Your task is to build a bridge using 1/8" thick plywood and wood glue only. Our objectives are that you will learn how to use 3d design tools, a laser cutter, and also that you learn a bit about structure. This project is inspired by the "toothpick" bridge project (google it).
Requirements and constraints
You are to design and build a bridge that meets the following constraints:
- Your bridge will rest on two pillars (that are provided).
- Each pillar measures 2.5" x 2'5", they are separated by 7". Pillars are the wood colored items in the diagram.
- Your bridge must fit within a 12" x 2.5" x 6" rectangular prism (blue region in the diagram).
- No portion of the bridge may extend below the plane defined by the top surfaces of the two pillars.
- There must be a 2.5" x 2.5" flat area centered at the top of the bridge upon which weight will be applied (red region in the diagram).
You may use only the following provided materials:
- One piece of 1/8" by 12" x 12" plywood (i.e. 1/2 of a 12" by 24" piece)
- Titebond wood glue
Design & Building Process
You should design your bridge using a 3D design tool such as solid works. You should use a laser cutter to cut the parts from the plywood provided to you, then glue them together using titebond wood glue.
We will evaluate your bridge in four ways:
- Overall strength: How much downward force can be applied on the bridge before it begins to fail? We expect your bridge to hold at least 50 pounds.
- 85% if it holds 50 pounds. 1 additional point for each additional 20 pounds, up to a total of 90 (150 pounds)
- Strength to weight ratio: We will divide the strength determined above by the weight of your bridge.
- Additional 2.5 points for S/W > 200.
- Up to 2.5 points for beauty
- Up to 2.5 points for craftsmanship.
An award will be provided to the builder of the best bridge in each category above.
To help you get started, I include some images of a basic design that you can copy. There are some important flaws in this design though. With a few adjustments you should be able to make a much stronger bridge.