The Hunter Wheel was a device intended to improve the efficiency of propulsion in U.S. Navy steam-operated ships in the late 1830s and early 1840s. At the time, as ships were transitioning from sail to steam engine

Steam engine

A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

 power, the understanding of the principles of efficiency of propulsion

Marine propulsion

Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting a motor or engine turning a propeller, or less frequently, in jet...

 of steam engine-powered ships was in its infancy, and not totally understood.

The Hunter Wheel was an experimental device which attempted to improve such propulsion efficiency.

Vessel type

At the time there were two types of machine propulsion for steam operated vessels:

• paddle wheel
• screw (propeller)

The Hunter Wheel was intended to improve the efficiency of propulsion of the “paddle wheel” type of vessel.

Design of the wheel

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

Cofferdam

A cofferdam is a temporary enclosure built within, or in pairs across, a body of water and constructed to allow the enclosed area to be pumped out, creating a dry work environment for the major work to proceed...

 placed around the paddle wheel drum and against the side of the ship.

Testing of the device in USS Union

The Hunter Wheel was tested in 1843 on the which had been modified to accept the device.

Result of test

It was discovered that Union’s engines wasted too much energy uselessly driving the paddle wheels through the water-filled cofferdam inside the ship.

Testing of the device in USS Water Witch

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.

Subsequent testing of the wheel

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.