Schematic Layout of a Typical Oliver Evans Mill
1. Begin with Ted Hazen (miller on left), miller empties sacks of grain into receiving hopper on mill's first floor. The receiving hopper would have a bin scales hanging from the ceiling joist above it. This is a box with a bottom hopper and gate above this bin hung from four rods connected to a large beam scales. The receiving hopper has a lid to keep things out of it when not in use and a wire grate over the 4 by 4 inch hole in the bottom of the hopper just above the gate. The gate has a diamond hole in it and a control arm on the mill's first floor. The diamond hole allows for a controlled flow of grain down the chute for the receiving elevator. The flow of grain can be completely shut off or open a little bit to a lot. The miller uses the inspection window on the elevator leg to see how full the elevator cups are. The miller might hang empty sacks on the open bin lid or on a ceiling hanger in this area. Also in this area is the holding bin on the mill's second floor. The holding bin allows for the grain to be received into the mill and stored in a bin but it is cleaned at a later time. A control gate is in the ceiling area above the receiving bin area. 2. The grain flows down the chute to the mill's basement. In this chute and or the return chute on the first floor would be a removable section of chute with a magnetic separator, a series of staggered horseshoe magnets placed in the chute to catch tramp iron. The grain falls down the chute and is picked up by the upturned cups on the receiving elevator. The bottom housing of the elevator that contains the free turning pulley is called the elevator boot. 3. The grain is carried up the legs of the receiving elevator. On different levels the miller would have hung sticks made out of broom handles in case the elevator belt and cups get stuck inside the box. It is better to tare up the wood on the stick than loose a finger. The stick is also used to tighten the tension on both free ends of the elevator belt when lacing or bolting it together. The grain is carried in the cups until it reached the top of the elevator and the down turned cups empty the contents down a chute. The top of the elevator is called the head, and this is where the driver pulley drives the elevator belt and driven pulley on the bottom. 4. From the receiving elevator head the grain flows down several chutes depending upon how the gates are adjusted. The grain can flow into the following areas: (1) the large floor-to-ceiling holding bin on the mill's second floor; (2) the millstone bin on the mill's second floor directly above the millstones on the mill's first floor. This millstone bin is shown second and third from the left of the drawing. In the third view (from the left) of the millstone bin is show a passive grain cleaner. A passive grain cleaner makes use of no mill power just the flow of the grain down the chute. A section of the bottom of the chute has been removed and a mesh screen filters out the smaller particles than the size of the grain. The trash falls into a sack that is hung on a chute with a sack-boy; (3) into the rolling screen. 5. The rolling screen (in the mill's attic) contains two reels of different mesh screen. A larger inner screen and a finer outer mesh screen. The inner larger mesh screen allows the wheat, rye, buckwheat, oats, and barley to fall through the opening but not the larger size corn. The inner screen is longer and its ends above a chute that directs the corn down to the corn bin above the millstones that are used to grind corn. The trash from the corn falls through the outer screen and down the bottom hopper of the rolling screen to be removed as it fills a sack or a barrel on the mill's second floor. The process of milling corn is continued in Part Two. The wheat, rye, buckwheat, oats, and barley are are caught on the smaller mesh outer screen while the smaller trash particles falls down the hopper below. This screen ends and the wheat, rye, buckwheat, oats, and barley falls down a different chute and into the smutter to the lower right of the rolling screen. 6. The smutter is attacked to the lower tail end of the rolling screen and receives smaller size grains to remove the smut and other particles attached physically to the grain while the rolling screen primarily removes material mixed in the grain. Material removed by these two machines are dirt, seeds, sticks, straw, chaff, fungus, smut, broken grains, and bugs. The smutter is a vertical machine with a drum on the top with a series of revolving disks with raised nubs up which the grain is bounced around and material clinging to the grain is broken loose. The mixture then falls down into an aspiration chambers on each side of the drum where a current of air that is generated by a fan below the drum. The heavier grain falls down a chute into the millstone bin below while the lighter material is aspirated away. One aspiration chamber blows its trash into the hopper blow the rolling screen and the other aspiration chamber blows its trash either out an exhaust duct on the wooden gable wall of the mill above the water wheel or into a box or chute. The clean grains fall into a millstone bin on the mill's second floor above the center millstone in the mill. 7. On the bottom of the three millstones bins on the first floor millstone area is a control gate. The gate allows the grain to fill the millstone hoppers and close off the flow for the chute to be removed by a set of 4 pegs that hold the removable section of chute in place above the millstone hopper. These three chutes are removable so the millstone covers can be removed and the millstones be cleaned or dressed.
A-1. Plan- Lower stationary (bed) millstone. Also shown is millstone shaft spindle, & bearing blocks. Millstone chute and cribbing around bed stone. There are 4 wooden stop blocks around the outer edge of the cribbing that hold the vat or millstone cover in place. B-2. Plan- Hopper & vat. Also shown is grain flow control gate in hopper. Miller's willow & part of shoe. There are two wooden pins on the bottom of opposite diagonal legs of the horse that fit into the top cover of the vat. C-3. Elevation- Hopper & vat. Also shown is damsel, horse (frame) and crook string to basement that goes over the roller on the front of the horse. D-4. Section- Hopper, vat & millstones. Also shown is damsel, horse (frame), shoe, crook string (leather), cribbing, bed stone, millstone shaft bearings, millstone spindle, driver, and runner millstone. The damsel is sitting on the balance rynd shown only in side view directy underneath damsel. Missing in the drawing is the top of the millstone spindle called the cocks head where the underside of the damsel, called the cock's eye sits upon it. 8. The process of milling wheat is done on the center millstone which is a 56 inch diameter pair of French Millstones. The grain fills the millstone hopper and the flow of grain is controlled with a gate on the front side of the hopper. This gate controls the flow or movement of grain out of the hopper into the shoe. The shoe can be raised or lowered to regulate the flow of grain into the millstones. The shoe is moved back and forth by the turning damsel which shakes the shoe this allows for a constant rate of grain into the millstones either a little or a lot. The shoe is held tightly against the damsel by the miller's willow an ash spring attached to the side of the horse frame. The shoe is hung from the horse frame and its longer end is attached a leather crook string which goes down through the first floor into the mill's basement where it is wrapped around a twist peg. A warning bell would let the miller know that the volume of grain in the millstone hopper is low and more grain needs to be added or the mill shut down. 9. The grain falls into the eye of the top runner millstone and moves between the two millstones. The top revolving millstone is called the runner while the lower stationary millstone is called the bed stone. The millstones would be adjusted to grind the grain coarse or fine. This process is called tentering and would be either done with a lighter staff and bottle weight or lighter screw and hand wheel. The grain falls down a chute. A value or gate in the chute would either send the grain to a chute which would feed into a meal elevator or down a chute into a meal bin. 10. The meal bin is located in the mill's basement. The ground grain or chop falls out of the chute onto a moving screen that oscillates back and forth above the bin. These bins were used in the Oliver Evans system of milling to do custom milling. This would allow the miller to grind small batches of grain rather than larger amounts done in merchant milling. The term batch milling is also used at times in place of custom milling since each farmer's grain or batch would be milled differently. The sifter screen is powered by the millstone spindle from a pulley and a leather belt that turns a smaller pulley with an eccentric that oscilates the one of the sifter screen back and forth. This is located at the head or higher end of the sifter screen and at the tail or lower end is a wooden spring attached to the side of the meal bin. The sifter screen has a removable panel which holds a variety of different size mesh screens. The larger mesh screen would allow whole wheat to fall through the screen and the wheat bran to tail out of the sifter screen and be caught in a sack or barrel next to the meal bin. This screen has either 16 or 18 openings per liner inch. Another double screen would be used with a small wooden box about 18 inches square that fits into the meal bin underneath the seperation in the two different sizes of screen. One mesh would be that of 16 or 18 openings per liner inch (or basically window screen size mesh), and the other would be twice as small or 32 openings per liner inch. Through the finer mesh screen toward the head of the sifter screen wound fall the unbleached white flour, through the larger screen over the box would fall the wheat cereal and what would tail out of the sifter screen would be the wheat bran. Another sifter screen would have a finer screen of 64 opening per liner inch would sift out cake and pastry flour would the rest would tail out the end. The tailings would would be mixed with whole wheat in the millstone hopper to continue grinding cake and pastry flour. Soft wheat is used to make cake and pastry flour and hard wheat is used to make bread flours while a mixture of the two is used to make all-purpose flours. Grinding buckwheat because of its hulls would require the double mesh screen. The large meal bin in the mill's basement has an over flow chute like the two large bolters in the second floor so the excess can be caught in a box or container. 11. The ground material or chop can be send down the chute into the meal elevator. The meal elevator carries the ground grain from the elevator boot up the lets to the head of the elevator. The ground material would fall our of the elevator down into the delivery chute, where a value or swell would contain a movable gate which is controlled by a set of long ropes on the mill's first floor. The miller could remain on the mill's first floor and either send the ground grain directly into the 14 foot reel bolter or the hopper-boy. The hopper-boy bypass chute feeds the ground grain into the conveyor (or auger) underneath and comes from the hopper-boy to travel only a short distance down a discharge chute into the bolter on the mill's second floor. The value can also send the warm ground flour into the hopper-boy to be cooled so it does not stick to the mesh screens in the bolter. When Oliver Evans invented the hopper-boy the millers were only grinding soft wheat. Soft wheat when it becomes warm and damp from grinding with the proper moisture content is tends to clog around the millstones, in chutes and in the screens of the bolters. Later the mill when the millers felt the hopper-boy was no longer needed the millers were grinding hard wheat or a mixture of hard and soft wheats would would not tend to clog as much. 12. The hopper-boy is a revolving rake in a low walled tub that is located in the attic of the mill. The underside of the rake has paddles which are turned inward so when material is delivered to the outer circumference of the tub the material is moved inward with each revolving pass of the rake. As the rake revolves the flour is turned over and it cooled. The rake is "floating" with a counter-weight which is attached with a rope over a pulled set into the vertical shaft above the rake. This allows the rake to float or move on the surface of the flour being cooled in the tub. This process is used when the amount increases with a large build up or decreased to a normal operating rate. When the mill is stopped the counter-weight allows the rake easily to be lifted for cleaning or to allow the hopper-boy tub to become a temporary storage area for ground meal. 13. The conveyor (or auger) underneath the hopper-boy can be operated in two directions. Putting a twist into the belt reverses its direction and send the cooled flour or meal by-passing the hopper-boy down a chute back to the mill's first floor for regrinding. Keeping the belt flat or straight sent the material in the direction toward the head of the large 14 foot bolting reel. The flour enters the bolting reel at the head or higher end. This is where the finer mesh screen or cloth is located. At the head is an inspection door and an overflow chute that dumps the excess into a small bin or box. This is a fixed bolter because it has no movable dividers underneath the reel. The first screen on this reel is 32 mesh openings per liner inch. Then at the welded divider it changes to 16 openings per liner inch. Out of the finer screen would come unbleached white flour and out of the larger mesh would come wheat cereal or wheat middlings. Then tailing out of the lower or tail end would come the wheat bran. Because of the two dividers underneath the reel and the extra hole pattern in the conveyor the bolter may have been originally set up with three meshes of screen rather than two. The bolter also has several gates underneath the conveyor on the west side so alternative grading can be done with the bolter. By opening one gate underneath the bolter it allows the material to flow directly down to the first floor where it fills a sack. Note: When I was at the mill I replaced the screen on the bolter that was removed and sold by the miller Raymond Watt when he retired in December of 1958. Mr. Watt sold the screen for 10 dollars. The bolter reel was not covered with bolting screen or cloth during the period that Bob Batte was the miller. People were not allowed on the second floor of the mill until Bob Batte became the miller in 1971. 14. The inspection holes and openings allow you to check, clean and oil the bolter. The long large side inspection doors that the window openings are covered with wire mesh screen and cloth are to keep out rodents and to keep down the dust. The round tear drop inspection doors are called wicket gates. The unbleached white flour would come out of the conveyor underneath the reel and go down through the floor by a chute into another conveyor mounted underneath the ceiling of the first floor. The flour goes down the conveyor and a chute to the white flour bin. The white flour bin has two separate sections this allows for one side to be filling and the other side being packaged, or the grind and bolting of the grain has been switched from wheat to perhaps rye. The flour comes down to the bin and underneath the top of the bin behind the lids is a value or movable chute that directs the flow from one side to the other. 15. The wheat cereal or wheat middlings comes down the chute from the conveyor into another conveyor also mounted underneath the ceiling of the first floor of the mill. The wheat cereal or wheat middlings goes down the conveyor and is deposited into a wall bin. Material can be drawn out of the bin in two ways. First by the narrow lid which is used to fill small sacks and second by the chute gate underneath that can be used to full sacks, or would also fill barrels in needed. Material that is collected in another part of the mill like from the basement sifter screen can be hoisted to the second floor and dumped into the bin from above. The double screen door is so the bins can be cleaned and the back conveyor or auger bearing oiled. 16. The wheat bran comes down the chute from the tail of the reel directly through the floor and into a conveyor underneath the ceiling of the first floor. Like the wheat cereal or wheat middlings bin the material can be drawn out of the bin in two ways. First by the narrow lid which is used to fill small sacks and second by the chute gate underneath that can be used to full sacks, or would also fill barrels in needed. Another option for this bin is a smaller lidded hopper on the second floor east wall. Material that is collected in another part of the mill like from the basement sifter screen can be hoisted to the second floor and dumped into the bin from above. The double screen door is so the bins can be cleaned and the back conveyor or auger bearing oiled. The one side of this bin formed the wall of the miller's office.
1. The process of milling corn is begun after the corn is either sent through the rolling screen or by-passing it and using the passive grain cleaner. A passive grain cleaner makes use of no mill power just the flow of the grain down the chute. A section of the bottom of the chute has been removed and a mesh screen filters out the smaller particles than the size of the grain. The trash falls into a sack that is hung on a chute with a sack-boy. The one used for corn would have a larger mesh screen than the one used for wheat which would have a smaller mesh. 2. The process of milling corn is done on the left millstone which is a 46 inch diameter pair of mill stones from Berks County, Pennsylvania. The grain fills the millstone hopper and the flow of grain is controlled with a gate on the front side of the hopper. This gate controls the flow or movement of grain out of the hopper into the shoe. The shoe can be raised or lowered to regulate the flow of grain into the millstones. The shoe is moved back and forth by the turning damsel which shakes the shoe this allows for a constant rate of grain into the millstones either a little or a lot. The shoe is held tightly against the damsel by the miller's willow an ash spring attached to the side of the horse frame. The shoe is hung from the horse frame and its longer end is attached a leather crook string which goes down through the first floor into the mill's basement where it is wrapped around a twist peg. A warning bell would let the miller know that the volume of grain in the millstone hopper is low and more grain needs to be added or the mill shut down. 3. The grain falls into the eye of the top runner millstone and moves between the two millstones. The top revolving millstone is called the runner while the lower stationary millstone is called the bed stone. The millstones would be adjusted to grind the grain coarse or fine. This process is called tentering and would be either done with a lighter staff and bottle weight or lighter screw and hand wheel. The grain falls down a chute. A value or gate in the chute would either send the grain to a chute which would feed into a meal elevator or down a chute into a meal bin. 4. The meal bin is located in the mill's basement. The ground grain or chop falls out of the chute onto a moving screen that oscillates back and forth above the bin. These bins were used in the Oliver Evans system of milling to do custom milling. This would allow the miller to grind small batches of grain rather than larger amounts done in merchant milling. The term batch milling is also used at times in place of custom milling since each farmer's grain or batch would be milled differently. The sifter screen is powered by the millstone spindle from a pulley and a leather belt that turns a smaller pulley with an eccentric that oscillates the one of the sifter screen back and forth. This is located at the head or higher end of the sifter screen and at the tail or lower end is a wooden spring attached to the side of the meal bin. The sifter screen has a removable panel which holds a variety of different size mesh screens. The larger mesh screen would allow corn meal to fall through the screen and the corn bran to tail out of the sifter screen and be caught in a sack or barrel next to the meal bin. This screen has either 16 or 18 openings per liner inch. Another double screen would be used with a small wooden box about 18 inches square that fits into the meal bin underneath the separation in the two different sizes of screen. One mesh would be that of 16 or 18 openings per liner inch (or basically window screen size mesh), and the other would be twice as small or 32 openings per liner inch. Through the finer mesh screen toward the head of the sifter screen wound fall the corn flour, through the larger screen over the box would fall the corn grits and what would tail out of the sifter screen would be the corn bran. Another sifter screen would have a finer screen of 64 opening per liner inch would sift out corn starch would the rest would tail out the end. The tailings would would be mixed with whole corn in the millstone hopper to continue grinding corn starch. In milling corn field corn is used. Corn meal can be bolted and unbolted. 5. The corn can be bolted on the second floor small bolting reel. To use the bolting reel and corn elevator remove the sifter screen. The leather belt moving the sifter screen need not be removed in fact it works better it is moving. A short chute fits in the cut in the bin and onto the boot of the elevator. The drive pulley needs to be engaged on the second floor of the mill to activate this elevator. This elevator carries the ground corn to the second floor to the bolting reel. 6. The ground material enters the bolting reel at the head or higher end. This is where the finer mesh screen or cloth is located. At the head is an inspection door and an overflow chute that dumps the excess into a small bin or box. This is a fixed bolter because it has no movable dividers underneath the reel. The first screen on this reel is 32 mesh openings per liner inch. Then at the welded divider it changes to 16 openings per liner inch. Out of the finer screen would come corn flour and out of the larger mesh would come corn grits. Then tailing out of the lower or tail end would come the corn bran. This bolter is build with no conveyor or auger underneath as in pre-Oliver Evans bolters. The sifted material would either lay on the bottom or fall down hoppers down a chute either into sacks or bins below. Because has a movable divider underneath the reel and the bolter has more flexibility in how it can be used. If divider is up the bolting reel sifts out three products: corn flour, corn grits and corn bran, then material comes out the three chutes on the first floor. If the diver is down then the corn flour is mixed with the corn grits and the material coming out the corn grits chute is corn meal, and corn bran comes out of its chute. 7. The inspection holes and openings allow you to check, clean and oil the bolter. The long large side inspection doors that the window openings are covered with wire mesh screen and cloth are to keep out rodents and to keep down the dust. The round tear drop inspection doors are called wicket gates. The one side has large double doors that open for easy cleaning or demonstrations to the public. The other side the doors can be slid out of place for opening also. 8. The chutes on the first floor are removable with 4 pegs each so they can be removed and hung out of place when the bolter is not used. The chutes can be used to fill sacks or barrels. The barrels can have lids with square holes the side of the chutes to cut down on the dust. 9. This millstone and bolter on the second floor can also be used to mill wheat, buckwheat, rye, oats or barley. The bolter becomes convent to produce a variety of products.
1. The sack hoist in mainly used in this process but can be used with the meal bins in the mill's basement. The tub or bucket has two round rollers on the bottom. It fits underneath the end of the sifter box screen so it can be used to catch tailings. Most sack hoists work only in the upward direction. This sack hoist works in the downward direction to unwind the rope only. It has no downward breaking motion and any weight on the end of the rope will drop faster than it is unwinding. Basically it will drop down and can be dangerous if you don't hold the rope and break the weight of the bucket. The rollers underneath the bucket means that if the bucket is not directly underneath the trap doors when the upward rope is engaged the bucket will roll along the floor until it reaches the trap doors and then it will be lifted upward. 2. The same line shaft in the mill's attic that engages the hopper-boy also engages the sack hoist. In the sack hoist the center pulley is always turning. The rope is wrapped around the top shaft with pulley and then once around the lower shaft with its pulley. If neither control rope is pulled only the center pulley and shaft will turn. If the control rope is pulled for the upward motion the upper arm is pulled down and the upper pulled is engaged and allowed to turn thus raising the rope through the floors. When the rope is released the counter-weight disengages the pulley and stops it lifting motion. Then if the other control rope is pulled it raised the lower pulley to unwind the rope from the upper pulley. When the rope is released the unwinding effect stops because of a counter-weight disengages the pulle and stops its lowering or unwinding motion. 3. Care must be taken so the sack or bucket on the end of the rope is not raised too far and thrown through the roof as it tried to go over the top rope pulley mounted underneath the ridge of the mill roof. Some mills in England has the rope going through a spring loaded control that stopped the lifting motion of the sack hoist if it lifted it too far. On each floor is a pair of trap doors with a round hole in the center to allow the rope to travel upward or back down. As the bucket or sacks comes up through the trap doors it opens them and then they are closed as the weighted objects passes it. This is so one man can operate the sack hoist by himself thus lowering the bucket or sack on to the closed doors. See Ted Hazen (miller on left) holding the neck of a sack. The control ropes reach all the way to the mill's basement and are independent of the holes in the floor for the trap doors. 4. The grain (mainly wheat) is dumped (see Ted Hazen miller on upper right) into a tempering and conditioning bin usually located in the mill's attic underneath the eaves. The attic and basement are not the ideal locations in the mill to store grain or flour products because of the heat and the dampness. But with the process of tempering and conditioning the heat of the attic is used along with water to do the process. Wheat is tempered and conditioned to toughen up the bran and make it come off in a larger flake rather than being brittle and breaking up into small particles that is then very hard to separate later in the milling process. Millers have been doing this process for centuries and it is still used in mills today but with the aid of mechanical instruments that moniteor the moisture levels in each batch of wheat. Long ago miller would have dumped the wheat into a bin and sprinkled water on the wheat and turned it over several times. Then they would have continued to turn it over and over again for a period up to 72 hours. 5. Some times after the grain is tempered and conditioned, the grain is run through a widely spaced pair of millstones to rub off the bran. One example of this would be to pearl barley. A widely spaced pair of millstones can be used as an "ending stones" to rub off adhered material from the grain such as dirt, fungus and smut. Another option with the mill is to begin grinding wheat on the one smaller pair of 48 inch French millstones sift the wheat out for one product (such as cake and pastry flour) using the mill's meal bins in the basement and then hoist up the tails to mix with fresh wheat grinding on the center larger pair of French millstones.
Note: Thanks to the Historical American Building Survey. Images courtesy of HABS for the use of drawing sheets #16 and #17 of 22 measured drawings of Pierce Mill. Pierce Mill, Tilden St. & Beach Dr. N.W. (Rock Creek Park), Washington, District of Columbia, DC. Survey number HABS DC-22 Technical assistance for the Pierce Mill HABS drawings was provided by T.R. Hazen, a Molinological Specialist and former National Park Service employee. The above text and concept by T.R. Hazen. Return to Home Page mailto:trhazen@hotmail.com
