Resurrected post. This was originally published on my old blog on April 23, 2014. I've fixed some broken links and made some minor updates to fix grammar and flow problems.
I needed another metalworking project for this Spring. For the past several years, I have tapped several maple trees in my yard and made maple syrup. After a few years of boiling the sap in pots on a turkey fryer burner, I decided I needed something a little bit bigger. And I decided that something wood-fired would be the most appropriate, and the most fun to build.
After looking online for ideas it seemed like the easiest plan would be to convert an old55-gallon drum to a wood-burning evaporator. With a used olive-oil drum bought on Craigslist, a couple of cheap steam table pans, a barrel stove kit, some black iron pipe for a frame, an oxy-acetylene cutting torch, grinder, and some tools, I slapped one together in a day. Finding used 55-gallon drums for sale is easy. Finding used 55-gallon drums for sale that didn’t contain toxic chemicals or flammable liquids is much harder. Luckily here in Massachusetts the Catania Oils Company imports and bottles olive and other oils under the Spagnoli, Marconi, and other brand names, so a used olive oil drum was cheap and easy to get.
In maple-syrup speak, the big pan you use to evaporate the water from sap to turn it into syrup is called, simply enough, an evaporator. But the burner is called an “arch.” (Don’t believe me? Look here for an example.) Presumably named after the shape that early wood-fired evaporators took, if you search the Internet for “maple syrup arch” you’ll come up with a host of plans and descriptions. So, technically, I made a wood-fired arch out of an olive oil barrel to hold a steam table pan evaporator. No matter the terms though – here’s what it looks like when done:
The design has a few notable features:
- The black iron pipe frame and barrel can be separated to make movement and storage easier.
- Two pans allow the sap to be warmed in the upper pan before being moved to the lower pan.
- The chimney is completely removable.
- It has a main evaporator pan and a warming pan.
Materials & Tools
- Used steel drum. This one contained olive oil and I bought it for $10 on Craigslist.
- 1/2″ ID black iron pipe. I used about 20 feet of it. Cost about $50 at Lowe’s.
- A barrel stove kit for the door and chimney collar. ($40 – $60. Got mine on Amazon.com).
- One full-size and one half-size steam-table pans. I bought mine new for about $30 with shipping from an online restaurant supply company. But you might find cheaper at a local auction or on EBay.
Total cost: about $130.
Most of this project was accomplished with the basic metal-working tools I already owned. The pipe base was cut on a cheap chopsaw, fitted with an angle grinder, and MIG welded together. The barrel was cut with my oxy-acetylene torch (using a fine #000 tip). A lot of grinding was done with a 4 1/2″ Harbor Freight angle grinder.
- Build a frame from steel pipe.
- Fit the barrel.
- Cut holes for the steam table pans.
- Add a chimney and stove door.
- Fire that mutha’ up!
Build a Frame
First, build the base. A very simple welded frame that was done using only a MIG welder and a few magnetic welding squares. I used 1/2″ iron pipe from Lowe’s. [Note: for version 2 I would use much heavier pipe or tubing. This frame has survived 6 years perfectly fine, but it does flex which can be disconcerting when playing with a drum full of fire topped with a few gallons of boiling liquid!]
Fit the Barrel
I sized the frame so the barrel would rest on its two ribs, and the top and bottom lip would overhang just 1/2″.
Cut the Holes
My intention was to have a main evaporator pan and a warming pan. I mounted each of the pans between the barrel ribs to preserve strength. For the main pan, I wanted it sunk in as far as it would go to move it closer to the fire. I basically cut two “flaps” in the top of the barrel and bent them upward (like swinging doors). Then I trimmed them down until the steam table pan rested on the front barrel lip and the flaps on each side helped hold it up.
Add the Stove Parts
Follow the directions that came with your kit.
Overall the whole thing was fun to build and worked well enough. One thing that proved tougher than I expected was getting the fire close enough to the bottom of the pans t really get a good boil going. I ultimately ended up adding a couple of half concrete blocks to the barrel to elevate the fire. But the whole system did work faster than the old turkey fryer.
If you are at all handy with metal I encourage you to try and make one of these.