Well in my physics class we were given this assignment. We are only allowed to use wood glue and round toothpicks. Has anyone else done this? I’m starting it this weekend, even though it isn’t due for well over a month. This is going to be a long and tedious process!
We also did the egg drop recently too. Our teacher allowed us to use as much notebook paper we wanted to and we could only use Scotch tape. It had to be in the shape of a cube. I made a cube that had corrugate (folded a bunch of paper) on the inside to support the egg. My project weighed 17.2g without the egg. My teacher said that it would work, but I had a strong feeling my little cube wouldn’t survive the 9’ drop… And it didn’t!
I can use as many toothpicks as I want, but there is a max weight of 50.0g. The ideal weight is around 30.0g. The bridge does not have to be designed to hold as much weight, but for maximum efficency. So if I can get an efficency of 500%, I’m pretty much gauranteed an A. I’m not restricted to a width per se, but the inner span of the bridge has to be ~5.1cm so it can hold the metal plate. I’ve got some designs thought up, it’s just the part of getting them together!
Have fun, and play around with designs, but you might not want to get too exotic. When I was in school, we had a similar contest/project. My bridge was a sort of space-frame/box-beam design which worked quite well and got a great grade, but was over-engineered to the point that it was able to support far more than the maximum weight that would be applied for a grade. As a result, the efficiency suffered, since it was heavier than it needed to be for the load.
Later, most of us went on to test to destruction, just for giggles. Mine just kept going and going, until it eventually underwent catostrophic failure all at once when a tension member pulled apart. The one that held up to the highest load was a ladder arrangement of half-inch sticks. Not much for efficiency or creativity, but effective enough.
Most of the ones that did well in the efficiency category were simple railroad-type trestles. There’s a reason why that design has been so popular for so long.
I did a similar contest in high school, but with match sticks (basically 30 cm square pieces of balsa). The design that always did well was a simple two-beam one, with seven or so sticks per beam and a few single or double stick cross-members at different points in the middle of the stack.
Is this a local contest (only for class) or part of the national physics bridge building contest? I had this two years (physics and AP physics), both times going to the regional contest at another high school uptown. Finishing 13th and 7th respectively out of about 500 regional contestants each year.
The winner of the regional the second year (also from my high school) had a thick frame suspension design with a single central tower. It weighed 22g and held about 55 kg. However, his biggest secret (In my opinion cheating) was he used some exotic glue his brother recommended (who had won two years prior). To be somewhat fair, we was also very good about contruction. Most people use either Elmer’s, some wood glue, or crazy glue, all of which seap into the wood, thereby increasing the weight a lot. This special glue only bound the surfaces, which allowed him to use like three times the amount of wood everyone else did. I had made a design identical to that the first year (except I had to use less wood so some beams were only three sticks deep while his was six or seven, etc. Mine only held 35 kg, at 33 g. Some other tips I learned was only using the dark balse strips as they’re from the center of the tree, “heartwood” and are harder to break (his bridge looked like it was made of oak instead of balsa, stress testing before building to find inner defects, and pre-stressing while building to provide extra force.
It’s just for my class. I’m in Hons Phys right now and I’ll be in AP next year. There’s only reason I’m taking it… I want to go into engineering and the teacher (my hon phys teacher) is awesome!!!
I would love to be able to use a different type of glue, but we can only use Elmers Wood Glue.
Cutting all of these little tiny toothpicks is nerve wracking!
If someone wants to see the egg project that failed, I could email them the pic and then they could host it for me. Aol won’t allow me to host pics, it takes way too long.
I started glueing things together last night. I made one of the rails, that’s two toothpicks tall by two toothpicks wide. I clamped it by using two pieces of aluminum, two vice grips, and a vice. Once I get it weighed, I’ll multiply it by four and that’ll be my approximate weight.
