Beckley Furnace was a blast furnace and as such it required a source of compressed air to operate. The nearby dam supplied the power to operate the air pump that provided that air. While evidence suggests that the original power source for the compressor was n traditional style water wheel, a hydraulic turbine was later installed to provide a more efficient power supply.
The turbine displayed here is a type of turbine called a Hercules wheel. We don’t know who made this particular wheel but its style of construction closely resembles those made by the Holyoke Machine Company in Holyoke, Massachusetts. Inventor John B. McCormick worked with that company during the late 1870s to perfect his design. That design was licensed to a number of manufacturers and copied by others. The design was evaluated in Holyoke at the famous 19th century test flume and found to be 85% efficient
The structure of the machine is shown in a figure from one of McCormick’s advertisements and shows the elaborate shape of the vanes in the turbine wheel (called the runner). These vanes extract energy from water as it flows through the turbine. The vanes are shaped to react both to the movement of the water as it enters from the sides of the machine (impulse) and also as it falls vertically through the machine and exits at the bottom (head). Turbine that work this way are called mixed flow turbines.
The power output of the turbine is determined by the volume of water that flows through It, the speed of the water as it enters the machine and the number of feet the water falls as it passes through. The volume of water in controlled by a movable gate cylinder that determines how much water can flow into the machine through the slots in the side. The gate is raised and lowered by a rack and pinion mechanism that can he controlled from outside the machine.
The gate in the machine on exhibit here is almost completely closed, but you can see the inner working through the slot out in the side of the casing.
The gate cylinder (1) is the inner metal sheet in the upper portion of the turbine. The turbine blades (2) are attached to the runner (3) which is the part of the machine that actually generates power. Water can only enter the turbine through the gap between the gate cylinder and the turbine outer casing (4). As the turbine sits today the gate is almost completely closed.
The gate is attached to two metal bars with slots out in them culled racks. One rack (5) is shown below. A metal shaft (6) passes through the machine and has two round gears (7) called pinions attached to it. The teeth on the pinions fit into the slots (8) of the racks. When the shaft is rotated the pinions will cause the racks to raise or lower the gate cylinder.
The shaft with the pinions on it has an external gear attached to it (which is damaged on this machine). This gear was in turn driven by another gear and shaft arrangement that allowed the gate to be controlled by an operator.
At the top of the turbine one can see a shaft coupling that attached the turbine to the air pump.
While water power is free, it is not without problems. The obvious ones are low water (draught) and freezing in the winter. Other hazards included floods and damage from ice floes passing over the dam in the spring. The Beckley site has experienced serious flooding on at least 3 occasions: 1827, 1938 and 1955. It is quite likely that the penstock assembly (large pipe) remaining in the wheel pit was moved by one or more of these events and is no longer in Its original location.
The turbine was mounted inside a metal casing attached to the penstock which served to carry the water from the dam to the turbine. The picture below shows the casing installed here is a close match to the one shown in a 1906 woodcut of a similar turbine.
While we know quite a bit about how the turbine worked, we do not know much about where and when it was made.
The turbine in this exhibit clearly looks like the one designed by John McCormick shown in the first column of this panel. However, no maker’s plate was found and there lo no record of when this machine was installed here in East Canaan. Because of that the name of the manufacturer and the date of manufacture are both unknown.
As is often the case with historic Investigation – the answer to one question raises more.
The second component of the blast system was the air pump comprised of two cylinders six feet in diameter and six feet high which operated as follows.
Figure 1 shown the piston rising in a cylinder. In this case air is being compressed as the space above the piston shrinks and the air is forced out of the top outlet port.
The inlet and outlet valves (red) control the flow of air in the top and bottom portion of the pump. When the piston is rising the outlet valve opens to allow air to escape and the inlet valve closes.
As air is being forced out of the top section of the pump fresh air in being pulled into the bottom of the cylinder as the upward motion of the piston creates a partial vacuum there. This lowered pressure allows the Inlet valve to open and external air pressure closes the outlet valve.
Figure 3 shows what happens when the piston reverses direction and moves downward. Now the air below the piston Is compressed and forced out of the bottom outlet port while fresh air Is pulled into the top chamber.
This blast pump had to supply a continuous blast of air at 1 1/2 to 8 pounds per square inch of pressure. The air was subsequently heated in a stove located near the furnace stack. The heated air or hot blast reduces fuel consumption and thus produces more iron at a lower cost. Beckley furnace was designed from the outset to use hot blast, the first such furnace built here in East Canaan.
One problem with a piston pump of this design is that the pressure of the output air stream falls when the two pistons reach the end of a stroke: one piston being at the very top of its cylinder and the other at the very bottom. This is called the “crossover” point where the pumping shifts from one side of the piston to the other. The crossover will produce a pulsation in the blast that disturbs the fire in the furnace and in the worst-case causes shifting of the contents of the furnace.
To reduce the effect of the pulsation a device called a “stuffing box” was connected to the output of the pump. This box was an airtight chamber which had a movable flap on the top. The flap had a weight sitting on It. As air was pumped during the stroke of the pistons the flap moved upward until the stuffing box was filled with air.
When the crossover point was reached and the pistons stopped pumping air the weight on the flap forced the flap downward and emptied the stuffing box into the output pipe. In this way the stuffing box acted as a pressure regulator maintaining the pressure at the crucial crossover point.
Choosing the correct size for the stuffing box and the correct weight for the flap was a tricky process and probably required considerable effort to get it to work properly. Later on rotary blowers powered by steam or electricity replaced the piston pumps and waterwheels providing for much tighter control of the air blast.
We don’t know the exact layout of the pumping engine used here at Beckley Furnace but we do know that the pumping cylinders had cast Iron tops and bottoms and that the leather seals on the pistons were lubricated with a mixture of shoe polish and sour cream.
The exact layout of the drive shafts and gears that drove the pump is also unknown. The only clue we have is the drive shaft segment on display near the turbine. This shaft connected to the top of the turbine (note the matching connectors) on one end and to a bevel, or crown, gear on the other end. What happened after that in currently unknown.
The drawing below shows the configuration of the two cylinders and the stuffing box. This configuration is based on a sketch in an old notebook and the picture below of a similar pumping engine.
The next exhibit on the tour is just above and behind you.