" gears, and transfer gears. The driving gear is where energy is input into the system of gears. It's the first gear to "feel" torque. The intermediate gears transfer that torque, and may reduce or increase it according to the gear ratios involved. The transfer gear passes the modified torque onto the next component in the machine, whether it's a wheel, a winch, a counter (as in an odometer - which is another kind of gear train) or anything that needs power.

This model has two driving gears, depending on which crank you turn. You'll see how compound gear ratios can reduce or increase the torque of the transfer gear, and the effects that has on power and speed.

Tools you will need to assemble this kit:

Utility Knife
Household Scissors
Sandpaper or a flat file, to smooth any rough edges
Wood Glue
Small clamps (or a few rubber bands will do)
Optional - 1/4" round or "rat-tail" file

The kit can be assembled from start to finish in about two to four hours. The kit includes everything you need except for the tools listed above. The detailed instructions are filled with photos and tips to make construction as easy as possible. We recommend that an adult help any kids under 12 to assemble this kit.

Most mechanical devices have gears in them to change torques and speed, and to control movements of other components. Understanding gears and gear ratios is an important step in developing mechanical skills and how machines work in general.

Tools required:
Scissors, Glue, Ruler, and a utility knife. Sandpaper is optional.

Assembly time:
For a Master carpenter doing a sloppy job: under an hour.
A person with no kit building experience being extremely meticulous: about 2 hours.
The model in these photos was built by Ron Toms in about one hour.

Assembled Size:
- Height: 6"
- Length: 12"
- Depth: 4"

Gear Ratio:
- 6.5 to 1

Shipping weight: 2 lbs.
Box dimensions: 12" x 12" x 2"

Quantity pricing info:
0 to 4 kits, standard price.
5 to 9 kits, 10% off
10 or more kits, 15% off
Bulk priced kits are not individually packaged. All parts, components, instructions and hardware for each kit are combined into one box.

Orders of $200 or more get FREE ground shipping!

For more discount pricing info, please visit www.RLT.com/wholesale

Price: $24.95
Minimum age: 8
Availability: In stock.

Item code: 14010

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.

(Click images to enlarge)