This model shows Dripps’s six-bladed propeller design, where each blade has a turned flange at its tip to help grip the water. The blades are separate castings bolted to the central hub. Such construction was the most common way to make large propellers in the nineteenth century, as it allowed ready replacement of the easily damaged blades. The model measures 9 1/2” diameter by 4” deep.

In 1838, U.S. Navy Captain Robert F. Stockton saw a screw-propelled boat designed by the Swedish engineer John Ericsson demonstrated in England. Believing that such a boat would be practical on American canals, he commissioned one, and it was delivered across the Atlantic the next year, the first iron-hulled vessel to cross the Atlantic. Originally named Robert F. Stockton but quickly changed to New Jersey, the boat proved too deep for canal use, and it became a tug boat on the Delaware River. As designed by Ericsson, the boat employed two screws—mounted in line but turning in opposing directions—and a rudder installed forward of the screws, an arrangement that made the boat difficult to control and maintain. In 1840, the boat was turned over to engineers at the Camden & Amboy Railroad for improvement. Under the direction of Isaac Dripps, the mechanics installed a new single propeller and repositioned the rudder aft of the screw. In this configuration, the New Jersey remained in service until 1871, the first commercially successful propeller steamer.

Isaac Dripps (1810–92) was a prominent railroad engineer. Born in Ireland, he arrived in the U.S. with his parents in infancy. He apprenticed to Philadelphia steamboat-engine builder Thomas Holloway in 1826 and in 1831 was hired by Robert L. Stevens to assemble the John Bull locomotive, newly delivered from England for the Camden & Amboy Railroad, although he had never seen such a machine before. He also acted as engineer for the John Bull’s first trip. Dripps continued as an engineer for the Camden & Amboy until 1854, during which time he and Stevens developed the cowcatcher and the bonnet spark arrester, among other early locomotive improvements. After a short time as partner in a locomotive works, he returned to superintending motive power for railroads, ending his career with the Pennsylvania Railroad. One biography says, “In the course of his career he devised innumerable mechanisms, tools, and the like for use in the construction of locomotives, freight and passenger cars, and steamboat machinery, but never patented any of them.”

Ref:

“Isaac L. Dripps,” Dictionary of American Biography (New York, 1930), vol. V, 458.

“The First Successful Screw Propeller,” The Locomotive Engineer, Jan. 1891, 6.

John White, American Locomotives: an Engineering History, 1830–1880 (Baltimore, 1968), 451.