Hi Folks,
I've gotten so much help from everyone here! Thought I'd pass along how I've built a small hobby size evaporator, in case it might be helpful to someone in the future.
By the way, as you read through this, be aware that I don't know how to weld. Oh, and I'm cheap. So all of this probably cost me well under $100. Okay, so here we go...
I started off with an ancient small, cheap, sheet metal woodburning stove. It had been retired for some time, so I didn't feel bad about chopping it up.
To give you a sense of scale, it's only around 13" wide. And the top is not long enough for even one steam tray pan to fit on it.
I first tried boiling sap in a pot on top.
stove_original.jpg
You can guess how well that went (not!)
So next I cut a chunk out of the top of the stove so I could fit a steam tray pan into it. I had to fit the pan sideways to have room in front of the smokestack.
mod1_boil.jpgmod1_boil_side.jpg
Now I could at least start boiling sap. But I wanted to fit a second steam tray pan on the "arch". But the stovepipe was in the way. I needed the stovepipe to come out the back of the stove instead of the top.
So next I cut out most of the rest of the top. This includes the part where the stovepipe came out. I also cut a chunk out of the back of the stove, and put a new flue in (using sheet metal screws and furnace cement).
Here's the new duct/flue connector: https://www.lowes.com/pd/IMPERIAL-6-...t-Boot/3134369
duct_flue.jpg
And here's how it looked after the work was complete:
evaporator_mod2.jpg
That worked fine for the rest of the season. After I got my systems dialed, I was able to boil off two gallons per hour. But there were still some big issues.
Problems:
1 - Sides of pans sticking off the sides of arch. Not only was that wasted square inches on the bottom of the pan, but the cold air under the part of the pan not over the stove wicked away heat from the sap and the pan. Not good.
2 - No grate means the fire burns inefficiently.
3 - To get enough air to the fire, I had to open the door a crack. This made the fire cooler. Especially since the air was coming in right under the front pan!
4 - The fire doesn't hit the bottom of the pans well. Unless I really worked to arrange the logs right, nearly all the heat was in the middle/back, and very little under the front pan.
5 - Needed a way to pre-warm sap.
In my next post, I'll talk about what I did to solve these problems.