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

1. Jan 19, 2008

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
LUCK??

3. The attempt at a solution
i FIGURED i would do a Truss design but idk if that is thye best one

2. Jan 19, 2008

### _Mayday_

Well what are you going to put on the bridge? Is there a mass that it need to be able to withstand?

3. Jan 19, 2008

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

Last edited by a moderator: May 3, 2017
4. Jan 19, 2008

### Feldoh

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.

5. Jan 19, 2008

### _Mayday_

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?

6. Jan 19, 2008

a project.. due tuesday WOW

Last edited: Jan 19, 2008
7. Jan 20, 2008

Will Elmers glue be enough to hold the load

8. Jan 20, 2008

### Feldoh

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.

9. Jan 20, 2008

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

10. Jan 20, 2008

### Feldoh

Not to be rude, but are you seriously asking how to glue toothpicks together?

11. Jan 20, 2008

### Rusk1

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
12. Jan 21, 2008

Yes.WhenI glue, it always sticksto the table

13. Jan 21, 2008

### RonL

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.

14. Jan 21, 2008

Now my only problem left seems to be how I will get the thing standing when I build it

15. Jan 21, 2008

### _Mayday_

Cross link a bas with toothpicks, then build on top. These problems should be part of the fun.

16. Jan 21, 2008

what is that? A Bas?

17. Jan 21, 2008

### OmCheeto

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.

http://en.wikipedia.org/wiki/Image:Parabelbåge.png
http://www.enchantedlearning.com/history/us/monuments/stlouisarch/printout.shtml

But I've never built a bridge before.

Good luck!

Last edited by a moderator: May 3, 2017
18. Jan 21, 2008

How can I make the glue dry really quickly

19. Jan 21, 2008

### OmCheeto

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.

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
20. Jan 21, 2008

### RonL

I think a base was implied.

21. Jan 21, 2008

Well.. I still have no idea how I am going tomake the bridge actually stand

22. Jan 22, 2008

elmers or titebond?

23. Jan 24, 2008

### PhysicsGuy9

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".

www.twigjig.com

Definitely the easiest way to build with toothpicks

24. Jan 24, 2008

### OmCheeto

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.

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.