The challenge: Build a device using only string, popsicle sticks, paper clips, and 1 rubber band to retrieve tennis balls from 12′ below in 3 min. Freshmen vs seniors, and no idea what to expect. They certainly weren’t expecting a freshman to win.
I built several devices, the first one was a band loaded set of jaws. It was lowered/retrieved with one string, and actuated with another. It worked well, but I thought I could do better. It could misfire (having to raise and reset) and required two hands. The final design was a box that was self actuating/locking. It looks cool too.
The key was the two pink sticks just under the ball. They were hinged by pieces of rubber band. As the apparatus was lowered over a ball, they would hinge up and then fall back into position once it was lowered far enough over the ball, locking it in. It was then raised to the second floor, dumped out over the top, and sent back down 9 more times. It was big enough to capture two at once. Two sticks and string kept it square and contained the ball. It was fastened together with bent pieces of paperclips through drilled holes in the sticks.