Project

Sanke Hood Vent

When I looked to get back into brewing several years ago I bought a set of three Sanke kegs intending to build a three-vessel system. They sat for a while waiting on a stand. But along came a two-burner, three-vessel, turnkey system from a guy getting out of the hobby. He had three keggles and also two extra Corny kegs that I picked up in the deal. I started out on propane with that system but then converted the keggles to electric heat. I thought about tinkering around and assembling a gas system with the leftover kegs but somewhere along the way I decided I could make a vent hood out of two them. At the time I was brewing in my driveway, which I didn’t mind so much, but this past winter I mentally committed that being in a temperature-controlled environment in the garage would be a big improvement.

Originally I was planning on strapping the keg pieces together with nuts and bolts. I did have metal shop back in eighth grade but I was never too proud of the coat rack I welded — so welding was off the table. However, I got to wondering about the different ways to attach metal plates together and that’s when I hit on rivets as an option. It turned out to be a fairly involved process but it had a certain steampunk appeal to it. So I studied about rivets, overlapping joints, strapped riveted joints, and last but not least, the double butt strap riveted joint. I had a plan! So let’s get started . . .

This is a lengthier project and will require some time. Don’t rush it. Whenever working with metal, it is always wise to recheck every measurement. Also never operate power tools under the influence of alcohol. Maybe you can pop some rivets while kicking a few back but be sure all the holes are pre-drilled. You may also need some tools you may not have but you may be able to bribe a friend with some brews.

Final note: Please make sure that any kegs that you modify were legally acquired. Just because you paid a deposit or bought them on a website like eBay, doesn’t make them legally yours.

Tools and Materials

  • (2) ½-BBL kegs
  • Rivets (stainless steel or aluminum)
  • Black automobile trim
  • (2) Sealed lights
  • ½-in. Flexible liquid-tight conduit ~4 ft. (1.2 m)
  • 14/2 (with ground) electrical wire
  • Ductwork, as needed
  • Inline fan (400+ cfm)
  • Exhaust vent w/damper
  • Cutting wheels (several)
  • Flap discs (coarse, medium, and fine)
  • Flat felt polishing disc (2)
  • 1-in. NPT stainless steel flange
  • 1-in. NPT tee
  • 1-in. NPT nipple, 4 in. (10 cm) in length
  • 1-in. x ¾-in. NPT reducer coupling
  • ½-in. flexible conduit barb
  • ½-in. x 1-in. bushing
  • Round weathertight junction box
  • Polishing compounds (black and green)
  • Reciprocating saw (metal and wood blades)
  • Angle grinder (4.5 in. or 11.4 cm minimum capacity)
  • Riveter
  • Step bit
  • Knockout punch (3⁄4-in. conduit)
  • Duct crimpers
  • Wire stripper
  • Clamps

1. Keg polishing

First thing I did was polish up the kegs. I picked the best keg for the left and right hood sides and the other keg for the middle and straps. Kegs were polished using an angle grinder, three different grit flap wheels, and flat felt polishing discs with black and green polishing compound. Hearing protection is a good idea and, of course, wear eye protection. Also wear gloves and long sleeves. l did leave off the final polish, green, until after riveting the pieces together (Step 3). I only used the coarse and medium flap wheels on the worst nicks and scratches and did a full pass with the fine one. After the flap discs, use the black metal polishing compound with a flat felt disc. When finished with the black compound, remove the residue from the keg with a rag and some mineral spirits. I cleaned the edges up with as best I could but hey, that’s what the trim will be for (Step 6).

2. Cutting the kegs

I used a cutting wheel (you will need several) on my angle grinder to cut the kegs. Make sure the kegs are de-pressurized, and then I recommend positioning the keg in a jig to secure while cutting, I wanted to have the handles at the top of each side so I marked the cut lines on the keg accordingly on the first keg. The hardest part with this sized cutting wheel was cutting the tubular sections at the top and bottom (the chimes), which are a bit thick. An 8-in. (20-cm) grinder would be helpful at these points.

The second keg was cut in half lengthwise like the first one but the top and bottom were not needed so those are cut off too. I found it easiest to leave several short uncut tabs along each cut. This left the keg intact until the very end at which point I cut the tabs. I ended up with four 2.25-in. (5.7-cm) wide straps cut from the flattest sections of the keg. I recommend extra care in laying out the cut lines so that the strap edges are parallel.

3. Riveting

The join is a double butt strap riveted joint. It’s a butt joint because the two plates being joined are butted up against each other in the same horizontal plane with two (double) straps.

Straps are recommended to be ½ the thickness of the joined plates, should you decide not to cut your straps from the second keg. The rivets used are blind (pop) rivets. Selecting the correct rivet size begins with rivet diameter, a common suggestion is 3x the thickest piece. How thick is a half-barrel? I discovered the thickness was 1.5 mm (0.059 in.), which leads to a rivet diameter of 4.5 mm (0.177 in.). Note here that rivet diameters are given in fractional inches or whole number millimeters with specific fixed lengths. Moving forward, the formula for rivet length is 1.5 x rivet diameter + sum of the plate thicknesses (grip). If we cut the straps from the keg, rivet length is then 10.125 mm (0.399”). Now we are in the ballpark for picking a suitably sized rivet! Pick your measuring system, calculate rivet diameter and length and then check the rivet specifications to see if your grip value falls in the range for that selectied rivet size. Using Imperial units, and the measured wall thickness of 0.059”, we need a rivet diameter of 0.177”, which is greater than a 5/32” rivet diameter so use the next size which is 3/16”, and the length needs to be at least 0.399” (10.125 mm). There is a 3/16” x 0.45” blind rivet (No. 64) that works for a grip range of 0.126-0.250”. Another item to note is that rivet diameters are nominal, which in this case means not exactly what they say. A nominal 3/16” rivet will use drill bit size #11 which is not a 3/16” bit, whereas a 5/32” rivet uses a #20 drill bit yet is not 5/32”. Given the importance of the rivet fit, I don’t recommend translating the drill bit number to fractional inches.

For rivet spacing, we need to define a row. A row is defined in relation to the pieces that the rivet will pass through, here the top and bottom straps and a plate (1/2 keg). For this project, I used two rows of rivets for the straps. One row passes through the top and bottom straps and the left half keg the other row through the same straps and the middle section. As constructed, the rivets are matched in pairs between the rows but we could zig zag the rivets instead as another option. There are two important rules for spacing the rivets needed here. The first is that rivets should be at a distance from any edge that measures from 2 times to no more than 4 times the rivet diameter. For a 3/16” diameter rivet, that means 3/8”-3/4” from the edge, which in this case is the edge of the strap or the plate. Thinking carefully, the minimum amount of strap width needed around the left side row of rivets for the joint is 3/8” + 3/8”= 3/4” and the same holds for the right row of rivets making the minimum strap width 1 ½”. Using similar reasoning, the maximum width is 4 x ¾”=3”. The widest strap that can be cut from the keg is roughly 2 ¼” and that was the size I used without cutting into the ribs for the strap. The second rule of thumb is that space between rivets in a row (pitch) should be between 3 and 12 times the rivet diameter. For a 3/16” rivet, the pitch is in the range of 9/16” and 2 ¼”. To apply the two rules, we need the length of the joint. Diameter of a ½ barrel keg is 16 1/8” making the circumference 50.66”. Half of that is 25.33” which is the distance along the round edge of the half keg and will also be the length (theoretical) of the straps. For simplicity, suppose we choose a 1-in. (2.5 cm) pitch. This would allow 25 + 1 = 26 total rivets in a row and leave 0.33 in. to split between the two ends. (The extra rivet is the one you start with.) That means the end rivets are 0.165” from the edge, too short. Let’s try a pitch of 1.5” instead. Divide 25.33” by 1.5” which is 16.887 therefore 16 + 1 = 17 rivets which would cover 24” leaving 1.33” for the end spacing and rivets could be started at 0.67” on either end. In actual implementation, measure the piece lengths and choose a suitable pitch. If a zig-zig pattern is used, the edge distance for at least one row will differ at the ends for at least one row.

Pick your two best straps for the tops and do make sure that the widths are the same on both the top and bottom pair. Mark the rivet pattern on the top straps (see image on the right) resulting from the selected rivet diameter and pitch. I chose to drill the top straps first, and later drilled the rest of the keg halves and bottom straps while clamped together (see image below). Use a center punch to start your holes. A small diameter pilot hole sped things up and cutting oil prevents premature wear on the bits.

After it was riveted together, I polished it for the last time with the green polishing compound.

4. Exhaust system

Recommendations were that 400 cubic feet per minutes (cfm) or 11.3 cubic meter per minutes (cmm) is the minimum hood exhaust speed that you should use for my sized system. My choice was a 6-in. (15-cm) Cloudline (model S6) inline fan. The duct run rises up into the bay between the floor joists and runs out through the band joist (see image to the right). I am proficient with a reciprocating saw and that is what I used to cut the band joist, which I did first.

Next, I marked the top center of the hood, held a short length of duct centered and upright over that point and traced the sides onto the hood top for the duct opening. I drilled holes inside the traced area that would fit a metal blade and then used the reciprocating saw to cut out the duct
opening. Control is key here, go slow. A hole saw could work here too (see image below). Foil tape was used on all connections except the fan, which included two large round clamps.

5. Electrical

The two brackets that support the hood also serve as electrical conduits. From the top down the pieces are 1-in. NPT stainless steel flange, 4-in. (10 cm) nipple, a tee, and a 1-in. x ¾-in. reducer coupling. There is a 1-in. x ½-in. bushing in the tee leading to a ½-in. barb flexible metal conduit fitting inserted into the flexible metal conduit that connects the two tees. The reducer coupling passes through the hood and a ¾-in. conduit nut holds the bracket to the hood.

I used a ¾-in. conduit knockout punch for the holes in the hood, which are located a quarter of the hood length from left and the right. The coupling screws into a round outdoor junction box. I drilled holes for the junction box in the back plate of the light. That makes the system sealed. I ran 14/2 Romex between the tees to the lights and out the top right flange. I added a small 2-in. x 3-in. (5-cm x 7.5-cm) metal junction box between the ceiling joists, which the flange covers. I added a switch to power on the light and the inline fan. Eventually, I will box out the duct with an access panel for the fan when I sheetrock. The lights were spray painted a metallic color matching the inside of the kegs. Each light has a Bluetooth/Wi-Fi color changing smart bulb.

6. Trim

The trim is an automotive-type trim. I took a ruler and measured all my cutting mistakes and found the largest one. Then I searched for a trim width that would cover it. These trims will sometimes just grip but I decided to use some multi-surface Gorilla Glue and it required clamping. The perimeter is long relative to the number of clamps I had so this took a few overnights. In retrospect, two long flat pieces of metal or wood may have worked with just a few clamps. A potentially useful option here would be to use an angled piece of trim mounted with perhaps a short rod connecting the two sides of the angle and going through the hood edge to act as a gutter to catch drips, a problem that sometimes pops up for me. Now that you’re done handling power tools and have installed your hood vent go ahead and pour yourself a homebrew. You earned it!

Issue: July-August 2022