Dempster Solid Wheel Windmills

Sketch of the Dempster No. 5 Windmill

NPS/Dempster Archive

In its early years the, Dempster Mill Manufacturing Company was known for its solid-wheel wooden windmills. These are windmills with a rigid wooden wheels compared with sectional-wheel windmills.

American windmills needed to point toward light winds and shut down in strong winds with minimal maintenance. Solid-wheel windmills were one of the first windmill styles created for use in North America. They have a rigid wooden wheel that adjusts the angle of the entire windmill head to control its speed. In slow winds, the wheel points into the wind for maximum efficiency. In high winds, the wheel moves toward the vane to minimize surface area and prevent damage from spinning too rapidly. Springs or weights draw the wheel back to face the wind more squarely when velocities subside, giving the mills steady rates of operation.

In the 1890s, the company began experiment with improvements in solid-wheel wooden windmill design. They produced three short-lived solid-wheel mills.

Solid-wheel wooden mills remained a significant part of Dempster sales through the 1920s. Though sales of the wooden vaneless and steel mills steadily increased. The Dempster No. 9 Solid was produced until the market no longer desired solid wheel windmills due to the introduction of self-oiling windmills.

Dempster created five models of solid-wheel mills from 1885 through the 1925.

Original Dempster Solid Wheel Windmill (1885-1909)

The first windmill manufactured by the Dempster Mill Manufacturing Company was the Dempster Solid Wheel. It was a wooden wheel windmill produced in ten and twelve-foot diameter sizes. The vane sheets were one of the most decoratively painted of any windmill produced in North America.

The Original Dempster Solid Wheel mill represents a very early example of a “pull-in” style of mill. The windmill turns on when a control wire is attached to a three-foot coiled governor spring. As wind speeds increase, the off-center wheel tends to turn away from the wind toward the vane. This action is counterbalanced by the tension of the governor spring. The spring pulls the wheel back to face the wind when the velocities decrease.

A smaller spring pulls the wheel and vane into a parallel position when the control wire is released from the governor spring. This causes the wheel to only show its edge to the wind. The mill would shut off if the control wire broke, protecting it from destruction in severe winds.

The Original Dempster Solid Wheel was manufactured until 1909 when the Dempster No. 9 Solid Wheel was introduced. Its sales already had decreased by the introduction of other solid-wheel wooden Dempster mills.

Beatrice (1892-1894)

The first of the short-lived solid-wheel wooden mills made by Dempster was the Beatrice. Perhaps its bad timing was the reason for the Beatrice failing. It came on to the market only months before the Panic of 1893, which began the most severe economic depress to strike the United States up to that time. The mill disappeared from the market within two years.

The Beatrice was a solid-wheel wooden pumping mill made in 10 and 12-foot diameters. It used the same wheel design as the Original Dempster Solid Wheel, but the head was different. Additionally, its vane stems were longer and the vane sheet was positioned farther way from the wind wheel.

New Era (1900-1903)

The second of the three short-lived solid-wheel wooden windmills was the New Era. It was introduced to the marketplace in 1900 in 10 and 12-foot sizes. It was only produced until 1903.

The mill incorporated many of the design elements developed for the Dempster Steel 1899 Pattern. The primary difference was that the steel mill was back-geared while the New Era was a direct-stroke pump. Customers could buy the New Era with either a wooden or steel wheel or vane. The wooden wheel was similar to the Beatrice mill design.

Dempster No. 5 Solid (1903-1909)

Taking the place of the New Era was the Dempster No. 5. It was the third of three short-lived mills, introduced in 1903.

The patent rights for the popular Eclipse windmill design expired and entered the public domain in 1901. Most windmill companies soon created copies or similar versions of this mill. Unlike companies that copied the Eclipse mills outright, Dempster modified the time-tested design. The Dempster No. 5 used a similar wheel and vane sheet as the Eclipse, but its governing and mechanical parts differed. Instead of using a weighted lever, the Dempster No. 5 used a coiled governor spring like its other mills.

This decision cut Dempster off from much of the market selling repair parts for the thousands of aging Eclipse mills. Dempster No. 5 mills never sold in the numbers expected, and they were discontinued after six years.

Dempster No. 9 Solid (1908-1925)

The dissatisfaction with the Dempster No. 5 mills, led to Dempster belatedly introducing its own pure copy of the Eclipse, the Dempster No. 9. The Dempster Mill Manufacturing Company made the No. 9 Solid in farm-sized windmills and larger railroad versions. The regular farm-sized pattern came in 10, 12, and 14-foot diameter sizes. From 1918 to 1922, they also produced railroad-pattern mills in 16 and 18-foot diameter sizes.

Unlike most Eclipse copies, the Dempster No. 9 windmills generally came from the factory with compression grease cups. These fixtures forced fresh lubricant onto the main bearings. The only other differences were paint color and minor changes in the castings. While the Eclipse is painted olive green with blood red trim, the wooden parts of the No. 9 were white, and the tips of the blades and vane were bright red.

The speed of the Dempster No. 9 is regulated by a side vane and a weighted lever. Increased wind velocities make the wheel spin faster and place more pressure on the side vane. This forces the wheel into a position closer to the principal vane slowing the speed of the wheel as its surface area is reduced. When this occurs, the weighted lever moves upward. When wind pressure decreases, the weight pulls the wheel back to its original position into the wind.

Self-oiling windmills designs took over the market in the 1920s. Dempster No. 9 became outdated and was replaced by the Dempster No. 11 oil-bath direct-stroke wooden and steel mills.

Sources

• Baker, T. Lindsay. 1984. A Field Guide to American Windmills. Norman, Oklahoma: University of Oklahoma Press. p. 182-183, 190-191.
• Baker, T. Lindsay. 2001. "Dempster No. 9." Windmillers’ Gazette. XX, No. 2 (Spring 2001) p. 8

• Baker, T. Lindsay. 2012. "Solid-wheel Wooden Windmills Made by the Dempster Mill Manufacturing Company." Windmillers’ Gazette. XXXI, No. 4 (Autumn 2012) p.2-7.

• National Park Service. Homestead National Monument of America. Dempster Mill Manufacturing Company Records, 1878-2010.

Prepared by Amy Neumann, 2019.