Science Fair Project
London Bridges Falling Down
Kate Howard and Kira Koziak
Statement of Problem

Which Truss Design supports the most
weight, the Warren or the Howe?
Project Overview

For our project we built bridges out of
balsa wood in two designs, The Warren
Truss or the Howe Truss. Then we tested
them by hanging a bucket from them and
measuring in pounds how much water it
held.
Research

The Warren Truss is the most used design
Variables

Independent- the truss design

Dependent- weight each truss holds

Constants- glue, bucket, wood, bucket securer, type of
sand, spot where we hang it, length of bucket to ground,
chain, type of styrofoam, person who pours sand

Control- Warren Truss. This is logical because it is the
most used truss design.
Hypothesis

The Warren Truss will hold the most
weight because it distributes the weight
more evenly than the Howe Truss.
Materials
Balsa wood
 60cmx60cm block of Styrofoam
 4572cm of Plastic Wrap(150sq ft)
 Superglue gel
 1 piece of graph paper
 Block and chain
 Exacto knife
 Large bucket
 Approx. 10lbs of water
 1 pen or pencil
 Truss designs (1 Warren and 1 Howe)
 2 pairs of safety goggles

Procedure
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Gather supplies
Wrap the 62cm x 60cm block of Styrofoam completely in plastic wrap with large sheet
of graph paper under the plastic wrap.
Draw a Howe design of one piece and a Warren design of another. These will be what
you use as a guide so all of your bridges will be the exact same size.
Build three of the Warren Trust designs. Make sure to leave a big enough hole at the
top to fit a chain through but small enough to hold the block of wood
Build three of the Howe Trust designs. Make sure to leave a big enough hole at the top
to fit a chain through but small enough to hold the block of wood
Break one trust by laying it across two tables and hanging the chain with the block of
wood from it. Hang the bucket from the chain and slowly pour sand into the bucket.
Once the trust breaks weight how much sand the trust held and record observations
and chart.
Repeat steps 6 and 7 for all five other trusts.
Graph all trials
Find the average of Warren Trust and average of Howe Trust
Graph averages
Compare and contrast
Procedure
Photos
Data and Observations
RED- TRIAL 1
T
R
U
S
S
YELLOW- TRIAL 2
T Category 2
Y
WARREN
P
E Category 1
HOWE
0
2
4
6
8
WEIGHT HELD IN POUNDS
10
Conclusion

The Truss that held the most weight on
average was the Howe Truss. The Howe
Truss’ average weight held was 8.27lbs
and the Warren Truss’ average weight held
was 7.13lbs.
Possible Experiment Errors

Some possible experiment errors were
gluing and it was hard to monitor how
they were being built so it was hard to
build each one the exact same way.
Applications and Recommendations

I would recommend that other people
monitor how they build the bridges so
that each bridge can be exactly like the
others
Works Cited

The Toothpick Bridge - Design and Build Strong Toothpick Bridges. Web.
<http://www.toothpickdesign.com/trusstoothpickbridges.htm>.