In the last update, I just had the two long beams of the bridge completed and my next step was to connect them using the cross pattern.
Making the Triangular Beams
The left most beam is 6 pieces, the smaller size was used for the cross pattern and the triangular support of the bridge. The middle one is 10 pieces and it’s what I used for the long beam base. The right one is how the two middle beams were connected with 4 pieces of spaghetti glued together. The strategy I had was to glue each layer individually and then glue it together by layer. For example, I would glue 4 pieces together and make 5 of those at a time. While waiting for those to dry, I would move to the next layer (3 pieces) and so on. Then I would go back and glue the 4 piece and 3 piece layers together.
Cross Pattern Base
As I was figuring out how to connect the two long beams, I realized that one of them was not straight, so I actually made another long beam. But after getting the hang of the process, it didn’t take too long to make.
I first measured how many pieces I would need to cover the 500mm distance with the cross pattern. The distance of each x was 25mm, and the short beams were about 80mm. But even though I measured the distance to be 25mm and marked it on the long beam it still ended up uneven.
So to create the cross pattern, I glued one side diagonally and then the other side diagonally in the other direction. Thinking back, the bridge might’ve been stronger if the x was on the same side. I also shortened the ends, so instead of it being 750mm in total, it was about 620mm. I used pieces of the extra long beam to reinforce the ends.
I tried tested just this piece by putting one water bottle on it, but it bent a lot and could barely hold the bottle. I was worried that maybe the glue made the spaghetti weak, or that the fact that the spaghetti I used was expired played a role in the strength.
Triangular Support
I had about 10 more smaller beams to create a support for the bridge. So I created a giant triangle and added smaller beams inside the triangle to support it. Since the only support for connecting the triangle was hot glue right in the center, I added 2 more beams in a t-shape to strengthen that point. It’s a little hard to tell in the picture on the right, but I also created an m-shape to further strengthen the sides of the big triangle. Then I added beams at the top of the triangles to connect the 2 in the center as well as diagonally from the shorter beam in the triangle to the ends.
Later I trimmed the pieces that were hanging off of the long beam (refer to cross pattern base picture) because they weren’t creating any extra support and it was just added weight. I weighed it before and after and the extra pieces were about 3-4 grams.
Final Test and Thoughts
It managed to hold a total of 8 bottles before breaking on the 9th one. Each bottle was roughly 508 grams, so the efficiently is (508*8)/198=20.53
The part that broke surprised me since I was expecting where the two beams were connected to be the weak point. But I think since I was wary of those points, the extra hot glue I put there made the points stronger so the other pieces of the bridge were weaker compared to it. I was also expecting the end part that was on the edge to break too because I actually broke parts of it and had to reinforce it later (parts of the spaghetti got burnt as well).
If I were to remake this bridge, I think I would use a different type of glue and try a different type of spaghetti. The glue I had was “washable school glue”, which might’ve made the spaghetti weaker. The spaghetti I had was also expired by about a year, but I’m not sure if that had any contributions to the strength of the spaghetti because it didn’t seem like it was inedible.
I would also work on making the ends cleaner so it is easier to connect. At first I left it uneven so when I was connect the 2 beams it would sort of intertwine, but that didn’t work. Then I tried to connect it with a flatter end, which was a lot easier and more flushed together.
Overall, I give this challenge a 10/10, it was fun to build and test how strong spaghetti could be!