UDS heat and smoke generation
A UDS allows for a very well controlled combustion process by regulating the oxygen supply to the fuel source through the inlet system. By making fine adjustments to the inlet openings, one can regulate the smoker temperature within 20 degrees F and even better once one gets to know the smoker well and gets more experience.
It is a sealed unit so all the heat energy and smoke coming from the fire will be available for cooking.
The only losses are heat and smoke through the chimney and radiated heat from the sides of the drum. Losses through the chimney can be controlled by adjusting its opening. The chimney opening should allow for good circulation to replace stale smoke with fresh smoke, enhancing the flavor of the meat.
For fire to burn (combustion), you need 3 elements:
- Fuel
- Oxygen
- Heat
Fuel
In a UDS, the fuel is charcoal and wood. Charcoal will supply the heat and some flavor, and wood will supply a specific smoke flavor.
Oxygen
Oxygen is supplied by the UDS inlets provided the chimney stack is open to allow for a flow of air.
Heat
Heat is generated when the fuel is lit on fire and then self-sustains until the fuel or oxygen runs out.
Building the UDS
Information on the internet
A quick search on the internet will give you detailed instructions on how to build a UDS yourself with readily available components from your local hardware store:
There are also several suppliers of UDS kits:
Building my UDS
The parts for the smoker I built were obtained from various sources:
The Drum Parts
I purchased a 55-gallon food-grade steel drum on Craigslist. They vary from about $20 to $50, depending on the thickness of the steel and what treatment they went through. Some may have been polished inside and some have been burnt out to remove harmful chemicals and the paint.
Pick a reputable supplier and look for a thicker steel and a guaranteed food-grade used drum.
The drum I picked had a polished inside, smooth sides (no ribs), and is made of slightly thicker steel than the usual drums, making it more efficient and durable.
It looked like this:
I studied plans on how to build a smoker with normal hardware store parts, did the calculations and figured out that it is slightly cheaper to buy a basic kit. You have to go through the exercise yourself to decide. What I did was to go online and to put all the needed parts in a shopping basket and then to look at the total amount. You might be surprised.
I did not want to go for the basic configuration as I wanted to build a BDS (Beautiful Drum Smoker) instead of a UDS. I was looking for a visually pleasing design as well as solid functionality and ease of use.
For my BDS components I used different sources:
From UDSparts.com I bought the basic UDS smoker kit. I then added the options of
- extended air intakes,
- swivel casters, and the
- adjustable heat shield/diffuser.
I added 2 porcelain covered cooking grates instead of one to allow me to smoke double the amount of meat if required:
For the smoke stack option I had to choose the mounted version instead of the threaded one as my drum lid did not have a screw cap. I also added this LavaLock handle for the lid:
For the lid hinge, I chose this hinge from bbqsmokersupply. The picture is copyrighted so I did not paste it here.
It is also available on Amazon for a slightly better price at the time of writing.
The thermometer that came with the kit could not be calibrated, so I bought one from Amazon. It can be calibrated and has a larger face to enable one to monitor the temperature inside the UDS from inside the pool.
To enable temperature probing inside the UDS, I purchased probe grommets for installation into the side of the drum.
I only used one of them in the BDS. It allows for a probe insert to measure the ambient temperature, as well as for cabled probes to be used to measure the temperatures inside the meat. After 6 months of usage, I have not had any issues with this grommet.
Building the UDS
The first step in the building process was to buy the drum. You need to know the drum characteristics before you can figure out the drum configuration and parts needed.
The second step was to order all the parts.
While waiting for the parts to arrive, the drum can be prepared.
Drum preparation
Clean out the inside of the drum per food-grade requirements and then strip the paint on the outside.
For this activity I found that the spray-on paint stripper worked better than the paint-on version. Also, it needs to be done in the shade to prevent the solution evaporating before it can do its job. I applied the stripper at the end of the day and by the next morning the paint was coming off in sheets.
Marking and drilling the holes for assembly
Once you have received all the parts, mark out all the hole positions in the drum and do a sanity check before you start drilling the holes.
In my case, the kit had some guidelines for the positions of the heat diffuser, the cooking grates, the inlets, and the smokestack. The rest of the items can be mounted per your specific functionality requirements and visual presentation needs.
I suggest you browse the internet to get ideas of what configuration and color scheme will work best for you.
Once you have marked out all the hole positions, proceed to punch a small dent in the centers of all the hole positions, followed by drilling a small pilot hole. In my case I then drilled bigger and bigger holes until I reached the final hole sizes.
In the case of holes larger than ½ inch in diameter, I used a titanium step drill bit. It can drill holes up to 1 3/8 inches in diameter. For bigger holes, a metal hole saw can be used.
I found that a corded 110 V drill worked much better for drilling steel than a battery powered drill. I started off using a battery powered drill but had to re-charge the battery very frequently and it took a lot of time away from the project. I then switched to a drill I purchased from Amazon. In my opinion it is a very good investment and it saved me a lot of time.
Once all the holes have been drilled and before you start painting, do a loose fitting of all the components. Mount all of them loosely and make sure all the holes are the correct size and are perfectly aligned. I had to do some small corrections to make sure everything would fit well.
Once you are ready to commit, it is time for painting the drum and the components.
Painting the drum
First, make sure the drum and components are clean and oil-free. To remove any oil, use denatured alcohol to wipe down all the surfaces.
Below is a picture of the drum and all the components cleaned up and ready for painting.
Start out by using high-temperature primer, followed by the high-temperature topcoat. It is important to apply several thin coats and to wait between each coat to allow them to dry.
A UDS temperature can easily go up to 350F, so I chose paints that could go to 500F.
Below are pictures of the paint cans I used.
Below is a picture of the UDS and components after applying the primer.
Below are pictures of the top coat painting of the drum attachments and the start of the assembly process.
Curing the paint
After completing the assembly, the paint needs to be cured.
I did a 2-step temperature process using the guidance on the paint cans.
I lit charcoal in a chimney starter and while it was getting ready, I coated the inside of the drum and all the surfaces of the cooking grates, the charcoal basket, the bolts and nuts, and the diffuser using cooking oil to allow the inside of the drum to be seasoned.
After the charcoal in the chimney was ready, I added the burning charcoal to the charcoal in the charcoal basket, closed the lid, and fully opened the inlets as well as the chimney to allow the temperature inside the BDS to get up to 200 F. I then throttled the inlets back to maintain 200F for about 30 minutes before I closed the chimney and the inlets to let the fire die down. I allowed the smoker to cool down normally.
The next day I repeated the exercise, but this time I brought it up to 350F for 30 minutes before shutting it down.
Since then I have used the smoker many times and have never observed the paint bubbling or peeling. Below is a picture of the finished UDS. I dubbed it SMOKY PETE.
Using my UDS
Below is a picture of the first time using the smoker. I smoked St. Louis style ribs and the results are shown in the pictures below.
I used probes to probe the meat as well as to monitor the smoker internal temperature. The temperature probe system I used (Tenergy Solis) was bought from Amazon.
The reasons I chose this system are:
- It has 6 probes and channels – allows you to probe thin and thick parts of various pieces of meat
- You can monitor the temperatures on your phone through a Bluetooth connection
- It has a graphing function so you can track the temperatures over time.
The Solis system works great; however, it resets the graph periodically, which is frustrating.
The ribs came out great! Please look for the rib recipe elsewhere on this website.
