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The Hopper-boy of Oliver Evans

The Hopper-boy of Oliver Evans

Theodore R. Hazen

The hopper-boy, or cooler, was invented in the late 1700's by America's best known milling engineer and inventor, Oliver Evans. This mechanical device, once commonly found in the upper floor of mills, is no longer in use. It faded out of popularity less than 100 years after its invention. Designed to cool hot flour coming off the buhr stones, the hopper-boy was automated and more sanitary than the traditional method it replaced. This was one of the five inventions that were to make Oliver Evans famous to this day.

Our story begins in 1782 when Oliver Evans and his younger brother Joseph moved from Delaware to Tuckahoe, Maryland. Here they opened a store on the Eastern Shore. However, his two older brothers in Delaware were planning to run a mill. Because Oliver Evans had mechanical training and interests, he was charged by them to design the mill machinery. He began to inspect local Maryland large and small mills. Prompted by the current inefficient practices, he began to formulate his ideas for a completely automated flour mill. His efforts started with paper models of bucket elevators. He went on to build several devices which together became his new system of automated milling.

After his September 1785 marriage to Sarah Tomlinson, Evans continued work on his revolutionary ideas and perfected the principle of the hopper-boy. By September 1785, after nearly two years work, the Evans brothers had invested in a mill on Red Clay Creek near Newport, Delaware. Their aim was to secretly revolutionize milling practices utilizing the devices Oliver Evans had labored so long to perfect.

Bucket elevators, conveyors, drills, descenders, and the hopper-boy were built for the mill from models that Evans had perfected. The devices were concealed from the public, and the doors were kept locked while the interior was completely renovated. These mechanical devices would become the heart of the American, or flat grinding, system, still used by smaller, custom mills into the early 20th century.

In the pre-Evans mill, millers or boys would carry freshly ground flour sacks up ladder like stairways to the top floor or attic of the mill. Sometimes it was hoisted up using ropes and buckets or sacks, and dumped on the floor where it was spread with a rake to cool and dry it. The miller's helper in this process was called the hopper-boy. The flour might remain on the floor for many hours, filling the loft with flour while waiting for the moisture to evaporate so it would not sour later. Egg laying insects loved it! After the flour was dried and cooled, it was bolted, where again it would be deposited in hoppers or bins to age and whiten. Evans invention cooled and raked the freshly ground flour mechanically: saving labor, time, and space; and, it did a better, more complete job.

The hopper-boy was a much more difficult device to invent than the bucket elevator. Evans would later say, "Both to spread and gather at the same time then seemed absurd, and the discovery caused months of the most intensive thinking, for the absurd always presented itself to baffle and defer me!" In 1795, Evans wrote and published his famous classic, "The Young Mill-Wright and Miller's Guide" (reprint for sale in SPOOM's Bookstore) that would be reprinted three times during his lifetime, and in twelve more reprintings after his death. In his book he describes how to build his inventions.

A Description of the Hopper-Boy

Ground wheat from the millstones would fall into a bucket elevator where it was raised to the hopper-boy on the upper floor. The hopper-boy was customarily enclosed within a circular or octagonal wall (not found in Evans original drawings or descriptions) that kept the flour confined. As refinements were made, these walls became more and more completely enclosing the device, however, this would defeat its purpose as it needed an exchange of air to complete its purpose.

The miller's hopper-boy once worked in a room in the loft with a rake. But Evans hopper-boy would fill the loft with a shallow, circular tub which contained a revolving rake usually about 12 to 15 feet long. The actual size would depend on the capacity of the mill. The rake, with arms of soft poplar, was turned by a cog wheel, and it turned the flour over and over by the use of paddles. The flour was eventually swept by the device into a chute that directed it to the bolter below. The size of the rakes actual varied from 4 to 15 feet long. Smaller machines had one discharge hole to one bolter, while larger machine had two discharge holes feeding two bolters.

In operation, the rake was attached to a central vertical shaft which effected the motion about 4 rpm's. To the shaft was attached a horizontal balance arm; the arm was pinned to the vertical shaft in the center. The rake itself would float upon the vertical shaft being governed by a counter weight that was tied with a rope at one end and ran up the vertical shaft through a pulley in the shaft to the rake at the opposite end. The rake had to be able to float to adjust to the volume of the flour dumped into the tub. The counter weight regulated the length of the time flour spent in the hopper-boy. The rake, always on top of the flour, moved the flour in a declining spiral to an off-center discharge hole, or holes. The action of the rake's paddles, or flights, turned the meal over many times before falling to the bolter.

Other of Evans inventions were designed to move material horizontally or vertically through the mill. These were the elevators, the conveyors, the drill, and the descender.

The elevator raised material vertically. It was an endless strap of (white) leather that revolved over two pulleys. To the strap were attached a number of equidistantly spaced small, wooded or metal cups.

The conveyor was made of maple or smooth hardwood paddles that were attached to an endless screw and arranged in two continuous spirals. The device was placed in a wooden trough and was used to transport material horizontal through the mill.

The drill is similar to the elevator and the conveyor in design. It has an endless strap, like the elevator, to which are attached blocks of popular or willow. Moving between two pulleys, the drill moves material horizontally along the bottom of a wooden case from machine to machine.

The descender was a broad endless strap made of leather like an elevator, but moved freely over two pulleys with different elevations creating a slight downward slope. The descender operates by the weight of the material, much as water falls over a water wheel, rather than by some outside force. The material moves on top of the belt at a controlled rate, much like an assembly line conveyor belt.

When Oliver Evans opened his automated mill on Red Clay Creek, it was seen by 5 Brandywine millers. J. Shiply exclaimed, "It will not do it, cannot do, it is impossible that it can do!" But he saw it with his own eyes, and millers of the era who declined to adopt Evans's hopper-boy were doomed to produce an inferior flour. Evans thought the most of his hopper-boy invention. He organized a company in Philadelphia which made and sold milling goods; however, they refrained for whatever reason from putting their name on their goods. Thus, it is impossible to prove that any Evans produced machinery exists today.

Early 19th Century Milling

In Evans's day, American millers used the old American or flat grinding system of milling. The fast turning millstones were set close together and placed a lot of pressure on the grain. They needed to be well dressed to do their job. The object was to produce as much flour as possible through one pass through the stones. Grind once, sift once was the rule. The meal would leave the stones hot and damp; the duller the stones, the hotter would be the flour. The bran was broken into fine particles, and the middlings turned into warm clumps which would clog the bolting cloths if not cooled before bolting. Hence the need for a device (or person) like the "hopper-boy."

The hopper-boy fell out of use with the coming of the high grinding, or gradual reduction process of milling that was popularized in the 1880's. In this method, the stones were set farther apart, and naturally produced a cooler flour. The flour was additionally cooled in the elevators as it was carried up through the floors in small cups.

Coffee Roaster and Cooling Pan

An adaption of the hopper-boy is still used in some coffee mills today to cool freshly roasted coffee beans before they are ground. The adaption of the hopper-boy or cooling pan is the round red device in front of the coffee roaster (that is silver with the red hopper) to the left.

Where is the Hopper-Boy Today?

Hopper-boys can still be seen today. Remnants are occasionally found in attics with only the rakes, vertical posts, or tub circle remaining. The uninitiated do not realize what these devices did. Complete hopper-boys can be seen today at (1) Klines Mill south of Stephens City, Virginia. (2) Pierce Mill, Rock Creek Park, in Washington, D. C. where a hopper-boy from the Boxman Mill, Linesboro, Maryland was removed and reinstalled in the Pierce Mill by the Fitz Water Wheel Company on the 1930's. (3) Colvin Run Mill, Fairfax, Virginia has a reconstructed hopper-boy. (4) The Duff Roblins Mill, Black Creek Pioneer Village, located just north of Toronto, Canada, has a reconstructed hopper-boy. (5) The Hagley Museum, Wilmington, Delaware, has a working, miniature model of the hopper-boy in an Oliver Evans Mill model. (6) The Staley Mill, the oldest mill inOhio, was built in1818, at the Staley Saw Mill Farm in Miami County. It has a hopper-boy besides other musuem pieces in the mill.

Note: A version of this article by T.R. Hazen appeared in
OLD MILL NEWS, Summer 1995, Vol. XXIV, No. 3, Whole Number 92, pages 8 & 9.

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Copyright 1996 by T. R. Hazen