Living History on the banks of the Stevens River in Barnet, Vermont
How Hydropower works at Ben's Mill
The cellar of the mill
Planer with pulley on the right
In order for the stream's water to make the turbine spin, and thus make the turbine output drive shaft turn, the "height" of the water must be maintained above the turbine inlet. That "height" of water is called the hydraulic (or "driving") head, and must be high enough to meet the turbine manufacturer's specifications for proper turbine operation. The driving head overcomes the inertia/friction of the turbine and associated shafting/ loads. The level of water is established at Ben's Mill by having a timber dam behind the mill. Water is directed from this mill pond into the turbine inlet. To establish water flow through the turbine, a gate is manually opened, allowing water to enter the penstock (a wooden cylindrical waterway/tube). The penstock directs the water to the turbine inlet, and when the Machinery Operator opens the turbine inlet valve, water flows through the turbine. The force of the water against the turbine wheel blades causes the turbine output drive shaft/main line shaft to spin. Water exits the turbine discharge and flows back into the river, downstream of the dam.
Assembly of the new wood penstock, Aug. 2009
This historic mill is outfitted with machinery dating back to the late 1800's. All of the machinery is designed to be belt-driven. Pulleys of varying sizes are located on the line shafts (below the main floor). These pulleys are aligned with the drive pulleys attached to the machinery on the floor above the line shafting. Using fabric belts looped around the pulleys, the rotation of the line shaft is transferred to the machinery drive shafts, causing the machinery to operate. Individual machine drive belts are engaged by Operator levers, which cause the belt to tighten around both the drive pulley and the machine pulley. The pulley diameters determine the speed at which the machines operate. They basically convert the slower line shaft speed to a higher machinery speed.
Hydropower History at Ben's Mill
West view of the mill and entire dam in the late 1970's
SLM for Ben's Mill Trust 2010.