Compound Mill Engine

This mill steam engine model is based on Arthur Woolf’s 1805 patent on a compound steam engine which provides greater efficiency than single stage engines. The dual cylinder cross-compound configuration has side-by-side double-acting cylinders driving a common crankshaft. The compressed air first expands in the High Pressure (HP) cylinder which exhausts directly into the Low Pressure (LP) cylinder for the last expansion stage. As the design progressed, I realized it was looking a lot like Elmer Verburg’s mill engine design so that’s how I named it.
HP cylinder is 0.89” dia. with 1.0” stroke, 3” flywheel.
LP cylinder is 1.33” dia. with 1.0” stroke, 2.2” flywheel.