The new DIY stainless fermenter

Yup I'm building a stainless conical fermenter from a keg. No special tools needed, I'm farming out the welding but we will get to that. First calculate the cone, I like to worked out the math so the arc was exactly 180 degrees and let the cone angle fall where it may. I cut it out with one of my favorite tools, a 4-1/2 inch angle grinder. The small radius was very tricky to cut and not perfect, but it must be cut out or you can't bend the cone.

So the internet would tell you that you need a slip roller to roll sheet metal and even with one, a cone is difficult, but lets make our own. Take two pieces or round bar or tubing, I used 1/2 inch because thats what I had, but 1.5 or 2 would probably be better. Grind a two small flats on each end of each bar 180 degrees apart. Now place on the bench a washer, one bar, another washer, the other bar and clamp. The thickness of the middle washer should give you a gap between the bars slightly larger than thickness of the material.

Next draw a bunch of radial lines on the cone (you want them facing up) and gradually work the sheet metal into a cone.

I guess that it for the cone, took me about an hour and a half. I cut the bottom off a keg, and cut a hole for a 4 inch tri clamp in the top and had it welded by someone who claimed they could do sanitary welding, but could not. So right now it is off at the second welder to have some things fixed. I should get it back end of next week, more pictures to follow.

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Wow! Great handiwork.

Definitely a very interesting thread. Without a video, it's tough for me to fill in some of the gaps. What gauge SS is that, and how do you "work" it? Do you just hand bend the metal close to the two bars? If you grab the sheet metal too far from the bars, does it bend in the wrong place? I imagine you just bend a little at a time, and keep working around the circle, but it looks like it'd be hard to get a hammer in there? Is the purpose of the radial lines just to ensure that all bends are in the same "plane"? What issues did you have with the welds, and how did you know they weren't good enough?

I guess for me, sometimes a picture "requires a thousand words"?

Looking forward to seeing how this turns out.

COOL! subscribed.

Subscribed as well. Would love to see more of the process of setting up the roller.

Also, What gauge stainless are you using?


Thanks

The lines are so you can make all the bends radial out for the center. There was no hammering involved, just bending the the metal gradually pushing up against the top bar. I'm not sure what guage sheet metal I would say 18 if I had to guess I may be able to measure it later

Very nice, subscribed.

sub:rockin:

So I found three business cards of welders at alro on the board where local businesses can advertise. One guy was on vacation, one was a mobile welder and was supposed to come and blew off the appointment twice, so I went to the third guy. He claimed he could do sanitary welding and the results are below. Not even close. When we discussed the fitting of the cone, he asked me to make it a little short so it would fit inside the keg. In hindsight, I should have left the cone long, then welded it around until almost to the end then trimmed it to get a perfect fit. So I cut out the piece you see and am getting it patched. I have cleaned up the rest of the welds with a wire brush and flap wheel so I wouldn't call them sanitary, but I will scrub them with a brush before each use. It is at welded number two and should be back Friday, more pics to follow

Wow, those welds look awful. Where is the cone though? I can't tell what the picture is.

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Looks like fun! I'm interested to see the finished product. Subscribed

The welder didn't purge the vessel. It really isn't surprising though, argon is expensive. Did he just weld a patch over the vertical seam?

fork said:

worked out the math so the arc was exactly 180 degrees and let the cone angle fall where it may.

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Cool project. Here's the math for anyone interested in building a cone from sheet metal:

https://www.homebrewtalk.com/f51/ne...nical-fermenter-94621/index2.html#post2609950

Yes he welded an inch and a half wide patch instead of making a patch to fill in the gap. As I said we should have left it a little long, then trimmer to fit. The cone isn't shown in the last pics just the patch that I cut out to be repaired. He certainly didn't purge it even though I specifically told him it needed to be sanitary welding and the first thing on my list of directions was all welds must be sanitary. But you live and learn. I knew I ran the risk of finding a ****ty welder when doing a small job like this. At least I will know for the second one, ill probably make another and maybe try and sell the better one to recoop some costs.

Bacteria will flourish in those welds

Yeah I agree but if they are mechanically cleaned (scrubbed) and acid sanitized before each use, I think it will be ok. I'm not convinced, though so we will see.

Nice job! Bummer about those welds.

fork said:

Yeah I agree but if they are mechanically cleaned (scrubbed) and acid sanitized before each use, I think it will be ok. I'm not convinced, though so we will see.

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The welder I went to had a device he called a "magic wand" it was a high voltage thing with a material on the end. He poured acid on the weld and ran this thing over it and it cleaned the weld up so well it was almost a sanitary weld. I took a fiber wheel to it and it wiped it clean.

My welds looked almost like those but now you can't even see them.

pics... pics...

yeah, sugaring on the back side of stainless welds is a common issue for people who only do structural work. I had toyed with the idea of making a conical. The combination of converting an existing keg along with the 2 clamp bending method might make it simple enough to give it a shot.

Any plan to try a single vessel brew? ferment in conical, rack off yeast, force carbonate and serve all out of the same keg? Call me lazy but only having to clean on brew day and after blowing a keg would be nice :rockin:

fork said:

Yeah I agree but if they are mechanically cleaned (scrubbed) and acid sanitized before each use, I think it will be ok. I'm not convinced, though so we will see.

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I bet you'll be ok. Do you think the acid will have any ill effects on the stainless or are you talking about star-san?

Monster Mash said:

The welder I went to had a device he called a "magic wand" it was a high voltage thing with a material on the end. He poured acid on the weld and ran this thing over it and it cleaned the weld up so well it was almost a sanitary weld. I took a fiber wheel to it and it wiped it clean.

My welds looked almost like those but now you can't even see them.

Click to expand...

Kind of like this?

Wow I have never seen a weld cleaner like that, very cool. As far as the acid it is no problem for the stainless. I plan on passivating the welds before first use using citric acid. Passivation uses acid to bind to or disolve free iron particles and other contaminates on the surface that could be introduced be welding grinding machining scratching etc. Also peracetic (acid). Is a common brewery sanitizer.

We use nitric/phos blend when any new stainless welding is performed at work.

Acid cleaning the weld zone is good, but back-side purge will eliminate the nasty oxidation.. The back side of the weld will oxidize (sugar) during welding, and even after ground, and polished clean, it will rust after being placed in service (the nickel is precipitated out of the base metal). This is actually pretty easy to overcome. A second remote shielding gas hose, some aluminum foil, and masking tape works well for a make-shift back-side shield.
Go miller... the power of blue

So I got the fermentor back from the second welder today. He purged the whole tank and the welds he did look great. Next I have to passivate it. Anyone know of any brick and mortar stores to find citric acid? Amazon has 5 lbs for 20$ I need about 3 lbs to get the right concentration to cover the welds but I'd rather not spend 20 dollars to dump it down the drain after an hour.

Make a thick paste of Bar Keeps Friend and scrub the entire inside and outside with it. That will passivate it.

Got this thing all done, put in a fridge, and filled it up this weekend. 10 gallons of hefeweizen. i still need to get the 4 inch triclamp lid configured for a thermowell and blowoff tube.

How are the legs bolted on?

There are stainless nuts welded to the outside of the keg, then the legs, which are made of unit-strut, are just bolted on.

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Awesome!!

Very neat. I tig weld some when I can see (not the best). I am wanting a conical fermenter so bad here. I have one batch in a carboy, another 11 gallon in a plastic food drum.

I was thinking of a pin-or-ball keg thou instead of a 1/2 keg.

Neat idea on the pipe "gradual" increment bender, a "gocart" tire in a press (or ewheel frame) over a rounded lower roller will also "bend" the metal into a arc conforming to the lower roller. I learned that on Metalmeet.com from some good guys. (metalshapers)

I have a small slip roll here. The rollers need cleaning, it imprints the rusty surface onto the stainless.

Great work man.
I am currently shooting for something similar to this using a keg.
I have an experienced welder and the keg.
I have the metal needed for legs and the cone shape.
I am still deciding on what to do to the top hole.

I REALLY! like your 4" tri clamp idea.
I just looked and I can get a 6" - 8" one as well just more money, but I think it will be worth it for me to be able to reach in with ease for cleaning.

I have a few questions for you all.

What size to make the bottom Tri Clamp Ferrule ?
Also what size hole would the bottom of the cone need to be to weld in the bottom tri clamp ferrule?

Then on the side I see you put yours pretty high up, do you have a cane on the inside of the keg you can swivel?
I was thinking of putting that part on the cone witha cane. but not sure.

Even though my welder is experienced I am thinking of taking some stainless to him and see how it looks when I say it has to be sanitary. lol

got any pics of the inside of the welds and if you had to grind them yourself after the welding was done? Did you need to use any acid to clean them of that Sugar stuff that sometimes forms.?

Any more pics of the top hole all setup with air lock and stuff?
1 last thing if you could message me and let me know how much it costs to have a shop do it right? lol thanks