Self-turning roasting spit driven by rising heat
A smoke-jack: a vaned wheel in the flue turns the spit by the fire's draught
The lower drawing shows a tall conical hood set over a fire; a horizontal vaned wheel inside the flue is spun by the hot air rising from the flames and, through a train of gears, turns a roasting spit. The note explains that this is the true way to cook roasts, since the spit turns slowly or quickly according to whether the fire is mild or strong. Above, a separate mechanism couples two large toothed wheels by a belt to an outrigger stand and a threaded spiral drum; the catalogue also connects the sheet with wire-drawing machinery.
On this page
Smoke-jack roasting spit
A conical hood over the fire channels the rising hot air onto a horizontal vaned wheel set in the flue, whose shaft drives gearing that rotates the spit above the flames. The device paces itself with the fire beneath it.
Turning speed governed by the fire
The note observes that the roast turns slowly or quickly according to whether the fire is mild or strong, so the rising draught of hot air both powers and regulates the spit's rotation.
Belt-coupled wheels and spiral drum
The upper mechanism links two large toothed wheels by a belt to an outrigger stand and a threaded spiral drum. The catalogue connects such studies to wire-drawing machines.