I am so glad that you're doing this.
re: 1. furnace construction. I have a piece of metal that should be exactly the right size, I pulled it out of a dumpster and set it aside specifically for this use. I'm stopping by the space very briefly today to pick up some clutter, and will put this in my pile I showed you for potential metal casting kit parts.
re: 2. flasks
I have Detailed Plans for flasks from the Dave Ginger book on building an aluminum foundry furnace. I will bring in these plans, and start construction of the flasks. The drawer sides we have will work perfectly for this. Chris, I'll bring you up to speed on what these look like, function, form, and purpose, and you can unleash your woodworking magic. Casting flasks are basically a matched pair of wooden boxes that stack on top of eachother and fit together tightly; there's usually a hinge on one corner and a hasp on the other so you can unlock them after and knock the sand off of the finished casting. Although they're called flasks, they're not flasky in any usual sense, and won't need a lathe. Wooden patterns, tho, especially the stepped pulleys and floating arm trebuchet bearings I want to make, do make good use of a lathe.
Here's a wiki article on flasks: http://en.wikipedia.org/wiki/Flask_(casting)
Here's the super duper wicked cool ZOMG we need to make these aluminum flasks: http://www.backyardmetalcasting.com/alumflasks01.html
re: 3. Thank god there are welders, I'm not one, and this is a hardware issue, so there you go.
re: 4. green sand for casting.
I have a crappy ball mill that I"m going to be refurbishing for this project. It was the first thing I worked on at the space, and it looks it. It's going to be made better faster stronger harder. I think I have all the parts I need for this, the one exception will be a large quantity of ball bearings. These can be purchased at axman, hopefully using the 10% off coupons we have; I need to find out exactly what size before we buy them, and hopefully someone who's not me can purchase them, as I am bwoke.
The ball mill will be used to pulverize kitty litter into bentonite clay powder, which is one component of the cheap green sand recipe; the other parts are water, and fine silica sand, of which I have a lot in a bucket at the space. The water should not be hard to find.
The ball mill will be good for initially "reconditioning" the green sand; down the road, we'll want to make a "muller", which looks like an industrial food procelssoer.
Again, I have Detailed Plans for this. once we start casting, it will be easier to make.
Once we get up and running, there are open source plans out there for the next level of better green sand recipes; I'll dig up a recipe for that when the time comes.
An aluminum ladder should provide excellent stock for casting, please bring it in.
One last thing;
The "Lost foam" method excites me much, as it's a really good fit for what we already have at the space.
Basically, you make a positive shape of what you want to cast out of pink construction foam. You know, the stuff that Pete's cnc machine cuts so well.
Then, you take that, and coat in what I think is drywall mud; basically thin runny plaster.
You let the postive dry for a couple days, glue on some square in cross section pink foam "sprues", submerge the coated positive in regular sand, leaving the sprues sticking up. Then, you put a coffee can on top of the sand, surround the sprues. You poor the molten aluminum into this. The can lets you build up "head pressure", and forces it's way down through the foam, burning the foam, and filling the resulting void with tasty tasty aluminum. Let it cool, empty the bucket, and you have your super duper metal piece, without worrying about casks, green sand, 3 part molds, or draft in your wooden patterns (that you're not using.)
Here's my favorite lost foam casting tutorial(got it via MAKE magazine, yay!) , it covers making exactly the kind of bearings I want to make for my floating arm trebuchets, as well as for when I ever get around to starting my cnc project: http://www.buildyouridea.com/foundry/lost_foam_howto/lost_foam_howto.html
That's my book length post for the day, if anyone has questions or comments, let me know. I'm really stoked about this, Jim, I'm glad you're pushing it forward.