I just finished roasting my first one pound batch of coffee beans. It took about 19 minutes (well, their still cooling...). Anyway, it's a pretty simple machine to put together, got most of it from this site:
**broken link removed**
Didn't really follow the instructions, but used the basic concept. The oven top cost me $68 (stuck it to me on shipping, could have gotten the full package for that at a local store). Went with the digital model, figured I might want to add a microcontroller. After doing a pound (good for a week), don't know if I'll bother.
Hit several hardware store, but couldn't find the aluminum material that was used, so had to find something. Ended up buying a three piece set of spring-form cake pans at Big Lots, $6. Had to fit 2 together, and cut part off. Stayed together by itself, so didn't have to drill holes or bolt anything together. Need to cut a small slot in the side to vent the schaff, but it wasn't bad. Think most of it burned up anyway.
I wasn't going to use the popcorn popper base, seemed like it would fail, and need to be re-done. Not knowing much about kitchen stuff, quickly found that 12" pots and pans aren't cheap, or easy to find in the 4" deep range. The popper was $24 at Walmart, so just settled. Opened the bottom to disconnect the heater, just pulled a wire off the thermostat, no wire cutting. Noticed that the shaft coupling was a compsite material, and the end cap plastic (no wonder it melted). Replaced the plastic cap with 3 wide washers and a cap nut. Figured the shaft coupler could handle the heat, and the washers and cap nut would shield it well from direct heat from the convection oven.
Not too bad for around $100, have to see how much coffee this thing can handle in one batch. Think somewhere between 1.5 and 2 pounds.