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CONSTRUCTION AND EVALUATION OF A PLOT COMBINE
FOR USE IN PLANT BREEDING RESEARCH

By
E311 flyjord

AN ABSTRACT

Submitted to the College of Agriculture of Michigan
State University of Agriculture and Applied
Science in partial fulfillment of the
requirements for the degree of

MASTER OF SCIENCE
Department of Agricultural Engineering

1962

 

ABSTRACT

Plant breeders around the world have stated that it is
desirable to combine small grain plots in the early stages
of a breeding program in order to judge the standing ability
of new strains.

Research funds saved by use of labor-saving machinery
permits additional experimentation.

The major problem in using combines for harvesting
variety plots is avoiding the mixing of the seeds between
plots. So far all the reported rebuiltand especially de-
signed plot combines require clean out time to completely
clean between each variety.

Only a completely self-cleaning plot combine will have
the necessary capacity for harvesting the high number of
plots in an early stage of a modern breeding program.

This thesis presents the design and development of a
plot combine that was built to test various cutting, thresh-
ing, separating, and cleaning principles and develOp para-
meters for the design of an acceptable self-cleaning plot
combine for small grain.

The essential parts of the combine were as follows:

1. A Q-row cutterhead with flail and fan action

for cutting, threshing, and elevating the grain
and straw to the separating and cleaning device.

{\J

. A swirl-chamber for separating the grain from
the straw and chaff.

3. A 5.75 hp 2-wheel garden tractor as a power
unit.

Four different types of flails were mounted in the

cutterhead and used on single rows of wheat, 12 feet long.

The experimental procedure was as follows:

1. Cutterhead losses of threshed and unthreshed
grain were caught on a canvas placed on each
side of the test row.

2. Swirl-chamber losses of threshed and unthreshed
grain, as well as the total straw and chaff
entering the machine, were caught in a burlap
sack connected to the outlet of the grain
separator.

3. The clean grain was collected in the grain box
on the machine.

The efficiency of the various parts of the combine were
calculated from measurement data gained from weighing the
material from each receptacle at the end of the tests.

Visible kernel damage was calculated as percent damaged
kernels in the grain box.

The total cutterhead losses of threshed and unthreshed
grain were larger than could be accepted for practical use
of the experimental machine. The highest percent of grain
recovered by the cutterhead was 84.4. This was obtained
with the propeller flails and a height of the cutterhead of
27 inches.

In general, the total cutterhead losses of grain de-
creased with increased plot yield. The cutterhead losses
of unthreshed grain were small compared with the cutterhead
losses of threshed grain except for the modified direct

throwing flails.

The swirl-chamber was tested with two shapes. Shape 1
gave the best solution. The average losses of threshed grain
were 2.34 percent at a straw separation of 92.1 percent. The
corresponding averages for shape 2 were 1.9 percent at a
straw separation of 77.9 percent. A strong relation between
swirl-chamber loading and separating efficiency was observed.

Because the percent cylinder losses as determined by
the regression equation Y = 0.487 - 0.00108 (flail speed in
rpm - 1240) were fairly constant in the speed range between
1,100 and 1,300 rpm, the pooled standard deviation of 0.47
percent provided a fairly good estimate of the dispersion of
the calculated average cylinder losses of 0.487 percent.

The visible kernel damage increased from 0 percent at
1,075 rpm to 3.16 percent at 1,300 rpm. It was concluded
that a peripheral flail speed above 1,300 rpm or 5,500 fpm I
should not be used for harvesting wheat plots under average
harvesting condition.

The plot-combine was found to be self-cleaning with
respect to the grain if the fan speed was reduced between

the plots.

CONSTRUCTION AND EVALUATION OF A PLOT COMBINE
FOR USE IN PLANT BREEDING RESEARCH

By

Egil dyjord

A THESIS

Submitted to the College of Agriculture of Michigan
State University of Agriculture and Applied
Science in partial fulfillment of the
requirements for the degree of

MASTER OF SCIENCE
Department of Agricultural Engineering

1962

7

/7CR36=

'27 «C35? (".22.

ACKNOWLEDGMENTS

The author wishes to express his sincere thanks and ap-
preciation to all who contributed to this investigation. In
particular, the contribution of the following are recognized:

Dr. W. F. Buchele, who as my major professor continu-
ally provided suggestions, guidance, and inspiration through-
out the entire investigation. His support through editing
the manuscript is especially appreciated.

Dr. E. H. Everson, Farm Crop Department, for warm
interest in the project, and for providing most of the
financial support. His suggestions are very much appreciated.

q.

He is also indebted to the other embers of the guidance
J

E?

committee, Dr. J. E. Grafius, Dr. . F. Hannah, and Dr. B. A.
Stout.

The W. K. Ke110gg Foundation and the Agricultural Re-
search Council of Norway which made this research possible
by granting me stipends for studies in the U.S.A.

Director Anton Letnes, chairman of the Joint Committee
on Mechanization of Field Experiments in Agriculture and
Horticulture, for recommendation of leave for me when under-
taking a graduate study in the U.S.A.

Mr. James Cawood, shOp foreman, who always did an ex-
cellent job in providing the necessary materials, tools, and
instruments for the work.

.Mr. Hormoz Alizadeh and Mr. Keith Ward, Agricultural

Engineering students, who helped me build and test the machine.

 

lABLE OF CONTENTS

INTRODLICTIOI‘ o o o o o o o o o o o o 0

REVIEW OF LITERATURE . . . . . . . . o

Harvesting methods for small grain plots

Principles of plot threshers . . .

Principles of plot combines . . . .

0

New threshing and separating principles

SELECTION OF COMPONENTS FOR THE COMBINE
Calculation of required capacity .
Cutting . . . . . . . . . . . . . .
Conveying . . . . . . . . . . . . .
Threshing . . . . . . . . . . . . .

Separating and cleaning . . . . . .

Propelling . . . . . . . . . . . .
CONSTRUCTION OF THE COMBINE . . . . . .
The cutting and threshing mechanism

The prOpeller flails . . . . .

The direct throwing flails . .

The modified prOpeller flails .

The modified direct throwing flails

The flail housing . . . . . . .

The elevating duct . . . . . . . .

Page

O‘x-L-‘Ul

\O

13
13
13

14
15
15
17
17
17

21

111

The swirl-chamber and the fan . . .
The controls . . . . . . . . . . .
Specifications of the combine . . .
TEST OF THE COMBINE . . . . . . . . . .

Experimental purpose and procedure

Grain collected in the grain box

Grain collected from the canvas

Grain, straw, and chaff collected

burlap sack . . . . . . . . .
Results of the field tests . . . .
Symbols used in the tables . .
Test 1. Two-row operation . .

,Tcst 2. Direct throwing flails

Test 3. Propeller flails, introduction

37
38
58
39

4O

Test 4. Propeller flails, cutterhead
adjustment . . . . . . . . . . . . . .
Test 5. Propeller flails, crOp-entrance
methods . . . . . . . . . . . . . . . .
Test 6. PrOpeller flails, slow ground
speed . . . . . . . . . . . . . . . . .
Test 7. Modified propeller flails . . .
Test 8. Modified direct throwing flails

SUMMARY OF THE RESULTS FROM THE FIELD TESTS . . .

The cutterhead efficiency . . . . .
The threshing efficiency . . . . .

Cylinder losses . . . . . . . .

7O
73
74

iv

Visible kernel damage . . . . .
The swirl-chamber efficiency . . .
Shape 1 of the swirl-chamber .

Shape 2 of the swirl-chamber .

Field results of self-cleaning efficiency

LABORATORY TESTS FOR SELF-CLEANING EFFICIENCY ,

The cutterhead fan . . . . . . . .
The air duct . . . . . . . . . . .

The SWII‘l-Chambel‘ o o o o o o o o o

PROPOSALS FOR FURTHER INVESTIGATIONS .
The suction cutterhead . . . . . .
The duct . . . . . . . . . . . . .
The swirl-chamber . . . . . . . . .

REFERENCES . . . . . . . . . . . . . .

Figure

10.
11.

12.
13,

14.

15.

LIST OF FIGURES

Right side of the plot combine . . . . .

Left side of the plot combine . . . . .

Right side of the combine with transmission
shield removed . . . . . . . . . . . . . .

The underside of the flail housing and the

..- 3'1 i ‘v
trig?! 2...? Q‘BI‘S o o o o o o o o o o 0 .

[0

Front view of the flails . . . . . . . .
Side view of the flails . . . . . . . .
The swirl-chamber . . . . . . . . . . .
Pattern of straw in the swirl-chamber .
Ground speed adjustment . . . . . . . .
Flail speed adjustment . . . . . . . . .
Peripheral flail speed . . . . . . . . .
Speed of cleaning fan . . . . . . . . .
Right cutterhead harvesting a single row
of standing wheat . . . . . . . . . .
Right cutterhead harvesting a single row
of wheat lodged so the heads entered
the cutterhead first . . . . . . . . .
Dr. W. F. Buchele and author rolling the
two sheets of canvas which were placed
on each side of the row to catch the

cutterhead losses of grain . . . . . .

Page
18
18

19

1'9
20
20
25
25
27
28
29
3O

35

vi
Figure Page
16. Left to right: cutterhead losses, grain
box content and burlap sack content . . . . 36
17. Losses in the row with the modified pro-

peller flails O O O O O O O O O O O O O O O 42

18. Great losses often occurred in the end of

the rows with the direct throwing and

the modified prOpeller flails . . . . . . . 42
19. Correlation between percent cutterhead

losses and total yield of grain in

Test 5 . . . . . . . . . . . . . . . . . . . 49
20. Correlation between percent swirl-chamber

losses and total yield of grain in

Test 5 . . . . . . . . . . . . . . . . . . . 50
21. Correlation between percent straw separation

and total yield of straw entering the

swirl-chamber in Test 5 . . . . . . . . . . 51
22. Correlation between percent cutterhead

losses and total yield of grain in Test 6 . 56
23. Correlation between percent swirl-chamber

losses and total yield of grain in Test 6 . 57
24. Correlation between percent straw sepa-

ration and total yield of straw entering

the swirl-chamber in Test 6 . . . . . . . . 58
‘25. Correlation between percent cutterhead

losses and total yield of grain in Test 7 . 65

Figure
26.

27.

Correlation between percent swirl-chamber

losses and total yield of grain in Test 7

and total yield of straw entering the
swirl-chamber in Test 7
Correlation between percent cutterhead

losses and total yield of grain in Tests

5 and 6

vii

"Correlation between percent straw separation

Page

66

67

72

7.
8.
9.
10.

11.
12.

13.
14.

15.
16.
17.

LIST OF TABLE

Laboratory analysis of test 3 . . . . . .

Adjustment of the combine in test 4 . . .

Weight of grain and straw in grams in
test 4 . . . . . . . . . . . . . . . . .

Percent of total yield recovered in test 4

‘ Adjustment of the combine in test 5 . . .

Weight of grain and straw in grams in

test 5 . . . . . . . . . . . . . . . . .
Percent of total yield recovered in test 5
Statistics for test 5 . . . . . . . . . .
Adjustment of thecombine in test 6 . . .
Weight of grain and straw in grams in test

6 . . . . . . . . . . . . . . . . . . .
Percent of total yield recovered in test 6
Statistics for test 6 . . . . . . . . . .
Adjustment of the combine in test 7 . . .
Weight of grain and straw in grams in test

7 . . . . . .-. . . . . . . . . . . . .
Percent of total yield recovered in test 7
Statistics for test 7 . . . . . . . . . .

Percent visible kernel damage . . . . . .

Page

41

. 43

43
45
46

46
47
48
52

53
54
54
61

62
63
64
76

INTRODUCTION

The plant breeders have an important job in developing
new and better varieties for human and animal food.

The success of finding better varieties is positively
correlated with the number of hybrid strains the plant
breeder has time and money to test. While the planting pro-
cess has been successfully mechanized with a capacity of up
to 250 plots an hour, the harvesting capacity is still today
not more than 30 to 60 plots an hour and represents a
"bottle neck" in the plant breeding work.

In working with thousands of different strains, the
plant breeder must be careful that the seeds do not become
mixed during harvesting. Commercial combines cannot be
readily used to harvest small plots of grain because of the
size of the combine and the difficulty in rapidly and com-
pletely cleaning them. Rebuilt combines have been used to
harvest large plots where the savings in labor are large
enough to justify the necessary cleaning time.

At the present time large farm machinery companies are
not interested in the development and production of machines
for experimental work and small companies which are inter-
ested in the production of experimental equipment, cannot
afford to spend the money to develOp the machines.

The responsibility for the mechanization of

experimental work, therefore, rests with the plant breeders
themselves and the agricultural engineers of state or
federal research groups. .

The design and development of custom equipment for
field research is a new field which will become increasingly
important in the future since increased use of labor-saving
equipment will release research funds for additional experi-
mentation. ‘

Mechanization of field experiments is one of the better
means of speeding progress in modern agriculture.

The purpose of this thesis is to report the construc-
tion and testing of a plot combine built according to the
following specifications:

1. Complete self-cleaning in less than 30 seconds.

2. Grain damage less than or equal to the ordinary
combines. '

3. Grain recovery efficiency better than or equal
to the ordinary combines.

4. Complete threshing without adjustment for
different varieties within the species in
small grain.
This thesis will present the design and development of
a plot combine that was built to test various cutting,
threshing, separating, and cleaning principles and to

develop parameters for the design of an acceptable machine.

REVIEW OF LITERATURE
Harvesting Methods for Small Grain Plots

Hunter and Johnson (1955) reported that harvesting of
experimental plots of small grain have generally employed
three methods:

1. Cutting the plants from definite lengths of rows
or number of quadrats by hand, bagging or wrap-
ping them to prevent shattering or loss of seed
during transportation, and threshing with a
small stationary plot thresher.

2. Similar to the aboVe method except that cutting
was done with a small plot mower, having some
type of catcher for collecting the plants as
they were cut.

3. Use a self-propelled combine to cut and thresh
the crap simultaneously.

Two other methods were described by Cyjord (1957). He
reported that a light weight, 4% feet binder propelled by
an 8 hp garden tractor had a capacity of 30 to 40 plots (20
feet long and 4 feet wide) per hour with a 3-man crew.

This provided a saving of 30 to 50 percent in labor, com-
pared with a 4-whee1 tractor with a steel catching plate
located behind the cutter bar for collecting the plants.

The sheaves from the small plots are threshed in the
field in areas of the world with a dry harvesting season.
In areas with frequent rain and cloudy weather, the col-
lected material is usually threshed in the barn.

In recent years a method called "combining in two steps"

has become popular among plant breeders in Germany. The
plots are harvested with a small garden tractor equipped
with a cutter bar and a catcher when the crop is ripe for
combining. The plot thresher is placed in the field and the
plot yield is threshed immediately after cutting.

flyjord (1961) observed the same principle in use at
Michigan State University except that the sheaves were tied
and threshed immediately after cutting.

Principles of Plot Thrashers

The plot threshers are usually built with a spike-
tooth or a raspbar cylinder, overshot concave, ordinary
straw rack, and a conventional cleaning system with sieves
and fan action. These threshers are not self-cleaning, but
they are relatively easy to clean with a blower or an air
compressor.

VOgel and Johnson (1934) described a self-cleaning
nursery thresher. This thresher contained no straw rack or
screens. The threshed grain,inc1uding straw and chaff,
‘falls on an inclined reciprocating steel plate which
directed the material into an air chute or venturi. When
the straw is long, the bundles are held by the butts while
the cylinder strips the heads. The butts are then cast
aside. .Otherwise, the whole bundle would pass through the
machine.

Vogel, Herman and Naffziger (1938) reported a

self-cleaning roller belt thresher for small samples. This
thresher consisted of a rough rubber belt traveling about 50
feet per minute. A rough cylinder with a peripheral speed
of about 100 feet per minute was pressed against the belt.
The samples were fed between the belt and the cylinder where
the threshing took place. This thresher had no cleaning
device.

Arawinko and Nielsen (1956) reported a thresher con-
sisting of a moving sandpaper belt pressed against a corru-
gated rubber surface. A half-inch of sponge rubber was
placed behind the rubber surface to provide flexibility and
a uniform pressure between the belt and the rubber surface.
The machine was built mainly for small samples of grass
seeds and no cleaning was provided.

Cunningham and Hannah (1956) reported a plot thresher
consisting of two rubber-covered rolls operating at different
speeds. The samples passed between the rolls in bags.

flyjord (1956) reported a nursery thresher in which the
tops of the bundles were fed into a centrifugal fan. The
threshing took place between the blades of the fan and a
corrugated‘concave. The fan was self-cleaning and the grain
(was blown up to a reciprocating chaffer sieve with air blast.
The sieve had to be cleaned between each sample.

Thielebein (1959) reported test results of a two
cylinder plot thresher with cyclone cleaning and no sieves.

The thresher cleaned itself completely in 14.7 seconds with

a variance of 0.174 seconds. The average threshing losses
for barley, wheat, rye, and oats were 2.9 percent with a
variance of 0.517 percent. The lost grain was of low
quality and the author stated that these losses were not
important to the plant breeder. The capacity of this
thresher was found to be 42 plots (49 square feet in area)

per hour or 120 plots (11 square feet) per hour.
Principles of Plot Combines

Liljedahl, Hancock, and Buttler (1951) reported the
rebuilding of an Allis-Chalmers Model 40 combine for har-
vesting 3-foot wide plots.

The combine was made self-propelled by integrating it
with an Allis-Chalmers G tractor. The power for the thresh-
ing mechanism was supplied by a 6 hp engine. The combine
was equipped with an air compressor and the clean grain
auger was replaced with a drawer to speed the cleaning of
the machine. The tailings auger was also eliminated.~ The
air blast was reduced to prevent loss of grain and the in-
side of the combine was streamlined so the lodging of grain
was reduced to a minimum.

The authors reported a labor saving of 80 percent,
compared with hand harvesting methods.

Hancock (1961) reported in a personal letter that three
combines similar to the one above were being used on sub-

stations in Tennessee and that three men can harvest 100

plots, 68 feet long, and clean the combine between as many
as 25 varieties with four replications each in a day. Han-
cock stated that, without the combine, he doubted they could
carry on tests of any value because the combine enables the
breeder to judge the standing ability of the small grain
varieties Just as the farmer would do in the field.

Hunter and Johnson (1955) reported that three self-
prOpelled plot combines have been constructed at the Oregon
Agricultural Experiment Station during the 1953 and 1954
seasons. The basic unit of these machines was an Allis-
Chalmers Model 40 All Crop Harvester, stripped of frame,
wheels, clean grain elevator and tailings elevator, and
streamlined inside as recommended by LilJedahl Hancock, and
Butler.

The combine body was placed upon a frame supported at
the front by an automobile rear axle and wheels and at the
rear by an automobile front axle. Each axle was shortened
by 12 inches. A 9 hp air cooled engine prOpelled the com-
bine and another motor of the same size operated the combine.
The combinaaweighed apprOximately 3,000 pounds. They were
used to harvest fertilizer experiments. A 3eman crew har-
vested 30 to 40 plots (50 feet long and 40 feet wide) per
hour with these combines.

From a study tour to England, Belgium, Germany, Denmark,
and Sweden, flyJord (1958) reported that Allis-Chalmers,

lhxnktell, and Massey-Ferguson 630 commercial combines were

rebuilt and used to harvest plots with areas varying from
220 to 1,300 square feet. The necessary idle time between
the plots varied between % and 2 minutes. None 0 the

visited institutions used the combine in plant breeding be-

cause of the long time required to cleg the rebung combines

between each variety.
Chalmers, Nation, and Raybould (1952) reported a plot

 

cOmbine designed in 1947 and tested in 1949, 1950, and 1951.
The idea of this combine was that if an endless belt rubbed
the grain against a sufficiently long concave or screen
complete threshing and separation would result.

The field losses of the first unit tested in 1949 were
between 12 and 17 percent and varied with belt speed and
concave clearance. The principle was modified in 1950 and
1951. The final combine,tried in 1951, had a 5-foot wide
rubber covered endless belt with rubber moulded rasp-type
beater bars bounded and riveted to the belt.- At a speed of
3,400 feet per minute there were 4,300 beater bar impacts
per minute. An Allis-Chalmers Model 60 harvester header was
used for cutting and feeding the grain to the threshing belt
and the whole unit was front-mounted on a Fordson Major
tractor. The total losses (1951) were reported to vary from
1.8 to 6 percent according to the harvesting conditions.

The report stated that the combine was easy to clean.

Farm Mechanization (1961) reported a small 2-foot com-

 

bine using the principle of the Gallic stripper. The combine

had a comb instead of a cutter bar. The cylinder consisted
of six fan-type beaters attached to a horizontal shaft. The
beaters stripped the heads from the comb, threshed them, and
blew them into a separating container at the rear. The
machine, while being practically self-cleaning, did require
some cleaning with a brush to prevent'contamination of the
varieties. The capacity of the combine was reduced con-
siderably by the checking of the cylinder for lodged seed
between varieties.

Hamblin (1961) reported a small plot combine consisting
of an ordinary cutter-bar, conveyor and rasp bar cylinder
carried on a 3-wheel chassis. Two of the wheels were under
the header and the third wheel at the rear was both steered
and driven. ‘The combine contained no cleaning device. All
the straw was removed from the combine at the end of the

plot and shaken to recover the loose grains.
New Threshing and Separating Principles

The Wild Model 50 Harvester Thresher (1959) was sold
in England for some time. The success of this harvester is
not known. The threshing was done by a series of rotating
corrugated plates on a horizontal shaft. The heads were
beat back and forth between these plates in the threshing
process.

Segler and Peschke (1952, 1953) reported experiments
1m1th chap-threshing. The sheaves were fed directly into a

10

chopping mechanism which cut the straw. The threshing
occurred in the fan which blew the material to the separator.
The length of cut of the straw ranged from 0.9 to 1.6 inches.

Buchele (1953) deveIOped an experimental thresher ‘
(patent No. 2.906.270) for small hard-to-thresh seeds. This
machine achieved threshing action by continuously rubbing
the crop against a perforated screen formed into a cone.

To get better threshing action he stated that the cone and
the rubber blade impeller could be rotating in the same
direction but at different peripheral speeds.

Segler (1957) reported the cone principle and four
other axial fed threshing cylinders. In two of the cylinders
a combination of prOpellers and beaters threshed and moved
the material, and a screen in the bottom separated the
threshed grain from the straw. A third principle used
helical bars to thresh and move the material and a screen
around the cylinder to separate the grain from the straw.

The fourth principle utilized a fan to pull the material
through a short cylinder which had no provision for separat-
ing the grain from the straw. A screen mounted directly on
the blades of the fan prevented the kernels from being hit
'by the blades. This reduced the kernel damage.

In Norway, flyjord (1958, 1959) observed experiments with
it forage harvester used for harvesting barley. The grain and
straw were blown into a wagon. Examinations showed larger
field losses than could be tolerated in practice. This

forage harvester was of a type equipped with a fan. A large

11

percentage of the grain was skinned and cracked (presumably
by the fan rather than by the flails).

Nordaune (1958, 1959) built and tested a precleaner for
this forage harvester using the swirl-chamber principle
suggested by flyjord (1958). From the results of his tests,
Nordaune concluded that the capacity of the swirl-chamber
was too small. This prevented its use as a precleaner for a
forage harvester.

Harris (1959) stated that preliminary chopping of straw
craps increased the capacity of the threshers from 30 to 50
percent. The author envisaged that the ideal equipment
would be a combination of a forage harvester with a detach-
able finishing thresher and precleaner.

Earm Mechanization (1959) reported that an English

farmer used the Lundell forage harvester to cut and thresh

a severely storm-damaged field of barley in the fall of
1958. The farmer replaced the cutter bar on a combine with
the forage harvester and used the widest possible clearance
between drum and concave to insure no threshing action in
the combine. The flail action threshed barley completely
*with small losses. The shear bar within the chopper was
removed and recommended flail speed for silage harvesting was

used.

Lamp (1959) and Lamp and Buchele (1960) described
cerrtrifugal threshing and concluded that wheat and other
Grains can be threshed by application of centrifugal force.

12

The threshing and separating process can be integrated,
eliminating the need for special grain separating equipment.
Air alone would be sufficient for cleaning centrifugally
threshed grain.

Lalor, working concurrently with the author at the
Agricultural Engineering Department, Michigan State Univer-
sity, has constructed a field-size cone thresher designed
to thresh and separate the grain from the straw in a per-

forated cone. He has obtained promising results.

‘ SELECTION OF COMPONENTS FOR THE COMBINE
Calculation of Required Capacity

The combine was designed to harvest the 2 center rows
in 4-row wheat plots, 12 feet long, and with a row spacing
of 12 inches. The harvested plot was calculated to be 2
x 12 feet = 24 square feet.

A maximum yield of 2,500 pounds straw and 2,500 pounds
grain per acre was assumed. This gives an assumed yield of
1.4 pounds straw and 1.4 pounds grain per plot. Consider-
ing an average speed of 2 miles per hour or 3 feet per
second, it will take 4 seconds to cut the plot. The com-
bine should, therefore, be able to handle

1,4 pounds = 0.35 pound of straw and 0.35 pound of grain
seconds

per second.
Cutting

The following cutting principles were considered:

1.‘ Conventional mower cutter bar.

2. Rotating blades on vertical shafts.

3. Rotating flails on a horizontal shaft.

The flail-type cutting mechanism was selected because
of' its simplicity and rewarding possibilities. It was
hypothesized that this. principle would give the 100 percent
self-cleaning action required of a variety plot combine.

13

14

Conveying

The following conveying principles were considered for

use behind the cutting mechanism:

1.
2.
3.
4.

Conventional inclined canvas or rubber belt.
Platform auger with chain and slats.
Air suction.

Combined throwing and blowing.

Combined throwing and blowing was the simplest self-

cleaning principle and could be integrated into the flail-

type cutting mechanism.

Threshing

The following threshing devices were considered:

1.

2.
3.
4.

6.

.7,
8.

9.

Conventional rasp bar, angle bar, and spike-
tooth cylinders.

Cone-type cylinder with axial feeding.
Conveying cylinder with axial feeding.

Rubber belt moving_ over a corrugated surface
with no Openings.

Rubber belt moving over a screen.

Corrugated rubber rolls moving at different
speeds.

Flail-type forage harvester.
Centrifugal fan.

Centrifuge or other devices using centrifugal
force for pulling the kernels from the heads.

A cambination of 7'and g‘was selected as the threshing

means as they could be accomplished by the above selected

 

15

cutting means.
Separating and Cleaning

The literature review showed that in all cases where
the conventional separating and cleaning principles have
been used, the machines were not self-cleaning. In plot
threshers where the separation of grain from straw and chaff
was done by air, it was possible to provide a self-cleaning
device.

Three possible solutions were considered as follows:

1. The conventional air cleaning device.

2. The cyclone. 1

3. The swirl-chamber.

The swirl-chamber was selected as a separating and
cleaning mechanism in this research because the author felt
that with further development it would provide a better
solution than the conventional air and cyclone cleaners used

on plot thremhers.
Propelling

Several power units were studied. The following were
considered more or less suited for the task:

1. Allis-Chalmers Model G tractor.

2. David Bradley Super, Model 575 garden tractor.

3. Simplicity, Model W garden tractor.

4. Simplicity Model 700, 4-whee1 garden tractor.

 

16

5. International CubCadet, 4-wheel garden tractor.

A consideration which affected the selection of a
tractor was that the combine should be short and have as
small turning radius as possible. The David Bradley Super
575 garden tractor with 5.75 hp engine was selected because
it provided a compact and simple solution of the power
transmission from the tractor to the cutting and threshing

mechanism as well as the fan.

 

CONSTRUCTION OF THE COMBINE
The Cutting and Threshing Mechanism

Figures 1 and 2 show the combine from the right and
the left side. Figure 3 shows the transmission.

The straw dividers were placed on 12-inch centers.
The throat was 12 inches wide at the gathering points and
narrowed to 2 inches at the point where the crop encounters
the action of the cutting and threshing flails. Figure 4
shows the straw dividers. To save time testing the machine,
the right cutterhead was equipped with a prOpeller-type
flails and the left cutterhead was equipped with a direct
throwing-type flails. Later, the modified propeller flails
and the modified direct throwing flails were constructed
and tested. Figures 5 and 6 show the different types of
flails. '

The prOpeller flails
The theory of design of the propeller-type flails was

to impact the heads of the crap from the 2 inches wide
cutterhead entrance into the center section of the flail
laousing where a series of direct throwing flails would
finish the threshing and produce air for transport of the
straw to the separator. Four free swinging prOpeller

flails were mounted at 90 degree intervals on the flail

17

 

 

Fig. 1. Right side of the plot combine.

"' ’ t‘ '. I, ‘ ~
a, - ,‘. '. :‘nfl-‘J’K "
, - .‘ . ‘ 5 ‘ " . "
. .1 “ EM 0
‘ I.
Ear-4’ .2: '

‘-.<

- ’- i
- ' £ ' .

‘ ' - '5.
' - J

 

19

/

 

Fig. 3. Right side of the combine with transmission shield
removed: transmission pulleys to the flail shaft are 1, 2,
3. 4, 5: 6 is the crank for the speed changer-pulley 2; 7
is idle pulley clutch, and 8 is the tachometer.

   
 

r- a"

   

dividers: (1) right cutterhead entrance, 2) fan intake,

Fig. 4. The underside of the flail housing and the straw
(3) steering wheel.‘ (From experiment No. 8.)

 

20

 

1 2 3 4

F1 . 5. Front view of the flails: (1) propeller flail,
(2 modified propeller flail. (3) direct throwing flail,
and (4) modified direct throwing flail.

l 2 e 4

Fig. 6. Side view of the flails: (1) propeller flail,
(2) modified propeller flail. (3) direct throwing flail,
and (4) modified direct throwing flail.

 

21

shaft in such a way that the leading edge of each flail was
1 inch to the right of the rear edge (Figures 5,1 and 6,1).
The leading edge of the next flail, 90 degrees later, was
3/4 inch to the right of the leading edge of the first
flail and so forth. The 4 flails covered thus a space of 3
inches behind the opening of the cutterhead throat on the
right side of the flail house.

Specification of the PrOpeller Flails

 

Length of flails . 5% inches
Width of flails 3 inches
Thickness of flails 1/8 inch

Flail head diameter 16 inches
Flail head periphery 50.3 inches

 

The direct throwing flails
The principle of these flails were similar to that of

the direct throwing flails of forage harvesters. FOur free
swinging flails were mounted at 90-degree intervals on the
flail shaft in such a way that as the crap entered the 2
inches wide left hand throat of the flail housing, it would
be cut, threshed, and thrown up to the cleaning device in

one operation.

22

Specification of the Direct Throwing Flails

 

Length of flails 6 inches
Width of flails 3 inches
Thickness of flails 1/8 inch
Length between cutting edge and bend 1% inches
Angle between line of gravity and cutting

edge 26 degrees
Shape of cutting edge Rbunded
Flail head diameter 17 inches
Flail head periphery 53.4 inches

 

The modified prOpeller flails

The modified prOpeller flails were constructed from
the ordinary propeller flails. Fbur pieces of steel
1 x 2% x & inches were welded to the outer end of each of
4 propeller flails so the angle between the line of gravity
and the cutting edge was 72 degrees. The front corner of
the cutting steel was ground to an angle of 40 degrees and
rounded. The rear part ofthe flails were cut away. Ex-
cept for these changes, the modified propeller flails meet
the specifications of the propeller flails. I

The modified direct throwigg flails
The modified direct throwing flails were constructed

from the direct throwing flails. Two pieces of steel,
1 x 5% x 1/8 inches were ground and welded to the edge of
two opposite flails‘nearest to the intake of the fan. These

23

flails act as cutting knives for the straws which are guided
into the fan. The other two opposite flails nearest to the
intake of the fan were removed. The specifications for the
chOpping flails are the same as for the direct throwing
flails except for the modification Just described.

The flail housing
The flail housing consisted of the right side straw

divider and cutterhead with 4 propeller flails, the center
section with 16 direct throwing flails, and the left side
straw divider and cutterhead with 4 direct throwing flails.
The 16 flails in the center section of the flail house were
mounted 4 on line and at 4 positions located at 90 degree
intervals on the flail shaft. Preliminary experiments
proved that it was necessary to design a fan housing for
these flails in order to secure sufficient air pressure in
the elevating duct to overcome the back pressure develOped
in the swirl-chamber by the cleaning fan.

The flail housing (Figures 1, 2, and 4) covers the
flailscompletely except for the crap entrance and the Open-

ing between the cutterheads and the ground.
The Elevating Duct

The outlet from the flail housing was 5 x 20 inches
and tapered to 5 x 13% inches during the first 9 inches of
duct length. The next section was 40 inches long and

Slightly tapered to 5 x 12-3/4 inches at the bend. This

 

24

bend had an internal angle of 87 degrees, but was rounded in
the upper side where the material was deflected down to the
11 inches long and 5 x 12-3/4 inches wide duct to the swirl

chamber.
The Swirl-Chamber and the Fan

Figures 7 and 8 show the swirl-chamber where the grain
is separated and cleaned from the straw and chaff. It was
made of 2 pieces of plexiglass 19 x 27-3/4 x 1/4 inches
mounted 12.5 inches apart. The swirl-chamber was created
between these walls by a strip of formed 28-gauge sheet
metal kept in desired position by 8 bolts. The shape of the
(swirl-chamber was easily adjusted by loosening one or more
of these bolts. The swirl-chamber could also be tilted for-
wards or backwards for finding the right position.

A Brundage furnace blower, AP 10, was used to provide
air for Operating the swirl-chamber. The capacity of the
blower was 1,500 cfm when delivered against a static pres-
sure of i inch of H20 at 625 rpm. Figures 7 and 8 show the
relationship between the fan and the swirl-chamber. The
swirl-chamber was constructed in such a way that the grain
and short straw with nodes were deflected across the outlet
opening. They then slid down the inclined front side of the
swirl-chamber perpendicular to the air stream. The heavier
grain passed through the air stream and drOpped into the

grain box, but the straw was carried out by the air stream.

 

Fi . 7. (1) The swirl-chamber, (2) fan with fan shutters,
(3 grain box, (4) duct from the outterheads, (5) burlap
sack.

‘ O

 

Fig. 8. Pattern of straw in the swirl-chamber.

26

The longer straw and chaff, which were not heavy enough to be .
carried across the outlet of the swirl-chamber were deflected
upward by the air stream and escaped through the clear

plastic tube to the burlap sack shown in Figure 7.
The Controls

The ground speed was adjusted in two different ways
during the experiments.

The two upper curves of Figure 9 show the original ad-
justment with a floating V-belt pulley (Figure 3). At each
engine rpm the forward speed of the combine can be set any-
where between these two curves. The lower curve of Figure
9 shows the relation between engine speed and ground speed
,with a slow speed pulley. The only way to adjust ground

speed with this pulley was to change the engine speed. The
curves were not extended above 3,000 rpm because this means
high ground speed which makes precision steering difficult

while operating the combine in the field.

Figure 10 shows the limits for the flail speed adjust-
ments. The curve between the upper and lower speed limits
represents the relationship which was most often used.

Figure 11 shows peripheral flail speed versus revolution
per minute of the cutterheads. Figure 12 shows the two re-
lations between engine and'fan speed which were used. Be-
fore changing from an 8-inch to a 7-inch pulley, a 5-inch

pulley was tried in the laboratory. The static pressure 1

GROUND SPEED, MPH

27

 
   

 

 

 

4-°L 0 MAX. SPEED
— 6] MIN. SPEED
3.6_ 0 SLOW SPEED PULLEY
3.2—
)-
2.8—
2.4—
? CONTINUOUS ADJUSTABLE
2"” v-sELT PULLEY
1.6-
" J
1.2 - /
0.8—
1;”;1 1 1 1 1 1 1 1 1 I 4 1 1
1300 2000 2200 2400 2600 2800 3000

ENGINE SPEED,RPM

Fig. 9. Ground speed adjustment.

 

FLAIL SPEED, RPM

28

 

 

1800- /
e
h -<. 0//
\
1600- o“/
<9 0
_ 997
9‘9 o
1400 09/ ' “‘5
s /

_ C) ‘3‘?€§KN\EB

L //// <XV£
1200 /® ‘1 oat-£3

‘96“ @

1000~ “Sems/

_ /E13 .

,o/
800- Us“ 0
a? 5.:ng
t w
(5)
600~
,0

4004

1,; a; 1 I . 1 1 I

1 l l L I
1800 '2000 2200 2400 2600 2800

ENGINE SPEED, RPM

Fig. 10. Flail speed adjustment.

29

*7r-——r'

6500

6000

1

4500*

.b
O
O
O
I

 

PERIPHERAL FLAIL SPEED, FPM

3500-

CH
C)
C)
C)
I

 

L

LLL L
r

l
900 l000

J

1 l J L

1 l 1 L
H00 1200 I300 I400

FLAIL SPEED, RPM

Fig. 11. Peripheral flail speed.

N
C)
C)
T

600—

500*

FAN SPEED,RPM

400 *-

300r

200 -

 

30

 

. 1
1800

4

Fig.

8/

G 7-INOH PULLEY
E.) 8-INCH PULLEY

1 I 1 1 l 1 1 1

2000 2200 2400 2600 2800

12.

ENGINE SPEED, RPM

Speed of cleaning fan..

1

31

deveIOped in the swirl-chamber was greater than the static
pressure developed in the flail housing. This created a
back pressure in the elevating duct so the flails were not
able to blow the straw up the duct into the swirl-chamber.)
The S-inch pulley was therefore rejected.

The air volume was controlled by continuous adjustable
shutters (Figure 7) marked 0 to 12 on each side of the fan.
0 means clOsed (no air intake) and 12 means open.

An adjustable air deflector was placed in the fan out-
let (Figure 8). The deflector controlled the air distri--
bution in the swirl-chamber and could be set according to a
scale ranging from 1 to 9.

The machine was steered by a level acting on a
pneumatic wheel in front of the tractor wheels (Figure 4).

The upper edge of the crop intake could be adjusted to
23, 25, and 27 inches above the ground. The corresponding

height of the cutterhead entrance was 11, 13, and 15 inches.

32

Specifications of the Combine

 

Width of cut

Type of cut
Threshing principle
Cleaning principle

Tractor-type

Engine

Horsepower

Torque

Tractor wheel
Steering wheel
Wheel base distance
Maximum length
Maximum height
Maximum width
Turning radius

Turning space diameter

24 inches (2 rows 12 inches apart)
Flail action (impact)

Flail action (mainly impact)

Air separation in swirl-chamber

David Bradley, Super 575 garden
tractor

4 cycle Briggs and Stratton
5.75 maximum at 3,600 rpm
4.51 maximum at 2,700 rpm
2.65 maximum at 1,800 rpm

rpm

6.70 x 15 pneumatic tire
3.50 x 6

52 inches

123 inches

78 inches

32 inches

72 inches

218 inches

TEST OF THE COMBINE

The combine was tested in an experimental field of

wheat planted in 12-foot rows on 12-inch centers.
Experimental Purpose and Procedure

The purpose of the experimental procedure was to deter-
mine the following:

1. Percent threshed plot yield recovered in grain
box.

2. Percent unthreshed plot yield recovered in grain
box.

3. Percent cutterhead losses of threshed grain.
4. Percent cutterhead losses of unthreshed grain.
5. Percent swirl-chamber losses of threshed grain.

6. Percent swirl-chamber losses of unthreshed
grain.

7. Percent straw in the recovered grain (of total
straw).

'8. Percent visible damage of the threshed grain.
The total plot yield was calculated by the summatiOn
of numbers 1 through 6. This total was used for calculation
of the different percentages.
'The sum of numbers 3 and 4 measured the total cutter-
head losses.
The sum Of numbers 5 and 6 measured the total swirl-

chamber losses and together with numbers 2 and 7, provided

33

34

an indication of the separating efficiency of the swirl-

chamber.

The sum Of numbers 2 and 6 established percent "cylinder

lessee"

or the total percent unthreshed grain entering and

passing through the threshing device.

The procedure for Obtaining these data was the following:

1.

ID

A piece of canvas 20 inches by 15 feet was placed
on each side of the test row. Because of the
nature of the rows, the width of the area actually
covered by the canvas varied between 11 and 20
inches (see Figures 13 and 14).

The row was harvested with the plot combine.

The combine was checked for complete cleaning
between the plots.

The two pieces of canvas were rolled as shown in
Figure 15. The rolls were inserted in a sack and
the grain and straw were shaken out before bagging
and marking.

The seed collected in the grain box (Figure 7)
was dumped into a bag and marked.

The straw, chaff, and grain blown from the swirl-
chamber were collected in a burlap sack (Figure
7). The content of this sack was placed in an-
other sack and marked.

The collected samples were brought to the laboratory and

analyzed according to the following procedure.

Grain collected in the grain box

The sample was weighed in the bag.

The sample was poured on the screen of an
experimental grain cleaner.

The empty bag was weighed and net weight ob-
tained by subtraction.

The unthreshed heads were collected from the
screen.

 

 

Fig. 13. Right cutterhead harvesting a single row of
standing wheat.

I
. ilk
. .: «3.,ng .
\'1"_‘_7“
. ' 1 \
l

1

Ly,
\ 1 “r

 

\

Fig. 14. Right cutterhead harvesting a single row of
wheat lodged so that the heads entered the cutterhead
first.

 

36

 

Fig. 15. Dr. W. F. Buchele and author rolling the two
sheets of canvas which were placed on each side Of the
row to catch the cutterhead losses of grain.

 

. , \ . ' ‘1 . ,
an» -,/ I , " ““11"
. , 7.

r,

Fig. 16. Left to right: Cutterhead losses, grain box
content, and burlap sack content.

37

The cleaned grain was weighed and recorded.

The unthreshed heads were counted, handthreshed,
cleaned, weighed, and recorded.

Weight of straw and chaff in the grain was found
by subtraction of threshed and unthreshed grain
from the total sample weight.

Grain collected from the canvas (cutterhead losses)

a.

b.
c.

d.

The sample was poured on the screen of the experi-
mental grain cleaner.

The unthreshed heads were picked from the screen.
The threshed grain was weighed and recorded.

The unthreshed heads were counted, handthreshed,
cleaned, weighed, and recorded.

Grain, straw, and chaff collected in the burlap sack

a.

b.

The sample was weighed in the sack.
The sample was poured into a big box.

The empty sack was weighed and sample weight
obtained by subtraction.

The unthreshed heads were handpicked, counted,
handthreshed, cleaned, weighed, and recorded.

The straw was handpicked into a sack.

The remaining grain was air-cleaned, weighed,
and recorded.

Weight of straw and chaff was found by sub-
traction of threshed and unthreshed grain from
the total sample weight.

The opening of the fan shutter was positioned to pre-

vent seed losses in the experimental grain cleaner. Samples

under10 grams were weighed on a scale with I 0.1 g accuracy.

Percent visible damage was determined by dividing the

38

threshed grain from the box several times on a Seedburo
sampler until two lots of approximately 150 kernels re-
mained. Visibly damaged kernels were picked out of the

sample by hand and the percent kernel damage was determined.
Results of the Field Tests

This section will give the data and deal with the
analysis of the obtained results. .The number of obser-
vations was too small for using statistical inferences, but
inferences can also be made with a small number of obser-
vations without statistics if the observed differences are

large and easily explained.

Symbols used in the tables

G = grain, threshed and unthreshed
T = threshed grain

U = unthreshed grain

S = straw

K = kernels of grain

H = heads of grain

The experimental procedure described in the previous
section was not developed in detail when the first field
tests were conducted. Tests 1, 2, and 3 of this section
describe tests in which the procedure was somewhat different
from the procedure used in the rest of the tests. The first
field tests with the combine were carried out on August 8,

1961.

 

39

Test 1. Two-row operation

Plots consisting of two rows of wheat (straw length
between 42 and 45 inches) were harvested and the following
observations were recorded.

1. Straw clogged the upper part of the duct between
the flail housing and the swirl-chamber at top
speed of the engine and a ground speed of ap-
proximately 1.8 mph.

2. The tendency of clogging decreased as the ground
speed was decreased.

3. The easiest steering was obtained at the lowest
ground speed.

A study of the above observations indicated that one
or more of the following changes must be made in order to
secure efficient two-row operation.

1. Increase cross-sectional area of the duct.

2. Increase air capacity of the cutterhead fan.

3. Decrease angle of the bend of the duct.

4. Sharpen flails to provide a shorter cut of

the straw.
Test 2._,Direct throwing flails

Test 2 was designed to detect any difference between
the right cutterhead with propeller flails and the left
cutterhead with direct throwing flails. Since the results
were obvious,only a few plots were needed to reach a con-
clusion.

The losses in the end of the plots were about twice as
large for the direct throwing flails as for the propeller

flails.) Figure 18 shows the heavy losses that occurred at

 

40

the end of the plots harvested with direct throwing flails.

Test 3. Prgpeller flggls, introduction

To determine the performance of the prOpeller flails,
one row was harvested over two plot lengths without stopping.
The straw was bent forward by the machine as in the previous
tests. The cutterhead rpm was 1,075. The speed variation,
however, was great.

The whole sample collected in the grain box was
divided by hand into the following parts:

Threshed seed in grain

 

box 153 grams

Unthreshed seed in grain

box 5 grams

Total grain weight 158 grams
Straw in grain box . 9 grams

 

The following observations were recorded after an in-
spection of the sample in the grain box.

1. N0 visible kernel damage.

2. Chaff was attached to a few kernels.

3. Eight unthreshed heads.

4. Ten completely threshed heads.

The threshed and unthreshed heads were below normal
size. Examination of the unthreshed heads showed that they
contained kernels of normal size. A larger percentage of
threshed heads than of unthreshed heads were attached to
the straw.

Three empty heads on ten inches straw

41

One empty head on six inches straw
One empty head on three inches straw

The largest piece of straw without heads was 7 inches; a

node was located on one end of the straw. Two pieces of*

straw were 6 inches. Most of the straw was split by the
flail action. The threshed and unthreshed grain on the
ground was gleaned by hand and analyzed. Table 1 gives

information concerning the distribution of losses.

Table 1. Laboratory Analysis of Test 3

-
"—Y

 

 

Source Weight in grams
Threshed seed in the grain box 153 73.3
Unthreshed in the grain box 5
Threshed grain on the 3011* 32
Unthreshed grain on the soil* 19
Total row yield . 209 100.0

 

*It was not possible to recover every lost kernel.

Because the loss of 24.3-percent grain was not con-

sidered excessive at this stage of development, it was.de-

cided to continue the development of the prOpeller flails.

Improvements based on test 3.

1. The cutterheads were equipped with better de-
signed side covers.

2. A tachometer was mounted for continuous obser-
vation of the flail shaft speed.

 

42

- r

’5 446:1” 9. 1.?
.:I 3’ g7 .g", '52:!

'41

 

Fig. 17. Losses in the row with the modified prOpeller
flails.

 

Fig. 18. Great losses often occurred in the end of the
rows with the direct throwing and the modified propeller
flails.

43

Tgst 4. Propeller_flails, cutterhead adjustment
The purpose of this test was to study the effect of the

 

cutterhead adjustment.

Two rows of the same wheat variety, here called plots
1 and 2, were harvested. In plot 1 the height of cut was
27 inches and in plot 2, 23 inches. This distance was mea-
sured from the ground to the lowest part of the cutterhead
entrance. The shroud over the throat bent the straw forward
so the butt and of the stalk entered the cutterhead before
the heads (Figure 13). Table 2 shows the adjustment of the
combine, Table 3 the observations, and Table 4, the results

of the test.

Table 2. Adjustment of the Combine in Test 4

 

‘Fan Air Shape
Plot Flail Ground Shutters Deflector of Swirl Height
No. Speed Speed Opening Position Chamber of Cut

 

rpm mph inches
1 1300 1.4 10' 4 1 27

2 1300 1.4 12 4 1 23

 

Table 3. Weight of Grain and Straw in Gram in Test 4

 

 

 

 

Cutter-
Plot Grain bog head Straw sack Total
No. _2_ U :§‘ T U ,_I U S G S
1 . 152 2K 44 43 1.7 0.9 ‘1K 182 198 226
1H 8H 1H
2 107 0 24 77 4.8 6.0 0.4 239 195 263

11H 1H

 

44

Table 4. Percent of Total Yield Recovered in Test 4

 

 

Buttg first

 

 

 

 

 

 

 

 

Source Hei ht of cut inches
2Z_. 2

33 %
Recovered Threshed 77.0 54.8
seed in Unthreshed Nil 0.0
grain box Total 77.0 54.8
Threshed 21.7 39.4
Cutterhead Unthreshed 0.9 2.5
losses Total 22.6 41.9
Swirl-chamber Threshed 0.4 3.1
losses Unthreshed Nil 0.2
Total 0.4 3.3
Total grain recovered 100.0 100.0
Total losses of grain 23.0 45.2
Total cylinder losses Nil 0.2
Straw in grain box 19.5 9.1
Straw in straw sack 80.5 90.9
Total straw recovered 100.0 100.0

 

A hypothesis stating that there was no difference in
the cutterhead performance from plot 1 to plot 2 can not be
tested with help of statistics and a probability table be-
cause no replications were taken. However, logical infer-
ences can also be acceptable. The increase of the total
cutterhead losses from 22.6 to 41.9 percent for a lowering
of the cutterhead from 27 to 23 inches above the ground,

was assumed to be beyond chance, and it was concluded that

45

the lowest cutterhead setting increased the cutterhead
losses. This conclusion could also be formed by looking at
the losses on harvested plots where no samples were col-
lected.

The increased swirl-chamber losses from 0.4 to 3.3 per-
cent were caused by the stronger air blast as a result of
Opening the fan shutters from 10 to 12. The corresponding
increase in straw separation in the swirl-chamber from 80.5

to 90.9 percent backed up this inference.

Changes based on observations made during test 4.
Insufficient air was delivered by the fan operated by an 8-

inch pulley. A 5-inch pulley was installed in the laboratory,
but it delivered too much air. A 7-inch pulley was mounted
and used for the remainder of the tests.

The cutterhead losses in plot 1 and plot 2 were found
by handgleaning. Experiments in the field showed that a
strip of canvas on each side of the row could be used for
recovering the cutterhead losses from the propeller flails.
This method could nOt be used with the direct throwing
flails because the canvas was picked up and wrapped around

the flail shaft.

Test 5, Propeller flailsI crop entrance methods

The purpose of this test was to determine if the
efficiency of the combine was affected by whether the heads

or butts entered the cutterhead first. Only two replications

of each method were taken.

justment and Table 6 shows

46

Table 5 shows the combine ad-

the observations.

 

 

 

Table 5. Adjustment of the Combine in Test 5
Fan Air de- Shape

Plot Flail Ground shutters flector of swirl Height Way of

No speed speed opening setting chamber of cut entering
__ rpm mph inches

‘3 1300 1.4 12 4 2 25 Heads

4 1300 1.4 12 4 2 25 first.

5 1300 1.4 12 2 2 25 Butts

6 1300 1.4 12 3 2 25 first

 

Table 6. Weight of Grain and Straw in Grams in Test 5

 

 

 

 

 

 

Cutter-
Plot Grain box head Straw sack Total

No T U S T U T U S G S
1K 3.7 0.5

3 172 1H 49 46 8H 4.9 3H 201 227 250
6.3 1K

4 126 O 65 49 14H 3.5 1H 188 185 253
‘ 0.2 0.7

5 184 O 46 49 1H 8.0 7H 289 242 335
0.3 4.5 0.7

6 67 4H 51 30 10H 0.2 3H 123 103 174

47

 

 

 

 

 

 

 

 

 

 

 

 

Table 7. Percent of Total Yield Recovered in Test 5
Heads first Butts first
Source Plot No. Plot No.

3 4 5 6

75 75 75
Recovered Threshed 75.7 68.2 76.1 65.2
seed in Unthreshed nil 0.0 0.0 0.3
grain box Total 75.7 68.2 76.1 65.5
Cutterhead Threshed 20.3 26.5 20.2 29.2
losses Unthreshed 1.6 3.4 0.1 4.4
Total- 21.9 29.9 20.3 33.6
chamber Unthreshed 0.2 nil 0.3 0.7
losses Total 2.4 1.9 3.6 0.9
Total grain recovered 100.0 100.0 100.0 100.0
Total cylinder losses 0.2 nil 0.3 1.0
Total losses of grain 24.3 31.8 23.9 34.8
Straw in grain box 19.6 25.7 13.7 29.3

Straw in burlap sack 80.4 74.3 86.3 70.
Total straw recovered 100.0 100.0 100.0 100.0

 

Table 7 shows the percent distribution for the test.

The losses were considerably greater than can be accepted by

either method of crop entrance.

The cutterhead losses of

threshed grain were the main source of the losses, but the

sum of the cutterhead losses of unthreshed grain and the

total swirl-chamber losses cannot be neglected.

48

Table 8 is a summary of the main results from Table 7.
It was impossible to draw any conclusion about which enter-
ing method of the crOp was the best. The dispersion was so
large that a large number of observations would have been

necessary to detect any significant difference.

Table 8. Statistics for Test 5

 

 

 

 

Source Heads first Butts first

X 5 X s

Threshed grain in grain box 72.0 5.3 70.7 7.7
Total cutterhead losses 25.9 5.7 27.0 9.4
Total swirl-chamber losses 2.1 0.4 2.3 1.9
Total cylinder losses 0.1 0.14 0.7 0.5
Total losses 28.0 5.3 29.3 7.7

 

A study of the observations indicated that there was a
pronounced relationship between the efficiency of the com-
bine and the plot yield regardless of entering method of the
crOp. Figure 19 shows that the percent cutterhead losses of
threshed and unthreshed grain decreased as the plot yield of
grain increased. Figure 20 shows that the swirl-chamber
losses of threshed and unthreshed grain increased as the
total yield of grain entering the swirl-chamber increased.
Figure 21 shows that the percent straw separation in the

swirl-chamber increased as the total yield of straw

49

 

CUTTERHEAD LossES,PERoENT

L 13 THRESHED
Q UNTHRESHED

®\ 0 TOTAL

1 -l l
150 20 «‘250 300
TOTAL YIELD OF GRAIN, GRAM

 

C) h) t» O) a)
I
g

1 L I

l_l l
7' 100 350

Fig. 19. Correlation between percent cutterhead
losses and total yield in Test 5.

. 50

4.0 *'

3.5 h

3.0»

2.5 e

2.0P

 

SWIRL—SECTION

SWIRL-GHAMBER LOSSES, PERCENT

 

 

"5’ AT POSITION 2
” G) THRESHEO
1.0 ~ EJ UNTI-IRESHED
0.51-
- E] E]
_”L L 1 1 IE} 1 1 1 1 1 L, 1
100 I 50 200 250 300 350

TOTAL YIELD OF GRAIN, GRAM

Fig. 20. Correlation between percent swirl-chamber
losses and total yield of grain in Test 5.

51

r

l00

  

STRAW SEPARATION,PERGENT

 

90-
L
so-
L szRL-SECTION
k AT POSITION 2
70 P 0

 

’1-
I;7Hl 1 1 1 L, I 1 1 1 1 1
,

I50 200 250 300 350 400

TOTAL STRAW ENTERING THE SWIRL‘CHAMBER
GRAM

Fig. 21. Correlation between percent straw separation
and total yield of straw entering the swirl-chamber in
Test 5.

\71
R)

entering the swirl-chamber increased.

gpppges based on observations made during test 5. A

slow speed pulley was mounted to give lower ground speed.

 

That reduced the rate of material entering the cutterhead
and swirl-chamber in the remaining tests.
The shape of the swirl-chamber was adjusted from

position 2 to position 1.
Test 6. Propeller flails, slow ground speed

The purpose of this test was to determine if the slow
ground speed and the shape of the swirl-chamber influenced
the cutterhead losses and the performance of the swirl-
chamber.

Table 9 shows the adjustment of the combine, Table 10
shows the observations, and Table 11 shows the percent

distribution.

Table 9. Adjustment of the Combine in Test 6

 

Shape
Fan Air de- of the Entering
Plot Flail Ground shutters flector swirl- Height way of
No speed speed Opening setting chamber of cut crOp

 

rpm mph inches
'1300 0.90 12 3 1 27
1200 .0.84 12 3 1 27 Butts
first
9 1100'. 0.76 12 5 1 27
10 1300 0.90 12 3 1 27

53

Table 10. Weight of Grain and Straw in Grams in Test 6

 

 

 

' Cutter- ‘
Plot Grain box pp pead Straw sack Total
No T U S T U T U S G S

 

7 113 0.5 7.5 34 12 11.5 1.3 260 172.3 267.5
3H’

 

8 290 .1.0 29 54 1.0 5.0 1,0 338 352.0 367

 

9 194 8K 10 55 11 16 9K 294 275.0 304
7H 6H

—_f

10 77 0 3 42 2.9 33.5 0 224 155.4 227
7H

 

54

Table 11. Percent of Total Yield Recovered in Test 6

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Butts first Plot No.
Source

7 8 9 10

“I 2? % $5
Recovered Threshed 65.6 82.4 70.2 49.5
seed in Unthreshed 0.3 0.3 nil 0.0
grain box Total 65.9 82.7 70.2 49.5
Cutterhead Threshed 19.7 15.3 20.0 27.0
losses Unthreshed 7.0 0.3 4.0 1.9
Total 26.7 15.6 24.0 28.9
Swirl- Threshed 6.7 1.4 5.8 21.6
chamber Unthreshed 0.7 0.3 nil - 0.0
losses Total 7.4 1.7 5.8 21.6
Total grain recovered 100.0 100.0 100.0 100.0
Total cylinder losses 1.0 0.6 nil 0.0
Total losses of grain 34.4 17.6 29.8 50.5
Straw in grain box 2.8 7.9 3.3 1.3

Straw in burlap sack 97.2 92.1 96.7 98.
Total straw recovered 100.0 100.0 100.0 100.0

Table 12. Statistics for Test 6
Source Butts firSt

‘ 3': a

75 %
Threshed seed in grain box 66.9 13.6
Total cutterhead losses 23.8 5.8
Total swirl-chambepglosses 9.1 8;:
Total cylinder losses 074 0.5
Total losses 33.1 13.6

 

55

The variability in the observations was large as shown
in Tables 11 and 12. The four observations showed that as
an average only 66.9 percent of the grain was recovered in
the grain box. The standard deviation was 13.6 percent
which means that the recovered plot yields had a large dis-
persion. An examination of the main source for this dis-
persion led to the swirl-chamber loss of threshed grain for
plot 10. This plot had a low yield of grain and straw and
Figures 22, 23, and 24 show that there was a relation
between the efficiency of the combine and the plot yield.

Figure 22 shows that the percent cutterhead losses of
threshed and unthreshed grain decreased as the total yield
of grain increased. The reduction in ground speed had no
significant influence on the size of the cutterhead losses
as a comparison between Figure 19 (1.4 mph) and Figure 22
(0.8 to 0.9 mph) shows.

Figure 23 shows that the percent swirl-chamber losses
of threshed grain decreased as the total plot yield of
grain increased. The losses of threshed grain were definitely
larger for shape 1 of the swirl-chamber than for shape 2 as
a comparisOn between Figures 20 and 23 shows. The losses
of unthreshed grain were negligible compared with the losses
of threshed grain. The data gave no reason to state any
connection between losses of unthreshed grain and the plot
yield or difference from Test 5. One difference, however,

between shape 1 and shape 2 of the swirl-chamber was evident.

CUTTERHEAD LOSSES,PERGENT
6

 

56

 

 

16 '-

l4)- \

12-

IO F D THRESHED

8 +- 0 UNTHRESHED

C) C) TTTDQL

6 _.

4. 0

25 Q

0 4,, 1 1 1 1 1 1 l I 1 1 (DE—L.
100 15 0 200 250 300 35

TOTAL YIELD OF GRAIN, GRAM

Fig. 22. Correlation between percent cutterhead
losses and total yield of grain in Test 6.

 

‘ \

28»

244

20-

16*

|2r

SWIRL—CHAMBER LOSSES, PERCENT

4.

p—

 

O—rtfi

g 1 Q 1 f If; I P [F1—
100 IE- 200 250 300 350

Fig. 23.

57

SWIRL’SECTION
AT POSITION 1

G THRESHED
E.) UNTHRESHED

G)

 

 

 

TOTAL YIELD OF GRAIN, GRAM

Correlation between percent swirl-chamber

losses and total yield of grain in Test 6.

58

100*
r— 9“..\~.\
98~
\
_ CD
0

.—
z 965
:3
a: L
1.0
a;lg¢i_
:2
9 -
’5:
m 92" G
<1
0- a
1.1.1
. .07
i
E .—
m ssL sw1RL-SECTICN

I. AT POSITION I

 

8 61:-

A 1 1 1 L, I 1 1

l I
150 200 250 300 350 400

TOTAL STRAW ENTERING THE SWIRL‘CHAMBER
GRAM

J

Fig. 24. Correlation between percent straw separation
and total yield of straw entering the swirl-chamber in
Test 6. '

59

The losses of threshed grain decreased with increased plot
yield for shape 1, but increased with increased plot yield
for shape 2. (This suggests that there must be a shape of
the swirl-chamber between 1 and 2 where the percent losses
of threshed grain are constant regardless of plot yield.)

Figure 24 shows that as the plot yield increased, the
percent straw separation in the swirl-chamber decreased.
This was the opposite reaction as was found for shape 2 of
the swirl-chamber shown in Figure 21. The percent sepa-
ration of the straw from the grain was definitely better in
Test 6 than in Test 5, but as the losses of threshed grain
was much higher, the adjustment of the swirl-chamber in
TeSt 6 cannot be considered to be an improvement. The sepa-
rating efficiency cannot be considered as satisfactory.

The reason for the decrease in cutterhead losses with
increased plot yield was the same as in Test 5. A.high
yield of straw made a better sealing in the throat of the
cutterhead so the flails did not throw the grain out so
easily. The decreased percentage of swirl-chamber losses
with increased yield of grain entering the swirl-chamber and
a corresponding higher percent of straw in the grain box,
must be connected with the lower air velocity at higher
loads on the swirl-chamber.

The best estimate of the combine efficiency would have
been the regression equation: Y = Y + b(X - i) where

Y = expected combine efficiency.

Y = average recovered yield computed from the
observations.

60

K and i = plot yield and average plot yield.
This linear regression equation would have determined the
combine efficiency with a smaller standard error of esti-
mate than what the standard deviation can provide. With
the few observations, the variation in flail speed and the
great losses, it was not considered worthwhile to compute
the regression equation. Even if the graph,based on a
regression equation, was available, it would be to laborious
to make the corrections in practice. Because the only
known observation would be the recovered seed in the grain
box, such a regression equation, if applicable, must use
the recovered seed instead of total plot yield for calcu-
lating the expected plot yield.

Test 7, Modified propeller flails

This test was Carried out in order to find a way to re-
duce the large cutterhead losses of threshed grain.

A bottom plate under the cutterhead, a front shield and
the modified propeller flails, pictured on page 20 and des-
cribed on page 22, were tested.

Three plots were harvested with the bottom plate under
the right cutterhead. The plate covered the opening from
the rear to the point where the flails were nearest to the
ground. No observations were taken because the results were
obvious. The bottom plate bent the straw so a large part of

the heads did not come in contact with the flails, and

61

Table 13. Adjustment of the Combine in Test 7

 

Shape
Fan Air de- of the Way of
Plot Flail Ground shutter flector swirl- Height enter-
No speed speed opening setting chamber of cut ing

 

 

rpm mph inches
11 1100 0.76 1 27
Butts
12 1200 0.84 1 27 first
13 1200 0.84 1 27
14 1200 0.84. 1 27 Butts
first,
15 1200 0.84 1 27 front
shield

 

remained unthreshed. The bottom plate was, therefore, re-
moved and a series of observations with the modified pro-

peller flails and the front shield were taken. Table 13
shows the adjustment of the combine.

The speed of 1,100 rpm was too low to prevent clogging
in the air duct. An increase to 1,200 rpm gave satisfactory

results with clean duct.

Table 14. Weight of Grain and Straw in Grams in Test 7

 

 

 

 

 

 

 

 

Cutter-
Plot Grain box head Straw saggg Total
No T U s T U 1_ U S G s
11 142 0.3 11 73 7.0 2.5 1.0 353 226 364
1H 16H 8H

12* 20 0.0 3.0 89 1.5 6.0 2K 514 117 314
3H 2H

15 71 0.0 9.0 37 7.8 1.0 1.0 242 118 251
17H 8H
14 107 1.0 21 45 42 1.0 2.0

74H 15H 145 198 166

15 160 1.2 19 p 73 27 3.5 1.5 180 266 199
9H 50H 6H

*Clogging in the cutterhead intake, so the cutterhead

losses of threshed grain were extremely large.

The modified propeller flails bent the straw more than

the propeller flails.

The losses in the end Of the plots

were therefore almost as high as for the direct throwing

flails. The number of unthreshed heads in the end of the

five plots ranged from 10 to 21.

63

Table 15. Percent of Total Yield Recovered in Test'7

 

Butts first

 

 

 

 

 

 

Butts first Front shield
Source

Plot No. Plot No.

11 12* 13 14 15

% % 7.
Recovered Threshed 62.9 17.1 60.4 54.1 60.1
seed in Unthreshed 0.1 0.0 0.0 0.5 0.5
grain box Total 63.0 17.1 60.4 54.6 60.6
Cutter- Threshed 32.3 76.5 31.4 22.7 27.3
head Unthreshed 3.1 1.3 6.6 21.2 10.2
losses Total 35.4 77.8 38.0 43.9 37.5
Swirl- Threshed 1.1 5.1 0.8 0.5 1.3
chamber Unthreshed 0.5 nil 0.8 1.0 0.6
losses Total 1.6 .1 1.6 1.5 1.9

 

Total grain recovered 100.0 100.0 100.0 100.0 100.0

 

Total cylinder losses 0.6 nil 0.
Total losses of grain 37.1 82.9 39.

 

Straw in grain box 3.0 0.9 3
Straw in burlap sack 97.0 99.1 96

 

Total straw recovered 100.0 100.0 100.0 100.0 100.0

 

*Plot No. 12 must be diaregarded as representative for
the modified propeller flails because of clogging in
the cutterhead inlet.
Table 15 shows the percent distribution of the recovered

grain and straw. The cutterhead losses of threshed grain

were large even if plot 12 is disregarded as representative

64

for the modified prOpeller flails because of clogging.

The main effect of the front shield was a pronounced
increase in the cutterhead losses of unthreshed grain, and a
corresponding decrease in the cutterhead losses of threshed
grain. The reason was that the front shield prevented a
large prOportion of the heads from coming in contact with
the flails.

Table 16 shows the main results of Test 7. Plot 12 was

disregarded in this summary.

Table 16. Statistics for Test 7

 

Butts first

 

 

 

 

 

 

No front Front

Source shi§;gw shield
X s X s
35 75 7 75
Threshed seed in grain box 61.7 1.8 57.1 4.2
Total cutterhead losses 36.7 1.8 40.7 4.5
Total swirl-chamber losses 1.6 0.0 1.7 0.3
Total cylinder losses ' 0.7 0.14 1.3 0.3
Total losses 38.3 1.8 42.9 4.2

 

It was obvious that the modified propeller flails and
the front shield did not improve the combine. The total
losses of 38.3 percent grain without a front shield and 42.9
percent with a front shield do not need further comments.

A discussion of the graphical appearance of the

56

N 01 b .1:
.b N 0 a)

CUTTERHEAD LOSSES, PERCENT
5

 

Fig. P50

.1
#fi 1 1 1

I
100 I50 200

65

1:1 THRESHED, N0 FRONT SHIELD
A UNTHRESHEO, .. .. ..

8 TOTAL, 11 II II

0 THRESHED, FRONT SHIELD

V UNTHRESHED, “ "

0 TOTAL, .. ..

 

 

I I I

1 1 l
250 300 350

TOTAL YIELD OF GRAIN,GRAM

Correlation between percent cutterhead

losses and total yield of grain in Test 7.

66

 

 

" SWIRL-SECTION
. AT POSITION I
2.8- OTOTAL
_ E) THRESHED
,_ 0 UNTHRESHED
2 am
DJ
Q)
m I"
LIJ
{ace
U) 0
u] a
U)
‘3 Ice
_, . o o o
33 ' /
“2° I.2~—
<1
35 ~ 0
I
8
31 - 0
E] G
0.4-
.
#IILL 1 L 1 1 1 1 1 J L L
100 150 200 250 300 350

TOTAL YIELD OF GRAIN, GRAM

Fig. 26. Correlation between percent swirl-chamber
losses and total yield of grain in Test 7.

67

I005

STRAw SEPARATION,PERCENT

 

 

1 1 1 L, 1 L, 1 1 1

150 200 250 _300 350 400
TOTAL STRAW ENTERING THE SWIRL-CHAMBER
GRAM

Fig. 27. Correlation between percent straw separation
and total yield of straw entering the swirl-chamber in
Test 7.

observations might be worthwhile.

Figure 25 shows that the percent cutterhead losses of
unthreshed grain and the total cutterhead losses decreased
with increased yield. This was also the case for Test 5
and Test 6. The cutterhead losses of threshed grain, how-
ever, seemed to increase slightly with increased yield,
which was not in agreement with the previous observations.

Figure 26 shows that the percent swirl-chamber losses
of threshed grain and the total swirl-chamber losses in-
creased with increased yield. The losses of unthreshed
grain decreased with increased yield. As the Only difference
between Tests 6 and 7, regarding the swirl-chamber, was that
the fan shutters were set back from full Opening to opening
5, this adjustment must be responsible for the opposite
reaction of the swirl-chamber with respect to the percent
losses of threshed grain.

Figure 27 shows that the percent straw separation in-
creased with increased yield of straw entering the swirl-
chamber. This was also an Opposite reaction to that ob-

served in Test 6.
Test 8. Modified direct throwing flails.

All previous tests with the flails mounted directly
behind the cutterhead‘entrance failed to reduce the cutter-
head losses. This test was made to determine if it was

possible to suck the heads and straw into the fan from the

69

side. The modified propeller flails were removed and a
metal sheet was mounted behind the cutterhead throat to

lead the grain into the fan housing. Experiments in the
laboratory showed that the direct throwing flails in the fan
housing threw out a large percentage of the threshed kernels.
The four flails nearest the fan intake were, therefore, re-
moved and replaced with two propeller flails mounted oppo-
site On the shaft. The direct throwing flails in the left
cutterhead were removed and the left fan Opening covered in
order to increase the suction of the fan on the right side.
The direct throwing flails left in the fan were not able to
produce any air suction of significance, and the modified
direct throwing flails, pictured on page 20 and described

on pages 22 and 23, were mounted nearest to the right hand
fan intake. The air suction was highly increased and
laboratory tests with oats showed that it seemed to be
possible to suck the heads into a fan moving between the
rows in the field.

A period of bad weather prevented the testing of the
fan suction cutterhead until September 3. Sprouting in the
heads was then so far advanced that taking samples was use-
less. The losses of threshed grain seemed to be less than
in the previous tests. The number of unthreshed heads, how-
ever, increased. This_was because the fan suction was not

large enough to pull the heads into the fan.

SUMMARY OF THE RESULTS FROM THE FIELD TESTS

The number of Observations in each test was not large
enough to permit the statement of conclusion. But when
considered in the light of each other, certain inferences
could be made with little risk of being wrong. The high
number of combinations in adjustment of the combine made it
convenient to use a grouping system for discussing the re-

sults.
The Cutterhead Efficiency

The following four different types of flails were con-
structed and tested in an experimental field of wheat.

1. The direct throwing flails.

2. The prOpeller flails.

3. The modified propeller flails.

4. The modified direct throwing flails.

The first three types were tested under natural condi-
tions and a limited number of samples were collected to get
an idea about the losses. The samples were too small to
determine the means and distributions of the losses exactly,
but they give an idea about the combine efficiency. Larger
samples were not considered important because the losses
were considerably higher than could be accepted, with an
average ranging from 28. 0 to 42.9 Percent for different

70

7T

flails and adjustments.

The highest percentage of recovered seed in the grain
box was only 82.4 percent of the total plot yield. This
was obtained in plot 8, Test 6, with propeller flails,
ground speed 0.84 mph, and butts entering the cutterhead
first. The largest source of losses from the flails was
the percent cutterhead losses of threshed grain. Plot 8,
Test 6, was the best single result obtained. The cutterhead
loss of threshed grain was only 15.3 percent, but losses up
to 39.4 percent were recorded with the propeller flails and
lowest setting of the cutterhead.

The cutterhead losses of unthreshed grain were small
compared with the losses of threshed grain. If Test 7,
plots 14 and 15, which was harvested with a shield in front
of the flails, were excepted, these losses were in range of
0.1 to 7.0 percent of the total plot yield. Observations
from Test 5, propeller flails, high ground speed, and Test
6, prOpeller flails, slow ground speed, are shown plotted in
Figure 28. This indicated that the total losses from the
propeller flails decreased with increased plot yield. The
total losses from the modified propeller flails were also
in agreement with this general picture.

The explanation for this relationship, which seems to
be independent of flail speed within the limits tested, was
simple. A high plot yield of grain was positively corre-
lated with a high yield of straw. The straw provided a seal

72

 

OUTTERHEAD LOSSES,PERGENT
6

 

 

 

I6 - 0
I4-
EJ TEST 5, TOTAL

12- 0 TEST 6. TOTAL
.0_ 0 TEST 5. UNTHRESHED
s v TEST 6, UNTHRESHED
6..
4t
21—

. 1 A l —L_L_
0L"100 15 200 9%50 300 350

TOTAL YIELD OF GRAIN, GRAM

Fig. 28. Correlation between percent cutterhead
losses and total yield of grain in Tests 5 and 6.

73

at the front of the throat which prevented the grain from
flying out of the throat when it was hit by the impeller
flails. An excellent demonstration of this was the test of
the direct throwing flails and the modified direct throwing
flails. The large losses of threshed and unthreshed grain
in the end of the plots occurred because this wall of straw
ceased to seal the Opening of the throat and support the
straw and heads being threshed by the flails.

The modified direct throwing flails were tried after
the kernels in the heads had started to sprout. The tap of
the heads and straw were led by vanes and suction into a fan
housing where cutting and threshing with the modified direct
throwing flails took place. The fan housing prevented the
threshed grain to be scattered on the ground. The vanes and
the fan suction, however, were not able to lead all the
heads into the fan and a large part of the heads remained
unthreshed. The test indicated that a stronger fan, passing
along the rows, would have been able to suck the heads into
the fan housing and thresh them with small losses of threshed

grain.
The Threshing‘Efficiency

The threshing efficiency was determined as percent
cylinder losses (percent unthreshed grain) versus flail
speed and percent visible damage of the kernels versus

flail speed regardless of entering way of the crop and types

74

of flails. .This was done because the number of observations
was too small to determine whether or not there were
differences between the entrance methods Or types of flails,
and because it is well known that speed is the factor which
has the greatest influence on the cylinder losses and visible

kernel damage by impact threshing.

Cylinder losses

Eight observations with propeller flails at a speed of
1,300 rpm gave an average of 0.34 percent cylinder losses
with a standard deviation of 0.42 percent. The range was
between 0 and 1 percent.

Five observations for propeller flails and modified
propeller flails at a speed of 1,200 rpm gave an average of
0.8 percent cylinder losses with a standard deviation of
0.56 percent. The range was between 0 and 1.5 percent.

Corresponding statistics for 1,100 rpm would have little
meaning because only two observations were taken at this
speed. The reason was that this speed was not sufficient to
blow the straw up to the swirl-chamber.

The best estimate of the relation between cylinder
losses and speed of the flails under the given field condi-
tions was provided by the following regression equation

”based on‘15 observations. Linearity, a common variance, and

independent Observations were assumed.

Y = 0.487 - 0.00108 (X - 1240)

75

where: Y is the expected percent cylinder losses.
X is the flail speed in rpm.

This means that 100 rpm increase in flail speed would
only give an expected decrease of .108 percent cylinder
loss. In other words, the cylinder loss was only slightly
affected by the flail speed in the observed speed range.
The observed dispersion in the cylinder losses must be more
affected by other factors than by speed. The closest ex-
planation was that different varieties had different
threshing characteristics. The flail types themselves must
also be assumed to be a source of dispersion in the obser-
vations.

Because the cylinder losses, as determined by the re-
gression equation, were fairly constant in the speed range
between 1,100 and 1,300 rpm, the pooled standard deviation
of 0.47 percent provided a good estimate of the dispersion
in the cylinder losses.

No correlation was found between cylinder losses and
plot yield in the available material.

Based on this study it was concluded that the flail-
type mechanism was able to give a fairly good completeness
of wheat threshing at a flail speed of 1,100 to 1,200 rpm or
a peripheral speed of 4,500 to 5,000 fpm under the given

conditions.

Visible kernel damage

The material from the field tests were investigated‘

76

with respect to visible kernel damage.
Table 17 gives the observations at different flail

speeds regardless of type of flails and entrance method of

 

 

 

 

the crOp.
Table 17. Percent Visible Kernel Damage
Flail speed, rpm
1075 . 1100 1200 1300
3 i % T %
0.0 0.5 0.8 4.2
0.0 0.0 . 0.6 4.1
0.0 2.1
0.0 2.2
0.5 5.0
0.2 2.6
0.3 ' 1.9
3.2
0.0 0.5 2.4 . ‘ 25.3

 

X = 0.0 i = 0.25 32 = 0.34 it = 3.16

 

An examination of the material showed that the three
observations with the direct throwing flails and the five
observations with the modified propeller flails indicated a
similar reaction to speed as the 11 observations taken with

the prOpeller flails. The dispersion of the observations was

77

so great that a large number of observations would have been
necessary to detect a possible difference in percent visible
damage due to entrance method of the crop.

The best estimate Of the visible kernel damage with
respect to speed was assumed to be a regression equation.
Such an equation, however, does not fit very well with the
observations. A more realistic approach would be to form a
hypothesis that the visible kernel damage is an exponential
function with respect to flail speed. Too little data are
presented to permit the drawing of such a conclusion at this
time.

No observations were taken of the moisture content in
the grain, but the crop was dry and well suited for combin-
ing when the test at 1,300 rpm was conducted. Six out of
seven observations at 1,200 rpm were carried out the same
day and at a higher moisture content in the grain than the
observations at 1,300 rpm. An equation for percent visible
damage of the kernels would only be appropriate at a certain
moisture content of the crOp or if a parameter for the
influence of moisture content was incorporated.

Regardless of these objections, the observations showed
that a flail speed above 1,300 rpm or 5,500 fpm should not
be used for harvesting wheat plots under average harvesting
conditions because of the high percent of visible kernel
damage.

A few plots were harvested with a flail speed of 1,400

78

and 1,500 rpm. No observations were taken, but the kernel
damage increased rapidly and were considerably higher than
can be accepted for harvesting plant breeding plots of I
wheat.

Splitting of the wheat kernels was the most common form

for visible kernel damage.
The Swirl-Chamber Efficiency

An evaluation of the swirl-chamber efficiency must deal
with the percent losses of grain and the percent straw
separation.

N0 attempts were made to take samples of sufficient size
to determine the means and standard deviations for different
adjustments with accuracy. The tests indicated a relatively
strong relationship between swirl-chamber efficiency and the
amount of grain and straw entering the swirl-chamber. For
shape 1 of the swirl-chamber, Test 6 showed that the percent
swirl-chamber losses of threshed grain decreased from in-
creased yield of grain. A corresponding decrease in straw
separation with increaSed straw load was also observed.

The most logical explanation to this reaction was that
the higher yields "overloaded" the swirl-chamber by decreas-
ing the speed of the air and thus decreased the percent
separation. Test 7, however, showed a relationship between
shape 1 of the swirl-chamber and the separation which backed

up the general picture for shape 2 of the swirl-chamber.

79

This relationship was best demonstrated in Test 5. The
percent swirl-chamber losses of threshed grain increased
with increased plot yield. A corresponding increase in
straw separation with increased yield of straw was also ob-
served. The difference in shape 1 and shape 2 of the swirl-
chamber can be observed in Figures 7 and 8. The swirl-
chamber is set at shape 1, but a line marked 2 can be ob-
served on the plastic wall. The difference in Operation
caused by the shape of the swirl-chamber was that shape 1
returned more grain and straw to the swirl (had a smaller
radius of curvature) than shape 2 and this overloaded the
swirl-chamber at high yields.

In shape 2 the grain and straw was directed more up-
wards toward the outlet of the swirl-chamber. The increase
in losses of threshed grain with increased yield was also
probably due to overloading. It must be assumed that the
difficulty for the kernels to be separated from the straw
increased with increased density of material in the swirl-
chamber.

The available observations were not considered suited
for forming regression equations for swirl-chamber losses
versus grain yield, but the following illustration was con-

sidered useful.

Shape 1 of the swirl-chamber

If plot 10 in Test 6 and plot 12 in Test 7 were excepted

80

from the calculation, the remaining seven plots, together
with the two plots of Test 4, yielded these averages:
2.34 percent losses of threshed grain.
0.46 percent losses of unthreshed grain.
92.1 percent separation of straw.
The range of these observations are as follows:
0.4 to 6.7 percent losses of threshed grain.
Nil to 1.0 percent losses of unthreshed grain.
80.5 to 97.2 percent separation of straw.
In plot 10, 21 percent threshed grain was lost in the
swirl-chamber. The corresponding straw separation was 98.7
percent. In plot 12 the corresponding numbers were,

respectively. 5.1 and 99.1 percent.

Shape 2 of the swirl-chamber

The four plots from Test 5 yielded these averages:
1.9 percent losses of threshed grain.
0.3 percent losses of unthreshed grain.
77.9 percent straw separation.
The range of these observations are as follows:
0.2 to 3.3 percent losses of threshed grain.
N11 to 0.7 percent losses of unthreshed grain.
70.7 to 86.3 percent straw separation.
A comparison between shapes 1 and 2 of the swirl-
chamber are difficult because the losses were also affected

by the flail speed, the setting of the fan shutters, and the

81

air deflector. '

The maximum capacity of the fan was used with shape 2 of
the swirl-chamber and, in spite of that, the straw separation
was inferior to that required of a plot combine.

Shape 1 gave a better solution in spite of the relatively
large losses of threshed grain. The losses of unthreshed
grain in the swirl-chamber were considered as a part of the
cylinder losses and will not influence the swirl-chamber
losses of threshed grain. This means that the swirl-chamber
had 2.34 percent losses of grain at a straw separation of
92.1 percent. It should be remembered that the average losses
for wheat, barley, and cats with the German experimental
cyclone-thresher were 2.9 percent.

The tests indicated that a swirl-chamber principle de-
sign of prOper size should provide an efficient self-cleaning

separator for a variety plot combine for grain.
Field Results of Self-Cleaning Efficiency

The combine was designed to be 100 percent self-cleaning.
The tests showed, however, that the relatively long straw
produced by the flails tended to clOg the duct and the
swirl-chamber. These elements were definitely too small for
harvesting two rows simultaneously. For one row harvesting
the duct and swirl-chamber together clogged in about 30
percent of the total number of harvested plots. The swirl-

chamber clOgged more easily than the duct. In some cases

82

the straw which the swirl-chamber did not separate clOgged
in the duct to the grain box, and in other cases, some straw
was long enough to clOg across the swirl-chamber itself.

The source of clogging in the duct was the bend at the
inlet to the swirl-chamber.

Complete self-cleaning with respect to the straw seems
to be possible with proper construction and dimension of the
duct and the swirl-chamber.

Some kernels remained in the swirl-chamber at the end
of the plots because they were in equilibrium with the air
frOm the fan. By reducing the throttle these kernels slid
into the grain box by their own weight.

Reducing the air speed in theswirl-chamber between the
plots by one or another means would be necessary for obtain-
ing a self-cleaning combine when this particular model of

the swirl-chamber is used.

LABORATORY TEST FOR SELF-CLEANING EFFICIENCY

In order to determine the self-cleaning ability of the
combine, the following tests were conducted in the laboratory

after the harvest season.
The Cutterhead Fan

Three handsful of wheat were introduced in the fan
when operated at a speed of 1,000 rpm. The fan was stOpped
and checked for remaining kernels after each run. This
procedure was repeated five times. No kernels were left in
the fan.

This test would have to be repeated several hundred
times in order to state the fan to be completely self-
cleaning. An absolute test for the self-cleaning ability of
the fan was, therefore, designed to save labor.

One handful of wheat was placed in the bottom of the
fan housing when the fan was stationary. Then the fan was
started and the speed was gradually increased to 1,000 rpm.
An inspection after stopping showed that no kernels were
left in the fan housing. Two replications of this test
were performed with the same results.

Since the fan must be operated at 1,100 to 1,300 rpm,

the fan was considered to be completely self-cleaning.

83

84

The Air Duct

The duct between the cutterhead and the swirl-chamber
was inspected between each of seven runs and no kernels were
found. Even with the small number of replications it was
stated that the air duct was self-cleaning with respect to

lodging of grain.
The Swirl-Chamber

The swirl-chamber was inspected between each of seven
runs. The result was in agreement with the field tests.
It was necessary to reduce the throttle setting in order to
allow the kernels left in the swirl-chamber to slide down
into the grain box. This model of the swirl-chamber design
was, therefore, considered to be self-cleaning with proper
construction when an air reducing technique is utilized

between varieties.

PROPOSALS FOR FURTHER INVESTIGATIONS

This research is considered as a preliminary investi-
gation to determine the design parameters of a plot combine
for plant breeding. Various ideas were tested and design
parameters gained.

The suggestions presented in this chapter were based on
the experiments conducted and previous experience with the

threshing of small grain in plant breeding plots.
The Suction Cutterhead

To prevent cutterhead losses the cutterhead should be
constructed according to the following specifications.

A centrifugal fan 7 to 8 inches wide, 24 to 30 inches
in diameter, and with a 4 or 6 blade impeller should be
used for harvesting 2-row plots in small grains. To reduce
the kernel damage to a minimum the fan wings should be faced
with rubber. The corrugated concave should be solid. To
keep the power requirement small, an auger should be mounted
on each side of the fan to auger the standing plants into

the fan.

For plots consisting of more than two rows, it is sug-
gested that a series of centrifugal fans 5 inches wide,
about 24 to 30 inches in diameter, and with crop intake on
one side of the fan housing are placed along the same shaft.

The space between each fan for entrance of the crOp should

85

86

be about 3 inches. A straw divider at least 18 inches long
should be placed in front of each fan. The fan shaft should
rotate clockwise when looking at the combine from the right

side.
The Duct

It is assumed that the proposed fan would deliver
enough air at a peripheral speed of 5,000 fpm to blow the
grain and straw in any desired direction to the separating
and cleaning device. The duct area should be approximately

70 to 80 square inches.
The Swirl-Chamber

The swirl-chamber should be constructed so the seeds
deflected across the outlet from the swirl-chamber will not
re-enter the stream of grain and straw coming from the
cutterhead. Several methods for accomplishing this are
possible. The most rewarding seems to be to use a series of
modified swirl-chambers to deflect the grain and straw to-
wards combs of i-inch rods placed é-inch center to center.
The grain and some short straw coming with the and first
will pass through the combs while the longer straw and the
grain, not seperated, will be deflected to the next swirl
for further separation. Two or three swirls and combs mounted
in series should be used for efficient separation of the

grain from the straw and chaff.

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