Hi Trader, the design of the LL pusher block is a flat piece of steel about 1/8" thick with another thicker piece of steel on top of it, making a step. The unburnt coal you see is resting on the 1/8" thick piece of the pusher or shovel. This section of the pusher shovel is about 2.5-3" deep from the step out to the leading edge that nudges the coal fire on every stroke.
Normally the pusher block would have about 1.5-2" of coal on it, what you see is a single layer of coal pieces, only about 1/2" of coal, there is a 1.5" gap from the ash over the top of the pusher into the hopper opening. I could put a 5" long piece of 2x4 on the pusher, and it would show through the hopper feed opening, and show just infront of the burnt ash.
As the pusher is moved in and out, the the thicker step is just below the hopper opening, the block pulls back, some coal falls into the recess, but onto top of the 1/8" thick section, the back and forth motion sort of pumps the loose coal forward out onto the grate.
The air holes for combustion start just underneath the pile of ash you see in the photo, the unburnt coal is sitting on the pusher shovel. So the design keeps the fire several inches in front of the hopper opening, and unless the cover was left off the hopper, I can see no way that draft and or air could backup through the hopper opening and into the hopper.
I haven't looked closely at the Alaska 'pusher-paddle' design, but it sounds like it has the combustion much closer to the hopper feed opening. Maybe not, but from the problem you had it is the only way I can see a fire getting back into the hopper. Maybe the gasket at the top of the cast iron grate is bad and lots of combustion air is blowing through the coal very close to the hopper opening?? Don't know.
I posted these photos to show what I had commented about early in this thread. My hack-job, dangerous, temporary chimney is still not allowing a hopper fire in my LL Pioneer stove, and it has every excuse to have a hopper fire.
I can see your concern, I think an over-the-fire draft check is in order, you want to make sure your venting motor and fan are very clean and pulling a good draft through the stove, providing a negative pressure on the whole unit. If I were you, I'd want the draft to suck the hopper cover down tight!!
Last edited by LsFarm
on Tue Mar 20, 2007 7:04 pm, edited 1 time in total.