This weekend I bought some materials to start tinkering with and to decide what is possible to perform as an experiment. I decided on using plastic as a material as it is readily available and has a slight flex, meaning it would not require as much force to observe deflection and stresses. I found a solution to making pin joints by pushing nails through holes in the plastic members to secure them (see photo). This seems to work quite well.
One potential variable to investigate would be the force required for a truss to deflect a specific amount (see photo below for a potential style of experimental rig). Plastic seemed to be well suited to this as the trusses deflected under some weight, yet this was still minimal (I tested the trusses with masses up to 400g), suggesting that for the actual experimant I will have to uses much heavier masses.
In one of my research books I read that in real life, the limit to acceptable flex is between 1/500 and 1/1000 of the trusses length. For the experiment this will not be possible though as the maximal deflection on a 1m long rig would be too small to read. On reflection I will still be able to learn about how the structure of a lattice girder affects it's strength even if I have to surpass the real life acceptability limit.
Today I tried three different types of structure, including a warren truss (which I intend to do my actual research on).
I plan to make a time plan and to design a virtual model of a warren truss on SketchUp this week, as well as continuing the research so that in within the next few weeks I can prepare myself for the actual experimentation.
Billy,
RépondreSupprimerPictures look great! Have we abandoned Macano? You should write a short post (here on the blog) as to why you switched directions on material, and relate it to the real life scenarios of bridges and cars/trucks. If Macano was an unrealistic representation, explain why.
Also, think long and hard about all your control variables. Make sure that you have isolated and contained as many variables as possible which may lead to systematic error.
Lastly, you'll want to make it as BIG as "practically" possible. Consider the cost of materials, transporting it in the back of a car (less than 2 m), but large enough to allow for true/relevant/reliable data collection. If it is too small, your data won't come out appropriately.
Doing well!!
Meeting at school:
RépondreSupprimer1) Post a link to the Royal Academy packet
2) Digital motion sensor? Digital Scale?(sign out from the Science Department)
3) Remote control Car?
4) Type up the "++" page onto the Blog
5) Try to relate to real life bridge as much as possible, considering ALL variables
6) Find pictures of cars actually going over the bridge to get a sense of height
7) Assume 1 car width bridge for reduction of variables
8) Use the school EBSCO host for academic articles
9) 2D Truss strength vs. 3D Bridge strength?
find the strongest/weakest 2D truss, then convert to 3D, see if the ratio remains the same
10) Stick to the Central Question --"what effect does the interior angle of beams have on the "structural strength" of a simple beam bridge?"