Step 1: Build a Grating Support Inside the Garbage Can
Next, you need to build supports for the grating. Using a 3/8" drill bit, drill three holes approximately 8" below the top of the garbage can, equidistantly placed around the circumference of the can. Then slide three 3" x 3/8" bolts through those holes and secure with a corresponding washer and nut. This will be used to hold the grating up while allowing the grating to be easily removed.
Step 2: Add Support for a Drippings Pan / Shield
For a pan, we simply used a disposable turkey pan which we folded slightly to fit snugly in the garbage can. You want the pan to rest about 7" below the grating, but to have ample room on the sides for smoke to pass from below.
To support the pan, we used two 3/8" threaded rods running parallel across the can. It's important that these be close enough together to support the pan (which could have a fair amount of turkey fat in it), but still far enough apart to allow you to move your wood chip pan through them without much tilting. We bought the threaded rod as a single 4' piece for a couple of dollars, and cut it to size with a saw. You want enough slack to stick out of the can slightly for support and to allow room for fasteners.
Drill 4 3/8" holes about 7" below the grating bolts and slide the rods through. Secure the rods on the outside with appropriate washers and nuts. It's not necessary to secure them on the inside, and that will make it more difficult to remove in the event that you need to when it is full of hot smoke.
Step 3: Add Heating Element
To actually turn the knob, we constructed a simple extension to the knob by gluing the plastic knob covering to a hole drilled in the end of a dowell. However, it turned out that we always wanted the heat all the way up, so this was never used during the actual cooking, once we calibrated the device.
You might consider putting the hot plate more in the center to have better heat shielding from the pan and more even smoke release, but I don't think it really matters. We were prevented from doing that by the geometry of our smoke rocks, but with bricks you could swing it.
Feed the cord through the hole at the bottom and attach to a properly rated extension cord.
Step 4: Add Thermometer to Lid
Proper temperature monitoring and maintenance is the key to good smoking, so you will want a BBQ thermometer to measure the ambient temperature inside the garbage can without opening the lid.
We bought a $20 BBQ thermometer from a hardware store that was designed for mounting. We didn't have a large enough drill bit available, so we drilled a small hole and enlarged it with tin snips until it fit, and then threaded the nut on securely.
Step 5: Prepare Wood Chips and Get Ready to Smoke
Actually finding enough woodchips might be tricky. For a turkey, we recommend applewood (or pecan, if you can find it), but oak and hickory would work in a pinch.
You want to soak the chips for at least 20 minutes prior to smoking, but there is no real upper limit. Get a pan that you don't mind destroying that's small enough to fit between your two threaded rods, about the size of the hotplate, and at least a couple inches deep.
Fill the pan with chips and move the can to a safe location, far from any buildings, but shielded from the wind if it's cold out. Obviously, the smoker will generate a lot of smoke, so you might want to keep it away from open windows/doors as well.
You should also have appropriate safety equipment ready, namely heat-resistant fingered gloves and a fire extinguisher. Still, the ambient temperature you are generally shooting for is around 230F, so the risk of fire is very low.
Step 6: Prepare the Turkey
We brined our turkey before smoking it. This is optional, but we strongly recommend it; the primary purpose of brining is to make the turkey juicier, and smoking a turkey for 10 hours tends to dry it out a little more than some other cooking techniques. We used a brine consisting of 2 gallons of water, 1 cup of sugar, and 1 cup of salt. This was just enough brine to cover the turkey in its 5 gallon paint bucket. We brined the bird overnight, for about 9 hours.
Because the cooking in a smoker is done by convective heat transfer from the smoke, we wanted to maximize smoke flow through the turkey in order to minimize cooking time and to cook the bird as evenly as possible. To improve the gas flow dynamics of the turkey's surface, we removed the excess flaps of skin and fat that obscured the openings of the turkey, and we widened the passage between the neck cavity and the main body cavity, the idea being to allow the smoke to flow freely through the interior of the bird. We also left the turkey entirely untrussed, and as spread out as possible, to increase its effective surface area.
We didn't even consider stuffing the turkey, as this would have destroyed smoke flow, added several hours to cooking time, exacerbated cooking unevenness in different parts of the turkey, and, in all likelihood, produced acrid black stuffing. We cooked our stuffing in the oven instead.
Then, we rubbed the outside of the turkey down with olive oil and salt in an attempt to keep the skin from drying out.
Step 7: Smoke That Turkey Out
You want to maintain a temperature of about 230F, for around 30-40 minutes per pound of turkey. You will need to change out the wood chips every hour or two, but don't sweat the exact timing. Changing the wood chips will require you to remove the grill, the drippings pan, and then the wood chip pan, so you will probably want two people, both with gloves. The garbage can lid will be quite hot once the temperature reaches peak, which on the first cycle can take quite a while.
Unforuntately, changing out the wood chips evacuates all of the smoke and hot air from the inside of the can, which basically drops the temperature most of the way back to ambient. In our case, this was exacerbated by cold temperatures and stiff winds, so much so that we had to add an insulator to our garbage can: a cardboard box. We folded the sides of the boxes evenly to make it octaganal, so it would fit more snugly.
The one modification we highly suggest would be a door for changing out the wood chips. Since the door would be at the bottom of the smoker, you would not lose much heat or smoke in the process of changing out the chips, and the whole process would go faster and smoother. Once we get around to it, we'll post another instructable with the modification.
Step 8: Enjoy Turkey
If you have trouble reaching the appropriate temperature and are running out of time, you could finish it off in the oven as you would a standard turkey. This will still keep most of the flavor, but should be avoided if possible.
Once it has reached the appropriate temperature, take it out and unplug the hot plate.
Then, dig in. But try to save some - this smoked turkey made some of the tastiest turkey sandwiches we've ever had.