In the Bajaj challenge we designed a vehicle that would:

• Travel across the zipline in the shortest amount of time
• Keep the driver and passengers safe (two ping pong balls), not allowing them to fall out at any point
• Have the balls fall out when the contraption was flipped over, like a real bajaj with open doors

In our first design, we decided to base our design around a roll of duck tape as this would have structural integrity and hold the balls well. We added additional foam to create walls to prevent the balls from falling out and cushioning in the front the reduce the impact when the design hit the wall at the end.  To connect the device to the line we utilized a modified binder clip.  Here is a breakdown of the design:

Our design (Team 5) performed well:

In the second iteration of our design, we utilized materials from the OEDK. From the first trials, we realized that the designs that performed the best were the heaviest  and had a smooth attachment that would allow for little friction when moving along the line.

 

We decided to optimize the weight based on the string and looking up the values online, we decided that 5 pounds would be appropriate and located a brass cylinder in the scrap drawer of the machine shop. This piece of metal was ideal because it packed a lot of mass into a small volume. We also decided that PVC junciton would work well to enclose the balls and the weight. To allow for smooth motion along the line, we utilized a pull that would glide down the zipline and could be attached onto the line quickly.

  

Here is a summary of the actions we completed to finish the design:

• Machining the metal so it would fit into the PVC junction
• Attaching a spring and foam cushioning to reduce the impact when the bajaj hit the wall
• Drilled holes into the top to attach a strap
• Modified a pulley so we could easily screw our design onto the line

All of these changes resulted in the final design:

This design performed very well and was the fastest design in the challenge in this round.

If I were to improve this design, I would probably remove the spring as it is not practical to have it bounce back so far and would instead add more foam cushioning that would minimize the recoil and reduce the impact to the wall and the vehicle.