My instructor calls it an 'air engine', but I think of it as a 'steam engine'. Air (or steam) goes in the quick disconnect (which has a red handle). It enters the metal block on the left. In the block is a piston which rotates the cylindrical fly wheel which can be seen on the back on the machine.
It's not an efficient or complex device, but I'm really excited to make a real machine. At class this week I began machining the piston which must be very precise. I got it to .0005 inches from true. For the record, that's pretty accurate. There are a lot of operations on this machine, so I'm expecting to be hard pressed to get it done. This also means that I won't have as much time to work on my Power Cube.
In order to make more time, I'm planning on using some vacation time to spend full days in the shop. I'll update on Power Cube progress when I have made meaningful progress. Not much has happened yet this semester.