Tower Efficiency = Mass Held by Tower / Mass of Tower

Strength Tower Problem Name: ______8th Grade Technology Period: ______

Problem You have been contracted by Verizon Wireless to design and build the most efficient cell phone tower. Verizon will assess your tower’s design by using the Tower Efficiency equation to hold a single point mass. Tower Efficiency = mass held by tower / mass of tower

Limits and Constraints 8” Tall (1/4” tolerance allowed) Only provided glue may be used 3” Minimum width (1/4” tolerance allowed) 4” Maximum width (1/4 ” tolerance allowed) The finished tower may not weigh more than 18 grams Must have 4 horizontal supports on the top and bottom of the structure

Guidelines 1. The mass of the tower will be recorded before testing. 2. When the testing device is ready, the student team will begin to apply the load to the tower at the rate he or she chooses. 3. The testing device will record the load. 4. The tower supporting the greatest load with the best efficiency will be the winner. The following equation will be used to determine the efficiency Tower Efficiency = mass held by tower / mass of tower

5. Neat, quality sketches must be submitted and approved before selecting the final design. Sketches must show a side view 6. Your design plan must be signed off on by the instructor before the start of construction. 7. Structures will not be tested if: excessive use of glue (coating of beams, large glue joints) 8. The final design package MUST be turned in for your structure to be tested

Materials 180 linear inches of balsa wood (5 x 36” sticks) One 3”x 5” index card “Gusset Plate”

Tools Balsa Cutter Straight pins (to hold wood in place while glue dries) Clothespins (to hold sides together during final assembly) Sandpaper

Tower Score Grading Top 6: 100, 99, 98, 87, 96, 95% Middle 8: 89, 88, 87, 86, 85, 84, 83, 82% Bottom 6: 76, 75, 74, 73, 72, 71% Structure above 18 grams: 55% Grading Criteria:

This rubric MUST be submitted with final design package and your completed tower. 10 points will be deducted if no rubric is submitted.

Little or no evidence of Design shows some evidence Design shows lots of evidence research or application to the of research, some applied to of research, research applied to Investigation design design design

0-2 points 3-6 points 7-10 points

1 or no sketches were At least 4 sketches 2 or 3 sketches were submitted submitted Sketches 3-6 points 0-2 points 7-10 points

1:1 Scale Drawing of Front 1:1 Scale Drawing of Front 1:1 Scale Drawing of Front view, 1:1 scale Drawing of view, 1:1 Scale Drawing of view, 1:1 Scale Drawing of Top view, and ¼ Scale Top view, and ¼ Scale Top view, ¼ Scale CAD orthographic. But missing orthographic. But missing orthographic. Included dimensions and title block dimensions or title block dimension and title block

0-2 points 3-6 points 7-10 points

Math is incomplete and/or not Weight estimation complete Weight estimation complete legible Weight but did not show work. and all work was shown. Estimation 3-6 points 7-10 points 0-2 points

Design does not meet most Design meets some, but not all Design meets all criteria criteria criteria Constraints 0-2 points 3-6 points 7-10 points

Many poor joints, large glue Some poor joints, some poor High quality joints, neat gluing joints gluing Workmanship 7-10 points 0-2 points 3-6 points

____ Total X 1.7= 100

Tower Score Grading Top 6: 100, 99, 98, 97, 96, 95% Middle 8: 89, 88, 87, 86, 85, 84, 83, 82% Bottom 6: 76, 75, 74, 73, 72, 71% Structure above 18 grams: 55%

2 Investigation Questions:

1. What tools are used to cut balsa wood and gussets?

2. How much does one liner inch of balsa wood weigh?

3. If one teaspoon of glue equals 4.4 grams. How many teaspoons of glue will you be able to use if you use all 180 liner inches of balsa wood?

4. What are good structure building techniques?

5. How much does a 1” x 1” gusset plate made out of an index card weigh?

6. How many gussets should be used? Where should gussets be used?

7. What is the exact size and weight of one balsa wood stick?

8. How liner inches of balsa wood will you be provided with?

9. How close should the structure weight to 18 grams?

10. What are some examples of “real-life” structures that need to withstand a load?

11. What are some techniques used to join wood. What type of type of joint are you going to use and why?

3 Weight Estimation

1. One liner foot of 1/8” by 1/8” balsa wood= ______grams 2. One square inch of an index card= ______grams

3. Total the linear inches of wood in one wall:

Total Vertical- ______

Total Horizontal- ______

Total Diagonal- ______

Grand Total (add up all parts above)= ______Actual Area for one wall (use your inventor file to find the area) ______

4. Convert total linear inches of wood to linear feet (linear in. /12 = Total linear feet)

______

5. Calculate weight of one wall (linear feet x ______grams per linear foot)

______

6. Total weight of structure (Wall weight x number of walls)

______

7. Total Weight of walls + Glue weight (One teaspoon of glue =4.4 grams )

______

Now do you have room for gussets? How many gusset plates can you use before going over the weight constrain?