joeq wrote:not sure what a windowstat is,
A "windowstat" is our fun way of saying "Open the windows & let some heat out of the house!".
The idea of the bi-metal spring is thus: As the stove gets hot, the spring expands and the flapper door closes letting less air in. Less air makes less heat. As the stove (and house) cools down, the spring contracts pulling the flapper open allowing in more air and making more heat.
I think your stove is similar to a stove a friend used to have. It has a hopper that you fill & as the coal burns fresh coal falls by gravity to feed the fire? The one he had liked to have the ashes shaken down after 7 or 8 hours. It would not go 12 hours unless shaken once. Also, we made a poker that he'd use to come up under the grate & scrape in between the grates as just shaking wouldn't always do the trick.
Oh, and don't let the ashed get up to the grate. If they get that deep they block the air flow. And.... if your stove is designed the same, you have internal "pipes" that go from the sides of the burn area to the back where they meet at the stove pipe. These pipes need to be cleaned now & then.