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