There are a number of Internet postings concerning modifying the Brinkmann Gourmet charcoal smoker. All of them address the issue of draft control. Some address the inadequacies of the stock thermometer as well. In reviewing these postings I concluded that they were largely 1) ugly, 2) ineffective and 3) unnecessary. So I devised my own modification for the draft control and it is described herein.
From the factory this smoker has no means of controlling the draft. There is a single hole in the bottom, maybe 1.5" in diameter, to let the air in. There is a small space between the lid and the main barrel to let the smoke out. Some have modified the unit to add one or more holes to the firebox together with a spinner damper. This is hard to do mechanically and it doesn't look so good. Others have attempted to plug the vent space around the lid and then add another hole to the lid once again controlled by a spinner damper. My design philosophy is that there is no need to control the exhaust since it will be completely controlled by the amount of inlet air, and that the existing air hole in the base provides adequate combustion air but needs to be throttled. Thus my only modification is to add a hinged damper plate to vary the size of the inlet air hole. This modification is very inexpensive and requires only the drilling of 3 1/8" holes and the bending of some bar stock.
I used a jar lid for the hinged damper plate, however any flat piece of metal will work. It must be flat and must not warp because of the heat. I drilled two holes slightly larger in diameter than the round bar stock in the edge of the jar lid. One hole is for the pivot screw, around which the plate rotates, and the other is for the control rod. Another similar hole is drilled in the base adjacent to the air hole. This hole is for the pivot screw which is secured by two nuts jammed together to prevent loosening (a single nut will back itself out since it cannot be tightened while still allowing the screw to act as a pivot).
The control rod is a piece of 1/8" round steel stock available at most hardware stores. The rod is bent in a sort of S shape at the lid end and in an L shape at the other end. The rod is fed through a single small hole drilled through the side of the base as close to the bottom as possible. When the control rod and damper are assembled a simple push-pull motion effectively controls the damper plate position, rendering the air supply fully closed when the rod is pulled and almost fully open when the rod is pushed in. The pictures below illustrate the change.
This image shows the damper plate in the open position together with the pivot screw and control rod. It is important to bend the control rod in a squared S shape to prevent it from coming loose.
Here the damper plate is in the fully closed position. The control rod is pulled all the way out.
Here is the control rod protruding from the base. This is the only bit of the modification that is visible externally.
This is a (low flying) bird's eye view of the entire modification.
As for the thermometer, I have learned to live with it. It has no numbers on it to indicate the internal temperature, only a range marked 'ideal'. I tried to calibrate mine by putting it in the oven at a known temperature of 150 degrees (the needle can be adjusted by means of a nut on the back). However when putting the thermometer back in service and checking it against the internal temperature measured with a separate oven thermometer, the lid thermo was way off. I reached the conclusion that the stock thermometer really measures the temperature of the lid rather than the internal air temperature. So my workaround is to use the oven thermometer as the ultimate authority for the internal temperature. I note where the needle on the lid thermometer is pointing when the oven thermometer indicates the ideal cooking temperature and then just use the lid thermo for reference for the remainder of the cooking session by maintaining the noted position of its indicator. It wouldn't hurt to add a real barbecue thermometer to the lid. These instruments have a probe that extends into the interior space so that they more accurately measure the air temperature rather than the lid temperature. Of course such a probe may interfere with the meaty contents so one must be careful with the placement. I can just say that I have been able to produce excellent results using the stock thermometer in the manner described.
Finally another worthwhile addition is the purchase of a grate for the firebox. This has two advantages. The first is to get the coals up out of the ash pile that will build up over a long cooking session. The second is to act as a strainer to remove and separate unburned charcoal from the ash. A standard round 18" grate can be purchased for less than $10 for this purpose. It can be supported by the existing vent louvers that extend upwards from the base of the firebox, or some small rocks or other non-combustible items can be used to support it. Some have suggested threading in some screws through the side of the firebox which would provide the best support mechanism. In my opinion it is very important to use lump charcoal or 100% charcoal briquets in this smoker if for no other reason than to prevent ash buildup. Ordinary Kingsford briquets produce much more ash than does 100% charcoal.