Instead of building a backyard firepit where someone inevitably ends up downwind and gets smoked out, I want to build a proper outdoor fireplace with chimney. My two-for-one idea is to incorporate a horizontal barrel smoker that can do double-duty as a propane grill. I intend to purchase the barrel smoker from a local manufacturer (LangBBQsmokers in Nahunta, GA) and have him customize the interior of it to accommodate propane burners, but that's not why I am posting this thread.
My idea is to be able to flip a steel plate to direct the exhaust from the fireplace either straight up the chimney for an ordinary fire or to direct it horizontally under the length of the barrel (thereby heating the barrel evenly lengthwise), turning the corner and entering the barrel on the side opposite the chimney, traversing the length of the interior barrel and then exiting back into the chimney.
How do I construct the intersection of the two "chimneys" (one vertical and one horizontal) with the flip plate to send the smoke in the desired direction? Any diagrams or photos of similar constructions would be most helpful.