Build a Balsa Bridge to Hold 20 lbs | Advice & Tips

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Homework Help Overview

The discussion centers around designing a balsa bridge for a class project, which must support a weight of 20 pounds while adhering to specific dimensions and constraints. The project is part of a high school AP physics course.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants explore various design ideas, including the use of different configurations of balsa wood and the implications of material constraints. Questions arise regarding the limitations of materials, the level of the project, and the importance of design constraints.

Discussion Status

Participants are actively engaging in the discussion, offering suggestions for design considerations, such as the potential benefits of laminating materials and exploring different structural forms like arches. There is a recognition of the need to clarify project constraints and material limitations.

Contextual Notes

Participants note the importance of understanding the specific requirements of the project, including the type of balsa wood available and the educational level of the assignment, which may influence design choices.

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Im building a balsa bridge for class but I'm struggling to find a design. The bridge must hold 20 pounds and have a trapezoid clearance. the minimum length is 14cm and the max is 20cm, min to max height is 5-8cm. Width must be 3cm. Here is my design so far, I would build two of these faces and connect them with horizontal lengths of balsa. I have 24 feet of balsa so please critique, advise, and even reconstruct my design. Thanks
 

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... and you are presumably limited to how much balsa you can use? (Otherwise you can just use a thick plank.) Does it only have to support a 20lb weight?

What level is this to be done at? Like a high-school project gets a different kind of answer to a college engineering class.

There are infinitely many designs - consider what happens when you put the balsa plank edge-up: pretty rigid right? You'll need at least two of these with the gap narrower than the width of the test weight. After that you can put anything you like up for the surface ... but I am imagining a std hobby sheet of balsa - if you have a pile of thin sticks it's trickier.

So you see how important the constraints are?

BTW: there is a simple design here which supports 220kg (485lbs).
The same site also has lots of tips and other designs, physics links etc.
 
Last edited:
thanks for the reply, I am limited to small sticks of balsa, i believe they are around 1/8 inch but I am not sure. This is for my high school AP physics B course
 
Find out of laminating is allowed. If it is, this is a way to really increase the strength.
 
OK - check out the balsa-bridge website for designs - those folk were restricted by weight.
You may like to try making an arch. You can build long beams out of short lengths like building a wall.

At least now you know your design need only be quite short and the load light :)
 

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