44L Round-Bottom Flask Fermenter Project

44L Round-bottom boiling flask fermenter project

Beermaking the complicated way
You can reach me at fred.niell@gmail.com

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flask used as a vacuum chamber in an early science fair project
Figure 1
Here the flask is shown as it was used in my first real science fair project in 1992. The flask was evacuated to maybe 5-10Torr and backfilled with He. In the center of the flask is an electrode which was connected to a tesla coil. The resulting discharge was beautiful. I won first place in my city science fair!

flask balanced about 1 inch above its center of mass
Figure 2
Flask shown in its gimbal-mount frame. Since the flask is suspended from axles 1" above the center of mass, the flask self-rights in the frame. The frame is made of 80/20 extrustions, and the hardware was less than $200. The MDF was left over from another project.

flask rotated just a bit above its center of mass
Figure 3
The flask is tilted a bit to show the function of the axle bolts. When released, the flask simply rotates (oscillates) back and forth settling at vertical after maybe 4-5 rotations. The bronze bushings are remarkably low friction.

taking apart 8-bottle wine fridgetaking apart 8-bottle wine fridge
taking apart 8-bottle wine fridgetaking apart 8-bottle wine fridge
Figure 6
Since any brewer worth his salt must have temperature contol over the fermentation process (especially if he wants to make any Lager or Pilsner type beers), I decided to add temperature control. I started with a Wine Cooler which was on sale locally. It has thermostatic control, and a nice little Peltier thermoelectric cooler with fans. Perfect! I dismantled it to salvage the power supply, cooler, etc.

Figure 8
Controller board, power supply mounted on the fermenter
Here's the wine chiller guts, mounted on the side of the fermenter. It's set to 65 degrees here, and maintains its original control range, 55F to 70F. It even still has the little light functionality. The light now illuminates the brewing beer.

Figure 10
After the first fermentation stage, washing out trub and dead yeast
Here's the pour after the first fermentation stage. The beer was racked (see figure 9, then transferred to a temporary vessel. The wide, round bottom of the boiling flask actuall performed perfectly for collecting the trub, and was extremely easy to rack. Keeping the racking cane above the level of crud was very easy. The white sudsy nature of the trub comes from me spraying water into the flask first to loosen the trub from the flask bottom. The sides were easily cleaned of any remaining hop residue with a quick spray down. Here's a quick video of the spraydown through the bottom view port.

The Flask
Back in maybe 1976 or so, lean manufacuring processes were being implemented across most industries. For the automotive industry it made a lot of sense, especially with the dawn of the Just-in-Time manufacturing craze. This was all prodded along by a shrinking economy and a number of influental books and magazine articles on manufacturing practices in the mid-to-late 70s. In the supply-and-demand dominated world of consumables sales for hospitals and scientific labs, this also made good sense. However, it was not always applied in the most expeditious or sensible manner. For example, Shering Plough required all chemistry labs to assign expiration dates to all materials and feed stocks, but a bottle of NaCl (simple table salt) has no explicit expiration date. Simliarly, American Hospital Supply Corp., began applying these techniques to their supply stream in order to reduce the amount of warehouse squarefootage required at any given time. All articles were assigned expiration dates, including things like glass vessels and flasks.

One day, my father (a salesman working at AHS) was for some reason visiting of the warehouses. He saw some of the warehouse workers tossing large boxes of glassware and flasks into the dumpster. One of the things they were disposing of was a cache of Pyrex 44L round-bottom boiling flasks. Of course, my father couldn't stand to see such a large, expensive piece of glass being tossed into the garbage just because it was "past its expiration date." So he rescued one. He had no idea what to do with it, but such a beautiful piece of glass didn't deserve such a terrible end. Presently, a 44L flask is a bit of an odd duck - not a standard size anymore. 22L flasks are made by a number of manufancturers, including Pyrex ones from Kimble-Chase. However, the closest I can find now is this 50L one from Wilmad for $871. Over the years, it has been host to a terrarium, an egg-nog dispenser, the vacuum flask in one of my science fair projects, and countless other odd jobs.

A similar flask from Wilmad-Labglass

Now what?
When my parents decided to move to an apartment close to me, it officially became my large, delicate, hard-to-store piece of glass. Luckily I have a similarly nerdy wife who allows such things in the house. So what does one do with a pyrex 44L round-bottom boiling flask? Good question. I decided it was time to use it as a fermenter for beer. And since I never settle for just any old simple project, I had to make it as complicated as possible. :)

The Fermenter
The fermenter consists of a cage made of 5/8" MDF panels, with appropriately-sized holes sawed into them to accept the neck and bottom of the flask. The top panel is cushioned with 1" vinyl tubing slit to make a sleeve around the inner perimeter of the neck hole. The two plates are fixed with 3/8" threaded rod at roughly 21" apart, with lockwashers and double nuts to fasten the plates. Then vertical members were added with the center of mass marked on them. 3/8" carriage bolts were fixed at 1" above the center of mass for the flask on each side, such that when suspended from the carriage bolts, the flask would self-right to vertical. A frame of 80/20 extrusion was made to suspend the flask. The carriage bolts act as axles, and bronze bushings were fitted to the axle-bolts to provide minimum friction to the rotation.

pouring out the cleaning solution
Figure 4
Showing the pouring action with the flask rotated. Little effort is required to tilt the flask to pour out the contents. Here we are cleaning out the flask and sanitizing it in preparation for its first fermentation experiment.

a better view of the pour
Figure 5
A little better view of the pouring action of the fermenter assembly.

The first batch

I decided to try and do a Pilsner for the first go. I mean, if you're going to go as far as building a fancy-pants fermentation vessel, you might as well go for the gold with the first batch, so to speak. I went over to Beer and Wine Hobby and picked up their Pilsner Urquell Clone kit. It's using Czech live culture yeast from White Labs, and a lighter malt - exactly what you'd expect in a Pilsner Urquell clone. The first 36hrs were done at room temp to get the yeast going, then dropped to 60F with the cooler.

At the end of 36 hrs of fermenting
Figure 7
At the end of 36hrs fermenting at room temp (65F) to get the yeast going. See the black rubber adapter at the neck of the flask. It is intended to adapt from 4" PCV to 2" PVC. Inside this fitting is a 2" to 1" reducer which accepts a rubber #7 stopper with a hole bored in it for the bubble lock.

Figure 9

Next came the temperature controller and the insulation. I used 1" "blueboard"-type High Density Extruded Polystyrene insulating board. Easy to cut, easy to work with. I simply cut pieces to fit with a utility knife and used "Good Stuff" expanding foam to seal up the seams and cracks. The temperature controller and cooler were mounted on scrap pieces of MDF and also sealed up with the foam. I suspect that I will add another layer of insulation, including the bottom next, however the ciller is getting the wort to the selected temperature within maybe 3-5 degrees per hour. Not too bad for a little chiller like this. In the photo on the top left the pump can be seen clearly. I have elected to use a pump and racking cane to transfer from primary to a temporary storage vessel while I clean the fermentation vessel. That way I can re-use the fermentation vessel for the secondary fermentation stage and clearing stage. The pump I chose is a simple self-priming diaphragm pump, capable of priming from dry for a few feet, and has an automatic pressure switch (Jabsco Par-Max 1. It was on sale at West Marine.

-Fred Niell

Design, text, programming copyright 7/2013 Fred Niell