In our final sessions there were three small design challenges. We built mini zip-mobiles, zip carriers and zip target droppers.
Time to build a zip-mobile. The challenge: make a sturdy structure that will fly down the zip line in less than four seconds using a paperclip, 2 straws, 2 sticks, 2 washers, tape and scissors. To make a device that zips, consider what arrangement will avoid too much friction or drag and think about how your centre of gravity will affect the flight.
Most of the students easily figure out which material should be in contact with the zip line so that the zip-mobile slides quickly.
This zip-mobile uses the sticks horizontally almost like wings. The design is symmetrical around the central attachment point which minimizes rotation.
Durability becomes an issue for this designer who wants to build a transporter for her stuffies at home. How can I make something really strong from such delicate materials?
The second challenge: now modify your zip-mobile to make a zip carrier that will transport a ping-pong ball down the zip line. You are given a cup as additional material.
Our third challenge was a complex design problem. The students are asked to modify their zip carrier to transport a marble down the line and to drop the marble on a target part way down. This has to be done without touching the carrier directly. There are several ways to tackle this challenge, but all involve some serious lateral thinking!
One team tries a remote string release mid flight. In multiple test runs they discover that the release needs to be before the cup is above the target. This helps because the marble is already moving forward along the zip line and moves in a curved trajectory (not a direct line down) once it is released from the cup.
Some of our young designers came up with a solution where the carrier cup is tipped as it smashes into a barricade. After some testing it becomes apparent that it's hard to get reliable accuracy when the cup is stopped at top speed. The marble usually comes flying out at random sides, occasionally hitting your friends! Time to rethink the prototype…
Maybe it's better to release the ball from a trap door in the cup rather than using a tipping mechanism?
After some experiments with vibrating the carrier mid flight, one group decides to stop the carrier and then pull out a lower release pin (without touching the cup). Ambitious plan.
