This design project tasked us with building a bajaj prototype that would transport people both quickly and safely.
Iteration #1: Hanging Cup
Our first iteration was essentially a tall passenger compartment made out of plastic cups, surrounded by a small cardboard and styrofoam frame/bumper. The tall passenger compartment made our device safe (i.e., the ping pong ball passengers would not easily fall out, unless our device flipped completely over). We hoped that the frame/bumper system would help dissipate force upon impact and therefore make our bajaj safer. We added weights (a jar of adhesive and a deck of playing cards) to this bajaj to help it gain speed going down the zip-line. Ultimately, this iteration proved to be safe but not very fast. Our first run used a plastic-lined paper clip to attach the device to the zip-line. This added way too much friction, so our device only made it about half way down the line. In the second run, we replaced the plastic paper clip with a metal one, and our device made it down the line somewhere between 3 and 4 seconds.
Iteration #2: Dolphin Helicopter
Our second iteration was largely a rebuild/redesign of the original. We ditched the small cardboard and foam bumper for a larger box shape, with a foam nose to absorb the impact. The passenger area was built near the front of the bajaj where the box provided an overhanging (but not totally enclosed) cover. The deck of cards and jar of adhesive were again included as weights. We also taped a block of wood to the bottom of our device to add additional weight over the previous iteration. Next, we completely redesigned the attachment mechanism for connecting our bajaj to the zip line. A 4-way PVC pipe was cut and outfitted to act as a bracket that rested on the line. The inside of the pipe was filed and sanded to remove a small ridge and reduce friction. We thought that having a connection with larger surface area would better distribute the weight of the bajaj and prevent it from sagging on the zip line too much. Lastly, we included a fin on the back of our device. In theory, this would prevent rotation of the bajaj along the axis of the zip-line; however, the end result was definitely to add style but no function. Because of the shape of our box, fin, and 4-way PVC pipe, we decided to call this device the “Dolphin Helicopter”. This device fared about the same as the first iteration (3-4 second descent, no injuries/deaths). The PVC connection was probably not as optimal as expected, since it may have introduced more friction to the connection. In addition, we believe adding more weight was necessary to obtain a faster descent.
This project was a lot of fun. Our first iteration was pretty functional and may have done even better if it had more weight. In the second iteration we got much more creative but failed to improve much since our device weight and connection method didn’t work as well as we’d expected. It was pretty cool to see all the different methods people used to reach the same goal and to see what elements led to the best bajaj’s.
