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I previously worked on Virtual Reality and other hardware at Valve.  I currently work at Google[x].

Prior to starting at Valve, I built computer peripherals such as keyboards, mice, and joysticks that were designed to be used inside MRI machines.  My company, Mag Design and Engineering, sold these devices directly to researchers at academic institutions who used them to publish scientific papers in peer-reviewed journals.

After work, I spend time on many different types of projects that usually involve circuit design, machining, material selection, and general fabrication/hacking.  My favorite place to be is my home workshop.

ben dot krasnow at gmail

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Wednesday, September 16, 2009

DIY stainless steel conical beer fermenter Pt.1

Please search my blog for "fermenter" to find all of the posts regarding this project.

I am building a stainless steel tank that will eventually become a very unique beer-brewing vessel. My idea is to make a tank such that the entire process can take place without ever having to transfer the beer from one tank to another. This vessel will boil the wort, chill the wort, provide a temperature-controlled fermentation period, allow the trub to be removed, and provide a secondary fermentation. This tank was designed with my experience in brewing about 30 5-gallon batches of beer using the extract process. I don't have much inspiration to do all-grain brewing yet.

Having said all of that, I am also learning to TIG weld, and this project will provide many different welding setups -- all in stainless steel.


I bought a stainless steel conical hopper, model TMS14514 from
http://www.toledometalspinning.com/products/hoppers/priceList.asp

Toledo Metal Spinning sent the item very quickly, and I am impressed with the quality. The edges are extremely flat, and the overall finish and dimensional tolerances are great.

It holds 6.4 gallons total, so a 5 gallon batch of beer should fit pretty well. The hopper is a continuous piece with no hole in the bottom. I will be mounting a butterfly valve at the apex, so I need to cut the tip off to match the diameter of the valve housing. I knew before I ordered the hopper that I would only need to slice off about 1/8" off the end.

I used a slitting saw in my milling machine to do the job. This left me with a super flat clean edge. 70 RPM, 0.5 inches per minute, however the feed rate is measured at center of the saw, and I programmed a G2 circular path. This means the feed at the cutting point is probably lower. I had problems with chatter, thus necessitating this low feed rate.

This is one half of the butterfly valve housing after I welded it to the cone. The blue hose is silicone, and is carrying argon to the backside of the weld. In addition to the foil on top, I have made a dam with aluminum foil and tape inside the neck of the cone to trap the argon in the space around the weld.

Since the first weld went so well, I decided to weld on the inside of the fitting as well. Ultimately, this was not a great idea, but the weld itself went well. I used a copper tube with a line of tiny holes drilled in it to disperse backing argon to the outside of the cone. I had a fair bit of room inside the valve fitting for the TIG torch and filler rod.

I used a die grinder to smooth out the interior weld. After putting it together, it leaked! I had used the die grinder too much, and made the metal thin enough where a tiny pinhole in the weld made it all the way through the metal. I re-welded the outside bead, and then realized that I should have just made a couple of passes on the exterior to build up material. Then I could die-grind away the inside until I ground into the weld bead. No need to weld the interior. This would provide a nice smooth surface inside the tank and ensure there was enough material to keep it structurally sound.


It looks good now.


I originally started to cut this hole with a high-quality hole-saw in a corded drill. After a few seconds, I realized it was probably not going to work. Stainless is just such a tough metal, cutting tools just bounce off it. I used a free-hand plasma cutter to make the hole.

I made another aluminum foil/tape dam around the wall on the interior.


The weld went pretty well.



This time, I learned how to do it. Instead of welding on the inside, I just built up a nice bead, then used the die-grinder on the interior until I ground into the bead. It's nice and smooth on the inside.

7 comments:

  1. Ben - You are living my dream. I asked a local welder of stainless if he could make something like this and he agreed but suggested I look at the 'fermenator'. The 'fermenator' looks great but they recommend not carbonating in it due to the pressure. I'm thinking about modifying the 'ferminator' to handle the pressure and would appreciate seeing your results. I'd be happy to share some grain recipes that might provide inspiration.

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  2. Hello, thanks for the comment. I agree that carbonating inside the fermentor would be a challenge. I usually carbonate at 10-15 psi, and the lid is 14" in diameter (surface area of about 22 in^2). At 15 psi, the lid will have 330 lbs of force pushing it off the fermentor. This is not too much stress for metal supports, but the amount of force will deform the lid and cause small leaks at the edges unless there is a really secure mounting system. I'm sure it's possible, as the tank itself and valves should easily hold 15 psi. Let me know if you go forward with your plans.

    My idea is to do the boil in the stainless conical tank, ferment it, then transfer to a keg for carbonation. I'll really be interested to see if boiling the wort in the fermentor works, as this would save many steps, and also sanitize everything by heat.

    You can search my blog for "conical" to see all of my fermentor related posts.

    I'd be interested to hear some of your favorite recipes, but so far, I am still an extract brewer and haven't tried all-grain yet.

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  3. I was thinking about getting 2 conical hoppers, probably need to beef up the flanges, and bolt them together at the flanges. The TMS121114 has a section of cylinder and cone, the cylinder resisting deformity at the flange, and volume of 6.7 gal in each segment so a total of 13.4 gal. Big enough for a 10 gal batch. My concern is that the wall of the hopper is pretty thin and I'm wondering if I should double wall it somehow. It looks like TMS will do a lot of the custom work for this.

    I would rather boil in a separate pot, with a perforated stainless plate at the bottom to strain grain, and a spigot below that to run the wort through the counter-current wort chiller into the fermenter/carbonator. That way the sterile wort never gets exposed to the air, only sterile equipment. This assumes a grain recipe.

    So I need a valve at the bottom to drain off yeast and dispense beer. A valve at the top to introduce wort and yeast and attach a bubbler. After the primary fermentation is done, I could introduce a little more sterile wort for the secondary fermentation, then attach a pressure relief valve. I'd need a second valve at the top to connect CO2 so it doesn't lose pressure as it emptys.
    Hopefully it all fits in a fridge.

    I started thinking about this process when my brother was in the Army in Germany and said that many of the breweries that he visited had unhopped beer. To make that you need very sterile conditions and although I have done it at home, the results have been spotty. Then I sat down at a bar for a Sierra Nevada Pale Ale on tap, and the keg was new. The bartender threw away the first glass because it was very yeasty. After that he started saving them for me so that I could use it for a starter. The grain brewing started after visiting a home-brew supply shop and smelling the grains available. The Papazian book has some good recipes, but once you start to think in terms of taste and smell, you will make up your own recipes. One thing that I do that I haven't seen elsewhere is with my approach to hops. Freeze dried vacuum packed are great. I use 5-10 ozs for a 5 gallon batch. I boil for about 30 seconds, then pull it out. You get a great herbal hoppy flavor and just a little bitter. Also a great foamy head.

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  4. The hopper from TMS is very sturdy. You could definitely weld two together and fill with it with 10 gallons if you wanted. The flanges are especially thick and very flat on the model that I bought.

    So far, I have been satisfied with partial-boil extract brewing, but I may try all-grain later.

    Good luck!

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  5. Looks Awesome! I wish I had the equipment and know how to do that also.

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  6. Hey Ben - I'm up and running. Is there a way that I can send you a picture? I got the 2 conical hoppers and placed spigots at either end and about 4" up from each end, then bolted the flanges together. I cooked my grains and then drained and sparged through a counter-current wort chiller after placing my yeast culture in the hoppers. After 4 days it started bubbling so I'll drain the yeast off the bottom every 3 days and then when it stops bubbling I'll pour in a pint of sterile malt and seal it. I'll need to stop by the welding supply for a CO2 tank to keep it charged while I drink. Next time I'll get a bigger boil pot, and find a bar with Sierra Nevada Pale Ale on tap and get the first pint of the kep for my yeast starter.

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  7. William, I'm glad to hear you have finished your project. You can email me a picture: ben at magconcept dot com. Happy brewing!

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