The Same Typical
Oliver Evans Mill Shown in Side Cross Section
This drawing shows a cut-away section of a mill equipped with the Oliver
Evans system of machinery, revealing some of the internal workings of the
mill. The mill is shown with three pairs of millstones, however,at one time
the mill may have had four pairs of millstones. The machinery shown was
installed in a restoration. For simplification, not all of the machinery
is shown. With the Oliver Evans machinery installed in a mill,such a mill
with three pairs of millstones can produce flour to supply seven bolters
(sifters) with ground flour. The millstones, on the first floor of the mill,
are the primary machinery and use 60% of the total available power. The
secondary machinery, the elevators, conveyors (augers), hopper-boy, bolters,
etc., uses the remaining 40% of the power generated by the water wheel.
It has a slightly different description being shown in side view because
of additional machinery amd over lap. There is still more machinery in the
real mill that is not shown for clearity such as more bins, elevators and
bolters. The original breast shot water wheel of this mill originally was
twice the diameter than what is shown in the drawing and what is at the
mill today. Another problem that many restored mills have over the years
with shrinking sizes of water wheels. It is not just because of lower water
tables than originally it is also partly do to their token operation as
a demonstration mill rather than a production operation.
Also shown in this drawing is the pot belly stove inside of the miller's
office on the first floor. Directly below that in the mill's basement is
a fireplace. The fireplace would have been used to heat branding irons for
branding barrel heads of flour barrels. The original level of the mill's
basement was originally 2 to 3 feet lower. The attic had storage bins or
garners for grain and tempering bins. The second floor had room size bins
in the area above the miller's office end of the building.
1. Grain- wheat or corn- goes into the RECEIVING HOPPER (behind
bins, no shown on diagram) and drops down a chute to the elevator in the
2. The elevator dumps the grain into the ROLLING SCREEN where a double
mesh screen filters out dirt and any other foreign objects. Different grains
go into different chutes and into different bins on the second floor.
3. At the end of the chute the (wheat) grain falls into the SMUTTER
or FANNING MILL. The action removes any mold that may have grown
on the grain or dirt that may be physically attached to the grain.
4. From the smutter or fanning mill the (wheat) grain falls into STORAGE
BINS, directly above the millstones.
5. From the bins the grain falls into the HOPPER that sits directly
above the hole in the middle of the MILLSTONES. The SHOE,
beneath the hopper requlates the flow of grain onto the BED STONE.
6. This is where the major work takes place. The grain falls onto the MILLSTONES
where it is cut, not ground or crushed by the rotating stones that move
at the rate of 125 revolutions per minute.
7. The ground grain is now warm and moist flour. It falls through a chute
into the basement elevators where ELEVATORS pick it up and carry
it up to the attic
8. The HOPPER BOY cools and drys the flour with a revolving rake.
9. The cooled, dry flour drops into the AUGER or CONVEYOR,
which moves it, while continuing to dry it, to the head of the BOLTER.
10. Aa revolving motion moves the flour over the BOLTER'S screens
that vary from fine to medium mesh. Flour falls through the finest mesh.
Middlings- are small bran flakes with some flour particles attached- pass
through the medium screen. And the bran, the coarest, falls out the end.
11. The flour, depending on its fineness, drops into different HOLDING
BINS and afterwards is loaded into barrels. Smaller sacks did not come
into common use until about 1900.
Note: Please save and view the above image seperately. It is much larger
than I can show it above and more detail can be seen in that way. Thank
1. The above drawing and text by T. R. Hazen appeared in "Today at
Peirce Mill-How it Works" (text and drawing), Peirce Mill, Rock Creek
Park, National Park Service (folder), G.P.O. 1990, reprint 1991, revision
and reprint 1995.
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