We used Onshape to create the design of our bridge. In order to ensure the design was iterable, we used simple master sketches so we could edit key values later if needed.

We also ran simulations in Onshape. Because Onshape's balsa wood configuration lacks the key stress and strain parameters required for simulation, we researched them and created a "custom" material. To simplify, we booleaned the bridge into a single part. While it may be oversimplified, it allowed us to test quickly. 

The simulations showed that our bridge would be able to withstand significant forces during operations. On the low end, five times our estimated value of 100 lbf, or 20 bricks. In the photo on the bottom left, the deformation has been scaled up by 10x for visual.

For our bridge deck, we used three wooden planks side by side and doubled them with a second layer to increase strength and stiffness. We stacked these two reinforced layers to create a thicker deck that could support more weight. Between the layers, we added perpendicular supports where the brick cart wheels would travel, helping spread the load and reduce bending. Finally, we used hot glue and tape to keep all the pieces securely connected and improve overall durability.

This idea of perpendicular supports is a key part of deck design and is a material-efficient way to increase strength.

In the end, our bridge was able to allow a cart carrying 19.5 bricks across the gap. We believe the key to our success was the perpendicular supports on the deck. The bridge ended up breaking somewhere where there were no vertical supports and had few to no cracks in the supports.