Atmospheric Rotative Steam Engine A general section of Francis Thompson's patent engine to work a rotatory motion on an improved plan, 1793 Front elevation, scale 1:24 Ink Inscribed: This is a double acting engine two cylinders being combined and the pistons of both fixed to the same rod, one acts to make the up stroke the other for the down stroke. Cylinders 40 inches diameter 6 feet stroke made 18 strokes per minute = 216 feet motion per minute nd