Step 3: Construction- servo mounting plates and pivot
The main servo mounting boards are cut from PCB material. The base plate is thin plywood and the pivot is a brass tube and plate that rotates on an aluminum rod. I first remove the copper plating from the circuit board material before cutting it to shape- this can be done either by etching or sanding it off. I like using this board as it's thin, light, pretty strong and it's easy to work with. The other cool thing is that if you want to use micro servos or actuators to build really tiny animatronics you can etch your wire traces directly on your servo mounting boards to minimize wiring and save space.
Be sure to use proper safety equipment when working with circuit board material- wear a dust mask when sanding and cutting it. The board can be cut with a Dremel and a cut off wheel or even a small saw. If you don't want to use PCB material then thin aluminum or plywood sheet will also work.
I made the plate that is sandwiched between the two servos from aluminum as it needed to have threads cut into it so it could be bolted to the main servo plate. Once the servos are installed a zip tie is run around them and fed through holes in the aluminum plate.
The pivot to allow the head to rotate as it turns is made from an aluminum rod and a section of brass tubing. A circlip is placed in a cut groove on each end of the aluminum rod to retain the brass tubing. A flat section is filed on the end of the aluminum rod and has two mounting holes drilled and threaded so it can be bolted to the servo mountig plate.
The brass tube has a wide plate soldered to it. This brass plate is what the finished foam head will be attached to. The brass plate also has a small hole drilled in it to connect the servo linkage that drives it.
I used standard R/C hobby servo linkages to connect the servos to the contol points. I try to make use of adjustable control arms and linkages whenever possible to allow some room for future adjustments. I also needed to add a helper spring to take some of the load off the servo that moves the head up and down.
Once the armature was finished I mounted it to an old welding helmet using an angle bracket so I could approximate the finished height.