How can I make a strong/durable balsa wood bridge?

Question

I need to make one for a competition. All I need are some ideas. Anything helps.

Overview: Students will design and construct a model balsawood bridge from their own plans that will carry a maximum load while using as little wood as possible, stressing neatness, craftsmanship, and creativity.

Materials: 1⁄4” x 1⁄4” square balsawood (ten 3 ft lengths usually sufficient) and water soluble Elmer’s-tyoe white glue.

RULES FOR SIZE:
1) Maximum length: 40cm
2) Maximum width: 10cm
3) Maximum height: 21cm
4) Minimum clearance: 10cm
5) Minimum span: 25cm
6) Maximum Bridge weight: 95cm

Construction Rules:
3) Joints must be at or within 1⁄4” of the end of at least one of the sticks (members).
No part of a stick may be glued to another stick except at the joints.

Here are the full rules:
http://mesa.ucop.edu/mesa_day_rules/CivilStructures_2013-2014.pdf

Best answer goes to the one with the best idea.

Answer 1

Look at how actual bridges are built, and look for patterns in their designs.

Triangles are stronger than squares.

Set up struts or something to distribute the force to the supported ends-have an overall arch shape?

Cut the ends/joints at an angle so there is greater surface area to glue and the joint is more secure.

If you can, build a bridge, put weight on it, and observe what fails. Then reinforce that area.

Have a broader base, so that weight is distributed over a greater area and it is less likely to slip.

Answer 2

Balsa Wood Bridge Designs Strongest

Answer 3

1

Answer 4

This Site Might Help You.



RE:

How can I make a strong/durable balsa wood bridge?

I need to make one for a competition. All I need are some ideas. Anything helps.



Overview: Students will design and construct a model balsawood bridge from their own plans that will carry a maximum load while using as little wood as possible, stressing neatness, craftsmanship, and creativity....

Answer 5

a triangle is the most stable form of structures. u can have diagonal braces for a rectangle which u divide it into two triangles. a diagonal brace is good for stress reversal. the structural engineers are very smart. before the advent of computer, structural engineers have to guess how the structures behaves by using similitude's (which is also called dimensionless analysis) as in the study of fluid mechanics. they build a prototype to see how the prototype behaves as the real structures. now, the structural engineer has a tool call finite elements using computer. if u know the properties of balsa wood, u can feed the information into the computer. it will tell u exactly how the prototype behaves. now if u know the properties of materials of the real bridge, u can feed the information into the computer too. it will also tell u exactly how the real structures behave too. that mean, u can study the co-relationship between the balsa wood structure and real structure and eventually built a model without using a computer. (architects do that quite often). working out and verifying the math on similitude between the prototype and the real structure using finite elements will be your final master thesis. theoretically, similitude of the balsa wood bridge should be the same as the real bridge. if u divide the similitude of the balsa wood bridge and the real bridge, it should equal to one. if they are different, u can do experiments to determine the constant of proportionality and verifies it by finite elements.

Answer 6

heres the notes I made for my students:

http://www.skillbank.co.uk/de/year1.htm



its the height that gives the stiffness. ex: Take a 12" ruler. lay it flat on table.

bend

it in the vertical plane. easy.

now in the horizontal plane - hard.