Finished High Tech UDS Ugly Drum Smoker Build

FINISHED HIGH TECH UDS UGLY DRUM SMOKER

Here are details of my high tech DIY UDS. It might give you ideas on how to build your own so feel free to copy anything that might work for you. Construction details follow in the posts below. These are not step-by-step, just a review of what I remember over the six months or so during construction.. This is a work in progress so there are a few modifications that will be made as time goes by and I'll update accordingly.

Background

Just for fun, I've bought, then sold, a number of used smokers off Craigslist over the years, both electric and charcoal, to find out what works best for me. My latest is a Masterbuilt 30" electric. It works OK but it has some drawbacks. After a while, I started thinking about a DIY drum smoker.

Although I prefer the taste and texture resulting from charcoal smoking, I'm getting lazy in my old age and wanted instant start up, minimum hassle, and minimum cleanup. Low operating cost was also a factor. And one big constraint was size: not much free space in the covered patio area. All these factors led to an electric smoker/roaster with a compact, vertical design.

Here is a partial list of the features I wanted:

1) A rotisserie for self-basting. I noticed that a spice rub is much tastier when it is frequently basted but I'm too lazy to do it by hand. 2) Precision temp control. I like the idea of tightly controlling the smoker temp as the final meat temp is approaching. 3) Low operating cost. With a typical electric a four hour smoke turns out to cost less than a buck in electricity. Much less if the smoker is well insulated - the goal was 10 cents per hour. 4) Easy cleanup. Although internal soot build up is not an issue for me, I don't like the accumulation of food splatters in my smoker. 5) Big cooking surface area. I often do a big batch with extra for the freezer. And 6) Lots of flexibility: with water pan, without; with lava rock, without; with hot smoke or cold smoke; high temps for roasting and browning, and low temps food dehydrating like jerky.

In short, I wanted it all. So I finally settled on a DIY drum smoker. Here is the result:



Wide Mouth



Overview

If you look closely at the top photo, the 55 gal drum has been split in two, separated by a rubber gasket. This forms two insulated housings for the internal parts. Below is a photo of the smoker in two pieces. They are held together by locating pins to keep the two aligned. Latches are planned later. If you are into electric smokers the photo below might remind you of an electric Brinkmann unit -- you guessed it.



Actually the drum itself is not a key part of the smoker. It simply forms the outside shell for the parts inside. At the seam between the two, the top and bottom are sealed off with a welded round sheet metal ring, then with gaskets.

Layout

There are three main assemblies inside:

First the top half consists of a UniFlame 360 sq in Kettle Charcoal Grill from Walmart which forms the hinged top, top grill support, and rotisserie shaft cutout. Second, the inside parts are from a Brinkmann (810-5290-4 Smoke'N Grill) electric smoker, less the top, handles, and feet. They look like this:The Brinkmann body tube was welded to the bottom half of the UniFlame BBQ. The other end of the Brinkmann tube was welded to a sheet metal sealing ring withe drum on the outside between the two. You can see the top half is simply an insulated tube with the BBQ top welded to the top of the tube, and surrounded by the drum.



This top assembly then fit into the Brinkmann lava rock pan containing the heating element and below that the base pan. Then, below that is a custom fabricated auxiliary heating element assembly.

Inside it looks like this:



The third part is the bottom sheet metal assembly which contains a Little Chief 250W auxiliary heating element. This second heating element adds heat to the main heating element to achieve higher temps, up to 350 deg. Also, the second heating element allows an independent and controllable source for burning the wood chips. The drum encloses all these pieces with an insulated space between. When both halves of the drum are together, access to the second burner is through through a door in the side of the drum. By splitting in two there is full access for cleaning plus easy access to the heating elements in case they need replacement.

The UniFlame, the Brinkmann, and the drum were all bought used from Craigslist for $15 each. The custom smoke chamber parts were made for about $50 from a local AC sheet metal shop, and the Little Chief heating element was $20 from eBay. So with less than $100 initially invested I was able to get started.

Highlights

Insulation And Seals

The drum is not really required for this smoker to work. However, it formed an outside housing with about a 3" space between the internal parts. This was filled with fiberglass insulation and fully sealed with silicone sealant.



Since the drum surface temperature does not exceed 150 deg at any one spot, most of the the outside surface is just warm to the touch so the drum's inside wall coating did not need to be burned out. With less heat loss it uses less electricity, higher temps can be achieved, and it makes for easier temperature control. A couple small holes in the top and the bottom provides humidity and pressure equalization.

All the seams have been sealed with 500 deg F high temp silicone to prevent air leakage and to prevent the fiberglass insulation from infiltrating into the cooking space. And the area where the two halves of the drums meet was doubled sealed, first with white fiberglass insulation rope on the inside, then a black rubber gasket on the outside, with the gray fiberglass insulation in between.



High temperature silicone sealant was used to provide a gasket between the top and the rim. In operation, the only leaks are at the rotisserie rod holes. Of course the top vent operates normally.



Rotisserie

The rotisserie was mounted close to the drum body on a bracket to reduce the overall width. But during testing the rotisserie motor got a little hot. Some motors don't seem to last very long, probably due to the heat. To reduce motor temps a polished heat shield was added, plus a small fan was mounted to the back of the motor near the gearbox. With the smoker's internal temps going full blast the motor now runs only warm to the touch.



Cooking Area

The original top UniFlame grill fits as usual. Below that three tabs were installed so a second grill to fit just below.



Below the BBQ grill, two Brinkmann smoker grills fit as usual. This allows for a large cook area.



Double Drip Pans

The original Brinkmann water-drip pan still fits but additional pan supports were added for a deeper stainless pan for longer periods between adding water.



Another drip pan can be added to cover a larger area closer to the top and direct the drips to the water pan below.



This prevents drips from accumulating at the bottom of the smoker. The pans simply lift out for easy cleaning.

Dual Heating Elements

There are two heating elements, the usual Brinkmann element (see previous photo) plus a Little Chief second auxiliary for extra heat and for the wood chips. The aux heating element assembly is mated to the bottom of the Brinkmann base pan.



Here is the rationale: First I wanted as much heat as possible to get the internal temps into the 350 deg range so the extra 250 watts adds to the Brinkmann's 1500 watts. Second, I wanted independent control of heating the wood chips so a pan containing the chips fits directly on top of the axillary heating element.

Ordinarily if the smoker is well insulated and the temperature control is tight, the heating element might not cycle hot enough to keep the chips smoldering. On the other hand, if the heating element is cycled hot enough to get the chips going, then the inside temp might swing too high -- not an easy compromise. And with most electrics, getting the smoke chips smoking and replenished over the course of cooking is sometimes a hassle. With a separate chamber for the wood chips accessible from a door on the side, managing the smoke is a snap. There are internal stops to precisely position the chip pan directly on the center of the heating element.



Control Box

The over-the-top control box was designed to provide as much flexibility in controlling temperature and smoke as possible - initially just for fun and dinking around. Thereafter, much of the features included will likely not be used much.



The top display is a calibrated meat thermometer. This is extremely important to minimize opening the top to check the meat temp. When not in use the probe is stored away in the control box mounting.

The square display next to the power button is a dual mode industrial PID temperature controller. (See: wikipedia.org/wiki/PID_controller ) This reads the thermocouple inside the unit and cycles the heating elements on and off to keep the desired temperature.

The two LEDs under the power switch indicate the on-off status of the main and aux heating element.

There are three toggle switches; from left to right: The main heating element can be manually be set to "on" or "off" or connected to the controller in "control." Same for the center switch for the aux heating element. The third switch links the aux heating element to the controller normally, or in reverse.

The two knobs control the power delivered to the heating elements through a solid state AC controller in both the "on" and "off" state. The left knob will add heat when the controller turns the heater off, from zero in the leftmost position and about 700 watts in the rightmost position. The knob on the right controls the wattage when the heating elements are on, from about 700 watts in the leftmost position to about 1750 watts in the rightmost position. Different settings are used depending on the configuration of the temp controller.

Results

With the very first automatic PID setting, the temperature controller easily held plus-minus one degree, about as good at it gets. After the top is lifted the unit gets back up to temp quickly - better than expected, even without the lava rock. But it takes quite a while for the smoker to get from 250 deg to 350 deg so extra time had to be figured in. It takes about an hour for the water pan to get to a gentle boil. With an outside temp of about 100 deg, the unit pulled an average of about 600 watts when set at 250 deg. So a four hour smoke runs less than $0.40 in electricity at our $0.15 KWH rate.

Here are a couple chickens. For testing these were placed with the legs in the middle so most of the drips would fall toward the outside. Only two handfuls of cherry wood chips were used for taste on the mild side.



The top drip pan directed the drips to the water pan below. With a light coating of ant-stick spray the cleanup only took a couple minutes.



Here is a beef chuck roast. Surprisingly moist, sorta tender, and nicely flavored with a one handful of Mesquite chips. The control box meat thermometer was used on this smoke, you can see where the probe was inserted in the middle. It hit medium rare on the first try.



Additional posts below cover the construction details........

1

Part 1 -- BBQ BOTTOM TO DRUM LID POSITIONING, CUTTING, AND WELDING

The first task was to get the BBQ bottom half to fit into the top lid of the drum by cutting a big hole using the saber saw.

My drum lid was in good pretty condition with only a few dents in the rim. These were straightened out with a pair of pliers. Then a tape measure was used across the lid to at many points to make sure the rim was round.

Finding The Center Of The Drum Lid

There are a couple ways to find the center of the lid. I used a wood measuring stick, about 3/8" tall, 3/4" wide and about 14" long. A center line was drawn down the middle and two pilot holes drilled for two nails. The pilot holes were drilled 1/2 the lid diameter using the inside edge of the lid flange, less a half nail width. The nails were driven through (without cracking the wood) from the opposite side, checked for the correct distance with a tape measure and one nail bent a little to get it exact.

With one nail up against the inside flange surface of the drum lid, a short arc was scratched into the center of the lid. Then the stick was moved to the opposite side and another arc was scratched. Then the stick repositioned at 90 degrees and another arc was scratched. And the process repeated until the arcs formed a point (or a small circular ring surrounding the center of the lid.) I used the marker to mark the center point of the arcs-ring, then used the tape to verify that the mark was in the center from all edge positions. If off the center, I repositioned the mark until it was equidistant from all edges. Once the center was found it was center-punched and a small hole drilled using a hand drill for accuracy, about the same diameter as the nail in the stick.

Hole Diameter

Next was to decide how deep the BBQ bottom will fit into the lid. I wanted to use the hinges so the BBQ bottom edge would have to be about 3-1/2 inches above the lid. It didn't have to be exact because I planned to notch the bottom of the hinges to fit. To get an approximate diameter I placed the yard stick across the BBQ, then on the inside measured down the 3-1/2 inches, applied some masking tape to the BBQ bottom in about the right spot, then made a mark. A second mark was made across the BBQ bottom and the distance was measured between the two, more or less, with a tape measure, adding 3/16" or so for the thickness of the BBQ metal. Then a hunk of cardboard was cut as a circle template for a trial fit. With the BBQ bottom upside down the cardboard template was placed over the BBQ bottom to see how deep the BBQ would fit into the lid. After a couple trials I got the correct hole diameter.

Cutting

On the wood measuring stick one nail was removed and a new hole and nail placed one-half the diameter of the planned hole in the lid. One nail was placed in the center of the drum lid hole and a few trial marks scratched corresponding to the hole diameter near the edge of the lid. Using the tape from the edge of the lid flange to the marks, I made sure they matched at different locations along the edge. Again, the nail was bent to get it exact. Then the lid was completely marked in a circle for cutting by using the nail to scrape the circumference, then cut with the saber saw. I tried to get an accurate cut but, of course, there were going to be gaps. The lid was then stripped of paint ready for welding.

Here is the lid with the center cut out:



Fitting The BBQ Bottom Into The Lid

With the hole cut the lid was placed on the drum, then the BBQ bottom was placed in the hole and the calipers were used to equalize the distance from the edge of the lid to the BBQ edge and then marked. The porcelain enamel was ground off the BBQ bottom where the lid edge mates with the lid. A number of 3/8" thick wood spacers were cut to match this distance, and clamped in place for welding.



Extra clamps were then put in place to keep the BBQ bottom and lid together and a series of short stitch welds were made where the two meet. You can see below the surfaces were ground to the bare metal for a good weld.



Cutting The Bottom Out Of The BBQ

Next was to cut the hole in BBQ bottom about 1/2" smaller than the inside diameter Brinkmann tube, leaving a 1/4 ledge for the welds. The welding was later done with the BBQ upside down from the inside of the tube. The hole is not too critical - it only has to be a bit smaller in diameter than the tube. I placed the tube on the BBQ bottom and used a ruler got it centered, with an equal distance between the lid edge and the edge of the tube. Then the position marked on the BBQ bottom from the inside of the tube. This mark, plus a little more margin was used to cut the bottom out of the BBQ.

2

PART 2 CUTTING THE DRUM AND WELDING THE TUBE TO THE BBQ BOTTOM

The parts going inside the drum needed to be measured at this point so the drum could be cut to match the BBQ and lid combination. The drum would them be used as a fixture to align the tube for welding to the bottom of the BBQ. The sheet metal sealing ring which butts to the bottom of the cut drum was needed to center the drum.
Inside Parts Measurement

The cut drum had to fit the total height of the top assembly, from the lid, including the bottom of the BBQ, plus the Brinkmann tube, less the sealing ring, less a little so the tube will seat into the Brinkmann lava pan, and then a little less for the gasket. Getting the tube straight on the BBQ was a little tricky.


The assembly was placed upside down, the tube temporarily put in place, then measured the distance from the tube to where the lid engages the drum. A bit was subtracted from this to offset the sealing ring thickness, the fit into the lava pan, and the gasket thickness between the top and bottom parts of the smoker. The tube was then sanded along the edge which mates with the BBQ bottom for a sound weld. The BBQ bottom was also ground to remove the porcelain enamel along the edge.

Cutting The Drum

The drum was marked at this distance along many points from the top and a flexible ruler was used to connect the points along the circumference. Then the drum was cut to this dimension using the saber saw.



Trial Fit

At this point a trial fit was made ready for welding the tube to the bottom of the BBQ. Here is the cut drum placed into the lid flange with the welded BBQ bottom piece.



Then the sealing ring was slipped over the tube, then the tube slipped into the drum where it meets the bottom of the BBQ. The sealing ring was then centered in the drum by using some wood spacers along the circumference of the drum's cut edge. These spacers were placed to make the distance between the edge of the sealing ring and the cut edge of the drum the same around the circumference.

Welding And Sealing

When clamped in place the tube was then welded to the BBQ bottom from the inside of the tube.

Once welded, the drum was removed from the assembly leaving the lid, BBQ bottom and the tube and one solid welded assembly. All inside surfaces along the welded seams were thoroughly cleaned and high temp clear silicone was applied on both sides of the seams..



Then the top side of the lid was cleaned, and where the silicone sealant was to be applied masked off, primed with high temp primer, then painted with high temp paint. When dry, the paint was masked off a bit and black silicone was applied. Therefore, the BBQ to lid seam was sealed from both sides, top and bottom.



Hinges

The hinges for the top were cut to fit the lid rim and repainted:

3

PART 3 BRACKETS FOR THE ROTISSERIE AND CONTROL BOX

The Smoker has casters mounted to two inch square tubing at the bottom so it was economical to fabricate the brackets from the same tubing by using a hand grinder, hack saw, and saber saw. The rotisserie brackets had to be offset from the drum surface since the lid flange was in the way. It took some work to cut away the unused metal so it would fit.

Rotisserie Rod Positioning

The rotisserie rod center line was established by referencing the hinge holes. A yard stick was used to span the BBQ where the rod would go and the position marked on the top edge of the BBQ bottom. A rat-tale file then hogged out just enough material so the square rod would slip in and align flush with the BBQ' top edge. Later the hole would be enlarged so the rod could rotate.

Non-Motor Side Rotisserie Bracket

The slot in the rotisserie bracket was first made as a hole, just large enough for the rod to fit. With the hole aligned with the rod, a transfer punch was used to mark through the bracket holes to the drum surface. Holes were then drilled and the bracket so the bracket could be temporarily screwed into position on the drum. then the bracket hole for the bushing was drilled for the correct diameter. With the rod in its slot and positioned through the bushing on the bracket, the bracket was welded in place.

Here is a detail photo of the non-motor end bracket. You can see how the 2" tube was cut to clear the lid flange. Note the welds.



The bushing hold was the enlarged to allow a slightly loose fit.



The bracket for the control box is much the same as the non-motor rotisserie bracket

Motor Side Rotisserie Bracket

On the motor side of the rotisserie things were a bit more complicated. There are actually two brackets. One was welded to the drum much like the non-motor end except it did not protrude above the lid flange, and the second bracket, tall enough for the motor to reach the rod center line, was bolted to the first, flat sides facing each other. The bracket welded to the drum also had two welded bolts for mounting the second bracket though largish holes for easy alignment.

Between the two brackets is a polished heat shield.







Welded to the second bracket is a flat piece of stainless which fits into the motor slots.



Rotisserie Shaft Clearance

Once things were aligned, the shaft slots were enlarged to the shaft would easily rotate.


Then the top was notched to fit over the rotisserie rod:

4

PART 4 FINISHING THE TOP ASSEMBLY

With the brackets done the top assembly was stripped of all the old paint, cleaned, degreased, then lightly sanded. The dents, scrapes, and scratches were filled with automotive body filler, sanded, then masked off for primer. The edge where the drum meets the lid was left bare.



Attaching the Drum To the Drum Lid

The top welded assembly that fits inside the drum, (drum lid, BBQ, and tube) were thoroughly cleaned and placed upside down for sealing to the drum flange. The flange area where the lid and drum meet was taped off then filled with black high temp silicone, and a thick bead was applied to the edge of the drum. Then the drum was placed into the lid flange area and pressed into place with enough force to cause the sealant to flow out of the flange area and seat completely into the flange. The sealant not only seals but glues the two parts together. When cured, the excess sealant was trimmed with a hobby knife flush with the outside lid flange.

Insulation

After curing the top assembly was filled with fiberglass insulation


Sealing Ring

The ring was then installed and again aligned with spacers so the outside ring would protrude equidistant along the circumference of the drum and welded to the tube. .


Then the ring was stitched welded to the drum edge. The welds were ground down a bit then sealant applied.

5

PART 5 -- SECOND DRUM CUT AND LOCATING CUTOUTS

The Second Drum Cut

As mentioned in the earlier post, the internal parts of the top half of the smoker were put together first then the drum was cut to match. Very easy - not too many precise measurements required. But the bottom is going to take some more work. There were only two concerns in cutting the bottom part of the drum: make sure the diameter matches the top assembly so the two sealing rings match up when the two halves are together, and that there was some room for insulation at the very bottom. The cut is close to the ridge along the circumference of the drum that indents then bulges out a bit. So the cut point was selected just above that. The bottom half of the drum was cut using the same procedure as the top.

Locating the Drum Cutouts

The bottom assembly consists of a removable Brinkmann lava rock pan which contains the main heating element. Below that is a fixed Brinkmann base pan welded to a sealing ring, which in turn is attached to a custom chamber containing a second heating element. The lava rock pan was temporarily set aside as it was not needed to locate the drum cutouts.

Here are the parts that were considered:

Just below the top flange of the base pan is the bottom sealing ring which is eventually welded to the drum.



Below the rectangular cutout is a fabricated sheet metal assembly consisting of a rectangular hat channel. The hat channel extends to the front where it is flush with the front door.



On the back there are two cutouts, one for the main heating element cord, and the cut-down rectangular end of the aux heating element assembly:



A local sheet metal shop that makes air conditioning duct work only cut and formed the pieces according to a drawing for about $50. Assembly would be a little tricky so I did this part myself. The parts were cleaned, cut, trimmed, and put together using a combination of pop rivets and stitch welds, then sealed with silicone. As indicated above, this assembly has two places where it pokes through the drum — the front door and the back panel.

Aux Heating Element Assembly

The aux heating element assembly, not quite fully assembled in the photo, was finished, here undergoing testing:



And the back side:



This assembly plus the base panwith the sealing ring installed, were placed upside down on a flat surface Then the distance was measured from the sealing ring, which corresponds to the drum edge, to the two positions where the door and rear panel would protrude. This measurement was then transferred to the drum and the cutouts made, less about 1/16 for final fitting with a file. I goofed and somehow did not get the drum seam centered on the back so it was eventually ground a bit and filled with automotive body filler. Have to pay closer attention.

6

PART 6 -- ONE MORE CUTOUT AND AUX HEATING ELEMENT ASSEMBLY WELDING

Aux Heating Element Standoffs and Clamp

The aux heating element is a Little Chief 250W (9810-005-0000) unit. Before fitting the aux heating element assembly into the drum three standoff brackets were made plus a capture clamp to hold it in place. These were pop-riveted. Two holes were drilled in the back panel area to allow the heating element ends to pass through. Crimp connectors would then attach to the heating element with high temp appliance wire which in turn were wire-nut connected to the cord exiting the back panel through a strain relief. Note that in the photo below there is a platform from the front of the door to the edge of the heating element so that the pan containing the wood chips slides smoothly directly on top of the heating element. Also note that the bracket that captures the heating element has two angled extensions that form a centering stop so the pan is centered on the heating element just below the chimney tube above.

Aux Heating Element Positioning

The aux heating element assembly fit flush with the door cut out on the front of the drum but on the back it would protrude a bit. So the door end was trimmed to match the curve of the drum.

The rectangular hole for the back panel was opened up just enough so the assembly would tilt in far enough to clear the front of the drum, then pulled forward so the front would fit flush with the front edge of the drum. The assembly was then mated with the base pan and checked that the sealing ring just touched the drum edge for eventual welding. To hold in place for more tinkering, thin shims were used to center the assembly in the cutouts. Before welding the rest of the bottom half was test assembled.

The base pan eventually mates with the top of the aux heating element assembly with pop rivets and there is a rectangular hole in the base pan to allow the heat flow up through a hole in the lava rock pan, then into the main part of the smoker.



The rectangular hole in the base pan was determined first, then four guide holes were drilled through the base pan then through the assembly's top flange. With both removed from the drum and with the holes lined up, the outline of the flange was marked on the bottom of the base pan, reduced 3/4 inch to compensate for the flange width, then the rectangular hole was cut. Once reinstalled and re-shimmed, rivet holes were drilled though the base pan and then to the assembly flange for a final fit, then set aside: these two pieces would be riveted together after the fiberglass insulation was installed.

Aux Heating Element Assembly Welding

After everything was checked again, the aux heating element assembly was welded in place. The welds were spaced more closely for these parts as the gaps had to be filled with automotive body filler. Once filled with body filler the back sides were sealed with high temp silicone sealant, primed, the prepared for final paint.

Here are the finished photos again for reference:





Main Heating Element Power Cord Cutout

There was one more cutout for the main heating element cord which comes out the back of the base pan and lava rock pan then through the side of the drum. These had to line up. First the heating element in the lava rock pan was raised a bit so the inside bracket would cover the upper part of the hole in the lava pan. Then the heating element bracket was drilled for clearance holes and corresponding holes were drilled for sheet metal screws. A small bracket was then fabricated to close off the gap below the bracket to completely seal the lava rock pan. With the heating element raised slightly additional spacers were added to the heating element support brackets. At this time a food can was recycled to form a chimney between the aux heating element space below and the upper portion of the smoker so when lava rock was used it would not fall through the hole. It was tack welded from the bottom.



Trying the seal the can against dripping leaks was unsuccessful. Welding such thin material was troublesome, high temp solder would not flow, and silicone sealer would fail. The obvious solution was to keep the smoke chip pan in place to catch any drips.

Again measurements were made and the cuts made to fit a two inch square tube which would be welded from the outside and protrude slightly from the drum, then through the base pan but just short of the outside edge of the lava rock pan.

7

PART 7 -- CASTERS, DOOR, SEALING RING, AND GASKETS

Casters

The casters were mounted on four two inch square pieces of tubing. Once located they were pop riveted in place then welded.



The welds were ground flush and plastic caps added to improve appearance. The caster's threaded stem got jam nuts so they won't come loose.



Door

There are several ways to make the door and I chose to use a piano hinge on hand. I tried several ways to match the radius of the drum but was unsuccessful. The sheet metal I had on hand did not want to bend the way needed. I finally remembered I had some scrap from a desktop computer case and cut out a hunk. This metal is quite soft and has less "spring" -- that is, it is less likely to bounce back to the original shape when bent. To bend a radius the metal had to be initially bent a bit tighter, in a smaller radius, so when it bounces back a bit it more closely matches the drum curve. I found that a gallon paint can was about the right radius and after repeated attempts it worked - a precise match.



The metal was so soft I was a little worried that it might bend if handled roughly so a second piece of steel was cut and formed then pop riveted to the door for reinforcement. The hinge was clamped tight against the door and a number of tack welds were made on the inside. These had to be good welds since they needed to be ground flush to get a good seal. Then a rubber gasket was made from some scrap and glued along the edge that closed flat against the drum with high temp silicone sealant.



Then, when centered over the cutout a center punch was used through the hinge holes to locate the holes to be drilled in the drum. When all the holes matching the hinge were completed the door was temporarily attached to the drum for fitting the door latch.

The adjustable bottom air went was salvaged from a small kettle style BBQ.

Door Latch

The door latch body aligned then center punched. It was too narrow to get two pop rivets so one rivet and one screw was used.

Insulation

Insulation was added below the aux heating element assembly and up the sides



Then insulation was added so surround the base pan:



At this point the sealing ring was welded to the base pan just below the top flange and sealed with silicone. Then the aux heating element assembly flange was sealed with a heavy bead of sealant, and the base pan placed into position, then they were pop riveted together. The two inch square tube for the main heating element cord was inserted, aligned, then welded to the base pan on the inside and then to the drum on the outside. The inside was sealed and the outside filled with auto body filler ready for priming and paint..



Once sealed the drum was turned upside down and the sealing ring stitched welded to the drum, and ground then taped off for later sealing.
.
Priming For Paint

The bottom half of the drum was stripped of the paint, the dents, dings, and gaps filled with body filler and masked of for priming.






The drum surfaces were again degreased and cleaned, tacked off, then the finished coat of semi-gloss paint was applied in three coats, with a 20 minute wait between coats. They were left for two weeks to cure (also for the sealant to cure -- see below).

Gaskets

Once the paint had cured the outside rubber gasket was applied to the bottom half of the drum sealing ring using silicone sealant as an adhesive. The rubber gasket was the door weatherstrip from a used 1992 VW Passat. It was about the right height plus had a lip which fit around the top sealing ring concealing the seam.



Internally, next to the rubber gasket are a thin piece of fiberglass insulation, then the white fiberglass rope gasket. The tube fits within the metal ridge on the right in the photo. The gaskets seal the two sealing rings not the tube. This prevents damage, wear and tear from frequently removing the top.



BBQ Top Seal

To get a leak-free seal for the BBQ top was a problem and I finally decided to apply a thick bead of high temp silicone sealant to the top where the top meets the corresponding edge on the BBQ bottom. I first cleaned both surfaces, then applied masking tape to the bottom edge. This was then coated with silicone grease so the sealant would not stick. Then a thick bead was applied to the top and the top seated on the bottom edge. After the sealant cured for a couple days the top was pried off the bottom edge and trimmed.

No smoke leaks have appeared - most of the top has a complete flexible seal around the edge:



Final note on silicone sealant -- I don't know exactly how long the thick sections of sealant take to cure internally so I waited two full weeks before the heating elements were activated for "curing."

8

PART 8: THE CONTROLLER BOX

Review

Here is a review of the info in the original thread. NOTE: I am not providing schematics. If you are qualified to do this sort of project you don't need them and can design your own..



The top display is a calibrated meat thermometer. This is extremely important to minimize opening the top to check the temp. When not in use the probe is stored away in the control box mounting.

The square display next to the power button is a dual mode industrial PID temperature controller. (See: wikipedia.org/wiki/PID_controller ) This reads the thermocouple inside the unit and turns the heating elements on and off to keep the desired temperature to plus or minus one degree.

The two LEDs under the power switch indicate the on-off status of the main and aux heating element.

There are three toggle switches; from left to right: The main heating element can be manually be set to "on" or "off" or connected to the controller in "control." Same for the center switch for the aux heating element. The third switch links the aux heating element to the controller normally, or in reverse.

The two knobs control the power delivered to the heating elements through a solid state (triac) controller in both the "on" and "off" state. The left knob will add heat when the controller turns the heater off, from zero in the leftmost position and about 700 watts in the rightmost position. The knob on the right controls the wattage when the heating elements are on, from about 700 watts in the leftmost position to about 1750 watts in the rightmost position. Different settings are used depending on the configuration of the temp controller.

Main Components



In the photo above, top left, is the $12.00 AC triac controller purchased off eBay and shipped from China. (search eBay for SCR Electronic Motor Speed Controller Dimmer Controls Temperature) It is laughingly rated at 4000 watts at 220v. It originally contained a heat sink suitable only or a few watts so the sink was replaced by larger unit and mounted directly in front of the cooling fan. The gate control is derived from the current drop across the load so it has no neutral connection. The fuse is rated at 20 amps. Originally the circuit had a pot for manual control. I replaced this with two resistor networks with external pots to the front panel switched under relay control. This also provided isolation.

In the center of the photo are two relays. One 12 Volt to control the AC to the main heating element via the resistor network mentioned above and the other 120 volt to control the aux heating element. The second set of relay contacts were used to switch the LEDs for status displays.

In the photo at the right is a 120v input, two output 5V/12V, 1 amp each, switching power supply also off eBay for about $10 shipped from China. (search eBay for AC-DC Power Supply Buck Converter Step Down Module Dual Output 12V1A 5V1A) The 12 volts is for the control box fan, the meat temperature display (positioned directly below in the photo), and one relay. The 5 volts is for the leds, the rotisserie fan, and the piezo low temp alarm (far left in photo - so far not used yet.) The power supply heat sink ran a little warm so a bigger sink was added.

The meat temperature display next to the power supply is also from eBay, $13 from China (search Digital DC Temperature Meter for K Type Thermocouple EGT Probe (Fahrenheit/12V) . It takes a K thermocouple and reads in one degree F increments. It was off several degrees and needed calibration. See the next posting.

In the center of the photo is the main power switch. One pole is for the main heating element, the other is for everything else.

Below the power switch is the PID temperature controller, also purchased through eBay for about $35 (shipped from the US, not China). It is a 120 volt MYPIN TA4. This controller was chosen because it reads out in F, has a wide array of control functions, and there is a good deal of user feedback and technical information available on-line (Google MYPIN TA4 for more). This controller is designed to drive a "solid state relay." Instead, I have it powering a mechanical relay to switch the resistor network which controls the current to the main heating element. Naturally the SSR output and relay were incompatible so I added a voltage divider and current limiter to drive a transistor which in turn switched the 12 volt relay coil.

Except for the power switch all connections were soldered for reliability.

Including the enclosure, the component parts totaled out around $100. The enclosure turned out to be a bit crowded (photo during initial testing).



One interesting event during initial testing: I bought five 2P2T (on-off-on) toggle switches, made in China, of course. One failed out of the box. Another failed after about 20-30 toggles. Opening up the switch indicated that the internal, spring-loaded cam which drives the spring contact was designed waaaaaaay too small, cracked and fell apart almost immediately. I bet the spares are just as bad. Trial and Error, Who Can You Trust?

Thermocouples

Both the meat temperature display and the temp controller take K type thermocouples mounted in stainless steel probes with threaded mountings. These also are from eBay, shipped from China, for about $5 each. I've tried three different positions for the thermocouple that measures the smoker's internal temperature and am still trying to find a sweet spot. Presently the probe is mounted low on the top of the BBQ section so it lifts out of the way then working with food on the grill or the rotisserie:




On the outside the thermocouple has a spring strain relief. I mounted the thermocouple wire in a length of split-loom tubing for protection and reduce the working back and forth that will eventually make the thermocouple wire break --always a compromise.



The thermocouple wire in the split-loom tubing is routed along the side of the smoker with wire clamps screwed into the side of the drum.



AC Cords and Plugs

The back of the controller has the corresponding AC outlets. The on on the top right is for the rotisserie, with the low voltage jack for the fan below. The top left is for the aux heating element. The one in the center is for the main heating element. The two wires in split loom tubing are for the meat thermocouple probe and the inside temperature probe for the temp controller. Both the aux heating element and the main heating element cords go to the bottom half of the unit and there are two hooks to keep them tidy (in another photo below)



Note on the fan. I live in the Phoenix area and the temps in summer can be a bit warm: ( July 2014) so in addition to the heat generated inside the control box plus the heat from the drum's surfaces, there are high ambient temps. But I measured the difference between the inlet air and outlet air of the box and there is only a couple degrees difference. So thermal stress is likely to be mostly related to ambient. The thin metal piece to the right of the control box photo above is a heat shield. I still might put a small piece of aluminum to isolate the fan from the air close to the drum surface.

Power Cord

I have yet to decide where the smoker will go in the covered patio area so I used a 12 foot, 12 gauge power cord. It is too long and messy so I adapted a conduit clamp as a hook and used two big pop rivets to hold it in place. It will be cut down to fit when I decide on the final location.

9

PART 9 -- PROBE TEMPERATURE CALIBRATION

So lets say I want to slow roast a ten pound prime rib and add maybe a handful of Mesquite to give it a trace of smoke, then use the propane torch to give it a char. Sounds good. But at $10.99/lb I'd better get it right the first time. North of a hundred bucks? Yikes!! With spending this type of dough you don't want shoe leather.

Thermocouples

The "K" thermocouples used for the meat temperature meter and the temperature controller can be used over a very wide range -330 °F to +2460 °F. Given the nature of the less expensive circuits used in low cost electronics and the wide range, chances are there will be errors, sometimes big errors, around the narrow band of temperatures used for smoking.

Quick check

Water boils around 212 deg F, so it is pretty close to the operating range of a smoker. More accurately, water boils at a specific temp depending on air pressure (altitude and barometric pressure). So if you know your altitude and barometric pressure, stick a thermocouple probe into some boiling water, you can, eventually, calculate if the reading is accurate. But I used a handy calculator just for this. http://www.csgnetwork.com/h2oboilcalc.html . (If the link doesn't work try Google.) To find altitude I Googled the word "altitude" plus my zip code and Wikipedia returned the altitude. To find the current barometric pressure I checked my local weather conditions and forecast.

Before calibration the temp display or controller needs to fully warm up. The MYPIN controller took about 10-15 minutes for the temp display to stabilize. Not a good sign I might add.

I used a small sauce pan with a air-vent type cover to heat the water over the stove. I let it boil away for ten minutes or so for the probe to temp equalize throughout. Then I tried to keep the probe in the middle of the pan and adjust the heat so the water just began to boil.



On the MYPIN controller there is a temperature offset adjustment available from one of the menus. So I pressed a couple buttons and the temp error was corrected. I took about 3 degrees off the MYPIN reading to get it to match the water temp. By the way, in the past I've adjusted mechanical dial thermometers by carefully rotating the bezel a bit so the scale matches up to the needle.

Meat probe temperature calibration

Other than boiling water the second common temp reference is ice. This is a bit tricky and not too close to the mid range of meat temps so I've sort of avoided using it. The range most important for the meat temp measurement is between 140 and 180 deg. There isn't much available as a reference standard to check in this range. I've avoided buying a "certified" or "traceable" temp reference since they are not cheap and STILL require re-calibration over time. So I looked for a reliable alternative.

Here is what I found:. A precision "immersion type" bulb thermometer bought off eBay for about $25 delivered. This was originally used in a laboratory chemical distillation test instrument and is made to precision standards. Although marked in 1/2 deg C, it converts to about one deg F. These don't go out of calibration very often. The scale is from about 30 deg F to about 230 deg F. For calibration purposes I chose 160 deg F, about 71 deg C.



For an easy calibration I simply brought the pan up to about 170 deg F on the stove then simply waited for the water temp to drop. At 160 on the thermometer I noted the meter -- off several degrees. Pretty easy.



There is one last consideration for reading the meat temp. When the thermocouple temp probe is inside the smoker a small amount of the high air temp is absorbed by the stainless parts outside the meat. This adds slightly to the internal temp of the probe so it might be off another degree or two.

To compensate for this I brought the kitchen oven up to the typical 250 degrees, more or less, using a store bought oven temp gauge. Then I preheated the water in the pan to about 150 or so, inserted the thermocouple probe into the pan, routed the wires through the over door and then waited for the water temp to increase a bit. After a while I then quickly removed the pan from the oven, carefully inserted the bulb thermometer into the water, waited until the temp stabilized on the thermometer, then took a reading off the meter. This was repeated until the bulb thermometer hit 160. I then compared this to the meter to figure how far it was off.

Adjusting

Before adjusting, my meat temp meter read about 4 degrees too high. Probably good enough but I wanted better. I opened the meter enclosure and there were two adjusting potentiometers (pots) on the circuit board. The board was not marked as to function. Usually one is for "gain" and the other is for "offset" (Google is your friend). I took a black marker and put a tiny dot on the adjusting screw slot, and a corresponding dot on the body of the potentiometer. Then got some paper so I could write down the position and number of turns on the pot. This way I could always get the turns back to the original setting if I **really** goofed up.

On my meter one pot did not have any effect when turned one whole turn so I returned it to it's original position. On the other pot about a half turn changed the display by one digit. So when I took the pan out of the oven and when the bulb thermometer read exactly 160 deg, I turned the pot on the meter's circuit board to match. Then I ran the temp up and down a bit and checked again to make sure is is repeatable. It was as good as it was going to get.

Final Check

So after things are calibrated that old bulb thermometer has one more trick. After smoking a good hunk of meat and when the temp probe is about to be removed I plan on digging out the bulb and quickly remove the probe and insert the bulb thermometer to compare the two. An easy check.

NOTE: Most older precision thermometers contain mercury. Handle with care.

10

PART 10 -- GENERAL CONSTRUCTION NOTES

Here are some tips and general info so you don't have to dig through all the posts and photos. This project took several months working weekends and nights. Don't underestimate the cost, time, skills, and effort required.

First a warning. Read and follow all tool manufacturer's instructions and warnings. This includes eye and face protection for sanding, grinding, drilling welding, handling chemicals and all the rest. Second, use an approved respirator when subject to dust and chemical fumes. Third, use hearing protection when cutting metal. Although it seems tolerable at the time, it will ruin your hearing (experience speaking). And forth, keep your tools sharp and in good condition. Don't attempt construction of the electronics portion of this project unless you are fully qualified -- there are fatal voltages present that can kill you and burn your house down.

1) Drawings: I used a drawing board, t-square, rule, and triangle to make scale drawings, side views, and cross sections, on how things would fit before starting any work. It took a lot of erasing to get it right.

2) Initial cleaning. I used oven cleaner to clean the insides of the used Brinkmann tube and the BBQ top. Much better for handling.

3) Fasteners:. Due to the frequent mechanical expansion and contraction due to heating and cooling, all nuts, bolts, and screws will eventually come loose. I used welding and pop rivets instead.

4) Welding: There is quite a bit of welding on this project. Much of the welding was done in stages. If you are lucky you have the equipment or know a friend or neighbor who has the equipment and can batch the welding into several sessions. This requires planning. If you have to use a commercial welding shop think real hard about how to schedule things and how much it will cost. The metal is thin so it requires some skill. I decided on "stitch" welding at somewhat long distance intervals between welds and then fill the gaps with sealant (see below). Also, the BBQ top will likely be finished in porcelain- steel. It needs to be ground down to the bare steel to make a good weld. Plan on using a **lot"" of clamps and wood spacers to hold things together for welding. In some cases I pop riveted and screwed things in place for later welding. Due to the curved surfaces holding things by hand can be a challenge.

5) Metal cutting: I used a saber saw, hack saw, tin snips, and a 4" sander-grinder. It is a challenge to make the cuts because of the curved surfaces. The blades have to be sharp for this to work. Don't be cheap - buy a pack of good fine teeth metal cutting blades and change them out at the first hint that they are getting dull. I went through five saber saw blades. Also plan on using a variety of files to smooth edges and make final adjustments.

6) Measuring and marking: I used a dial caliper, a good steel ruler, another flexible ruler, a metal yard stick, and tape measure. Also a compass came in handy. For some fixed measurements I made a compass from a wood stick and a couple nails, previously discussed. I applied masking tape to the area to be marked so there was a good marking surface and used a Sharpie Ultra Fine Point as a marker. I also taped the marker on to the compass to make larger circles, arcs, and lines where a flat ruler wouldn't work.

7) Drum: Much discussions on this forum already. Mine originally contained an FDA approved food additive and because of the thick insulation and sealing I didn't bother burning-out the inside coating - it would never get close to overheating and fuming. Mine had dents and dings so body filler (Bondo) was used to fill the defects before priming then painting. I should have marked the spots with a marker, then taken photos. When the paint is stripped off the dents and dings are more difficult to see -- I missed a couple. The original paint on the exterior of the drum was removed using regular chemical paint stripper. Remember to use gloves, long sleeves, face shield, and good ventilation -- very nasty stuff. For the strip process I used a disposable plastic drop cloth with wood spacers to get the drum off the ground. After application, I waited, then remove the softened paint with paper towels, then rinsed with plain water using a spray bottle and more paper towels. A final wash with detergent and a rinse with a hose got the remaining residue off. Under the paint was some sort of varnish which would not dissolve. It was not removed, just lightly sanded with 350 grit wet-dry, then primed.

8) Drum brackets: putting brackets on a curved surface is a challenge. See the section on the rotisserie for more info.

9) Sealant: I used several tubes of Surebond SB-188 High Temperature Silicone Sealant (black and clear) which is advertised to hold up to 500 def F continuous. It is a little more expensive than caulk from your big box home center which is rated up to 400 deg F. See Google for availability in your area.

10) Paint: I have a compressor and all the paint gear but the area is small enough to use spray cans. If you are not proficient in painting a little practice will help. I got the surface spotless-clean (used gloves for handling), a degreaser (from auto paint supply stores), masked, primed with auto type sanding primer, degreased again, etc. I like Rustolium auto engine enamel in the spray can, and regular semi-gloss in quarts for a finish coat. I used automotive primer which is easily wet sanded with 360 grit for a smooth finish.

11) Insulation: I used regular R13 Kraft Faced Roll 15 in. x 32 ft from the big box home improvement store. The paper backing was stripped off and then pulled apart to fit the thickness in layers.

12) Brinkmann parts: The used Brinkmann lava rock pan had a few rusted out pin-holes so I had to buy a new one. Look closely to find defects.

13) Sheet metal fabrication: I had a small local shop which specializes in air conditioning duct work do the custom sheet metal shearing and forming. They need detailed sketches to do the work. Don't count on it being precise so allow for largish tolerances. For the sealing rings a plasma cutter does a great job -- ask if the shop can do this.

14) Temp Control: The temp control box for this project is over-the-top. Other options are a lot easier and cheaper

15) I waited two weeks for the the paint and sealant to fully cure then thoroughly cleaned all internal surfaces with a rough cleaning pad using Simple Green, then rinsed and dried. After a couple days to make sure things dried out, I brought the temp up to 350 degrees for four hours, then repeated the next day. I did not see any smoke and did not detect any chemical smell. You might have different results and it might take longer to "cure" the smoker.