Hi /DIY/. I was wondering if you can offer a little advice on my costume. Basically I'm doing a classic robot, complete with cardboard boxes and that flexible aluminum tubing (basically like pic related). I'm building a couple of things to make it a more realistic robot, eg flashing LEDs, robot voice box, etc. I want to include a couple of motorized functions, which is where I need your help. I already have an arduino uno and two motor sheilds.

First motorized function is to make the head spin all the way around. Keep in mind this is basically just one cardboard box spinning on top of another. How should I hook up the motor? Is there some sort of material that I can use as a gear around a neck, or should I figure out how to 3d print a big old 10" gear, or what? I measured, and it turns out I need a 10" collar to be able to fit my fat head through it. Also, is there some kind of bearings that I can use to help it spin, or how can I mount the head to the body so it can spin freely? How strong of a motor am I going to need to spin the head, assuming it weighs, say, 2 lbs and has friction of cardboard against cardboard?

Second motorized function is just to open a small door on the front of the robot. I have a small metal fuse box that I'm going to mount in the front, and I'll just need the motor to open the door with a lever or something. Any advice on how to gear something up so that the motor, which spins, can move a metal plate through the motion of opening it? Sorry, but I'm just not a very mechanical person, and I just cant visualize a simple system for opening a door through a 90 deg. swing. Should I use a linear actuator that pushes at the top of the door? how strong would it have to be?

Sorry if these are trivial questions, but I'd appreciate your help.