15"

8"

2 motors (I used motors from those moving reindeer, available for $9 each (about $13 plus shipping) from http://www.cwebdirect.com/pivetarm.html )
(Kit #1 will work fine) you also need the following PVC:
10'   1/2" PVC
10'   3/4" PVC
4      3/4" PVC Elbows
6      3/4" PVC Tees
2      3/4" PVC 4 Way Tees
4      3/4" to 1/2" Bushings
5      1/2" PVC Elbows
8      1/2" PVC Tees
1      1/2" to 1/2" PVC Joint

This provides the up/down movement of the head. You can increase or decrease this movement by moving this motor higher or lower on the prop.

I used a piece of a wire coat hanger for the linkage on he top motor and hot glued a short piece of plastic on the crank and used the metal bar that came with one of the motors (a section of metal cloths hanger can also be used here).

The lower motor is attached to the swinging inner frame. In fact, the base of the swinging unit is built just to have a place to attach the motor.

The arrow is pointing to another swing point. The 1/2" PVC which has the skull attached at the top is placed thru a 3/4" 4 way tee. It remains loose allowing the motor to turn the 1/2" PVC for the left/right head movement.

The 4 way Tee has 3/4" to 1/2" bushings on the two sides to hold it tightly in the structure which the 1/2" PVC slips in from top to bottom.

There is an identical 4 way tee at the top, just below the skull.

This arrow show a short section of coat hanger used as part of the crank. I just drilled a hole thru the PVC and bent the coat hanger so it would not fall out.

Moving this motor and attachment point up or down will control the amount of up/down movement of the head.

All motors are attached using plastic ty-wraps thru the existing mounting holes in the motor and around the PVC.