I've got a few old shirts and jeans that don't fit / damage / bad style, I can apply those to the tree, apply chainmail, and strike. Traditional padding would probably be some type of wool or leather, as these are easy to produce, I figure denim will suffice. I can throw a T-shirt over the whole thing as well, as you often see crusaders wearing a robe over their armor, mostly to keep the armor out of the sun and keep it from heating in the light, but it'll still add a bit. There's also a few bits of old wood, the neighbors tore up and rebuilt their deck last year and I grabbed a few of the best-looking pieces of wood. All of it was pretty bad, but this is the best >.>
So, I could easily take a 2x4, layer some jeans over it, toss chainmail on that, and then a loose T-shirt over the whole thing, prop it against a tree, and strike. I will NOT be doing any fancy machine though, namely because 1: I'm too lazy to build, and 2: It'd take some effort to get the machine to produce enough force. A dead-drop, that's easy, but swinging an axe hard enough to damage steel would take some engineering.
Current plan is to make a sheet of 16g 1/4" Euro 4-1, as this is a solid size, if a bit "thin" for armor. At machine-cut prices (let's be honest, flush saw cuts would be useless here) a square foot would cost $30. But $42.25 will buy 7 bags of rings and ship them, all costs accounted for. 7.5 bags would make a square foot, so that's just under a foot. $24.80 will foot 3 packs, giving 40% of a square foot.
I wonder if Kickstarter would let me do such a drive for such a small scale experiment...