We did a practice run a while back, before getting bogged down with the permits. One lesson learned was that it was difficult to get to a boil and maintain a boil with 20+ gallons of liquid. I thought about my time camping using the MSR whisper lite and MSR heat exchanger. The heat exchanger works like a champ – for a camp stove. So we decided to give it a whirl and make an “analogous” contraption for the brew setup. Well, this turns out to look like a ghetto homebrew project, but it works like a charm and is going to save us tons of time, propane, and heart aches (by creating some other ones when we use it!) Details and pics after the break.
The heat exchanger concept was based on MSR’s version which is a conductive type metal “folded” into an accordion shape and wraps around the pot. It captures the heat around the pot, the conductive metal heats up and then transfers the heat back into the pot. I also wanted to construct mine so it went believe the brew pot to capture any heat from the flame that dispersed horizontally. The trick was getting the accordion folded.
Step one: Materials. Really you only need a sheet of metal (copper would be ideal, but it’s $$$$, so I settled on aluminum, especially since i didn’t know if this project would work). Also, an appropriate sized metal brake and/or other bending materials, tin snips (or equivalent), hose clamps (x3 depending on the vertical size), and pop rivet equipment (rivets, gun, drill, etc.).
Note: I ordered this from Mcmaster Carr, who adds on freight after they ship the item without authorization from the customer. After getting this “unauthorized” charge of $75 for shipping this, I felt slightly taken advantage of.
Step 2: Make the “accordion.” It took us a few moments to wrap our heads around the first few bends, but after that it is just repetitions… tedious repetitions. The key is to make the runs perpendicular to the brew pot as short as possible. Also, the length between those should be relatively short, but there is a trade off between convenience and “short as possible.” The shorter they are, the more difficult the bending, the more bending needing to be done, and the more material you need.
We decided on about 3/4″ for the first type of bend, and about 2.5″ for the second. This was due to convenience. 2.5 is the minimum bend on the brake we used, and 3/4″ was the dimension of another piece of metal. Also, we used a 30″ brake, so we cut the aluminum down to size (partially seen in first pic). Many thanks to Taso and Molly for the use of their brake and to Taso for helping with the project and hanging out until the wee hours of the morning.
Note (to the non-metal experts like me): I tried doing the bends several ways and only one way worked: Using a very sharp metal corner for the folds. Obviously, this is what a brake does, which worked like a charm. For the other folds, we still used the same piece from the brake, but manually sandwiched the sheet between that piece and our other guide using clamps. Then we used a rubber mallet to pound pound pound. Apologies to the neighbors as the time passed from 9 to 10 to 11:00 PM.
Step 3: Cut to size, and cut to fit. Pretty much says it all. Cut it so it wraps nearly all of the way around (minus 2-5 inches) and cut out areas for your valves.
Step 4. Add the clamps. Fir this I used hose clamps. They are intended for this exact purpose, except here, they are tightening the exchanger around the kettle, not a hose around a barb. Instead of getting clamps that go all the way around the kettle, I got some that were about 12 inches long and cut them in half. Next we attached each side of the hose clamp onto each side of the exchanger using pop rivets.
Step 5: Clamp the exchanger around the kettle.
Here is the exchanger on the pot. Again, this looks a little surly, but it’s functional! Last time it took 3 hours to get to a boil, never getting to a rolling boil while this time it got there as we were collecting the runoff and it happily boiled over from a vigorous boil. happily = the boil. Not so happily = brewers and cleaners.