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Homework Help: I need to build a bridge out of toothpicks. MAJOR HELP NEEDED

  1. Jan 19, 2008 #1
    1. The problem statement, all variables and given/known data

    weight limit-100grams
    roadbed must span 500mm of gap
    must provide space for hook (15mm x 15mm)
    Must be only built of round toothpicks and glue.
    Anybody have a clue How to do this/

    2. Relevant equations

    3. The attempt at a solution
    i FIGURED i would do a Truss design but idk if that is thye best one
  2. jcsd
  3. Jan 19, 2008 #2
    Well what are you going to put on the bridge? Is there a mass that it need to be able to withstand?
  4. Jan 19, 2008 #3
    http://homepage2.nifty.com/SUBAL/BCTOPE.htm [Broken]
    Last edited by a moderator: May 3, 2017
  5. Jan 19, 2008 #4
    There is no "best one" do whatever you want to do. If you want to build a bridge using a Truss design, do it. However whatever you plan to do I'd suggest reading up on how the bridge actually supports itself and objects.
  6. Jan 19, 2008 #5
    My knowledge on such areas isn't that great, but I have done a similar version of this using different material. Triangular structures used in bridges and in the links provided, proved very successfull for myself, though I'm afraid that is all I can offer you. What is this for a competition?
  7. Jan 19, 2008 #6
    a project.. due tuesday WOW
    Last edited: Jan 19, 2008
  8. Jan 20, 2008 #7
    Will Elmers glue be enough to hold the load
  9. Jan 20, 2008 #8
    The whole point of the project is to experiment until you get something that works, I'd suggest trying Elmer's glue and if it doesn't work try something else.
  10. Jan 20, 2008 #9
    I went out and got some wood glue. Now I am wondering how I wll glue this thing. How can glue the two sticks w/o iit stickin to the surface
  11. Jan 20, 2008 #10
    Not to be rude, but are you seriously asking how to glue toothpicks together?
  12. Jan 20, 2008 #11
    its really quite simple. i remember when we did this in middle school the person who won was the one who used the most glue. that's about all there is i think.
    Last edited: Jan 20, 2008
  13. Jan 21, 2008 #12
    Yes.WhenI glue, it always sticksto the table
  14. Jan 21, 2008 #13


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    Gold Member

    Two solutions, build on a sheet of wax paper, or put a coat of paste wax on the table.

    If the rules absolutly confine you to use white glue, or a woodglue, then titebond I, or II might produce a quicker set time.
    If allowed, a CA type (instant glue) using an excelerator, will give a 15 second or quicker lock.
  15. Jan 21, 2008 #14
    Now my only problem left seems to be how I will get the thing standing when I build it
  16. Jan 21, 2008 #15
    Cross link a bas with toothpicks, then build on top. These problems should be part of the fun.
  17. Jan 21, 2008 #16
    what is that? A Bas?
  18. Jan 21, 2008 #17


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    Gold Member

    I do not know what a bas is.

    I would study the winning designs.

    http://homepage2.nifty.com/SUBAL/BCPrE.htm [Broken]

    It appears the latest winners have laminated their toothpicks into sturdier larger beams.
    I would imagine the best design would be a single solid arched pole that gets larger at the bases.


    But I've never built a bridge before.

    Good luck!
    Last edited by a moderator: May 3, 2017
  19. Jan 21, 2008 #18
    How can I make the glue dry really quickly
  20. Jan 21, 2008 #19


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    Gold Member

    hmmmm..... good question. have you tried a hair dryer?
    Try and keep the glue thickness at a minimum. This will help speed the drying.
    Maybe you can put the bridge in the oven at about 175'F.

    here's good link about wood glue tricks:
    http://www.diyinfo.org/wiki/Wood_Glue-Avoiding_Gluing_Problems [Broken]
    although round toothpicks don't strike me as the ideal working material.

    And remember that the strength comes mainly from the toothpicks, not the glue.
    Though you want the glue to stick well to the toothpicks, so you want them to be clean.
    I would wear gloves to keep the oil from your hands from contaminating the toothpicks.
    Last edited by a moderator: May 3, 2017
  21. Jan 21, 2008 #20


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    Gold Member

    I think a base was implied.
  22. Jan 21, 2008 #21
    Well.. I still have no idea how I am going tomake the bridge actually stand
  23. Jan 22, 2008 #22
    elmers or titebond?
  24. Jan 24, 2008 #23
    Ya, holding the thing together while the glue dries is the hardest part. This site has some really cool "jigs" that you can use. You can make some amazing trusses using "TwigJigs".


    Definitely the easiest way to build with toothpicks
  25. Jan 24, 2008 #24


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    Gold Member

    I do believe the world now has enough people.
    Only on Earth can I imagine a company devoted solely to the manufacturing of plastic thingamajig devises for putting together toothpick structures.

    I do want a set though. :approve:

    And the prices top out at $39.95.

    I did experiment with wooden clothespin jigs. They have to be modified to hold 7 toothpicks.

    I was curious if the contest allows modification to the individual toothpicks. Can you sand them to a courser roughness such that the glue adheres better? Can you clip the ends? Can you flatten the sides such that the toothpicks take on a hexagonal shape? Would anyone notice if you used 2 part epoxy glues in the internals and wood glue on the outside?

    I was going to recommend titanium rods imbedded in the structures, but I was sure that was cheating.
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