Our trip to Maker Faire Detroit 2011 has been filled with many bumps along the way and one of those has been the development of the dry ballast system. Many solutions have been tried and tested, but we finally settled on a jam-free BB dispensing device!
The device works by inserting a dowel rod with a specific pattern of holes perpendicular through the dispensing pipe. A servo with a custom made dowel-to-servo coupler (made with LVL1’s new laser cutter!) spins the dowel rod back and forth at a programmed rate determined by code on a Teensy 2.0, kindly donated by PJRC (http://www.pjrc.com/). As the dowel rod spins, BBs drop into the holes from the top and eventually fall out the bottom as the dowel rod rotates around.
As one could imagine, a major problem with any dry ballast design is jamming. We made two design choices to prevent this. First, we chose to spin the dowel rod back and forth, which prevents pinch jams between the holes and the pipe wall from permanently jamming the device. Second, to prevent bottle neck jams in the pipe, we chose to use a Sprite Zero bottle circa 2011 for its convex bottle neck and to taper the PVC pipe where it meets the bottle in order to create a smooth, fluid funnel.
After several days of testing, the dry ballast system has been successful and is ready to strut its stuff at Maker Faire. Come by the White Star Balloon booth at Maker Faire Detroit 2011 and check out Speedball-2 in action! You’ll be glad you did!