Compound beam engine of the Fall River Line steamer "Puritan" (1891). The steel-framed engine, built by W. & A. Fletcher Co. of Hoboken, New Jersey, was the largest vertical beam (ie walking beam) engine ever constructed. Fletcher compound beam engines were unusual in that the connecting rods of the two cylinders were attached to the skeleton beam at different points, giving them a different stroke. This particular engine, for example, had a high pressure cylinder with bore of 75 inches and 9 foot stroke while the low pressure cylinder had a bore of 110 inches by 14 foot stroke. The different stroke lengths of the individual pistons in Fletcher engines has been a source of much confusion to historians, some of whom have assumed that the ships had two separate engines while others have concluded the second stroke length must be the dimensions of a third piston in a triple expansion engine. The reason Fletcher compound beam engines had this unusual arrangement is not known, but at least some of them were capable of disabling the high pressure cylinder and working as simple expansion engines.