instructables
Warren Truss Popsicle Stick Bridge
by Kiara Vargas
Hello there! In this informative step-by-step guide, I
will take you through the procedure done by me and
my team in order to develop an effective and cost
efficient Popsicle stick bridge using a warren truss
pattern. Whether you're reading this to pass some
leisure time or are attempting to build a bridge of your
own, I hope this guide leaves you very informed and
that executing this project was as much fun for you as
it was for me and my team!
Step 1: Organizing a Team
The first order of business for any team is to make
sure everyone is assigned a part in the project. The
following is how our team was organized (it includes
roles and dates for each job to be done) :
Bridge building (December 17th): All members
Justification for bridge design (December 5th) :
Andrea Castillo and Stella Bagno
Video production (December 20th): Oliver Perez
Math for the bridge (December 5th): Juan Zapata
Putting together the booklet (December 17th) : Kiara
Vargas
Narrating the video (December 19th): Thatcher
Strand
CAD sketches (December 11th): Juan Zapata and
Thatcher Strand
Warren Truss Popsicle Stick Bridge: Page 1
Step 2: Why a Warren Truss Pattern?
The Warren Truss design has equilateral triangles in
the framework to spread out any load of weight
placed; loads on the diagonals alternate between
compression and tension (approaching the center),
with no vertical elements. While elements near the
center must support both tension and compression in
response to live loads. This configuration combines
strength with resourcefulness of materials and can
therefore be generally light and efficient. Because it
spreads out the load equally throughout the bridge
and it is relatively simple to build, my team and I
chose the warren truss design to build in order to
complete the project.
Warren Truss Popsicle Stick Bridge: Page 2
Step 3: The Math Behind the Reason
What's engineering without some math to back up our Which is how much force half of the bottom popsicle
project? We took into account the math that goes into stick is holding. Multiplying by 2 tell us that the
building our bridge. These are our findings:
popsicle sticks at the bottom are holding 44.90N per
triangle, but this force is divided equally by the 3
We wanted to be putting 105 lb of force on our bridge, popsicle sticks that are at the bottom of each triangle.
which translates to 467.063 Newtons. This means
that if the weight is distributed evenly, every triangle
To find the force going on the popsicle sticks on the
will be receiving 38.9N of force, and the four corners
side of each triangle:
touching the table will get 116.7N each. To find how
much force of the 38.9 Newtons is going into each
We can use cosine since we already know the force
side of the triangle, we use tangent and cosine times applied on the adjacent side of the angle and the goal
the force in Newtons. To do this, the equilateral
is to find the force applied on the hypotenuse.
triangle must be divided in two, creating two right
triangles, as demonstrated by the imaginary line.
Cos(30) = (x/38.9)
To find the force going on the popsicle sticks on the
bottom per triangle:
Multiplying by 38.9 yields
38.9 cos(30) = 33.68N
Since the new side is going straight down, like the
force, we can use tangent to find the force applied on
the opposite side of the angle.
Which is how much one side of a triangle is holding.
Multiplying this by 2 reveals how much force is
applied to both sides of the triangle, 67.38N.
Tan(30) = (x/38.9)
Multiplying the whole equation by 38.9 and solving
gives us
38.9 tan(30) = 22.45N
In conclusion, each triangle will support 44.9N at the
bottom and 67.38N at the sides.
After doing this math, my team and I were certain
that the warren truss design was the best option.
Warren Truss Popsicle Stick Bridge: Page 3
Step 4: Does This Mean the Design Is Flawless?
Of course not, nothing is perfect! One particular weakness was taken into account. The bridge will most likely to
fail at the circled locations shown in the picture above, since it is when the gap begins and will push against the
table, acting as a lever where the force input in the middle of the bridge yields an output of about 2 times as much
if the force is applied directly to the middle.
Step 5: Sketching Out a Plan
Before physically constructing the bridge, we decided to create computer generated sketches in order to have
some blueprints and to see what was to be expected. The pictures above show the 4 sketches done.
Left picture: 3D sketch of the bridge
Top right picture:Front view sketch of the bridge
Middle right picture: Side view sketch of the bridge
Bottom right picture: Top view sketch of the bridge
Warren Truss Popsicle Stick Bridge: Page 4
Step 6: Materials
Now that a plan has been laid out, it's time to get
building! The following is a list of materials needed to
create the bridge:
depending on the size of glue gun that will be used)
.Rulers (2 in order to measure a total of 24 inches/60
centimeters)
.Popsicle sticks (Approximately 160 sticks)
.Clothespins (At least 12)
.White liquid glue (1 bottle)
.A pair of scissors
.A hot glue gun
.A pen or pencil
.Glue sticks for a hot glue gun (numbers of sticks vary
Warren Truss Popsicle Stick Bridge: Page 5
Step 7: Building the Side of the Bridge
1. Begin with making 11 triangles. Take 3 Popsicle
sticks and lay them out in a triangle shape. Attach an
end of one side stick to an end of the bottom stick
with hot glue (be sure to place the side stick at a 45
degree angle). Repeat this with the other side stick.
The point where the two side sticks meet should not
have the sticks overlapping, but rather side by side
(This is shown circled in red on the top picture on the
right). Repeat the entire step 10 more times.
2. Attach the triangles. Get two triangles and turn one
upside down (One triangle should have the bottom
stick facing down while the other should be facing
up). Attach 1/3 of Popsicle stick with white glue on
the middle of a triangle side where it will overlap with
the other. Add hot glue on the Popsicle piece and the
ends of that side and attach the other triangle. Add a
clothespin to the part with white glue. Repeat this
step until all triangles are attached.
4. Connect the top and bottom of the structure. Glue
1/3 pieces to the middle of the bottom stick (seen
circled in blue in the picture on the top right) of each
triangle with white glue. Glue down Popsicle sticks to
connect the triangles together with white glue
(specific alignments seen circled in red in the picture
on the left). Secure the glued parts with clothespins.
5. Wait 30 minutes for white glue to dry; afterwards,
remove clothespins.
6. Add reinforcements. Apply hot glue on points
shown in the middle right and bottom right pictures.
Your end product should look like the picture on the
left.
7. Repeat steps 1-6 once more.
As an end result, you should end up 2 sides for your
bridge.
3. Wait 30 minutes for white glue to dry; afterwards,
remove clothespins.
Warren Truss Popsicle Stick Bridge: Page 6
Step 8: Attaching the Sides
1. Lay out the pattern (shown in the picture on the
right). Stand both of the sides upright.
2. Connect the sides by gluing (using hot glue) the
sticks following the pattern. A total of 19 sticks should
be used.
3. Add reinforcements. Go back with the hot glue and
apply some to all the points that had been glued done
previously.
4. Once the glue is all dried up, flip the bridge upside
down and repeat steps 2 and 3.
5. Wait for glue to dry.
Viola! Your bridge is now finished.
Warren Truss Popsicle Stick Bridge: Page 7
Nice. That is probably the best constructed popsicle stick bridge I have seen.
Warren Truss Popsicle Stick Bridge: Page 8