My big creation in 2002 was the witch stirring a cauldron. The cauldron I bought already had a hole in the center of the bottom, so this was perfect for sticking the shaft of a motor through. I built a platform out of wood for the cauldron to sit on. The legs of the platform raised the platform enough so that the motor driving the prop could hang from the underside of the platform. The shaft of the motor stuck up through the platform and through the bottom of the caudron. The motor I used was a gearhead motor I picked up from Jameco. It had 10kg-cm of torque and rotated at 20 rpm. This was powerful enough, but it was way too loud, especially when the motor got loaded down a little. It would have been obvious that it was motorized. As a result, I decided to put the witch in the front window of the house so that no one would be able to hear the motor. To attract attention to it, I had a strobe light running at high speed shining on it. The platform and the table it sat on were just below the level of the window, so I didn't need to worry about hiding the platform from the spectators.
The arm is what made this prop look good. The arm consisted of two pieces of 1/2x1 inch wood, each of which was about 8 inches long. In hindsight, these were only barely long enough, so they probably should really be 9 or 10 inches long each. The two pieces were connected with a small hinge, and another hinge was used to connect the arm to the shoulder of the frame, which was also made out of wood. Since this is sort of how the human arm is really constructed, this gave a fairly realistic arm motion. I built it with the arm perpendicular to the frame. To make it a little more realistic, the arm probably should be angled down slightly. Here is what it looked like underneath to clothing.
The "broomstick" consisted of a dowel attached to a metal plate, which was attached to the shaft of the motor. The hand of the witch consisted of a stuffed glove that was attached to the arm with a bungie cord. The hand held a short piece of PCV tube. This tube was slipped over the dowel so that the dowel could spin freely within the witch's hand while still pulling the arm around the circle.
This prop was free-running, meaning it was constantly moving. It had no microcontroller. The only electronics in this prop were the motor and the 12 volt power supply for the motor.
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Page last modified on 02/06/2003