Sometime this summer I’m planning to replace most of the coal forge flue. Essentially everything above the smoke collector box will be new. The original sheet metal was 20 gauge and it is rusting away after many years of use. The smoke collector box is modular and made of 7 gauge and only a few years old.
The new flue will be the same size and shape as my current one but it will be 14 gauge and modular so the front, back and side pieces will be removable. The current flue was MIG welded but the new one will be hex bolt joinery.
I will make a new type of topper to deal better with our regularly strong wind and I will add a smoke shelf and damper. I drew the damper plan this morning but the dimensions are not yet a settled issue. I will have a few more months to think about them.
My sketch is not very accurately done either at this point. I plan to make the smoke shelf out of 14 gauge and it will be bolted to the back wall so I can remove it if I need to make a modification. The damper will also be 14 gauge but I may encounter some warping issues from the heat. The axel and handle will be something like 3/8” round pivoting in a couple of 3” pipe or tube sections welded to 1/4” x 3” x 3” flanges and bolted to the front wall.
The next thing to think about will be how to lock the damper in the open position.