How to build a bridge - School of Computing and Engineering

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How to build a
bridge!
The Romans
frequently built
bridges with
several small
arches on top of
one another.
This slideshow contains tips, hints and
several interesting bridge designs.
Tools and Equipment
• Not all of this is necessary, but all of it is
very helpful.
“One only needs two tools in life: WD-40 to
make things go, and duct tape to make
them stop.”
-G. Weilacher
Use the glue
you are
given!
• Most glue is stronger than the wood itself
• As long as you use glue for what is was
designed it might not really matter
CA Glue (aka superglue) – High
School Use
• Dries quickly
• Very strong
• Comes off your
fingers naturally
within two weeks
• Must use in a
ventilated area
Excellent for gluing two
sides together!
Wood Glue – Middle School
Use
•Good brand of wood
glue
•Three types available
•Clamp for ½ hour
•Water clean up
•Excellent for
laminating beams
together
Tools
•All of these tools are recommended but be careful
as they are sharp and can injury you if used
improperly.
•Scissors, ruler, square, level, and sharp blades
More tools
•Binder clips make excellent clamps (and are cheap)
•You need a sanding block and plenty of sandpaper.
Even more tools…
• Files will help
you to shape
the wood.
• Pins are
available at
hobby stores.
You must have
many.
A 3/32” square file is particularly
helpful in making notched joints.
•This is a ceiling tile
that has been glued
to a thin piece of
wood.
•The wood keeps it
level and prevents
pins from pushing
through.
• A ceiling tile works very well to build on. It
provides a level surface that you can pin into.
• Alternatively, you can use several sheets of
cardboard stacked together.
How To Build Your Bridge
Planning
• The success of your bridge is roughly 50%
design and 50% construction!
• A full scale template is highly suggested.
• Use a ruler and make your plan full scale
and symmetric
• Glue sticks together to make an actualsize ruler – two thick, three thick, etc.
• Tape your full scale plans to the board and pin a
piece of wax paper on top. Plan templates are
available from me!
• The wax paper prevents the glue from ruining
your plans.
Use your balsa
sticks wisely as
you can only use
the materials you
are given.
• Glued joints will be stronger if you pre-sand all
of the wood.
• Choose the best pieces of wood for the vertical
and horizontal major components.
• Darker wood tends to be brittle but stronger.
Construction
•
•
•
•
•
•
Take care to make good joints.
When you are done, gently sand it.
Extra glue adds weight, but not strength.
Make sure to follow the gluing directions!
Take your time!
CA glue is a solvent for itself. That means
if the glue has cured, don’t add more or it
will dissolve itself.
• Make the beams
first.
• Each beam is
clamped with binder
clips
• Alternate the clips
so that the beam
does not warp
• Sand each beam
until it is flat after it
dries
• Make each side
one at a time
• The aluminum
pins are
available at any
hardware store
• Don’t pin through
the wood!
• Complete each
side and then
remove it from the
wax paper
• Leave the pins in
place for the
second side to
insure that they are
identical
• Put the sides
together and
cross brace
them
•Sand the entire bridge!
•Note that this design
has an undertruss
which is not allowed
in this year’s
competition!
•Insert gussets where
needed
Baking Your Bridge!
• You can loose A
LOT of water
mass by baking
your bridge!
• Low setting for
about 15
minutes
• Seal in a plastic
bag after baking
Bake at your own risk!
Bending Wood
• To bend wood, soften
it first over boiling
water.
• Steam softens wood.
• Bend, pin in place
and let it dry.
• After dry, glue it
• Be very careful not to
burn yourself or your
Never pin through the wood!
teammates!
Truss Designs
Howe Truss
K Truss
Warren Truss
Pratt Truss
Types of Joints
Gussets improve
a joint
End joint
(weak)
Lap Joint
(best)
Notched Joint
(better)
Loading your bridge
• You have 5
minutes to place
your bridge on the
load frame and
position it with the
loading bucket.
• You have 20
minutes to load
your bridge to
failure.
Good Luck!
• Bridges are rated on efficiency.
• Your bridge needs to be light and strong!
• Awards are given for the top 3 teams in
both divisions.
• Judge’s Choice award will be given at the
discretion of the judges.
• The high school winner may receive a
$1000 scholarship if they choose to enroll
at UMKC in the School of Computing and
Engineering!

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