DIY 2x6 AOF air tight construction questions

[tuolumne]

Hello, I would appreciate some advice from those who have tried some of these things before. I would like to build a 2x6 in the next few years, and I am trying to nail down the design now so that I can start scrounging materials. First, my engineer inclinations push me towards as much boiling efficiency as possible. I intend to build the arch and buy the pans; 2x4 drop flue sap pan and 2x2 syrup pan. How deep are typical flues on this size pan so I can plann accordingly? I have drawn up some sketches, wherein the two rails below the flue would be tube steel to combine structure and aof supply into one piece of steel. Now I have read some concern about tube steel warping more than angles. How concerned shoud I be? I had also intended to use TS for the door, since it is easiest for me to work with and already on hand. I had thought that this would provide additional torsional strength that will resist warping.

Regarding the AOF, I had planned to drill holes in the tube. Would it be worth the effort (and dimensional change to arch) to cover the tubes with blankent and brick and poke through nozzles? Will mild steel nozzles hold up? I do have a stick/TIG welder, but have never attempted to work with TIG or with stainless. If the aof supply is separate from the arch structure it could be SS pipe, drilled and tapped for ss nipples that would avoid welding those.

Is there a reason besides economics that most arches I've seen incorporate very thin plate for walls and floor. The cost of thicker plate in the grand scheme of things would be fairly small. How thick should the face plate be to maintain a solid seal with the door? I had thought to add a steel angle frame that mates with the door for additional stiffness.

For primary air I had intended to cast a refractory block with ice cream cone nozzles. Is this worth the effort over drilling mild steel angles? The grates in the large leader arch I've boiled on are cast iron, but they span a much greater distance. Would mild angles hold up? What percentage of the forced air wants to be diverted to the aof nozzles versus the ash pit and under fire air?

I'll post some sketchup renderings once the design evolves a bit for further insight. Thanks for the help, Chad

[moeh1]

I asked about the icecream cone idea too recently, the feedback was that drilled firebricks were just as good, cheaper and easier.

[RileySugarbush]

I suggest you buy or decide on your pans first so you can make sure your arch is right. My drop flues are 7" deep, but it varies, as does the spacing and width of the group of flues.

Hollow structural steel could work fine, but you have to be careful that one side is not significantly hotter than the other or it will distort. So cover with ceramic blanket or always have air flowing through it.

My home built arch is all relatively thing wall angle steel. 1 1/4 x 1/8. Skinned with 16 gage steel and painted. Holding up fine. AOF is an added in manifold of 2x2 steel tube. 16 nozzles of 1/2" stainless hydraulic tubing. You can weld stainless to carbon steel with MIG, and the stainless holds up better to the heat of your arch. Not a problem if the air is always on.

Insulate the firebox with blanket under brick. In the flue area, just blanket works fine. Also, the upper 6" of the firebox doesn't need brick. My brick is just dry fit and held in with friction and it works fine. If you minimize the amount of brick, the arch eats up and shuts down faster, with less heat capacity.


Inverted 2x2x1/4" angles ( v down ) work great as a grate! 1/4 to 3/8 gaps between them provide all the room air flow you could want for AUF.

[tuolumne]

I'm sure you're right about purchasing the pans...we're reluctant to spend any extra right now. Are you talking about SS hose or fittings for nozzles? Why are the grate angles inverted, and how are they held from tipping? Is your AUF supplied from the same blower as the AOF?

[RileySugarbush]

Two blowers, one my old low press 210cfm under fire blower and I added a high pressure over fire blower. Controlled separately with separate inlet dampers. The nozzles are hydraulic tubing which is solid wall 304 stainless, 0.4 inch ID and 0.5" OD. These are welded with directly into the sq steel tubing along the sides of my firebox and in the back they are welded to carbon steel pipe extensions to reach over the firebrick. This was a retrofit to my existing arch. The air exits the nozzles at 80mph.

Both can be seen here before I installed it into my arch. Once installed, I packed some ceramic blanket around them so that only the ends are exposed to the heat.

http://www.youtube.com/watch?v=LhiEyMjVx5g&context=C3033e7fADOEgsToPDskKn9viiJv79HFa1JHeZX8qg

The angle are welded with an angle steel on each end, with the right spacing and with angles open up so they file with ash, insulating them from the coals. The hold up very well.

[tuolumne]

...with angles open up so they file with ash, insulating them from the coals.
While not very scientific, this is the sort of information that is so helpful.

Why do you dampen inlet air versus outflowing air? Why either of those options versus a variable speed control? I would like to cut back on current draw and noise if I do not need full power at times.

[wiam]

Why do you dampen inlet air versus outflowing air? Why either of those options versus a variable speed control? I would like to cut back on current draw and noise if I do not need full power at times.


Some motors will not last long on a dimmer. It burns them out. I have been told that a damper on the inlet side of a squirrel cage blower will lower the amp draw but I have not put a meter on one.

[dGarnier]

welding stainless is not so easy...you need to somehow keep O2 away from the weld until it cools. On the weld side the argon will shield it for you, but the back side of the weld is not shielded. Also you should know what alloy your welding so you can use the right alloy filler and SS tig rod is $$$

[tuolumne]

OK, separate supply for AOF and AUF, but both coming from the rear so I can run them through a divided preheater. What CFM to I need for AOF? I am assuming that 100-300 is good for the AUF on a 2x6. If this is a low pressure blower, what size tube will I need for the AUF? I would like to use rectangular or square steel tubing as the rails on either side, running AUF up one side and AOF on the other.

[xulgiy]

I did it all with square tubing, but I'm not sure I had enough pressure for mine. I ripped it all out and stuck a furnace blower in the back of my 2x5 oil drum rig. Drilled a bunch of 3/8 holes in the ramp through the fire brick and 3/4 holes in the brick I used as grates...I now get it ripping and boil 18gph +. My next unit will be more efficient!..:lol:

5590

[Waynehere]

Here is a thought I was having. I want to install AOF in my 2x6. I was thinking of putting the 2" tubing outside the arch and then run some 1/2" nozzles through the frame of the arch toward the fire. Any comments on this thought?

[Flat Lander Sugaring]

Here is a thought I was having. I want to install AOF in my 2x6. I was thinking of putting the 2" tubing outside the arch and then run some 1/2" nozzles through the frame of the arch toward the fire. Any comments on this thought?
i believe some one did that with stainless tubing on here it seemed to work< the only thing is if you pre heat the AOF and tubing on outside you will want to insulate it so no one gets burned.
Some one said if you keep air flowing through the exposed tubing on inside it might not warp or wont, well I used steel tubing for like an oil fill tubes on a oil tank probably 1/4 thick maybe a little more and they warped.
Definitely insulating the tubing is key to longevity inside the fire box.
I'm going to start my 2x6 arch build this coming week, iv been like ADK been planing this for a few years im finally going to pull the trigger

[Waynehere]

Two blowers, one my old low press 210cfm under fire blower and I added a high pressure over fire blower. Controlled separately with separate inlet dampers. The nozzles are hydraulic tubing which is solid wall 304 stainless, 0.4 inch ID and 0.5" OD. These are welded with directly into the sq steel tubing along the sides of my firebox and in the back they are welded to carbon steel pipe extensions to reach over the firebrick. This was a retrofit to my existing arch. The air exits the nozzles at 80mph.

Both can be seen here before I installed it into my arch. Once installed, I packed some ceramic blanket around them so that only the ends are exposed to the heat.

http://www.youtube.com/watch?v=LhiEyMjVx5g&context=C3033e7fADOEgsToPDskKn9viiJv79HFa1JHeZX8qg

The angle are welded with an angle steel on each end, with the right spacing and with angles open up so they file with ash, insulating them from the coals. The hold up very well.

So Riley, how did your AOF work out for you? I would like to do something similiar... :)