Building a Balsa Bridge
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Transcript Building a Balsa Bridge
Prepared by:
Barry Sparrow and Sal Ienco
Civil/Construction
Sault College
You will need:
Balsa wood
Tape
Cutting knife
Clamps
Books
Math set
Glue
Cardboard
Pins
Sandpaper
Pencil
•Cut accurately
•Take your time
•Be careful
•Total length to be 450mm
•Save your off cuts (scraps)
Cutting
Video
Cut both truss
sides at the same
time
Use
tape to hold
parts in place
Use ‘white’ or
carpenter’s glue
Be sure to glue
all contact faces
Be
neat
Use a damp cloth
or tissue to clean
up
Pins can hold parts
temporarily
Use scraps as
spacers
Check
the
alignment
Complete the
truss gluing
Use
more tape to
hold parts in
place
Use books or
similar weights to
hold in place until
glue has dried (12 hours)
Gluing
Video
Remove
books
Cut away tape and
remove carefully
Remove
any
pins and
remaining
tape
Repeat
process for
side 2
Now
the truss
sides can be
assembled
Measure and
cut the cross
members
Make sure
bridge is
minimum width
(40 mm)
Glue
top and
bottom cross
pieces in place
Line up cross
members with truss
webbing
Use
spacers or
blocks to keep parts
straight
Sand and trim before
gluing to ensure a
good connection
Once
the
connections have
glue applied the
truss can be put in
place
Apply glue ready for
the top cross
members
Use tape to keep
cross members in
place
Install
top cross
pieces
Diagonal bracing
installed later after
glue had dried
Books
keep
everything in place
until glue sets
Spacers keep sides
straight up (vertical)
Let dry for 1-2 hours
Use
clamps where
needed to install
final cross pieces
To
deal with
compression forces,
extra material is
added at each truss
end
Adding
gussets
at bottom
corners
increases the
connection
strength
For
this bridge,
diagonal bracing
material was
made from ½
thickness pieces,
cut along the
length
Cut
and assemble ½
thickness angled
bracing
These pieces are
used on each end of
the bridge to keep it
from collapsing
sideways
Trim to size after they
are in place and the
glue has dried
Install
bracing
Note gusset added
at top cross
member
After
glue dries,
bracing can be
trimmed and
sanded
Diagonal
‘X’
bracing is installed
Cut to fit
Use pins or tape to
hold in place until
glue dries
Install
bracing
on top as well as
bottom of
bridge
Note extra
gusset at
support point
Bridge
is
complete
Touch up
lightly with
sandpaper
It’s ready for
testing
Testing Video