ASME International

The American Society of Mechanical Engineers

COLVIN RUN MILL

A HistoricMechanical Engineering Landmark

Fairfax County Park AuthorityGreat Falls, Virginia

May 20, 2001

Grain How and Mechanical Systems in Colvin Run Mill

The arrow line in the diagram below shows how grain travels through the automated milling mechanisms atColvin Run Mill.

The grinding process: numbers 1 through 11

First, grain is weighed in the beam scale (1). It is then gravity-fed into a storage bin (2) in the basement. Fromthere, a grain elevator (3) carries it up to the top floor of the mill. Then it falls into chutes (4) leading to storagebins (5) on the floor below and to the grinding stations (6) on the main floor. From the grinding stations, flourfalls through chutes to another grain elevator (7) which carries it to the top floor where it is conveyed (8) to thehopper boy (9) to be raked and cooled. It then falls to the floor below and travels through the bolting chest (10)where it is sifted and finally falls back down to the main floor where a barrel packer (11) packages it forshipping.

The major mechanisms: numbers 12 through 18

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OF COLVIN RUN MILLDIAGRAM OF THE MAJOR MECHANISMS

Top of elevator18.top floorsbasement gear assembly to equipment onVertical drive shaft: transmits power from17.Hoist16.Greater face wheel15.Wallower14.Horizontal drive shaft13.for its appearance of an oversized bird cage)Trundle (also known as "bird cage gear"12.Flour packer: for flour shipped in barrels11.of flour according to finenesswheat from flour: produces various gradesBolting chest - separates bran or skin of10.action of large paddle inside tub)Hopper boy - cools and dries flour (by stirring.9Conveyor - carries raw flour to hopper boy.8to top floorFlour/meal elevator - carries raw flour/meal.7Hopper - holds grain about to be ground.6Garner - holding raw grain for immediate use.5material, dirt, straw, smut, chaff from grainRolling screen and fan - removes foreign.4floorBulk grain elevator - carries grain to top.3Bulk grain bin - storage.2to millBeam scale - weigh-in bulk grain delivered.1

Introduction

Built circa 1813, Colvin Run Mill is the solesurviving operational nineteenth-century water-powered mill in the Washington, DC, metro area,and its restored mechanism is a nationallysignificant example of automated technologiespioneered in milling and later adopted acrossAmerican industry. The mill utilized revolutionarydesign concepts developed by the leadingmechanical engineer of the day, Oliver Evans, in his1795 book, The Young Mill-wright and Miller’sGuide. Evans’ key conceptual breakthrough,demonstrated in the Colvin Run Mill, was to link allthe processes of grinding into one continuous flowoperation by using gravity and mechanical devicesthat eliminated manual handling of grain, meal, andflour.

Automation required many mechanical motions andsome entirely novel devices invented by Evans,including a mechanical hopper boy, a raking deviceused to cool flour. Colvin Run Mill exhibits the soleoperating hopper boy known in the United States. Incombination, Evans’ milling innovations boosted

output while curtailing labor costs. In the long run,they provided direct precedents for the massproduction technologies that came to epitomizeAmerican manufacturing.

While other industries rose up by adopting similartechniques and technologies, Colvin Run Mill ranon quietly as a commercial mill for over a century,grinding grain received from local farmers forshipment to distant markets. Commercial millingended at the site in the mid-1930s and thereafter themill was abandoned. Citizen interest inspired theFairfax County Park Authority to acquire theproperty in the mid-1960s. After a completerestoration, the mill opened as a museum in 1972and visitors today can observe its historicmachinery in full operation.

Facility History and Significance

Colvin Run Mill is a working example of OliverEvans’ (1755-1819) automated process thatrevolutionized late 18 and early 19th century flourmilling in America. His innovative concepts werethe foundation of the modern automated industriesthat followed. He was granted a federal patent in1790 on milling improvements, and by 1792 morethan 100 mills had adopted his machinery. Locally,George Washington received one of the firstlicenses to use Evans’ system in his mill on DogueCreek in Fairfax County.

Flour milling was one of the most importantservices performed in 18th and 19th century Virginia.In 1774 George Washington wrote, “The whole ofmy Force is in a manner confined to the growth ofWheat and Manufacturing of it into Flour.” Whilesome large plantations operated their own mills,most people depended on one of the many water-powered gristmills scattered on local waterways fortheir flour and meal. Wheat and corn productionincreased in northern Virginia as tobacco yieldsdeclined in the 18th century, and local farmers founda wide market for their grain and milled flour alongthe eastern seaboard, in the West Indies, and inEurope. Thus, merchant mills like Colvin Run Mill

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began to develop in northern Virginia to serve thegrowing demand of local farmers and worldmarkets.

The circa 1809 merchant mill along Colvin Run,built by William Sheppard, stands on land onceowned by George Washington. Although he diedbefore the construction of the present mill,Washington recognized the potential of the locationas an ideal site for a mill and had established a millseat here in the 18th century. Philip Carperpurchased the mill from Sheppard in 1811 and in1813 he paid the first documented tax on flourproduced here.

The location of the gristmill was determined by itsproximity to a reliable source of falling water and tothe turnpike. Over time, a thriving rural villagegrew up around the mill as other businesses andservices were established by entrepreneurs eager toserve the mill’s customers. Along with the mill, ablacksmith shop, several general stores, a postoffice, and a schoolhouse became centers forneighborhood commerce and community activities.

A series of merchant millers operated the mill from1813 through the mid-1930s and their prosperitywaxed and waned with the agricultural economy.John Powell, who owned the mill during the CivilWar and Reconstruction, was especially hard hit.He filed for bankruptcy in 1872 and the milleventually was sold. By the 1880s, the localeconomy was on the upswing and the mill wasabout to enter its most prosperous period.

From 1883 to 1934, the Millard family owned andoperated the merchant mill along Colvin Run. FirstAddison, then his widow Emma, and finally theirsons Sam and Alfred modernized and rebuilt themill pond, the mill race, and the machinery. By1930 it was estimated that over one million bushelsof grain had passed through Colvin Run Mill. In themid-1930s Alfred died, Sam retired, and theirmilling business ceased. Shortly thereafter the statehighway department began construction of a newroad that went through the mill race, cutting the milloff from its power source. The mill was abandonedto sit idle for many years until local communitysupport sparked its acquisition by the Fairfax

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County Park Authority. The Park Authority thenbegan an extensive restoration that includedreconstructing the waterwheel and tunnelingbeneath the modem road to reestablish the mill race.

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Technical Background andDescription

Oliver Evans’ auto-mated milling systemintegrates several ele-ments into a contin-u o u s p r o c e s s t h a tgreatly reduces theamount of manuall a b o r r e q u i r e d t ooperate a gristmill. Heintroduced his im-provements in themachinery for grind-ing grain into meal

and flour in Chapter IX of his miller’s guide:

These...machines are...applied...so asto perform every necessary movement of thegrain, and meal, from one part of the mill toanother, or from one machine to another,through all the various operations from thetime the grain is emptied from thewagoner’s bag, or from the measure onboard the ship, until it be completelymanufactured into flour...and separated,ready for packing into barrels, for sale orexportation. All which is performed by theforce of the water, without the aid of manuallabour, excepting to set the differentmachines in motion, &c. This lessens thelabour and expense of attendance of flourmills, fully one-half.

-- Oliver Evans, 1795

In Colvin Run Mill four machines automaticallymove grain and meal from one part of the mill toanother through a continuous grinding and siftingprocess.

Grain elevators – buckets attached to endlesscanvas or leather straps which revolve over twopulleys – carry grain to upper levels at a rate ofthree hundred bushels an hour.Wooden Archimedean screws (or conveyors) –which prior to Evans had been used only to liftwater – push grain and meal horizontallythrough chutes and machinery.An automated shaker assembly sifts andseparates ground grain into different grades.A mechanical rake – called the hopper boy –stirs and spreads meal to cool and dry.

The mill machinery is powered by a twenty-footdiameter overshot waterwheel made of white oak.Inside the mill, gears with teeth of rock mapletransfer the waterpower to the grinding stones. Adense and durable wood, rock maple was difficult towork, but those qualities also made it an idealchoice for gear teeth under heavy loads. Throughouttheir work, millwrights achieved considerableaccuracy in shaping wooden parts, but theirmechanisms often included wedges that allowed amiller to adjust for the effects of aging, drying, orswelling of the material. The wooden waterwheeland gearing reflect Colvin Run Mill’s origin in theearly nineteenth century, as millwrights increasinglysubstituted iron for these parts after 1850.

The most imposing fixtures on the first floor of themill are the three grinding stations located along thewest side of the building directly above the cog pit.Two stations are equipped with pairs of millstonesthat are similar in their basic features. In each, the

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bedstone, which remains stationary during grinding,is fixed in the floor and rests on a special set ofbeams called stone bearers. An iron drive shaft thatholds and turns the upper, or runner, stone comes upthrough a hole in the center of the bedstone. Therunner stone may be raised or lowered as needed toregulate the fineness of the grind.

Waterwheel

Colvin Run Mill is powered by a twenty-footdiameter overshot wheel made of white oak. Tenarms extend out from a two-foot diameter woodenshaft. The shaft passes through the brick wall of themill from one bearing block fitted into the outerwall of the tailrace to another block inside thebasement of the mill.

a clockwise direction (when seen from outside themill) and produces up to twenty-six horsepower.The waterwheel turning outside at a rate of 10 rpmspins the top grinding stones inside at 100 rpm.

Cog Pit and Gears

The cog pit extends the length of the mill along thewest wall. It is nine feet wide and is excavated fourfeet below the level of the basement floor. Theentire gearing that transmits power throughout themill is contained within a husk frame – a heavyopen framework of white-oak posts and beams thatis set upon the building foundation but not tied intothe walls of the mill. The husk frame and themachinery enclosed within it are said to be“floating” rather than fixed within the mill.

Around the outside of the wheel are sixty bucketsinclined at an angle to catch water falling from theflume above. Each bucket holds approximatelyfifteen gallons (or 125 pounds) of water. The weightof water filling the buckets turns the waterwheel in

The gears transmit power from the waterwheel to allthe machinery in the mill, including three shakerboxes in the basement, the three grinding stationson the first floor, the bolting chest and hopper boyon the upper floors, and the grain elevators thatoperate throughout the four floors of the mill.

Fitted onto the interior part of the waterwheel shaftand taking its power directly from the waterwheel,is the ten-foot diameter greater face gear. A series

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of wooden teeth, made of rock maple, are set intothe rim of the greater face gear to engage woodenteeth on the eight-inch diameter vertical powershaft. The vertical shaft extends up to the top floorof the mill and transmits power from the water-wheel to the machinery on the upper floors and tothe grain elevators.

To transmit power to the grinding stones on thefloor above, the greater face gear engages a series ofother gears. Two of these gears, called wallowers,take their power directly from the greater face gear.The wallowers have “teeth” formed of twelve-inchwooden pins sheathed in metal and set between twosolid wooden three-foot eight-inch diameter disks.

Each wallower is attached to a sixteen-inchdiameter horizontal wooden drive shaft set at rightangles to the waterwheel axle. On each end of thesmaller shafts, opposite the wallower, is anotherwooden toothed gear called the lesser face. Thelesser face gears are seven feet eight inches indiameter.

Hopper Boy

The hopper boy is a mechanical raking machineinvented by Oliver Evans to cool and dry flour as itcame from the millstones prior to being sifted.Grain elevators carry the warm, moist flour fromthe shaker box in the basement up to the top floor ofthe mill where it is deposited in the hopper boy.

Colvin Run Mill’s hopper boy is a circular woodentub, eight feet in diameter, with low side walls andan open top. A long counter-balanced arm mountedon a center post extends across the enclosure androtates when power from the waterwheel istransmitted to it by the vertical shaft. Flights,inclined wooden paddles on the underside of thearm, stir and spread the flour evenly until cooled.As the flour is raked, the flights push it to the centerof the hopper boy where it falls through a hole intoa chute leading to the bolting sifter on the floorbelow.

Facility Contribution

Colvin Run Mill is an outstanding example of thebeginnings of early America’s technologicalinnovations. Restoration work conducted by theFCPA from the mid-1960s to 1972 returned the millto operational condition and restored its earliestappearance. Today the mill grinds again, providingflour and corn meal not for the ports of the world orfor neighboring households, but for visitors fromboth. Standing as a reminder of the beginnings ofAmerica’s technological might, it is a masterpieceof timeless craft skill and a landmark design thathelp launch the industrial era.

Open to the public since 1972, the mill is thecenterpiece of a historic site that also includes anineteenth century miller’s house, a circa 1900general store, and an interpretive barn with adjacentworking blacksmith shop. The historical facilitiesare used for interpretive exhibits, demonstrations,and special programs that provide educational andrecreational experiences for visitors of all ages.

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Text of the Colvin Run Mill Plaque Bibliography

1.Miller’s Guide. Reprinted by Arno Press Inc.: 1972.

2. Ferguson, Eugene S. Oliver Evans, InventiveGenius of the American Industrial Revolution.Greenville, DE: The Hagley Museum, 1980.

3. Ford, Thomas K. The Miller in 18 th-CenturyVirginia. Williamsburg, VA: ColonialWilliamsburg, 1973.

4. Netherton, Ross D. Colvin Run Mill. Fairfax,VA: Fairfax County Office of ComprehensivePlanning, 1985.

Evans, Oliver. The Young Mill-Wright and

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® 2001

ENGINEERSTHE AMERICAN SOCIETY OF MECHANICAL

INDUSTRIES.FOUNDATION OF MODERN AUTOMATED

DEMONSTRATED HERE WERE THEGRISTMILL. THE INNOVATIVE CONCEPTSORDINARILY REQUIRED TO OPERATE A

REDUCED THE MANUAL LABORTHIS INTEGRATED MACHINERY GREATLY

STEPS TO PRODUCE FLOUR AND MEALCONTINUOUS GRINDING AND SIFTINGANOTHER THROUGH A SEQUENCE OF

GRAIN FROM ONE PART OF THE MILL TOMACHINERY AUTOMATICALLY MOVES

WATERWHEEL, A COMBINATION OFEVANS. POWERED SOLELY BY A

MILLING PROCESS ORIGINATED BY OLIVERCENTURY. ITS OPERATION IS BASED ON A

THINNOVATIONS EARLY IN THE 19OF AMERICA’S TECHNOLOGICAL

THIS MILL IS AN OUTSTANDING EXAMPLETHE AUTOMATED PRODUCTION SYSTEM OF

c. 1809COLVIN RUN MILL

ENGINEERING LANDMARKHISTORIC MECHANICAL

The American Society of Mechanical Engineers (ASME)

John R. Parker, P.E., PresidentRaymond L. Jackson, Vice President, Region IIIVirginia W. Ross, Region III History and Heritage ChairD. Yogi Goswami, P.E., Senior Vice President, Public AffairsVictoria A. Rockwell, Vice President, Public InformationDavid L. Belden, P.E., Executive DirectorCecilia Noblett, Director, Eastern Regional Office

The ASME History and Heritage Committee

R. Michael Hunt, P.E., History and Heritage ChairRobert M. Vogel, SecretaryWilliam J. Adams, Jr., P.E.John K. BrownWilliam DeFotisPaul J. Torpey, Past PresidentHerman Viegas, P.E.Diane Kaylor, Staff Liaison

The ASME Washington D.C. Section

Pamela Forshay, ChairHorace Whitworth, Vice ChairIheanyi Eronini, P.E., SecretaryGurmukh Mehta, TreasurerRonald D. Rolfe, History and Heritage

The Fairfax County Park Authority (FCPA)

Frank A. de la Fe, Chairman of the BoardRichard Thoesen, Board Member, Dranesville DistrictPaul L. Baldino, DirectorMike Kane, Deputy DirectorLee Stephenson, Resource Management DirectorEugene Biglin, Site Operations ManagerMichael Henry, Colvin Run Mill Historic Site, AdministratorAnn Korzeniewski, Colvin Run Mill Historic Site, Assistant Administrator

Acknowledgement

The ASME Washington DC Section gratefully acknowledges the assistance of theFairfax County Park Authority for the use of their photographs.

The History and Heritage Program of the ASME

The History and Heritage Landmarks Program of ASME (the American Society ofMechanical Engineers) began in 1971. To implement and achieve its goals, ASMEformed a History and Heritage Committee initially composed of mechanical engineers,historians of technology and the curator (now emeritus) of mechanical engineering atthe Smithsonian Institution, Washington, D.C. The History and Heritage Committeeprovides a public service by examining, noting, recording and acknowledgingmechanical engineering achievements of particular significance. This Committee ispart of ASME’s Council on Public Affairs and Board on Public Information. Forfurther information, please contact Public Information at ASME International, ThreePark Avenue, New York, NY 10016-5990, 1-212-591-7740.

Designation

Since the History and Heritage Program beganin 1971, 213 landmarks have been designatedas Historic Mechanical EngineeringLandmarks, Heritage Collections or HeritageSites. Each represents a progressive step in theevolution of mechanical engineering and itssignificance to society in general. Sitedesignations note an event or development ofclear historic importance to mechanicalengineers. Collections mark the contributionsof a number of objects with specialsignificance to the historical development ofmechanical engineering.

The Landmarks Program illuminates ourtechnological heritage and encourages thepreservation of the physical remains ofhistorically important works. It provides anannotated roster for engineers, students,educators, historians, and travelers. It helpsestablish persistent reminders of where wehave been and where we are going along thedivergent paths of discovery.

The 125,000-member ASME International is aworldwide engineering society focused ontechnical, educational, and research issues.ASME conducts one of the world’s largestpublishing operations, holds some 30technical conferences and 200 professionaldevelopment courses each year, and sets manyindustrial and manufacturing standards.

The Nominator and Authors

This brochure was compiled from sourcesfound in the Colvin Run Mill Historic Sitelibrary and it was edited by Ann Korzeniewskiand Ronald D. Rolfe.

Mr. Rolfe is an analyst in the MissileTechnology Division, Bureau of ExportAdministration, U.S. Department ofCommerce in Washington, D.C. He is anASME member and past Chairman of theWashington D.C. Section. An avid fan ofhistory and technology, this Landmarkdedication effort has been a perfect mergingof these two interests.

Ms. Korzeniewski has worked at Colvin RunMill Historic Site for ten years and has beenassistant site administrator since 1997. Shesupervises the site’s volunteer program,historic artifact collections care, museumeducation and public programs, museum sales,and visitor services.

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