This one is built entirely from tincans and scrap wood.  This unit is quite powerful for what its made from.  If you would like to build this model I sell plans for it.  The plans are only $7.50.   Simple tools and a steady hand can put this together in about 2 to 3 days.   The displacer chamber for example is built out of a hair spray can and a coors beer can for the displacer.   A coffee can for the burner and an upside down can at the top for ice or water to help cool it.  The rest is quite obvious... standard 3/4" plywood.  It will run about 500 rpm and actually could run a small generator, such as a "hankscraft" type PM motor to power a small light or charge a couple of D cell type nicads.  If your interested in the plans for this little beast send me an email at elenz at windstuffnow dot com.  Now you can purchase them online using paypal service.   Simply click on the "Buy Now" button above.  When payment is recieved I will send you an email with the download site.  The File is in pdf. format.