Wood burning stove style reverse flow smoker.

[SouthamptonSmoker]

I am from Southampton in England and have been testing the water with smoking brisket, and have found this is something which I would like to progress.

I have been using my garden fireplace for smoking. Which is essentially works as a vertical smoker and I use a large water tray to manage the heat.

It is clear to me that this is not the best way.

I also really enjoy cooking outside, and as such I want to combine a few things and hopefully have a really useful dynamic device.

I want a stove, an oven and a smoker box. To achieve this I am pretty much copying a stove, and hoping to have a smoker box on top. The fire box will be 500mm square, the other half is for the oven. The smoker box will be 400mm x 400mm x 1000mm

My only concern here having the fire box 500mm away from the smoker box, and ensuring that the cut out is suitably sized to get the heat up there. I have looked at calculators and the firebox is twice the size it needs to be for the smoker, so I hope that is half the battle.

I will also increase the size of connections to what the calculator suggest by 50% to increase flow.

I have attached a couple images of my design, my current smoker and a muse I have used for influence.

The side plates will be laser cut profiles and tied together with dull polished stainless steel bars. The smoker and firebox will be corten steel. The idea is to have some really nice looking finished metal supporting two rusted boxes.

As you can see by the model, I have not got my head around how the top attaches to the bottom, I also do not want to take to much stove space up. The flue needs to be selectable between oven and smoker box, but I can sort all the engineering out without a problem, really I just want to understand if this could work as a reverse flow design.

Let me know what you think.

Greg

[inkslinger]

For some reason these images are not displaying. Can you try to re-upload?


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[inkslinger]

Just from reading what you are trying to accomplish.... I think you may want to explore a reverse flow smoker with a warming box (oven) above the firebox.

You can have baffles designed in such a way to allow no smoke to enter the warming box or lots of smoke. You can also have baffles set to divert minimal heat to the warming box or a lot of heat to the warming box. The same goes for the smoke chamber... lots of heat and smoke or none at all. I suppose it all depends on what you are looking to get out of that oven. Max temp? Etc.

Im not sure how hot people have been able to get their warming cabinets depending on their design... but I’m sure there in an answer out there somewhere.

Personally, I would take heed to the ratios output from the calculators. Messing with firebox and throat sizes change the smoke flow and heat transfer dynamic a lot. You may end up with a high maintenance design... which will cut into beer drinking time drastically.



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[Big T]

Welcome aboard!! That's an interesting design. The pit calculator is designed for an offset smoker, there's not one out there for a vertical or something such as this. I'm not sure how well the heat will flow out the bottom of the fire box (FB) and into the oven. It looks like most of the heat would get trapped in the top of the FB or sent to the upper smoke box. I see that there's a factory built unit available so maybe it'll work just fine.

[ajfoxy]

Definitely an interesting design. Look forward to seeing how this progresses. And welcome to the crew.

[Dirtytires]

Looks like the smoke box will burn logs nicely and you will have a hot flat surface above it. Not too sure anything else is going to be too effective to cook food. I could be wrong but it just doesn't look like a design that would be too easy to control or cook with. I think, as mentioned, that a reverse flow with a nice warming cabinet would fit your needs much better.

We see quite often someone wanting to re-invent the smoker only to wind up with frustration.

On the other hand, if you want to make it and prove us all wrong we will be happy to help you along the project as best we can.

[SouthamptonSmoker]

Thanks for the reply.

Cant see an issue with the pictures my end, have anyone else had an issue?

I been thinking about this and got a couple points to put out there, to see if you guys agree.

My recommended firebox to cc opening is 54'' squared. If maker the riser from the firebox this size up to the cook chamber would this not suffice? I hear comments on the forum that an efficient smoker will use about the same amount of wood regardless of size. So surely this principle would apply, and we could consider the riser as just a longer section of baffle plate?

We could go on step further and add the riser to the area of the cook chamber and crunch the figures back out, but I do not think this would make much of a difference?

Also consider things that may help me if it is a bit cold. Insulating the smoke chamber. Has anyone trialed an aluminium baffle plate. I was wondering whether the increased conductivity would help keep the plate temps stable and also help it warm up quicker.

It really does need to perform as an oven and stove most efficiently. I can compromise on the smoker, as I already have one that works well, but if i could crack all in one complete unit this would be perfect.

I will see if can model some form of riser so you guys can comment.

The other option is having two fireboxes and completely independent. All the design looks boxy, and simple, it is actually really how i want it. Putting an offset box gets a little away from what i trying to achieve look wise.

Put simply, i do not want an american style smoker. I want my own style. I may one day build a normal one, but i like to be different first.

Wish me luck, and i will keep you guys informed for advise.

Many thanks

[SouthamptonSmoker]

As promised, I have model the rises, as per the calculator recommends for firebox to cook chamber dimensions, the flue at the top is 4" (100m) and appropriate length as per calculator 27" (i made it 685mm)

I also added to more feature so there is a bit more understanding of the thing. I may decide to put a bbq grill on the right hand side above the oven.

In regards to the oven and stove, this should be Aga equivilent. IE - fully replace a cooker inside.

I also added a gate a built, so you can get a feel of my design. Instead of the burnished stainless steel inner skin, think of CorTen rust and you will see the contrast i want.

Let me know what you think.

[ajfoxy]

I like your gate. And as stated before I'm keen to see how this progresses. An interesting if unconventional design.

[The Czar]

Wow this will be a interesting build for dang sure


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[SouthamptonSmoker]

So I gone ahead with the stainless profiles. Got the tube in to make the spreader beams.


So it begins!!!!!


I have 40 caps to weld on after machining them, going to be little top hats, so I can sink an M12 thread in there. Machine them nice and tight and hammer them in, then stick a nice tig weld around the outside, going to be a shame to grind it off and blend it in.

Just a note I do love the metric system, I love a whole number, I suppose your equivilant would be 1/2" UNC, UNC is much coarser than Metric standard though.


I thought I would attach a couple more pictures. Tubes in ready to go, picture of a stairgate i built, my shop at home and a shed i built for my daughters.

Will keep you posted on progress, going to be a long project. The boxes are going to be mental. This is the easy part. Need to CAD out the boxes to be sure of all these baffles and the insulation. I am also not anything thicker than 3mm (1/8") CorTen, which would be a massive waste, so will be using thicker normal mild steel inside and insulating.

If it dont work at least it will be fun making it.

[mp4]

Awesomeness!

[Bricklayer2]

Oh Yes TOOOLS , Looks like you have the means for a very interesting build. Looking forward to the progres

[Big T]

Keep us updated!

[ajfoxy]

Nice workshop and by the look of the slat gate, you are no stranger to metalworking or welding. Should be an interesting build. Please document and take heaps of photo's. And don't forget to post the photo's here.

[SouthamptonSmoker]

I like metalworking for sure, is my only hobby I have kept at for years.

Here is a few pictures of my progress. The 40 threaded inserts I needed to cap the tube of are done. Took me all day to machine them. Will be welding them to the tube tomorrow and grinding flush. Hopefully will be able to blend them, as if it is a solid bar.

[Dirtytires]

looks like you got the ‘bling’ ready but nowhere to put it. Kinda surprised you picked the flashy part of the cooker to start on. Looks great tho.

[SouthamptonSmoker]

Thanks - I will explain my madness.

The stainless side plates are the supporting structure for the boxes. I need the frame, as I need to make the boxes fit it, rather than the other way around. Once the frame is together I will be able to tack the boxes supported by the frame, because they have to fit perfectly, I thought this would be the best way - essentially builds itself.

[SouthamptonSmoker]

Got 20 inserts welded in,just in one side. Welded one piece both sides which i will be using as a datum. Going to bolt a couple plate - one each end and use it as a go/no go gauge. Think it will be the best way to get all the pieces the same size. I am shooting for 1 metre.

Few pictures below. Welding around a 1" bar is difficult, so not the prettiest, but they did clean up nicely.

[Big T]

[SouthamptonSmoker]

No pictures this time, been looking at firming up the dimensions and just want to sound it out with you guys.

I loose an 1'' all around on the cook chamber insulating it, the inner box will be 6mm mild steel.

So I worked out the calcs again, in particular I am just wanting to confirm I am putting the baffle plate high enough.

The firebox to cook chamber opening should be 39'' square. So I made the riser from the firebox to cook chamber this dimension 4'' x 10''.

Once we get up top, I am going to put the baffle plate 3'' high, 3'' x 13'' so the same size as the cook chamber opening.

This leaves me exactly 8'' x 37'' of cooking space. I am installing the grates 3'' above the baffle plate. This leave me exactly with 8'' of height to the top of the chamber and 37'' long. I am pretty happy with one shelf, but I could put a smaller canter lever shelf coming in 12'' from each side if there is some benefit of having different heights in the chamber..

What do you guys think?

[Rodcrafter]

Welcome to the crew!

This is going to be interesting to say the least. There is a question you asked I didn't understand; "My recommended firebox to cc opening is 54'' squared. If maker the riser from the firebox this size up to the cook chamber would this not suffice? "

Now as far as the riser going to the top box I believe if you insulated it well it would carry the temperature vertically nicely. As for the "baffle plate" what you're describing is really a shadow plate the way you're using it. I believe if you move your exhaust stack to the other end of that top box it will carry the smoke/heat across the box well. The stack wouldn't really have to be that tall since this portion is a vertical cooker, but it will need a damper on top of it.

As for the oven working, if you don't insulate between the FB and the oven heat will transfer right through the side of the FB into the CC. How to control that I'm not too clear on by what I'm seeing.

I really would like to know what the "super charger" is?

As BigT said I don't know how the air will move around the CC withe the opening so low?

I have never made anything like this, so all my input is based on other odd smokers that I have made.

I hope it works out, the skill you have will make it be a awesome looking cooker.

[SouthamptonSmoker]

Thanks for the reply Rodcrafter.

what I meant about the question, was considering in pure engineering what we are trying to achieve in this reverse flow design, is draft, an ability to manage the smoke to efficiently maintain itself.

Considering smoke as a fluid power, my only deviation from the design is a section of my cook chamber 'baffle plate' is vertical. How much this will affect the flow of the smoke I consider a little difficult to quantify. Some of my thoughts consider it would slightly increase the draft, as the heat would flow directly from the top of the cook chamber - which would be the highest section. I even consider a baffle at the bottom of the firebox, as an emergency slam of heat if required. I guess I don't know, and I am trying to apply engineering to it, and probably over thinking it.

I intend to insulate the oven, preferably with fire bricks, the cook chamber a fibre board. I did not intend to insulate the riser, i thought 3mm standard skin of corten, but i can be swayed for sure. I am still thinking heat rises, so i was considering cutting a 3" tube and using it as a direction baffle just above the riser, for two reasons, prevent a hot spot and to stop turbulance just above the riser as the smoke would be guided to its new orientation, as well as pulled by the draft.

There was a question I didnt understant, about the moving of air when the cook chamber opening was so low?

I can work the top box several times, it is the bottom i need to get right first time. Regardless, mistakes cost lol. Which is why i started on the supporting structure, as i am not quite ready to push the button on what goes in the middle yet.

Really appreciate your help.

I have no idea what a supercharger is either - I am using inspiration rather than complete influence. As you can see from the smoker design itself lol - Everyday is a learning day

[Rodcrafter]

I get it now as far as you're not using all the details of the factory built unit.

The thing you asked about that actually BigT and me both mentioned;
"There was a question I didnt understant, about the moving of air when the cook chamber opening was so low?"

We were looking at the factory built picture and it looks like the opening from the FB to CC is at the bottom of the FB.

If you are going to firebrick the oven how will you heat it?

[SouthamptonSmoker]

I intend to have some baffles so i can divert the heat flow. I am hoping to heat the oven the same way as the commercial version by creating a path all around the external sides.

I have spent a bit more time adding some detail to the model of the cook chamber, using the dimension I look into yesterday. I have made some parts transparent so the flow path can be seen.

Hope this paints a clearer picture.