I built this little smoker primarily to make smoked beef jerky. It is made almost entirely from stuff I had laying around. My thinking was I only needed to maintain about 145F for a few hours fueled by large lump charcoal and hickory wood. Easy enough..not so much. The first batch I started the fire on charcoal and maintained it with hickory wood until the jerky was finished. I thought the more smoke the better the flavor. Again...not so much. The smoke flavor was overwhelming and it was awful. One whiff and I felt I should drop on the ground and get below the stuff so I could breath. I did a second batch using only charcoal and not wood. It was alright but the smoke flavor was still quite strong.
It is basically a tank that is 22" in diameter and roughly 36" tall. It has a 20lb propane tank on the side for a fire box with a damper between the fire box and the smoke box. The firebox has it's own flue/vent and so does the smoke box. The flue on the firebox has a damper that automatically opens when the damper between the firebox and the smoke box closes so the fire doesn't smother down. The damper between the firebox and the smoke box is controlled by a PID to maintain what ever temp I set. It works very well. The heat comes in below the plate you see in the bottom of the smoke box and comes up all around it. There is a pipe on the back of the smoke box with a blower that sucks the air out of the top and forces it in below the plate in a swirling motion. It keeps the whole smoke box roughly the same temp top to bottom.
I decided that I had to have a source of heat that doesn't smoke to get my jerky dry without being too smoky so I added an electric element in the bottom of the smoke box below the plate.
On the left you can see the inlet from the firebox and on the right you can see the pipe that returns the air from the top of the smoke box. It is strategically located to cause the air to swirl around the tank. This makes the all the jerky get done around the same time. I did some testing today and with the ambient temp around 23F, the electric element alone got the smoke box up to 134F. In warmer weather it will perform better.
I did install a second PID just for the electric element so 1 PID controls the damper between the fire box and the smoke box and 1 PID controls the electric element .
I lit a fire in the firebox and set the temp on both PID's to 220 f. It seemed to work perfectly. The electric element pretty much stayed on and the fire box add a little more heat to get right up to temp and stay there. That will work great for smoking meat.
On my next attempt at making jerky I plan to get the smoker up to temp using only the electric element (obviously it will have to be warmer out for this to work) and then after the jerky has been in for a while I will start a fire and let it assist in drying the jerky. Then I will just let the fire die out and finish on electricity. Hopefully this will impart a nice smoke flavor without being so overpowering and I can do the whole process from start to finish in the smoker.
Here is a picture of the control panel. I haven't put on the labels or cleaned up the external wiring yet because it is still in the testing phase right now.
That's a weather proof stainless steel box. I had it laying around so reused it. On the lower right you can see the solenoid that controls the cylinder that operates the damper between the firebox and the smoke box.
Here is a picture of the flue damper on the firebox.
When the damper between the firebox and the smoke box is closed it pulls on the cable and holds the fb flue damper open. When the fb to sb damper opens, the spring snaps the fb flue damper closed. This works pretty good to keep the fire good and hot.
In short, a simple smoker can be more complicated than you think.