Bridges to Nowhere

Design Problem: Design a small foot bridge that can be safely navigated using minimal materials.

Criteria:

Stairs

stairs must satisfy the 7-11 rule
stairs must span a minimum of 22"

Bridge

must be a minimum of 32" long.
must be a minimum of 22" wide.
must have a minimum of 18" clearance from the ground.
bridge must have a continuous walking path

Stairs

must return people back to the ground

Constraints:

Materials

8' 1X2
2'x4' 11/32 BCX plywood
Up to 6 sq. ft of additional plywood as needed (thickness will vary)
Nails/wood screws as needed

Design Process:

To design my ramp, I sketched out a basic ramp design that would conserve as many materials as possible. I used triangles because of my knowledge from previous problems. Then after practicing blueprint skills, I made my technical drawings. During construction the only difficulty I ran into was cutting the supports all at the same angle and height. It took some time to make sure the measurements were precise. I learned which saw is best for cutting two by fours at angles.

Blue prints

(technical drawings):

Evaluation:

Part I: Our bridge passed bridge inspection.

Part II: Our bridge is safe to use. We thoroughly tested our design (which included running and jumping on it) and concluded that it was very durable. All five of our teammates could stand on the top of the bridge at the same time, meaning that it can successfully hold over 600 pounds.

Our bridge satisfies the criteria listed in the design specifications. The bridge face itself was designed to be exactly 32 inches long and 22 inches wide to both meet the requirements and conserve materials. The minimum height of the bridge was 18 inches clearance. The bridge, stairs, and ramp all exceed this, measuring a height of 21 inches.

The bridge looks aesthetically pleasing. Our bridge has a unique look that is emphasized by the star painted on the top along with our signatures. It looks neat and clean except for the most part, with the exception of one piece of wood that had to be used due to limited materials to attach the ramp to the bridge. The design looks sturdy, causing me to want to walk on it even if I did not make it.

For my part of the project, the ramp, the blueprints are almost exactly like the finished product. The design matches. For this part of the project, no extra wood that wasn't planned for in the blueprint was needed. The only slight difference is the triangular support pieces are smaller than drawn on the blueprint. This is an improvement that helps with material efficiency.

For the ramp, no extra wood was needed that was not accounted for in the blueprints. We knew ahead of time that we were going to use an extra sheet of plywood that was not in the original set of materials.

Final Model Images:

Results:

My ramp design was successful. The drawing and finished product match. As shown in my blueprints, I was able to build my ramp without any modifications from my original plan. Because of this, the ramp is aesthetically pleasing. It looks neat clean. After lots of testing, it was concluded that the ramp is extremely sturdy. It is safe to use. It was considered by my team mates and I to be the most structurally stable part of our project. You can stand on it on anywhere without it leaning or tipping. It does not creak or move at all. My ramp is 21 inches tall, allowing it to lay flush with the rest of our project pieces. It was build to the correct dimensions to exceed the minimum height required.

Comparison of Blueprint to Final Product:

Improvements:

In order to improve my ramp design, I would make its slope less steep. The would make it easier for everyone to go up and down the ramp without any doubt. By decreasing the angle cut into the supports, the main board's incline would be more gradual. To do this, I would have to increase the length of the main board to still reach the same height of 21 inches. Using more materials, which decreases efficiency and increases costs, is the trade off of making this adjustment.

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