As mentioned in the title of this project, there will be some moving parts. As walking is a step too far, I decided to make the large cannons move as if they are firing.

Looking at  the movie you can see the cannons fire one at a time. When it fires it moves backwards, and forward while the other cannon is fired. This looks like something we can easilly do using a single servo.

The lite-green blocks are part of the cannons, and they will slide over a piece of 1.75 Filament. In the middle is a SG90 servo with a single straight horn attached.

I thought that if I could power the servo with 2 AA batteries and use a 3.3V Arduino Pro Mini  it would be easy to wire and compact setup.

Unfortunately that does not work. Although some specs mention that the SG90 servo will work at 3V, I suppose they just mean the logic level for the PWM input. The power for the servo motor should definitely be 5 V, or it wil not move. Or if it does, the movement will be weak and sometimes unpredictable.

So 5V it is. I'll just use a small USB powerbank then. And that works fine, the servo responds to my commands, though not really as fast as I anticipated. But lets try it anyway.

After printing all parts and assembling it ( which I found to be really hard) it turned out that it all did not really work like I had envisioned it. The friction in the cannon movement and the loose coupling between the cannon and the servo just make that it does not work. Either the cannons only do a very short stroke which is barely visible, or the servo-horn just jams. And the movement itself is also not very satisfying as the servo is simply to slow.  I think something like a solenoid will work better.

After a quick search I found some realy small solenoids which I ordered. But since that will also require a redesign of the head itself I think I'll save that for later.