The Hunter Wheel was an experimental device which attempted to improve such propulsion efficiency.
At the time there were two types of machine propulsion for steam operated vessels:
The Hunter Wheel was intended to improve the efficiency of propulsion of the “paddle wheel” type of vessel.
The Hunter Wheel was named after Lt. William W. Hunter and consisted of a conventional paddle wheel drum placed horizontally within the vessel below the water-line. The paddles were so arranged as to project from a suitable opening in the side of the ship when at right angles to the keel. Water was kept from entering by a cofferdam placed around the paddle wheel drum and against the side of the ship.
The Hunter Wheel was tested in 1843 on the which had been modified to accept the device.
It was discovered that Union’s engines wasted too much energy uselessly driving the paddle wheels through the water-filled cofferdam inside the ship.
The device was testing also in with the following result:
The wheels lost much of their power pushing water through the encased area inside the hull, forfeiting between 50 and 70 percent of their potential power.
Testing continued through 1846 but failed to increase the efficiency of the paddle wheels.
The device was also used in the construction of but it was found to be unreliable and inefficient, and Allegheny was later converted to screw-propelled.