Baffle Plate end gap on centre feed

[PetesMeat]

Hi Everyone,

Just sorting out the baffle plate on my centre feed smoker. Someone said to make the gap equal the throat opening, which pitcalc says should be 78 sq inches

I have done the maths and this works out to a mere four inch gap, which when devided by two is only two inch gap at each end. This does not seem like a lot....

The cook chamber is 49x19inches footprint, so the baffle would be 19 deep by 45 with a two inch gap, which equates to a 76 square inch gap, which is pretty close to the throat opening size.


What should I do? Make it as per the maths (i can always cut a bit more off the end of the plate if I need to) or just make the gap a bit bigger.... Hmmm. Decisions....

[bluecatfish]

I would make it just a little bigger. In my opinion if it is smaller than throat opening it would hamper the heat and smoke flow through the CC. I think it would be easier to add just a little to each end of the BP if needed than cut it.
jm2cw

[PetesMeat]

Well right now, the throat opening is very oversized (144 sq inch, recommended size is 78) I am going to have sliding adjustable baffle plates, as my design allows for it very easily and I have spare steel of the right size.

My thought though, with Centre feed, the baffle plate and the throat opening is kind of one and the same thing...? I have a shaddow plate over the opening and surely the restriction of airflow will happen at the baffle plate gaps, so why bother restricting it twice? M feeling is to let the air come out of the oversized throat then the slow down will happen under the baffle plate. This may even help distribute heat, as more heat is retained under the baffle.

What do you think?

Pete.

[PetesMeat]

This is the throat and shadow plate as it is now. I added up the four openings around the shaddow plate, adds up to 96sq inches, so that will act as a bit of a throat too...

[bluecatfish]

I am anxious to hear what Gizmo has to say about this, he is the expert on center flow.

[Puff]

Me too! His Egor design has some similar build elements.

[Gizmo]

The FB generates 2 things:
REAL hot radiated heat.
Boatloads of REAL hot air.

Radiant:
The bottom surfaces of the roof of the FB and the lid of the "top hat"(shadow plate) takes the first hit from the radiant heat which they then absorb and SLOWLY transfer that heat to it's top surface and re-radiates it on up to the bottom of the main BP and so on....

This gives the convective heat output of the FB a chance to spread the heat ALL over the cabinet and greatly reduces the hot spot that would be right over the FB throat without it. It also helps step down the FB temp to a level in the CC that we like to cook at.

In my opinion the throat in this design is the gap around the edge of the top hat lid - once all that hot air hits the comparatively HUGE volume of the CC it RAPIDLY expands and speeds up and can easily slip through even a small gap.

Convective:
Edgar called for a 72 sq. inch throat so that's exactly what I gave him. I designed him with adjustable BP gaps at both ends. I ended up adjusting those gaps to about 3/4 inch on each end which is a total combined gap of 30 sq. inches. Sounds constrictive doesn't it? What you need to remember is that you can pass the same amount of air through a smaller opening if it's Much Hotter and thinner and very highly motivated (faster) especially when you add the stoking qualities of the cabinet/draft/stack etc. I wouldn't worry much about the numbers you've listed so far - shouldn't be a big deal.

Then again I could be completely wrong.

[The Czar]

Good grief Gizmo....


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[PetesMeat]

So in a nutshell gizmo, your saying leave the top hat as it is and have the baffle plate gaps adding up to the requires throat size?

Pete

[Gizmo]

That's the biggest gap they'll ever need to be. You can always add a steel plate to each to close it off if you want to experiment with a smaller gap(s) later.


Sorry DC but I think that is actually what's going on in one of these things…..

[Rodcrafter]

I'm not sure Gizmo, but I think DC is commenting on the last line in your very nicely said explanation.

"Then again I could be completely wrong. "

When I read that I wanted to say the same thing he did, when I stopped laughing.

[The Czar]

Well yeah… The guy writes a novel… And then at the very and throws stick a dynamite in the pond…


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[Rodcrafter]

[Gizmo]

Mongo like dynamite!