Your Mission: There is a 20′ PVC pole. Build a device to go up the pole as fast as possible and stop within the top 12″ for <$10. There couldn’t be any attachment to the ground either, so no calibrated line attached to the ground or control cables.
I first tried to make a jumper. Springs would allow it to shoot up the pole and a gripper would prevent backslide. Well, they were no where near powerful enough, so I tried another plan. An electronic wheeled climber with a limit switch would climb the pole. This proved inadequate, though I’d still like to try it someday.
Finally, I decided lighter-than-air was about the only way to go. But how do I make it stop at the top. A flash of genius during a music class made it possible. Fiberglass collar, and trigger actuated brakes.
Left: balloons attach to loop in string near bottom center of picture. Pulls on paperclip trigger, lifting collar on pipe. When the collar passes the top of the pipe, the sloped triggers slide out of the collar because the pipe isn’t there to hold them in anymore, and the lift from the balloons is transmitted to the brakes on the lower end of the collar. The brake is a paperclip bent in an L shape with the short portion of the L facing up on the inside the collar. The balloons pull up on the outside portion of the L, causing it to rotate and the inside portion grips the pipe because the inner diameter of the collar effectively shrinks. Paperclip on pipe is slippery so a rubber band wrapped around the clip provides friction. You can see a dark shadow on the collar above where the brake penetrates the collar.
Left: Brakes activated and collar moved back down the pipe for testing. Duct tape allows collar to be opened and secured around pipe. Triggers are hard to see. They are halfway up the strings between the brakes and the balloons. Actual stopping position would be trigger hole just above top of pipe.
Materials: fiberglass, paperclips, rubber band, 6 balloons, string, duct tape, 1st place victory!