Part 2: The 'Flying Crank' Motor Platform

At the left is a picture of the completed motor platform, intended to give you an advance look at what you will be constructing. It folds up into a relatively small unit for storage, or it can be easily disassembled if desired. This is the piece that makes it all happen. The mechanism is really fairly simple, and if used with the ghost marionette descibed in the previous section, should not need a counterweight.

The Crank:

The arm of the crank, as mentioned in part one, is a piece of flat aluminum stock, 1 inch wide. The best length for the marionette described above is about 10-12 inches, and the pivot will attach at about 8 inches out from the motor shaft for best results. The ghost and its arms will rise and fall about twice the length of this arm. Experimentation is recommended, and you can always tap an extra hole in the crank for the pivot assembly closer to the motor, if it becomes necessary to restrict movement.

For attachment to the motor shaft, you will need to drill two holes in the crank arm, spaced to accept both legs of your small U-bolt. It is important to make sure that when the bolt is attached to the motor shaft, the aluminum does not drag against the platform members. The clamp attaches as shown at right.

Note that the aluminum stock is twisted 90 degrees so that the wide dimension of the end holding the pivot assembly is parallel to the ground. Use a vise and Vise Grip pliers to do this. You will find that the bar bends relatively easily. A picture of the completed crank is shown on the first page of these instructions.

The pivot at the outer end of the crank, to which the control lines attach, consists of nothing more than a bolt attached to the bar through a hole, with a wide fender washer that is set so as to spin freely, using the bolt as an axel. The fender washer has three holes drilled with equal spacing around its perimeter, forming the attachment points for the lines leading to the marionette's head and arms. The part sequence is illustrated in the photo at left; left to right: Nut...crank...lock washer...nut...lock wahser...nut...flat washer...drilled fender washer...flat washer...head of bolt. This assembly can easily be moved to the various holes you may have drilled into the crank arm to adjust the extremities of the marionette's movement.

The image at right shows the holes drilled into the finder washer for attachment of the marionete control lines. Be sure you adjust the nuts so that the fender washer can spin freely but not wobble. Be sure to oil the pivot with a light oil, such as 3-In-1. Admittedly, this is hardly an industrial part, but it moves slowly and will work for many seasons before needing replacement. It is very inexpensive, and you can always build a spare to keep on hand.

The Frame:

The structure of the motor platform is constructed from the 1-inch angled aluminum stock mentioned previously. The finished platform is quite rigid, and can handle a substantial amount of weight. The two 4-foot sections of this stock should be cut up as follows: Cut one 20-inch section from each bar. Cut 2 14-inch lengths from the remains of the first bar, and a 16-inch and 12-inch section from the remains of the second. The 'leftover segments' are shown at left, minus the two 20-inch sections that will form the motor mount.

The motor mounts, as shown at left, to the two 20-inch parts. The 16-inch front member and 12-inch rear member are shown as they will be attached, and this process will be described below. Leave a 3-inch recess between the front of the frame and the gearbox of the motor. The Dayton motor accepts 10/32 machine screws for mounting, and you will need 4 of these. Once the rig is finished, the motor may easily be removed for servicing, if necesary. (Our video explains in detail where to drill the mounting holes, but it is not difficult to determine this clearance for yourself.)

The attachment of the front and rear bars is accomplished as shown, with 1/4 inch bolts. Note that there are a pair of 'limit nuts' positioned as shown in the photo to keep the stock from bending when the attachment nuts are tightened. Position these just at the lower edge of the crossmembers, both front and back. Use lock washers to fasten the crossmembers securely. When both crossmembers are attached, the frame becomes quite rigid. (The video describes in detail where the holes shouls be drilled in the motor mount members, but it should not hard for the mechanically savvy builder to deduce this from the pictures at left and below.)

The arms shown being attached to the front crossmember are intended as mounting surfaces for the pulleys required to control the arms of the marionette. The arms can be pivoted to adjust the positons of the arms of the marionette, and will control how the arms of the ghost move when it is flying. Use 1/4 inch eyebolts, with the eyes positioned upward, to attach the arms to the motor platform. The eyes serve as the front hanging mounts for the platform.
Use a lock washer between the crossmember and the arm to keep the arm from moving under load. Make sure the mounting nut on each arm is tightened securely.
The arm pulleys attach to eyebolts mounted at the ends of the arms as shown, using nylon twine or ty-wraps (which make it much easier). This allows the pulleys to twist as the crank changes position. The control lines for the marionette's arms lead through the pulleys to the crank pivot. The pulley wheels should be reasnoably close to the plane of the pivot when the lines are under tension. This is somewhat automatic, because the pulley will swing toward the pivot when under load. You must make sure that the lines and pulleys do not snag on the crank when it is in operation. Adjust the horizontal angle of the crank on the motor shaft to assure this. In other words, don't let the crank's pivot end hang down too far towards the floor.
The mounting eye for the pulley supporting the marionette's head attaches to the center of the rear crossmember. We use an eyebolt with a 4-inch long shaft, and locate the eye below the frame, where the head pulley can be attached. The top of this long bolt - extending above the frame - is fitted with a fender washer (like the one used for the crank pivot) drilled with a single hole. This is used for hanging the back of the frame. The diagram shows how to add the additional hardware for a counterweight, should you decide to fly a heavy marionette. The counterweight should be a bit lighter than your weighty ghost. (The marionette described in these instrctions should not require a counterweight.)
The image at right shows the motor platform with the control lines installed. The thick lines should be blackened with a permanent felt tip marker to keep them 'invisible.' If you want to keep the lines to your marionette thin, cut the lines such that they hang just below the pulley when the crank pivot is farthest the pulley for each line. Attach lengths of nylon monofiliment (thin fishing line, or whatever you wish) to the control lines at this point and run them to the marionette's attachment points. Hang the motor platform and test your arrangement with the motor running. The motor's electrical lines are nonpolar, and can be atached to lamp cord, although we recommend a grounded (three-prong) cord set. The ground lead (usually green) of the cord set should be securely attached to the motor platform.
What happens when it runs?

The movement of the marionette, when suspended from this slow-moving apparatus, is amazingly natural-looking. The body of the ghost slowly rises and falls, and the arms gesture independently of that movement. You really have to see the effect to believe that it can be achieved with such a simple rig. Experiment by moving the pivoting arms to different positions. What this does it to change the phase relationships (relative timing) of the moving parts. You will notice that the marionette tends to turn slightly to left and right as she flies. This adds to the drama, as if she were addressing a group of guests. If you find that the movment of the ghost's arms is shaky, add some weight beneath the hands (such as a fishing sinker.)


Onward To The Last Part...