Drop flue for small flat pan

[berkshires]

I have a small old sheet-metal woodburning stove I've modified to make an evaporator. I've fitted it with full-size steam tray table pans. The back gets a pretty good boil, the front more of a simmer.

Looks like this:
1474314744

I'm thinking about how to make the back pan more of a drop flue pan, rather than flat-bottomed. Unfortunately I can't find anything this small (and shaped correctly) to fit on my stove. So I'm thinking about how to modify my own pans.

I read this thread on drop tubes: http://mapletrader.com/community/showthread.php?6647-Adding-fins-to-bottom-of-flat-pan-(-)&highlight=custom+pan. It seems like a pretty big project. I'm wondering if there isn't an easier method.

One thing I was thinking about was having one of the custom machine shops fabricate a corrugated bottom. I could then just cut out the bottom of one of my pans and solder it in place. I made a little model of what I have in mind:

1474514746

So I'd cut a chunk of the bottom out of the back pan, insert the new piece, and then solder it in place. I'm thinking I'd want the channels to be a few inches deep, but wide enough that I could still easily clean it out. And the whole thing would be around 10 inches by 14 inches.

So I guess the heart of the question is - am I crazy? I have not worked with sheet metal much, so I don't know if it's feasible to get that drop-in piece made for a reasonable amount of $$. Is stainless too hard to bend and solder/weld, such that making the drop-in piece would not be easy even for someone who knows what they're doing? I don't want to spend much, so if it's a huge hassle to make, it's probably out of my budget.

GO

[acafro]

I'd say unless you're pretty familiar with welding or soldering stainless you're in for a huge project.

I weld mild steel quite frequently and I wouldn't even try to weld stainless.

Each grade of stainless requires different approaches to welding it. And from what I understand food grade stainless is pretty difficult if you don't have the correct equipment.

I've also never been able to bend stainless cleanly without a brake. Nor have I figured out how to solder it.

My honest opinion is save your money and invest in one made by someone who knows what they are doing.

You can probably find someone to custom build you a pan to fit your set up. Lots of manufactures out there.

But if you're hell bent on modyfying your pan I'd have the custom shop make the modification for you.



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[madmapler]

My first year, my brother and I modified a pan with drop tubes. It's pretty easy to do if you have any experience soldering. Use silver solder on stainless. You drill the holes in the bottom and flare the copper pipes. It definitely improved the boil. The more tubes the better. If you lay it out it probably wouldn't cost much to have a pro solder it. I still have it and could post pics later if you want. It's a tin pan, not stainless.

[maple flats]

I've soldered SS, first time was with a torch (poor, messy results, but it didn't leak). Then I asked a master sheet metal worker (a friend, now deceased) and he said I needed to use soldering irons and to use a product called sal ammoniac to tin the iron after filing it totally clean. Then I had a liquid flux for SS and I used silver solder. It worked well. I was repairing an old SS kettle which I later sold. After practicing on 2 pieces of SS I got to where I could make a truly neat solder joint, then I applied the patch to the bottom of the pot I was fixing.
I was using 316 SS, that's the only type I tried, but I think steam table pans are 316SS, check to verify.
You may also want to get it professionally welded.
I had one end of one of my SS syrup pans separate from a partition a couple of years ago. I contacted the pan Mfgr and they said to either bring it back and they'd fix it or to take it to a welding shop and they'd pay the bill. Because of the distance to the mfgr I went to a welding shop that does SS. They only charged $30 and the pan mfgr sent a check to me promptly in full.

[RileySugarbush]

Copper drop tubes are probably way easier to solder and they work very well for a simple home made drop flue system. There are several discussions on how to do it if you dig around.

[berkshires]

Thanks everyone for the responses!


I'd say unless you're pretty familiar with welding or soldering stainless you're in for a huge project.

I weld mild steel quite frequently and I wouldn't even try to weld stainless.

Well then we're on the same page. I have no plan to try to weld anything. There are companies that weld or solder stainless all the time, that people here use and recommend. Companies like: http://stainlesssteelcreations.net/48inx24inx7i.html, http://nwstainless.wixsite.com/northwoods-stainless,or A&A metals (no website).

My question was whether my design would be too hard for them, and too pricey. You say you have lots of experience welding mild steel. Based on your experience, would companies like these have a tough time fabricating a piece like this?


My honest opinion is save your money and invest in one made by someone who knows what they are doing.

LOL, yes, that's exactly what I'm suggesting. Then I would just need to solder in the fabricated piece they made. While I only have experience soldering copper, I think after practicing on some scrap stainless I have lying around, I should be able to solder in one piece, right?

GO

[berkshires]

My first year, my brother and I modified a pan with drop tubes. It's pretty easy to do if you have any experience soldering. Use silver solder on stainless. You drill the holes in the bottom and flare the copper pipes. It definitely improved the boil. The more tubes the better. If you lay it out it probably wouldn't cost much to have a pro solder it. I still have it and could post pics later if you want. It's a tin pan, not stainless.

Sure, it would be cool to see pics of your pan! What did you use for the copper drop tubes? But you really think it would be easier to fabricate a dozen drop tubes, cut the right size holes for all of them, and solder them all in to a steel pan, than it would to just cut one hole, and solder in one custom-made welded piece?

GO

[berkshires]

You may also want to get it professionally welded.

Do you mean if I get this piece fabricated, I should get it welded rather than soldered? Or you mean I should get it welded in, rather than soldering it in myself?

Regarding soldering SS - the flat pan I have is 300 series SS, but they don't specify exactly what type. Do you think it matters much for soldering?

I found the following website with tips for soldering SS. These steps look about right to you? http://www.artmetal.com/blog/raspero/2013/04/here_is_an_effective_method_for_tinning_hard_to_so lder_metals

GO

[berkshires]

Copper drop tubes are probably way easier to solder and they work very well for a simple home made drop flue system. There are several discussions on how to do it if you dig around.

I've only found one discussion of it. I linked it in my first post on this thread. If you have any other discussions, I'd be interested in reading them too.

I know you made one of these (you talked about it in the thread I referenced). Do you have any pics? And I'll ask you the same question I asked madmapler: you really think it would be easier to fabricate a dozen drop tubes, cut the right size holes for all of them, and solder them all in to a steel pan, than it would to just cut one hole, and solder in one custom-made welded piece?

Or are you suggesting that the piece I'm talking about is too hard to fabricate, and no-one will be able to do it without costing an arm and a leg?

GO

[RileySugarbush]

I built several for my steam table pans on my block arch. I'll find some photos. Bill Warner ( warners point on here) built one with 120 tubes in a flat pan. Easiest to cut holes with a greenly punch, or a step drill will work if you are careful.

I built my first one with pipes and soldered caps on the bottom. Later ones I used water hammer arresters so I didn't need to solder on the caps.

Once your get the touch, and use the right flux, it is easy to solder copper to the stainless. Multiple, small solder joints, where you can back up and fix mistakes, are easier than one big solder joint.

Bet with your idea of soldering the long joints of your design is likely to be very difficult.

[RileySugarbush]

Link to drop tube pan fabrication photos:

https://www.dropbox.com/sh/uekyxmghj6hcaxr/AACnxyG0GAOEKSi_M6AqKNDaa?dl=0

[Wanabe1972]

Are you are looking for just an improvement in your GPh ? If you are only tapping a dozens or so taps there are improvements you could do to your arch that you could do. Open up the width of the top of your stove so fire hits more than 2/3 the pans. You could add a little blower, the first rig i boiled on was just an old metal fan in front of the ash door. Do you have grates to get the fire up off the floor and air passing through? If you widen the top out you could brick the thing and put some heat to the pans. The drop tube pans are pretty neat and I've soldered SS before. Im not sure of the grade of these steam pans but I thought they soldered really easy if you have a good clean tight joint. Jeff

[berkshires]

Link to drop tube pan fabrication photos:

https://www.dropbox.com/sh/uekyxmghj6hcaxr/AACnxyG0GAOEKSi_M6AqKNDaa?dl=0

Very cool, thanks!

GO

[madmapler]

14752 This is how we did it. It was an experiment that worked well and we probably would have added more and gone deeper if we didn't get an evaporator the next year. As Riley said, it's simple to do and it costs very little.

[berkshires]

Are you are looking for just an improvement in your GPh ? If you are only tapping a dozens or so taps there are improvements you could do to your arch that you could do. Open up the width of the top of your stove so fire hits more than 2/3 the pans.

LOL. That's exactly what I just spent this weekend doing. I'm kicking myself for not having taken photos. :( But yeah, I basically created "wings" on the arch so that the part of the pans that were sticking off the sides are now over fire instead. I plan to boil on my flat pans this season on this new setup, and I'm hoping my modifications will give me at least a 20-30% boost in boil rate. The modifications I'm talking about doing to the back pan would be for next season (2018). I know that's a long time from now, but I'd like to do my homework on this rather than flying by the seat of my pants (which is what I did last year).


You could add a little blower, the first rig i boiled on was just an old metal fan in front of the ash door. Do you have grates to get the fire up off the floor and air passing through?
Nope. Wood just sits on the bottom of the stove. I'll have to look up these grates, I'm not familiar with them. They sound like a good idea, though. It would have to be just the right sized mesh, I'd think, so the ash could fall through, without all the coals falling through too.

GO