Iron production at Hopewell Furnace required a blast of air to bring the heat of the furnace above 2800 degrees (Fahrenheit). The water wheel supplied the power for this air blast by pumping a pair of pistons inside two blowing tubs. Compressed air moved from the blowing tubs into a receiving box between the tubs, and then through a long pipe to enter the furnace through the tuyere, a cone-shaped nozzle attached to the end of the pipe.
The Hopewell water wheel is a 22-foot diameter "breast" wheel which was made predominately of chestnut and oak wood. A breast wheel is commonly found in areas where the headwater is between 5 and 12 feet high. It gets its name from the fact that the water turns the wheel by flowing in halfway up the wheel instead of having the water come in at the top of the wheel, as is the case with an "overshot" wheel, or turning the wheel from underneath, as is the case with an "undershot" wheel.
The wheel itself turns when water flows into the spaces in the wheel, called buckets, on one side of the wheel, which then makes that side heavier than the other. Gravity then works on the heavier side of the wheel which causes it to turn. The turning of the wheel can create 5-15 horsepower that can then be used to run the blast machinery of the furnace.
In 1805, a 22-foot breast wheel, much like the one that exists today, was built to replace the former 30-foot overshot wheel that had been in use from about 1771 to that time. This happened when the furnace lost rights to the west headwater and Hopewell Dam was constructed to provide a new source of water power. Since the original installation of the 22-foot breast wheel, there have been several instances of the wheel being replaced or repaired:
1830: The water wheel was replaced with a locally made wheel, which broke within on year.
1834: The wheel was replaced once again by one hauled in from Hibernia.
1879: The wheel was replaced for the final time while the furnace was in operation.
1883: The furnace went "out of blast" for the last time. The wheel sat dormant and mostly forgotten until 1935 when the Hopewell property was acquired by the Federal Government.
1941: The Civilian Conservation Corps began restoration on the wheel, which was halted with the disbandment of the CCC after the United States entered World War II.
1949-1952: The 1879 wheel was recreated.
1988: Another restored wheel was dedicated on August 7, 1988. After 36 years of stop-and-go turning in the park, the 1952 wheel began to vibrate unsteadily while turning and it became clear that the wheel needed to be replaced.
2006: The most recent development in the ongoing story of this water wheel is that in 2003 it once again became apparent that the wheel needed to be replaced. After more careful work in historical restoration, a new wheel was dedicated on August 5, 2006.