Passive air over fire.

[Mark B]

Look up hand crank blowers. Then try to come up with a way to power the crank with something other than hand power. While hand power will give the necessary air needed, that would get real old real quick. To get the necessary air flow you will need to turn it at about 25-40 RPM on the crank. Maybe a 12V motor, a deep cycle battery and a drive belt could do it. Also consider a small solar panel or 2. While my first solar was just 2 panels and they charged a 4 battery bank, it was enough to power the sugarhouse during daylight and about 3 hrs after sunset. Then I had to fire up the generator.
Where there's a will there's there's a way.

You could try a low rpm electric motor and gear it to run through an older lawn tractor transmission to get rpm reduction. Have set this up for turning a spit in a BBQ made in an old oil tank. Low gear may get you the rpm's you need.

[djblech]

Would increasing the diameter of the stack increase draft to help aof? I am planning to put in an 8" stack and reduce it just above the arch to 6". I am hoping this will act like a expansion chamber and increase draft.

[RileySugarbush]

Trying to get AOF velocities with stack draft is probably not going to happen. In my system, the AOF pressure is 8 inches of H20 across the nozzle. Thats about 0.3psi, and that is what gives the jets the 80 mph velocity that lets it mix well. If you managed to get anywhere near that much suction with your draft, which is really impossible, it would just draw up through the grate since that is a much easier path. So it would act like a normal system with great draft.

[Super Sapper]

Would increasing the diameter of the stack increase draft to help aof? I am planning to put in an 8" stack and reduce it just above the arch to 6". I am hoping this will act like a expansion chamber and increase draft.

Reducing to 6 inch would only reduce your draft as it is restricting your air flow. I would go with 8 inch all the way.