275 tank rig, Exhaust Pipe for AOF

[Indiana-Jones]

I'm building a 275 tank rig and getting close to installing the plumbing for the blower. Has anyone used auto-exhaust pipe? I'm thinking it would be something that I could form myself and weld in 3/8 nipples to direct the air. Would 2 1/2 inch be big enough? I have 4 1/2 inches between the drop flues and the outside wall of the tank. Thinking that I could lay them the down the inside corners or should they be up under the pan rails? In the fire box, I have some 3/8" rock wool that I could use to protect the pipes. Looks like gray felt.

At this point, I'm thinking that a Vermiculite cement mix is going on the ramp. I could protect the pipe a little with a thin layer.

I have searched the Maple Trader, read and searched some more. Lots of great ideas, I thank the guys that I have copied from. When you see the pictures you will know who your are.:mrgreen:

[smokeyamber]

I used 2 1/2 pipe on the blower setup in my barrel rig, worked great. I only was doing forced air not AOF, but don't see an issue. Previous comments on AOF mentioned to make sure you are always running the air through the pipes to protect them from the heat. Like your build so far, I may copy YOUR work :evil:

[Indiana-Jones]

Thanks for the information. I'm going to make some more trips to the salvage yard to see what I can come up with. I have not found a blower yet, or got my insulation plan set. I'm starting to panic, things here need to get done and I'm running out of weekends. I may need some time off work. I'm south enough to maybe tap in February.

Thanks again.

[C.Wilcox]

The build is looking great. If you haven't welded it permanently into place I would highly recommend you make that vertical back wall into an angled ramp. I have almost the exact same setup as what you're building and I think the back half of my pan should be boiling better. When I look down in the pan I can see a definite line where the vertical wall comes up. In front of it the boil is awesome. Behind it the boil is lazy. I think if more of the bottom of the pan was directly exposed to the fire the whole thing would boil better. I'm seriously considering taking the bricks out of mine and changing it this winter if I can find the time. Just a thought for your consideration.

[Indiana-Jones]

Do you think that a two stage ramp would help? I could cut the wall loose at the top, trim back the flat area and have the top edge hit the back pan about halfway back?
The wall now is 10 inches leaned back, bottom to top, it is just hard to see in the photo. It hits the back pan 12" back on a 24"X 36".

Thanks for the input.

[C.Wilcox]

I just noticed your signature and it looks like I may have spoken too soon. If you're running a drop flue pan my comments don't really apply. I mistakenly assumed you were using a flat pan. With a drop flue I think you'll probably have a serious boil with the way you currently have it set up.

[Indiana-Jones]

Hello,

This is what is came up with and I don't think that it is very good. There is some air out of the pipes, but not what I had hoped for. Not sure if I don't have the wrong type of fan, or too many right angle turns. The fan moves a lot of air when she not restricted. 320 CFM.

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Mounted the fan blowing up into a box that covers the ends of 2 inch pipe. For a test I cut a plastic jug in half tall ways and made a scoop directly to one of the pipes and didn't see any improvement. Maybe I'm expecting to much. Any suggestions??

[maple flats]

A squirrel cage blower will not do much. You need high pressure, but not high volume. The rest of your design looks like a good start. You should also run air across the front, aimed rearward, and across the back of the firebox, aimed forward. These are to create the most turbulence. I think you should consider joining the two, right at the rear of the firebox. Be sure to plan so that can be insulated too. Try to find a high pressure blower. Instead of centrifical force moving the air, it will have paddles throwing the air. With your welding skills you might be able to make one. Mine only has 4 paddles, just be careful to balance it.

[Indiana-Jones]

I guess I need to start a mad search for a proper blower.
Dave, did you make your blower? Do you have pictures? Are the blowers that are in high efficiency furnace's to blow up the PVC chimney high pressure?
I have a lot to get done before the season starts and here in central Indiana it starts early. I might forget the AOF for this year and insulate/brick the thing.

Thanks for the help, lord knows I need it.

First Edit. Is this what I'm looking for? https://www.surpluscenter.com/item.asp?item=16-1436&catname=electric

Second Edit. Would the blower box with the pipe end inside like I have work if I had the correct high pressure blower? Answer= NO. Did a test with a shop vac.

[xulgiy]

Looks great! I have a very similar setup. I piped mine from the outside up one side a made a manifold that blew down from all directions. I too had very little air. Sad to say... 10 hours of work later, I ripped it all out. What I did was put a false bottom in the fire box with diamond lath, and drilled 3/4" holes in my fire bricks for grates. I then drilled 1/2" holes in the fire bricks on the ramp at an angle to blow the air straight towards the door. Then I cut a hole in the back of the oil drum, and shoved an old furnace blower in the back. I get a ton of of air now with the whole back of the drum being a plenum, and she burns hot! I'm boiling 20GPH or better on 2x5 pans with no hood and with 4 1"x8"x24" drop flues.

[Indiana-Jones]

Hi, Xulgiy,
I can see the under the grate air idea in my minds eye, but the back wall, did you weld nipples to the wall to direct air through the holes in the bricks?

The only smart thing that I have done lately is trade some syrup for dumpster diving privileges at a heating and cooling contractor's shop.
Looks great! I have a very similar setup. I piped mine from the outside up one side a made a manifold that blew down from all directions. I too had very little air. Sad to say... 10 hours of work later, I ripped it all out. What I did was put a false bottom in the fire box with diamond lath, and drilled 3/4" holes in my fire bricks for grates. I then drilled 1/2" holes in the fire bricks on the ramp at an angle to blow the air straight towards the door. Then I cut a hole in the back of the oil drum, and shoved an old furnace blower in the back. I get a ton of of air now with the whole back of the drum being a plenum, and she burns hot! I'm boiling 20GPH or better on 2x5 pans with no hood and with 4 1"x8"x24" drop flues.

[xulgiy]

No. I just drilled through the brick at a sharp angle so that the air blows straight at the door. I used a mason bit for the brick and then a metal bit to punch into the back. I was over thinking and over fabricating everything, then just figured I'd try the drilling. I think that I still could tweak it a bit, but for a $300.00 total investment, 20 gph ain't too bad.

[maple flats]

I guess I need to start a mad search for a proper blower.
Dave, did you make your blower? Do you have pictures? Are the blowers that are in high efficiency furnace's to blow up the PVC chimney high pressure?
I have a lot to get done before the season starts and here in central Indiana it starts early. I might forget the AOF for this year and insulate/brick the thing.

Thanks for the help, lord knows I need it.

First Edit. Is this what I'm looking for? https://www.surpluscenter.com/item.asp?item=16-1436&catname=electric

Second Edit. Would the blower box with the pipe end inside like I have work if I had the correct high pressure blower? Answer= NO. Did a test with a shop vac.

I did not make my blower, it came from a factory that closed, it was about 100 yrs old, 3 phase motor, I had to replace the motor and make a motor mount, it was free, the blower not the motor, I had the motor. I will get some pictures and email them to you, might not be for a few days however. A shop vac is still not high pressure, just high volume. What you need is the turbulence not the volume. With high pressure you will feel air out the nozzles. The angles are not an issue, just the air supply. Your air tube design is somewhat similar to mine , you just need to get a good blower. I don't know but I doubt the exhaust blower is high pressure, most likely just a squirrel cage or a simple blade design.

[maple flats]

My air distrubution is thru a 4" pvc pipe. The blower sets outdoors, under my head tank platform. Then I used a fernco to connect to 4" pvc. When that gets to the floor, under the evaporator, it y's into 2- 3" pvc with a ball valve in each to regulate the flow (valves also free from closed factory dumpster). One 3" hooks to a 4" 24 ga stove pipe that goes under the the fire. This pipe has 3 rows of 1/4" holes drilled to fan the air under the fire, in operation this valve is about 1/4 open. The second connects to a 2" square tube that enters the slope and connects to a 2" manifold going in both directions to the sides, then forward and then to the door opening. I have 1/4" black pipe nipples welded to the 2" box tube 1 each side of the door facing to the rear, one every 6" facing to opposite side and one every 6" across the back facing forward. Each of these nozzles faces down 15 degrees into the fire. The valve for this part is typically 1/2 to 2/3 open after the fire is full burn. To light I close the top to about 25% and open the bottom to about 50%. Then with the firebox 1/2 full, no kindling nor paper, I aim a 500,000 BTU weed burner torch in at about 1/2 flame. In about 30 seconds it is well lit and I close the doors. The original draft door is fully closed all of the time. As the fire gets to full speed I start opening the top air and reducing the bottom air. I am not a welder but had a good friend do it. When he gave the manifold to me I thought the point where the tube entering the slope joins the u shape that there should be a flare to the tube but that is good without a flare. I get good air blowing out each nozzle topside, I never checked flow under but it works extremely well. If you had access to the motor unit on an old insulation blower it would be high pressure. My old one (still not for sale) turned at 16,500 rpm. It was not a paddle design but the rpm made up for that. A high pressure blower will be loud so you will want a sound hood to direct the sound away from the sugarhouse.

[Indiana-Jones]

Dumpster diving I found a couple of draft inducer fans from high efficiency furnaces. They turn better than 3000 RPM and seem to do the job. They have a 2 inch output that works well with the rigid conduit that I have used for the pipes. This weekend I got most of my fab work complete and did a test blow. I can hear the air whistling out of the nozzles, so I think that this is what I'm going to have this year. I have not thought much about air under the grates. I have a leaf blower that I could use to get the fire started. I'm going to keep my eyes open for rig improvement equipment for next year.
I real hope the the guys at Sunrise Metal Shop get my pans built soon. I have a three day weekend next week and plan to insulate and brick.

Then it is on to sap collection and tapping prep.

I have heard a insulation blower before, they are a very powerful device.

Thanks for the replies