Activity
2: Grades 5-8
Geodesic Domes |
|
As
you watched the segment "The
Second Earth," you observed how dome structures
were used as containment areas for several ecosystems.
Unlike traditional domes, these structures did not
have a surface formed from solid building materials.
Instead, there were assembled from a geometric framework
of connecting rods. These open frame structures are
called geodesic domes. They were invented by Buckminster
Fuller over fifty years ago. If you examine the dome,
you'd find that the basic unit of the frame is a triangle.
As triangles are joined together, they form a pattern
of increasing geometric complexity. The final result
is a curved and sturdy surface that approaches spherical
geometry.
|
|
|
This
activity page will offer:
-
Cooperative group activity in mathematics
- Experience
in constructing a classroom geodesic dome
- An
operational definition of geodesic dome geometry
Constructing
a Geodesic Dome
Domes can be built at any size. It's
all a matter of scaling the plans. The basic frame for a geodesic
dome requires two lengths of connecting rods. It also requires
a connection joint that can adjusted to the number and angle of
intersecting rods. In this activity, you'll get to assemble a
model dome using two lengths of newspaper rolls. The joints will
be formed from masking tape. As you'll discover, even a paper
and tape model forms a sturdy, reinforced structure.
MATERIALS
- Scrap
newspaper - Any size would work, as long as pages are consistent
in size.
-
Masking Tape
- Scissors
- Ruler
marker
PROCEDURE
- Work
in teams of four. As a team you'll need to produce 65 tubes
that form the framework of your geodesic dome. Each tube is
formed from a stack of three newspaper sheets. Roll the stack
from corner to corner to form a tight tube. Use masking tape
to prevent it from unraveling.
- Trim
down your rolls to produce two tube sizes. The longer tubes
are 26 inches (or 65 cm) long. You'll need 35 of these longer
ones. The shorter tubes are 24 inches (or 60 cm) long. You'll
need 30 of these shorter ones.
- Create
the base by taping ten of the long tubes (26 inches) together
to form a closed geometric shape called a decagon.
 
- Tape
a long tube and a short tube to each of the ten joints of the
decagon. The tubes should be arranged to produce an alternating
pattern of long pairs and short pairs.
- Use
masking tape to secure the tops of the adjacent short tubes
together to form a series of five triangles.
- Likewise,
form a series of five larger triangles by securing together
the tops of the adjacent long tubes.
- Connect
the adjacent tops of these ten triangles together using a new
row of short tubes. As you join these together, you'll form
a zigzag like pattern that begins to curve the dome surface.
- Locate
the alternating joints where four short tubes come together.
Tape a short tube to each joint and position it straight out
from the joint as shown in the diagram.
- Connect
the end of this tube to the adjacent joints using two longs.
When this step is completed, you will have formed a distinct
5-sided star pattern in the dome's framework.
- Connect
the tops of these triangles with a row of longs. This produces
a pentagon.
- Connect
a short to each joint of the pentagon. These five shorts should
meet in the center of the dome. Secure this final joint.
Questions
-
Did you need to use the ruler to measure the length of each
tube?
- What
was the basic geometric shape of this frame?
- What
other shapes did you observe?
- What
was the maximum number of tubes that came together at any one
joint?
EXTENSIONS
Think About It
How
would increasing the number of component triangles affect the
shape of the dome?
Small
Scale Model
The plans for building a geodesic dome are scalable. In fact,
you can use the steps above to build versions using either plastic
straws or wooden toothpicks. Suppose you needed to scale the measurements
to straws that are 20 cm long. If you opted to use the uncut length
of the straw as the longer rod, what length would the shorter
one need to be cut to? Explain.
Dome Support
The curved shape of the dome structure helps reinforce its integrity.
This produces a lightweight structure that can withstand a good
deal of force. You can explore this characteristic of domes using
an empty and cleaned half shell of a chicken egg that has been
prepared by an adult. Put on safety goggles. Position the shell
on a tabletop so that its end points up. Carefully balance a textbook
on the shell's pointed end. You'll probably need to support the
book to prevent it form slipping off the curved shell surface.
Slowly increase the size of the book stack until the egg cracks.
To uncover the weight that eventually "broke" the egg, place the
books on a bathroom scale. Apply your observation to the use of
domes in architecture.
To
prepare the egg: The adult places the egg
on a dish - remember this can get messy. The adult then uses
a sharp modeling knife to score a ridge along the surface of
the shell. The ridge should be positioned so that it divides
the egg into two equal halves. To prevent the shell from premature
cracking, use a new blade in a gentle back-and-forth sawing
motion within the ridge until the shell separates into two halves.
Geodesic
Dome Advantages
Compare and contrast a geodesic
dome design with a more traditional dome built from reinforced
cement. Think about the advantages of the geodesic style. You
can learn more about dome structures on the Internet at sites
such as:
World
Domes and History http://www.takenaka.co.jp/takenaka_e/dome_e/
history/hisindex.html
What
are the advantages in material simplicity?
What are the advantages in illumination?
What
are the advantages in placing and lifting supports?
WEB
CONNECTION
Inventions
by R. Buckminster Fuller
http://www.westnet.com/~crywalt/inventions/invtotal.html
This site presents an autobiography by Buckminster Fuller, the
inventor of the geodesic dome.
Applied
Synergetics - Geodesic Domes
http://www.applied-synergetics.com/ashp/html/domes.html
Here is a site that offers a freeware DOS utility program in which
the user constructs geodesic domes.
The
R. Buckminster Fuller FAQ: Geodesic Domes http://www.netaxs.com/people/cjf/fuller-faq-4.html
The site offers a set of questions and answers that explores the
geodesic dome as a housing unit.
The
activities in this guide were contributed by Michael DiSpezio,
a Massachusetts-based science writer and author of "Critical Thinking
Puzzles" and "Awesome Experiments in Light & Sound" (Sterling
Publishing Co., NY).
Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools, Wayland,
MA
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools,
Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland,
MA
Gary Pinkall, Middle School Science Teacher, Great Bend Public
Schools, Great Bend, KS
|
