Building a Balsa Bridge - PowerPoint PPT Presentation

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Building a Balsa Bridge

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  1. Building a Balsa Bridge Prepared by: Barry Sparrow and Sal Ienco Civil/Construction Sault College

  2. Assemble Materials You will need: Balsa wood Tape Cutting knife Clamps Books Math set Glue Cardboard Pins Sandpaper Pencil

  3. Prepare a drawing layout on cardboard

  4. Cut the balsa pieces • Cut accurately • Take your time • Be careful • Total length to be 450mm • Save your off cuts (scraps) Cutting Video

  5. Check all of your cut pieces Cut both truss sides at the same time

  6. Lay out all of the pieces for one truss before gluing

  7. Begin gluing the pieces Use tape to hold parts in place Use ‘white’ or carpenter’s glue Be sure to glue all contact faces

  8. Gluing the pieces

  9. Gluing Be neat Use a damp cloth or tissue to clean up Pins can hold parts temporarily Use scraps as spacers

  10. Final truss assembly Check the alignment Complete the truss gluing

  11. Allow the glue to dry Gluing Video Use more tape to hold parts in place Use books or similar weights to hold in place until glue has dried (1-2 hours)

  12. Remove books and tape Remove books Cut away tape and remove carefully

  13. Truss complete Remove any pins and remaining tape Repeat process for side 2

  14. Cut the bracing and cross members Now the truss sides can be assembled Measure and cut the cross members Make sure bridge is minimum width (40mm)

  15. Assemble the two sides Glue top and bottom cross pieces in place Line up cross members with truss webbing

  16. Bridge Assembly continued Use spacers or blocks to keep parts straight Sand and trim before gluing to ensure a good connection

  17. Glue truss to cross members 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

  18. Apply top cross members Install top cross pieces Diagonal bracing installed later after glue had dried

  19. Add weights and let glue dry... Books keep everything in place until glue sets Spacers keep sides straight up (vertical) Let dry for 1-2 hours

  20. Install final cross pieces Use clamps where needed to install final cross pieces

  21. Add pieces on truss ends To deal with compression forces, extra material is added at each truss end

  22. Add gussets at corners Adding gussets at bottom corners increases the connection strength

  23. Prepare cross bracing For this bridge, diagonal bracing material was made from ½ thickness pieces, cut along the length

  24. Prepare endbracing 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

  25. Bracing at ends Install bracing Note gusset added at top cross member

  26. Trim bracing After glue dries, bracing can be trimmed and sanded

  27. Install top & bottom bracing Diagonal ‘X’ bracing is installed Cut to fit Use pins or tape to hold in place until glue dries

  28. Bracing Install bracing on top as well as bottom of bridge Note extra gusset at support point

  29. You’re done! Testing Video Bridge is complete Touch up lightly with sandpaper It’s ready for testing