Egyptians as Engineers

Objective

To construct a LEGO vehicle to pull a load up a ramp.

Description

Students build LEGO vehicles and sleds that are strong enough to drag a given amount of weight up an incline, thus mimicking the Egyptian methods of pyramid construction. This project incorporates engineering concepts into the standard fourth grade geography unit on Ancient Egypt.

Procedures

Notes:

• This activity is set over a four week period, but this is not necessarily the actual time that it takes for completion. The four week time frame refers to a one hour, thirty minute session per week. Depending on the students' background with LEGO construction, more time may be allowed for building the actual vehicles.
• It is a very good idea to have a solid background in building with LEGO bricks, and the kids should have had a good amount of experience in LEGO construction as well. If this is not the case, then it is very important that before doing this project you review the basic techniques of LEGO construction:
• How to build sturdy vehicles;
• How to attach the motor to the RCX;
• How to attach wheels to the motor and RCX; and
• How spacing of LEGOs affects the meshing of gears;

Week 1:

Introduction to Inclined Planes:
An inclined plane is considered a simple machine because it delivers a mechanical advantage by magnifying forces. It is easier to use an inclined plane to lift a load than to lift it vertically. You use the same energy with an inclined plane, but spread the applied force over a longer time. The same work is being done in either case, but less force is needed, and therefore inclined planes make it easier to lift stones.

Inclined Planes Demonstration: (See Diagram 1 in handout)

1. Attach a bottle of glue to a simple LEGO car.
2. Tie a broken rubber band around the glue and lift the weighted car by the rubber band to a certain height.
3. Observe the amount the rubber band stretches.
4. Pull the car without wheels up the plywood ramp to the same height.
5. Observe the reduced amount of stretching.
6. Place wheels on the car and pull the car up the ramp.
7. Observe the least amount of stretching.
8. With each step, the reduction in the stretch of the rubber band illustrates a decrease in the force necessary to lift the same amount of weight to the same height.

Rover Building Techniques: (See Diagram 3 in handout)
In order to build a LEGO rover powerful enough to drive up a ramp and pull weight, gear down the cars so they drive slower, yet increase their strength. This is achieved by attaching a small gear on the actual motor, which will transfer energy to a larger gear connected to the axle and wheel.

Week 2

Completion of the Egyptian rovers:
By the end of the hour, the students should have constructed a vehicle that is capable of driving up a plywood ramp set at a 30-degree angle to the floor. One problem students may encounter is wheel slippage. Wheels take advantage of friction, which depends partly on how much force is acting in the direction perpendicular to the surface in contact with the wheel. Therefore, to provide more friction, students should add more weight to their cars.

Week 3

Introduction to Friction and Surface Area:
Friction is a force that offers resistance to movement when one object is in contact with another. The least amount of contact surface area between two objects provides for the least amount of friction. A practical example of this concept is the snow sled.

Note: Another factor of friction is weight, as illustrated with the wheel.

Sled Building Techniques: (See Diagram 2 of handout)

• Wheels on the sled are not allowed.
• To attach the sled to the rover, use a motor attachment cable. For best results, attach one end to the underside of the rover.
• Each sled should have two beam runners (or similar construction with minimal contact area), which the rover is able to pull up the ramp without additional weight.

Week 4

The Final Test with Weights:
As each group test-drives their rover-sled with weights up the incline, discuss the reasons that the particular rover-sled is able or not able to pull the weight. Recall the concepts:

• Contact surface area of the sled
• Gearing of the motor
• Amount and dispersion of weight on the rover
• Size of the wheels
• Stability of both the sled and rover

Discuss the best combination of the above factors for the ideal Egyptian rover-sled to place the capstone on the pyramid!

Discussion

• After this project, what do you know about building the pyramids?
• Would you have wanted to help build the pyramids? Why or why not?

Continuation

To further incorporate math with this activity, you may choose to graph the weights that each group's rover was able to pull up the ramp. This extension would then demonstrate the usefulness of graphs in their ability to display a large amount of data at one time for visual comparison.