homemade airtight door

[tuckermtn]

I have a friend who is making me an airtight front door for my 2.5 x 8. plan is to have a blower from under the arch blow toward the front and up through some grates - but wondering if I should bother to have air injection all over the place like I've seen on other rigs, or can I just keep it simple and have the air go through the grates? looking for simple and relatively reliable -

[Gary R]

I'm no expert, but here's my 2 cents. Adding air over is a good thing. All of the more efficient commercial arches use it. It makes sense to burn up all the flue gases in the firebox. Both air methods you mentioned would be reliable. I added air over to mine. It is not simple. It requires plenum's, nozzles and brick cutting. I would suggest adding the air under the grate this year. It's usually simple. I would think about adding air over after this season. Gives you more time to figure it out.

[Paddymountain]

I have a 2.5x8 that I made new airtight doors for ,and also have made it
forced air on top of the grates. What I did was run a 2x4 box beam down each side of the evaporator and out through the back . There I mounted a
squirrel cage fan on each side. I have a 1/4 inch hole drilled every 4 inches on the box beam . The box beams take the place of the row of firebrick at grate level. I just continued from there up with firebrick. I ran a test boil in November and it looks like it's going to work well. I agree air over fire is the way to go,it burns up all the gases ,I have hardly any smoke coming from the stack.

[smitty76]

I agree with Gary R. I have a 2x6 smallbros that I built an air over draft for it and it is not simple. I would also use an under draft til the season is over to construct an over draft. I have been using mine for 2 yrs now and it does make a difference.

[StewieSugar]

but wondering if I should bother to have air injection all over the place like I've seen on other rigs ... looking for simple and relatively reliable -

There are two reasons for injecting air after/over the fire box - to burn off any remaining gasses and to create turbulence. If we focus on the turbulence aspect, I think there is something simple you can try.

If you look down the flue pan when it's on the arch, most setups are designed to have nice and smooth channels for the flue gasses to pass through - starting at the fire box and going to the stack. In general, these gasses flow evenly and straight along the flues.

While their moving along, the gasses heat up the sap, which cools down the gasses. Near the front of the flues, the gasses are all equally hot. However, near the end of the flues by the stack, the gasses end up being hotter near the bottom (away from the flues) and cooler near the top (inside the flues), which reduces the efficiency of heat transfer. This is because the gasses up near the top of the flues have sap on all sides, which cools the gasses down faster than the gasses along the bottom of the flue where there is sap at just the tips of the flues.

What you want is the oppossite - you want the hot gasses up inside the flues and the cooler gasses down below. The way to achieve this is with turbulence.

By injecting air after the fire box, you'll create some level of turbulence, which is a good thing. However, it sounds like folks say that it can be a challenge do this.

As an alternative, though, a trick we often use in the electronics world is to add baffels along the flues. Baffels can be just about anything that breaks up the nice, smooth, even channels along the flues. You simply want to add some physical obstacles along the flues such that the gasses get pushed around and get mixed up.

I have a simple flat pan setup, so I cannot offer great advice. However, leveraging my experience in the electronics world, I expect some fire brick would do the trick. Place a few small pieces of fire brick (or other heat-proof material) on the bottom of your arch - about 1/3rd and 2/3rd down the flue area. The taller the better, but make sure they don't make contact with your flue pan or severely obstruct air flow.

As the gasses flow along the flues, they'll hit this fire brick, get pushed around, and get all mixed up. The result will push some of the hotter air upwards, which will increase your efficiency.

[twobears1224]

STEWIE:like a boulder in a river.i like your thoughts and i,am going to do the firebrick thing in my little fuel drum arch.

delbert

[jrthe3]

do you guys have any pic of how your airtight doors are made

[darkmachine]

Pics of the door would be great, we are going to have one fabricated for our arch as well, i've been looking all over for different pictures of doors.

[tuckermtn]

Ours is in process- I'll get some picts up when its done...

[Bucket Head]

I have pics of my air tight door and air tight ash pit door in the photobucket album.

They have worked fine for two years now.

Steve

[Bucket Head]

Sorry, I lied. I do not have those pics up on the photobucket. I will try to post them soon.

Steve

[Bucket Head]

Guy's,

The pictures of my air tight doors are in the "Modifications" album on Photobucket. Sorry for any confusion.

Steve

[twobears1224]

thanks for the pic,s.. anybody else got pic,s of there airtight door??

delbert

[Pete S]

Where do you get the "wick' or seal that serves to seal at the pan bottom?

Thanks!

[maple flats]

I used to be in the outdoor furnace business. The door gasket looked like that. Try contacting a furnace dealer or contractor. In 1999 it sold for about $2 a foot, don't know the size, likely double that now but other sizes are sure to be available too. What we used was some non asbestos woven fabric with a rope of ceramic insulation inside.

[twobears1224]

you should find it at most any hardware store.my local store has it on rolls.

delbert

[Bucket Head]

Is it a True Value chain hardware? I used to get mine from a store that was affiliated with True Value. Try them first if you have one near. The store near me was recently sold and is now affiliated with another chain and they do not stock the material in bulk/roll anymore, which is of no help.

Steve

[twobears1224]

yes it is buckethead.

delbert