|Copper Tubing Framework For The Head
Construction of the head starts with building a framework to support the foam and other components such as eyes, hoses, etc. The frame also provides support for hinged joints such as the jaw and neck. Tubing for special effects will attached to the frame before covering with foam.
The framework does not have to be complex, but does need to have enough supports to help maintain the desired shape. Additional supports are added in areas where either mechanical devices will be attached (such as the eyes), or to provide points to attach springs or cable controls.
Two light duty springs are stretched between the lower jaw and the top of the head to pull the jaw closed. This way, a cable can be attached to from the neck to the lower jaw to pull it open. An alternative to this would be to attach a gear-driven motor to the head frame, and use a gear or wheel with an arm extension to "push" the jaw open and closed. The spring would only have to be strong enough to offset the weight of the foam and fabric of the lower jaw, and to keep stress on the motor to a minimum.
The eyes and a mechanism to open/close the iris will need to be secured in place underneath the foam. To start, a section of tubing is attached with loops, which were later bent into coils for the eyes to be glued onto. This will probably be modified again before the covering stage, as I have not decided on the design for the final mechanism yet.
Side view with jaw open
The lower jaw is soldered to a piece of brass tubing that slips over a length of 1/4" copper tube. When the copper tube is soldered to the head framework, this creates a hinge to pivot the jaw open and closed.
Early front view, showing coils where eyes are to be mounted.
|The movable iris in the eyes will need some method for opening and
closing the hinged section. One possible method is shown here, where a motor-driven
actuator pushes a rod forward about 1/2" when triggered. Once power is removed, it
returns to the default position. I chose not to use this unit for several reasons. The arm
is too long, and as a result, does not push/pull evenly on both ends. In addition, the
range of motion of the actuator does not provide enough range to make a visible opening
and closing in the iris.
These issues were resolved by rotating the eye assembly 180 degrees so the pivot is at the inside and not the outside edge of the eye. By using the actuator to push/pull on a hinged lever, this increases the final range of motion to almost 1" at the loop attached to the eye.
There is nothing that says the actuator must be positioned in line with the sections to be moved. The final assembly mounts the actuator 90 degrees with a lever rod passing through the actuator arm. The lever is curved to allow for the full motion of the arm without binding. A "T" shaped piece of tubing slides over the lever, and is secured with tin solder. The assembly is mounted to the head frame, above and behind the eye brackets.
Test mechanism. This design has to pivot the sections of the iris on the outside, requiring a long rod to push/pull the loops. The extra length causes the motion to be uneven if either one of the eyes bind during the motion.
The actuator mechanism is similar to one used to open and close door locks in a car. When 12V is applied to the red and black wires, nothing happens, but when the yellow and blue wires are then connected to the positive, the mechanism extends, then retracts once power is removed.
The coils for the eyes were removed, and brass bezels for the lenses were added. The rear of the mounting was cut out to allow the iris section to swing back, behind the bezel.
|Stick-on Velcro is used to hold the E.L. backed iris mechanism to the bezel. The white tube is cardboard, with a speaker mounted in the rear. This acts as a reverberation chamber for an electronic growl.|
|A brass tube was soldered to the top of the head frame, and two ball
bearings were inserted into either side. Frameworks of 1/2" copper tubing passes
through the bearings, allowing the head to pivot up and down. The bottom of the frame will
attach to the neck tubing. Stainless steel hose clamps were placed on either side of the
tube passing through the bearings to keep the section centered, and to prevent the
bearings from falling out of the brass tube.
The large opening created by this assembly will allow the CO2 extinguisher funnel to be attached to the frame, extending down and forward to the center rear of the throat.
Just below the jaw hinge is a length of 1/4" tubing that springs attach to. Two springs are connected between the jaw and the frame just below the eyes. These springs hold the jaw closed. Originally, I had planned to use a cable to pull the jaw open. However, when observing the range of motion the head can move on the frame, I noticed that the jaw would be pulled open if a link could be made between the jaw and neck frame. The linkage between these would have to be able to move up and down the neck frame. To do this, I added two smaller springs, attached to the jaw support, and looping around the larger 1/2" tubing of the neck frame.
A cable guide made from a piece of curved copper sheet and 1/4" tubing is attached to the "T". The cable control for the head (and jaw) extends up the neck, through this guide, and attaches to the rear of the head. When the cable is pulled, the head pivots up. The two spring loops slide up the neck framework, and pull back on the jaw support, causing the lower jaw to swing open in the process.
A steel cable runs from the bottom of the neck to the back of the head. A twist of copper wire around the rear tubing keeps the cable centered, and prevents it from slipping to either side. This image also shows the addition of a piece of tubing with a loop that centers and supports the CO2 extinguisher horn. This was later removed, and the funnel strapped to the neck assembly instead. Attached to the head tubing, the funnel followed the movement, pushing into the throat as the head tipped up.
Rear view showing the assembled neck framework with the bearings attached to the head. A 1/2-3/4-1/2 "T" connects the open frame to the neck. Two sheet metal screws secure the "T" connector to the 3/4" neck tubing. The cable guide to tip the head up and down is mounted to the top of the "T" connector.
Plastic mesh is used to enclose the front of the head, to provide support for thinner foam covering. Dense foam is used to build up support around the eyes, then thinner foam will be added in layers to shape brow ridges, etc.
|Once the plastic mesh has been attached to the frame, foam can be glued
easily to the surface using contact cement. For areas requiring more relief or higher
levels of detail, I use dense foam. For the rest of the areas, sheets of foam rubber
follow the curves easier, or thin sheet can be glued over the top to smooth and round out
The thick gray foam used in the lower jaw has the outer edges rounded with a razor blade, then sheets of thin foam are glued over the outside edges. The edges of the sheet are then trimmed and angled down to the gray foam, creating a gum line to insert the teeth.
Sorting the teeth.
Before gluing in teeth, they are sorted by increasing size, and a matched set for the upper and lower jaw are separated. A piece of firm, dense foam is used to prop open the jaw while working. To mount the teeth, a hole is cut into the foam using the tooth for position, shape and size. A layer of hot glue is squirted into the hole, and a small amount put on the bottom of the tooth. The tooth is then positioned in the hole, and the glue allowed to cool. Hot glue is then built up around each of the teeth to fill any gaps around the tooth, and make a smooth shiny surface at the base of the tooth.
Teeth are glued into the jaw in pairs, increasing the size towards the back of the jaw.
Once the lower jaw is complete, foam sheet is glued in place inside the upper jaw. A gum ridge needs to be built up around the outside edge, again following the tube framework. The upper teeth are positioned to fit on the outside edge of the lower jaw.
|Foam is glued to the plastic mesh. Thin
foam is glued over the top to round edges and make subtle shapes, such as with the
eyebrows and nose areas.
Teeth are hot glued into place in pairs, starting at the front, and working back.
The teeth follow the line of the copper tube frame of the jaw. This positions them so that they are inside the edge of the upper jaw when the mouth closes.
|Experimenting with some pink bumpy foam, I created a tongue using several
layers glued together with contact cement. Bright red Plastic Dip adds color and texture
to the foam, that has been "textured" with a razor blade. The main problem with
the liquid plastic, is that the fumes attack the contact cement, causing it to come apart
at the seams. It can be glued back together once the plastic dries, or an alternative,
such as hot glue must be used.
The final tongue is constructed by taking a length of vinyl coated copper electrical wire and forming a large loop. A piece of bumpy pink foam was wrapped around the loop and hot glued in place. Once the glue had cooled, the tip was cut into a forked end, and the bumps cut off with a razor. The copper wire maintains the curve of the tongue. The foam was then coated with red Plastic Dip, toned down with a little white titanium oxide powder.
PlastiDip liquid plastic fumes cause the contact adhesive to come unstuck. The foam can be reassembled after the plastic dries, or use hot glue to hold the foam in place under the rubber.
|Progress on the head: (October 19, 2000) The head is almost completely
roughed out with foam, except for the back of the head. As I start to add foam for the
neck, an arrangement will be made to allow access to the rear of the head for adjustments
and maintenance. Access is required for adding powder to the container, and changing
batteries on the sound assembly.
The neck and back of the head need to be completed in a way to allow access to the inside of the head assembly.
The head is almost entirely roughed out in foam.
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