Witch Stirring a Hanging Cauldron
The Witch - Page 2
The motor that turns the "neck" is a 6 RPM 12vDC gear motor that I purchased from www.allelectronics.com, however they do not seem to have that motor that now. This 5 RPM gear motor could probaly be used. The motor is attached to a 1"x1" piece of steel angle stock long enough to span the two "sides". Two inch screws mount the motor assembly to the frame. The "neck" is a section of 1/2" PVC with an end cap attached to the bottom. The end cap was put on below the bottom reducer so the pipe and cap spins at the bottom of the center T-connector.
A short crank arm made of aluminum stock is attached to the motor. This arm was built using the same technique as is used in Phantasmechanics's FCG. Another piece of aluminum stock is used to make an arm that is attached to the 1/2" neck pipe. A third piece of stock is used to loosely connect the two arms. This linkage changes the rotary motion of the motor into a reciprocating (back and forth) motion of the arm attached to the 1/2" pipe. You can adjust the amount of turning motion by varying the length of the arms. (The large washer on the motor arm was not used for this prop.)
The lower arm is made of lightweight aluminum stock that was bent around the the 1/2" PVC and attached with a screw and nut. In this picture, you can see how the 1/2" pipe is going thru the 3/4" reducer into the T-connector. The 1/2" pipe must be loose here. The reducer just acts as a guide. The end cap (which is hidden from view) provides the spin point at the bottom.
The other end of the lower arm is connected with a short bolt and lock nut with washers on both sides and in between. This connection must be loose enough to allow ease of movement.
The 1/2" PVC "neck" is guided thru the 4-way connector with another 3/4" reducer. Once again, the reducer just acts as a guide. The 1/2" pipe must be free to turn at this point. Both of the reducers are dry fitted into the connectors so they can be removed if necessary.