For the wire armature, I will use 16 gauge (1/8th inch) aluminum armature wire and 18 gauge copper wire along with a little 24 gauge copper wire for small details. I like the aluminum wire because it bends easily and doesn’t have too much bounce back. Bounce back means that the limb doesn’t stay exactly where you move it so you have to bend it farther than you want in order to get it in the right place. The down side of aluminum wire is that is doesn’t last all that long and your puppet will break and need to be mended at some point during production. I use the 18 gauge copper wire to strengthen the armature. Copper wire doesn’t bend as nicely as the aluminum and has more bounce back, but when the two are combined, I am very happy with the result.
I know that during a long production some of the puppets will break. When I skin and clothe my puppets, I try to keep in mind that I am likely to need to open them up again at some point for repairs. It is unavoidable when using wire armatures. That is why some people, who have big budgets, prefer to use ball and socket armatures. They are much less likely to break. The trouble they have, besides their high cost, is that their joints can become loose at very inconvenient moments. I can’t offer much information or opinion on puppets with ball and socket joints. I have made costumes for them, which has given me a chance to feel how they move, but I have never animated one.
Here is a site I just discovered that sells a variety of armature kits and other stop motion supplies: http://www.stopmotionstore.com/index.php?main_page=index&cPath=25. He’s got a ball and socket armature on there for $159.99.