Nuts and Volts - September 2017

of the jaw attachment point and try to line up the servo arm. Don’t worry if you are off a bit as the hole in the skull through which the wire runs may be enlarged later.

Next, cut the slot for the wire that will attach the jaw to the servo (Figure 16).

The wire I use is 0.039 diameter stainless steel I get from McMaster-Carr. It is only sold in packs of 100/12 inch lengths, but I have found plenty of other uses for this wire in other projects. These are longer than you will need, but hold off cutting them for now. If you are adding LEDs for the eyes, you may need to enlarge the eye sockets to accommodate them.

The same 1/8” bit you have been using should be fine for this, as well. You can simply use the plain LEDs or insert them into a pair of eyeball blanks. I purchased a pair of wired two-pin headers and soldered an LED to each one (Figure 17).

The header attaches to the board and the LEDs are pressed into a hole you drill in the eyes. I then apply some hot glue to the eyeball to attach it to the skull. This is the method I use for my characters as it is an inexpensive upgrade that seriously improves the look.

Finally, you will drill a small hole in the jaw to accept the wire that connects to the servo. Insert the wire in the slot that was cut earlier. Next, attach the wire to the servo horn which is placed in the 1:00 position on the servo. I use a special J bend tool to bend the wire to shape, but you can do the same thing with a couple of pairs of needle nose pliers (Figure 18).

It is now time for a little disassembly work. Remove the jaw springs from the skull. This is a simple process that requires the removal of a couple of screws. Your jaw should now pivot smoothly.

Tighten up the zip ties a bit so the jaw moves easily, but is still pulled up to the skull. Place the wire next to the jaw attachment hole and after adding a couple of extra inches, mark your cut. I like to leave a small space between the teeth when the jaw is in the closed position to keep them from banging together when speaking.

After inserting the wire through the hole, carefully bend the end to keep it from coming loose. Be careful with crimping down on the jaw with your pliers because it is easily damaged if you use too much force! Cut off any excess wire for a clean connection (Figure 19).