A smoker is a cooking implement which uses wood smoke to flavor and preserve food. This process usually takes longer than standard cooking but is well worth the wait. The most important properties of any smoker are its abilities to retain smoke and hold food. This all started as a project for our high school engineering class so this is our first attempt at building something like this. There are definitely ways this design could be made better but we are still going to show you what we did so it can hopefully help you with your own projects.
Step 1: Acquire a Filing Cabinet
Choose the base for your smoker based on how much meat you want to smoke and how much work you want to do on it. Remember, bigger isn't always better. Older filing cabinets are usually made of thicker steel which will have better heat retention. Most cabinets will have paint which must be removed either by sandblasting or burning. We used an older cabinet for our smoker and we were more than satisfied with the end product.
Step 2: Remove Paint
This step is especially important in the process of making your smoker. The easiest way to do this is with a sand blaster or power washer which will strip the paint clean off with relative ease. If you don't have access to these materials, burning the paint off is the next best thing. You'll have to start a relatively large fire in the cabinet to get it good and hot but before you do so be sure to remove any essential components that you don't want damaged. After it has cooled some, you can use metal brushes to scrape off any remaining paint.
Step 3: Create Airflow
Smoke from the fire on the bottom must reach the parts of the smoker with food and eventually leave out the top. The best way to do this is to cut holes in the bottom of the drawers. Use an oxyacetylene cutting torch to remove part of the bottom of each drawer. Make sure to wear all proper safety equipment and use common sense. Once this is done you have to create two controlled openings, one for air to enter and one for smoke to leave. A flue at the bottom will be the intake and a chimney at the top will provide an exit. Again, use an oxyacetylene cutting torch to cut a rectangular hole on the bottom of the front face of the cabinet and a circular hole on the top of the cabinet. The flue was made by bending sheet metal into rails and sliding another piece of sheet metal along the rails. The rails were fastened with sheet metal screws to attach them to the cabinet and keep the sliding door from falling out. The chimney was made by rolling the same sheet metal into a tube and tack welding it so it stayed. Then a door that pivots on a screw was added on the top of chimney. The flue and chimney designs allow you to regulate airflow into and out of the smoker.
Step 4: Make Racks
These racks will hold the meat up off of the drawers. You can make these racks out of just about any metal you want but we used 3/4" angle iron. Each rack consisted of two running bars and multiple cross bars. The distance between each cross bar will depend entirely on what you want to smoke. Smaller things like chicken wings will require more crossbars that are closer together while larger items like pork shoulder don't need as many. As they won't be bearing much weight, you only need to tack weld the cross bars to the running bars so they stay together. Before smoking, you'll want to season the racks. This essentially means covering them in vegetable oil and getting them very hot. The oil will become attached to the metal and form a protective coating, this same method is often used with cast iron skillets.
Step 5: Install Heat Source
The most important quality of your heat source is its ability to burn at a very low heat. Depending on your preference you can use a standard fire, a propane burner, or an electric burner. We chose to use a propane burner because it's portable and doesn't have to be checked every half hour. The heat source should be installed as far away from the food as possible because you want to smoke instead of cook.
Step 6: Create Smoke
Now comes one of the most important parts. Your wood chips should be put in a metal tray or box and suspended above the heat source. There is a sweet spot where the chips are close enough that they release enough smoke but don't burn up too quickly. This will take adjustments so don't be frustrated if at first your chips burn up or smoke too little. If you find your wood chips are getting too hot and there isn't room to raise them up higher you can put your chip box in a tray of water. The water has a higher heat capacity than the metal and will only transfer only some of its heat to your wood chips. You can buy metal boxes that are made to hold wood chips or you can make your own which is what we did. We took sheet metal, bent it into the shape of a box and welded the corners. Then we filled the box with chips and set it over the burner.
Step 7: Finishing Touches
After a few tests, you may find there are some things you wish to add or improve upon. We found that smoke tended to leak from the back of our cabinet and we welded over where the smoke was escaping. A thermometer can be useful to monitor the temperature inside the smoker. We found that the drawer handles would get warm so we took metal coils and wrapped them around the handles. The coils remained cool to the touch and made opening and closing the drawers much easier. We decided to add a small prep table on one side to put meat on, which we made with some spare wood. You may also find that you lack appropriate BBQ themed decorations. We had some old bicycle chain laying around so we decided to make a pig which would be our mascot.