When I built the workspace I constructed a forge with an overhead hood designed so I could walk all around it and work from all sides. The problems were, it took up too much room and it didn’t draw well, probably because the flue was undersized, so, I built a side draft style which has worked well.
There is no smoke shelf or damper. I light a piece of paper and toss it into the smoke collecting chamber to establish an updraft before lighting the coal. Occasionally there is a really strong west wind which creates a downdraft and some smoke in the room.
During cold weather I place a door over the opening overnight to prevent cold air from coming down the chimney and as I do that I think a damper might be a handy addition.
This design does not incorporate a smoke shelf at the top of the smoke collection chamber but the volume reduction which happens in the truncated pyramid accelerator section seems to work well in creating a strong enough updraft. Perhaps a smoke shelf or damper would make it even better.
The original smoke collection chamber rusted out after about 10 years and was replaced. The original 18 gauge sheet walls were replaced with 10 gauge sheet. I also incorporated angle at the corners and fitted the walls with machine screws to make any future replacement easier. The “air-tightness” is accomplished by sealing leaks with black silicone caulk.
Some blacksmiths caution about putting any bend in the flue but I have had no problem with the 45º jog design. There is a large wall cutout where the flue passes through which serves as a generous fire break. This was fitted with sheet metal flashing on inside and out and filled with insulation. The flue topper incorporates an expanded metal screen to prevent birds from entering.
I set up a dual air supply with the noisy electric blower outside on the north porch covered with a weather shield. The quiet hand crank blower is indoors. I mostly use the electric blower. The optimal motor speed is selected then the screw check valve adjusted for the optimal fire (with the blast gate closed). For the rest of the forging session the air supply is controlled with the blast gate or, less often, turning the motor off and on.
I built a tong rack along the front and set one bucket under the ash dump and another one where it is easy to deposit clinkers.
There are probably about as many forge designs as there are blacksmiths. These are some other references:
Pitched forward Side Draft Forge:
Nice Hoods without smoke shelves:
Smoke shelf:
Fabricated firepots:
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