Final Bridge

This is the video of the final test of our bridge! The bridge wiped out all competition, holding a whopping 128 pounds!

This engineered bridge solved many of the problems of our old bridges, focusing on lateral and vertical braces in the form of triangles, the strongest shape.  The tri-ply "skeleton" of this bridge was found to be the strongest per-pound way to connect the popsicle sticks, with the outer layers splitting the difference in length of the inner chain of sticks, and therefore minimizing the vulnerability of the joints of the bridge.  Overall, our group was very proud and excited by this sturdy bridge.  Future modifications would include exploring with using string in an effective way, something which we found nearly impossible throughout the process.  Our group even braided a string which was used in our second prototype, but we did not see this as an advantage to the strength of the bridge.  This bridge weighed 201 grams, was 53 cm in length, 10 cm wide, and 9 cm tall. The next version we would make would have more vertically oriented sticks on the lower level, toward the outer lengths of the bridge, the location of the break.  This bridge was very solid, and any significant improvements would require exploration with other "skeleton" shapes and forms.

Note that this design, unlike previous models, has a top layer that has the identical width to the base.  This change was made to provide stronger contacts between braces, which held the bases together, and the levels of the bridge.  Also note the increased lateral bracing on this bridge, compared to previous models.

This is the progression of our bridges... The oldest bridge is in the foreground, and the final bridge is in the background.

Calculations

Data
1 popsicle stick = 1.1 g
1 popsicle stick + one popsicle stick volume of hot glue = 4.5 g

Using the data above we concluded that the same volume of hot glue as one popsicle stick weighed much more than the popsicle stick (3.4 g is found using subtraction to represent the glue's mass vs. the 1.1 g of a popsicle stick)

Inertia of Popsicle stick in multi-dimensions
Which way is stonger?

The Popsicle Stick Horizontal-

The Popsicle Stick Vertical-

The Vertical Popsicle Stick has much greater Inertia, therefore much greater force is needed to strain or break the stick.

mass suspended from the bridge : bridge's mass ratio
After our final test, we found one calculation which we found to be incredibly impressive.  Our bridge weighed in just over 200 grams (201 to be exact).  Our bridge successfully held 128 lbs before the weights crashed to the floor as seen in our video.  Using the conversion factor from pounds to grams, (1 pound = 453.59 grams), we found out how many grams our bridge held (58,059.82 g).  By dividing the suspended weight by the weight of the bridge, we found that our bridge was able to support x300 its weight!
1:300

Prototype 2

After testing both Ant Bridge and Prototype 1, our group realized that Prototype 1 would be a better design, making it our final design. The bridge was 217 g, 54 cm long, 10 cm tall, and 14 cm wide. The main difference between prototype 1 and 2 was that we made many more triangles on the second prototype.  We made the base and the top of our bridge mainly out of triangles.  This new strategy was better than our last prototype's strategy, but yet it was not perfect because the top of our bridge was not flat, and unproportional to the bottom.  This caused the top of our bridge to start to snap when compression increased.  Our future modifications were to make the top of our bridge equal in width to the bottom, as well as orient the top-layer of popsicle sticks vertically to increase inertia, giving our bridge more strength.  Also, the joints of prototype 1 proved very weak, as the popsicle sticks met at an angle. In the future, glued areas that experience great stress when weight is applied should have a larger surface of contact, and ideally flush.  Another point of weakness for this bridge was that the upper railings had cross-supports in an "X" style.  The bracing technique used created stress on the bridge, even when weight was not being applied, therefore causing the top level to twist.  In future models, the top layer's popsicle sticks will be oriented vertically and bracing will not apply stress to the skeleton.

Prototype 2- Notice a progression in the efficiency of the mass of this bridge, compared to the previous designs.

Ant Bridge

Our group decided that we needed to come up with two small, but different designs and put them to the test to find out which worked best.  Eric and Jack took one approach, while Michael and Nick took another.  Nick took pride in his design which was later named Ant Bridge due to its minuscule size.  Ant Bridge was designed by using a base of posicle sticks guled together with five single popsicle sticks coming to a center point above, and then pieces of string were added to the bottom of the bridge to help with tension.  Ant Bridge weighed 54 grams.  It was 20 centimeters in lenthgh, 12 centimeters in width, and 9 centimeters tall.  Ant Bridge failed at 75 pounds.  The length of Ant Bridge also contributed to its high holding capacity.  Ant bridge was a very short bridge, therefore the force (tau) was smaller due to the very short radius for the force to be applied.  Another reason Ant Bridge was successful, was that our group learned that the fewer joint parts with a greater surface area of contact, the stronger the bridge would be.  We did not consider Ant Bridge to be a failure, but the primary problem with it was that it was too small.  It was necessary to use a large amount of glue for this model.  Future modifications of our design will consist of a much larger bridge and less glue, so that we can really understand if this design can be successful at a large scale, under the weight requirements.

Prototype 1

When we were assigned this project, our group was spilt in half into 2 teams, working on two very different bridge designs.  One was abstract with a novel design, and the other was a variation on a conventional, modern bridge.  Eric and Jack started on the later concept and it was named Prototype 1.  Our first prototype was 33.5 cm long, 11 cm wide, 12 cm high, and weighed 114 g.  Our prototype was based on a trapezoidal prism figure.  It held 65 pounds before it broke.  The center of the lower side rail broke first, which then caused the bridge to snap, twist and collapse.  We decided that our faliure was due to a weakness in our base.  Our base consisted of 3 popsicle sticks vertically oriented, with minimal bracing in the horizontal or vertical axes. Our modifications consisted of  using more triangles to cross brace the base, making it stronger on the bottom in future models.  Overall, it was a good first prototype, giving us much to learn from and modify in future bridges.