Agriculture Handbook No. 171

LIBRA R Y^

{mS'K-^ "X"' ' : :ORD

i, JAN 21^9:0 ^i

j

U. S. DEPARTMENT OF AGRICULTU1«l|

Increasing

Potato-Harvester

Efficiency

II

By A. H. Glaves and G. W. French

UNITED STATES DEPARTMENT OF AGRICULTURE

Agricultural Research Service
CONTENTS

MAIN OBJECTIVES

Complete Recovery of the Crop

Minimum Damage to the Potatoes

Clean Sample

Low Hiirve.sting Costs

GENERAL DIRECTIONS

Choice of Method

Choice of Machine

Choice of Accessories and Specifications

Efficiency of Operating Crew

Capacity of Potato-Handling Eqviipment.

Preventing Unplanned Interruptions

Maturity Acceleration and Other Preharvest

Precautions

SPECIFIC DETAILS OF OPERATION

Blade Control and Performan oe

Page

1

I

2

2

2

3

3

4

4

4

4

5

5

5

Page

SPECIFIC DETAILS OF OPERATION—Con.

Factors Affecting Separation 5

Pitch of Aprons 6

Magnitude and Frequency of Agitation __ 6

Rubber Covering for Apron Rods 7

Relation of Pitch to Rubber Covering 7

"Undersweep" and "Boiling" 7

Thinning the Flow and Increasing the

Scatter 8

Vine Elimination 9

Reducing Spill-Out Losses 10

Reducing Clod Problems 10

Efficient Hand Sorting fl

Transferring the PotatoesInto Hauling Equipment. 11

Crew Communication and Coordination. 12

Safetv of Workers 12

SUMMARY OF PRACTICAL SUGGESTIONS-. 13

ACKNOWLEDGMENTS

Acknowledgment is made to the Red River

Valley Potato Growers Association for providing

the Red River Valley Potato Research Center

facilities and a research farm, and for cooperation

in conducting the research. The interest and suggestions of the Association's research committee

and the cooperation of individual potato growers

are also acknowledged.

In addition, the authors wish to thank the manufacturers who loaned or donated equipment, provided transportation, aided in making distant

contacts, manufactured components differing from

usual specifications, and contributed helpful suggestions. Items sujDplied by manufacturers included five potato harvesters, three potato diggers,

one vine burner for field use, four vine beaters,

and miscellaneous machine parts.

The manufacturers who made significant contributions include: Food Machinery & Chemical

Corp., John Bean Division, Lansing, Mich. ;

Brady Manufacturing Corp., Des Moines, Iowa ;

Champion Corp., Hammond, Ind. ; Curl Manufacturing Co., Twin Falls, Idaho; Dahlman

Manufacturing Co., Inc., Braham, Minn.; Deere

& Co., Moline, 111.; Lockwood Grader Corp.

(Division of Dual Manufacturing and Sales, Inc. ),

Grand Forks, N. Dak. ; Mayo's Manufacturing Co.,

East Grand Forks, Minn. ; New Holland Machine

Co., New Holland, Pa.; Silbaugh Manufacturing

Co., Humboldt, Iowa; W. B. Skinner Co., East

Grand Forks, ]Minn. ; Wollery ^Machine Co., Minneapolis, Mimi.

('ooperation, assistance, and suggestions from

members of the staff' of the Departments of Agricultural Engineering at the Minnesota and North

Dakota Agricultural Experiment Stations, and

also from the staff' of the Agricultural Marketing

Service, U.S. Department of Agriculture, located

at East Grand Forks, Minn., are acknowledged.

Appreciation is also due A. J. Dubuque, engineering aid, Agricultural Engineering Research

Division, Agricultural Research Service, East

Grand Forks, Minn., for assistance in the implementation of this research and for part of the field

observations in Florida and Idaho ; also to R. E. L.

Greene, pi'ofessor of agricultural economy and

agricultural economist, Florida College of Aoriculture and Agricultural Experiment Station, and

to J. S. Norton, formerly agricultural engineer at

Florida Agricultural Experiment Station (now

located at Massachusetts Agricultural Experiment

Station), for valuable assistance in carryino- out

this i-esearch in Florida.

Jordan H. Levin, Agricultural Engineerino'

Research Division, Agricultural Research Service"

East Lansing, Mich., directed and greatly assistecl

in the preparation of the material in this publication.

Washington, D.C. Issued December 1959

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington 25, D.C. - Price 15 cents
Increasing Potato-Harvester Efficiency

By A. H. GLAVES and G. W. FRENCH, Agricultural Engineers, Agricuhural Engineering Research Division,

Agricultural Research Service

Mechanical potato harvesters haA^-e come into

increasingly wide use since the late li)40's. An

estimated 75 percent or more of the potatoes grown

in Idaho and in the Eed River Valley of Minnesota and North Dakota are harvested mechanically. Use of harvesters is increasing in other

important producing areas as they are being

improved and adapted to meet various difficult

conditions.

Numerous models equipped with a variety of

features and accessories are now commercially

available to meet the wide range of requirements.

The choice of a machine should be based on local

<ionditions, including size of the individual

operation, opportunity to do customwork, preferred method of operation, plans for marketing,

manner of disposing of the crop, and ultimate

utilization of the crop.

The decision to adopt mechanical harvesting involves more than the selection, purchase, and use

of a single machine. The harvester alone is a

major investment. If purchased new, a machine

costs from about $3,400 to about $10,000.

For maximum efficiency of operation, the harvester should be equipped for bulk handling of

the crop, and complementary companion equipment should be provided for hauling and rapid

unloading. If the haul to packing plant or storage

is short, two trucks with self-imloading boxes will

be required to keep the harvester operating continuously. Three or four trucks may be required

for longer hauls. Bulk-unloading facilities with

liigli capacity help to reduce the number of trucks

required.

The total investment in equipment, including

harvester, trucks, boxes, and Inn filler, may be

niore than twice that in the harvester alone. 'The

investment amounting to several thousand dollars

emphasizes the need for careful planning and

maximum utilization. The factors affecting efficiency are complex and must be carefully considered to obtain maximum efficiency and most

profitable use.

In spite of the large sums of money invested by

potato growers in harvesting machines, little published information is available on the effective

operation of this equipment. This is probably

because the machines are frequently built by small

manufacturers in limited quantities or custom

built in local .shops. Furthermore, the development of such equipment has been rapid in recent

years and has involved rapidly changing features

and specifications. The comi)lexity of the machines themselves, as well as operating problems

under diverse conditions, has made the preparation of comprehensive printed instructions difficult and costly.

This publication is based on research by the

Agricultural Engineering Research Division,

Agricultural Research Service, U.S. Department

of Agriculture, conducted mainly during the

1950's. It includes suggestions based on field observations. Its purpose is to provide information

for practical use by potato growers in the efficient

operation of mechanical equipment, in both the

direct and the indirect methods of harvesting.

MAIN OBJECTIVES

Certain main objectives should be borne in mind

in all mechanical harvesting operations. The

most important of these are discussed in the following paragraphs.

Complete Recovery of the Crop

The difference in cost between harvesting with

98-percent recovery and with 100-percent recovery may be much more than 2 percent of the value

of the crop if complete recovery requires excessive

depth of operation and results in inadequate sep515906°—59

aration of the potatoes and the hauling of much

soil to the storage or packing house. A harvester

with two 26-inch aprons, each lifting an average

depth of 4 inches of soil and traveling at 2 miles

per hour, would lift 8 to 10 tons of soil per minute.

Operating one-half inch deeper than necessary

would require the lifting of another ton or more

of soil per minute and might recover only a few

more potatoes, possibly with inadequate soil separation. Under adverse conditions, a skilled operator may be forced to harvest with less than 100-

percent recovery.
AGRICULTURE HANDBOOK 171, U.S. DEFT. OF AGRICULTURE

Minimum Damage to the Potatoes

Mechanical injury can easily reduce the grade

of 10 to 15 percent of tlie 3'ield, or even jeopardize

the salability of an entire lot. The seriousness of

all mechanical damage tends to increase with time

while the potatoes are in storage or are beinghandled in trade channels. Altliough potential

loss from damage is difficult or impossible to estimate accurately, much can be done to minimize

damage. Proper precautions before har\est and

careful operation of harvesting and handlingequipment should limit immediately detectable

damage losses to 5 percent or less.

Clean Sample

Potatoes should be free from tare materials—-

clods, adhering soil, stones, weeds, and vines—that

add to the cost of hauling, subsequent handling,

and tare disposal. "Clean sample'' means potatoes

that are free from such materials. Subsequent

handling operations are more easily accomplished

with a minimum of injury to the tubers if the tare

materials are removed iirst. Hauling operations

have been observed where tare materials constituted from 20 to 25 percent of the weight of tlie

load. Percentage of tare varies with local conditions, care in machine operation, and amount of

hand sorting. Tare should generally be held below

5 percent and can often be as low as 2 or 3 percent.

Low Harvesting Costs

The three objectives just discussed (complete

recovery of the crop, minimum damage to the potatoes, and clean sample) can be attained without

costs can be reduced to a minimum only by fullseason use of equilament and the sustained highcai)acity operation that is made possible by good

machine nuiintenance. Care is required to preserve the dependability of the original machinery.

Unplanned interruptions are costly in proportion

to the number of people made idle in the coordinated operations. By full mechanization, labor

costs can be reduced as mucli as 80 percent. Mechanical harvesting aiid bulk liandling eliminate

arduous labor and can reduce harvesting and

handling costs as much as 50 to 65 percent as compared with older hand methods.

Mechanical harvesting costs vary with field conditions; hauling costs vary with the distance

hauled. With favorable Held conditions and a

haul of 4 miles or less, costs as low as 15 cents

per hundredweight for harvesting and hauling

are possible.^ The goal of mininunn damage to

the potatoes should not be overshadowed by undue emphasis on low unit costs attained with rough

handling at higher speeds.

increasing the cost of harvesting. Harvesting

' Additional information on handling costs may be

obtained from the following pul)lications :

DOWNING, LEWIS .!., HEMPHILL, PEKKY V., and

ScHicKELE, RAINER, OBSERVATIONS ON POTATO HARVESTING

COST BY HAND AND BY MACHINE IN THE RED RI\'ER VALLEY.

20 pp., illus. N. Dak. Agr. Col., Agr. Expt. Sta., and

Red River Val. Res. Cen. Agr. Econ. Rpt. 7. Apr. 1953.

[Processed.]

GREENE, R. E. L., KUSHMAN, L. .J., NORTON, J. S., and

SPURLOCK, H. C. MECHANICAL HARVESTING AND BULK

HANDLING OF POTATOES IN FLORIDA AND ALABAMA. 47 pp.,

illus. Fla. Agr. Expt. Sta., Agr. Econ. Ser. .^-HO, 47 pp..

Jan. 1954. [Processed.)

NORTON, J. S., GREENE, R. E. L., and KUSHMAN, L. J.

EQriP:MENT FOR MECHANICAL HARVESTING AND HANDLING OF

IRISH POTATOES IN THE SOUTHEAST. Fla. Agr. Expt. Sta.

Bill. 579, 32 pp., illus. 1956.

EiGURE 1.—Typical Red River Valley scene showing 2-row direct harvester with crew of 6 workers for hand sortin»-.
INCREASING POTATO-HARVESTER EFFICIENCY

GENERAL DIRECTIONS

Choice of Method

It is importfiut to choose the method of operation

best adapted to the pavticadar conditions and

objectives. liither the direct or the indirect method of harvest can be nsed. There are advantages

and disadvantages in each.

In the direct method, the potatoes are chig,

elevated, and transferred into containers or bulk

trucks in one operation (ñg. 1).

In the indirect method, the potatoes are dug and

generally windrowed (fig. 2). After an adequate

lapse of time, generally betAveen 20 minutes and

2 hours, the harvester with suitable accessories

picks up, separates, and transfers the potatoes into

containers or trucks for transportation to storage

or packing plant. The indirect method can be

used to obtain high harvesting capacity from a

lighter and more simple machine than the two-row

direct harvester. Another advantage of the indirect method is the ability to ''open up'" a field

without di'iving the truck on rows of undug potatoes (see fig. 2).

A previously used two-row digger can be

equipped with windrowing accessories and continuect in service for indirect harvesting (fig. 3).

This permits the change to mechanized harvesting

with smaller capital investment in new equipment.

The following types of windrowing accessories

have been used for this purpose. Most of them

have been custom made to individual specifications.

1. Single-apron, cross-conveyor type, which deposits potatoes in a windrow approximatelj' where one row

grew. '

2. Twin-apron, center-delivery type, which deposits potatoes from two rows about midway between the positions

of the rows.

3. Resilient rubber-covered, nuiltiple-roller type, which

deposits potatoes in a pattern similar to that laid down

by the single-apron, cross-conveyor type.

4. Padded rectangular-funnel type.

5. Twin-funnel type, which deposits potatoes from two

rows in two individual bands, to be picked up by a

l:^vo-row harvester equipped with pickup accessories.

BN-SJ5G-X

FIGURE 2.—A single-apron indirect harvester. This harvester with a single 26- or .3ó-inch primary apron has

high capacity when used indirectly to pick up a two-row

windrow.

FIGURE .3.—Standard two-row digger equipped with righthand-delivery, single-apron wiudrower. Different

windrow ijatterns can be laid down to suit different

plans of pickup. In this view, the potatoes are laid

down in pairs of windrows as the machine makes adjacent passes by alternate trips in opposite directions.

Other types of windrowing accessories having

longer convej'ors for depositing potatoes in fourand six-row patterns have also been used to a limited extent. Encouraging success has been

achieved with these, which indicates the possibility of higher capacity operations becoming more

general as further improvements are made.

"Single-apron''' harvesters (harvesters designed

for one-row direct operation) are most commonly

used for harvesting potatoes by the indirect

method. Tliey are modified b}' removing the

blade, adding a structural cross member inside the

primary apron if necessary, and adding suitable

windrow retainer plates. Harvesters designed for

two-row direct operation are sometimes, but less

frequently, used for indirect harvesting. Certain

combinations of conditions during the drying interval between the first stage and the second stage

(pickup operation) affect the capacity of the onerow machine for soil separation with reduced

apron speed and a minimum of agitation. Among

tliese conditions are: Soil type, stoniness, soil

moisture, relative humidity, wind velocity (and

even wind direction, wliere the fiekl is near a large

body of water) air temperature, cloudiness (or

brightness of sunshine), stage of maturity of the

potatoes, amount and nature of weed growth, soddiness, and amount of vine material.

In muck soils and heavy soils with high moisture, greater soil-separating capacity can be realized without excessive agitation by indirect operation tlian by direct operation.

The indirect method is often ])referred for its

cleaner work under adverse weedy or wet heavysoil conditions. Furtliermore, it is sometimes preferred for potatoes that are to be sold without

being washed, as wlien they are to be used for certified seed or unwashed table stock.
AGRICULTURE HANDBOOK 171, U.S. DEPT. OF AGRICULTURE

For indirect harvesting, the windrowing must

be carefully done. Frequently, with the indirect

method, the damage during windrowing far exceeds the total damage during subseqvient operations—pickup, elevation, separation, loading, and

unloading.

Improved windrowdng equipment is becoming

available. In numerous instances, two two-row

digger-windrowers are used to keep one singleapron pickup harvester operating at full capacity.

This allows slower travel speeds for the cliggerwindrowers.

The travel speed of the indirect harvester can

generally be faster than optimum for the diggerwindrower. Under certain conditions affecting

ease of separation, as explained previously, indirect harvesting more than doubles the capacity of

the single-apron harvester harvesting only one

I'ow direct, and it can greatly increase the capacity

of a two-row machine beyond its capacity with

direct operation.

Choice of Machine

It is essential to choose a machine that is suitable

to the area, the chosen method, and the specific

harvesting conditions—especially those conditions

that cannot readily be changed, such as soil, topography, stones, and field size. Stone clearing is

sometimes a prerequisite for satisfactory mechanical harvesting ancl may have to be included in a

longtime plan.

Choice of Accessories and Specifications

The best choice of optional accessories or ma^

chine specifications depends on soil type, method

of operation, and other factors already mentioned;

also on such factors as tuber size range and intended use, including use for certified seed, washed

table stock, dry table stock, chips, french fries, and

special potato products.

Efficiency of Operating Crew

Teamwork of the crew and the ability of the

harvester operator are of utmost importance. One

day's work of an unqualified operator may greatly

reduce the net returns by lowering the grade and

salability of the potatoes and increasing the

amount of culls. The loss in quality, loss of operating time, and failure to care for the harvester

may be two or three times as costly as the wages

required to secure a good operator. The quality

of the operator's work depends on his intelligence^

aptitude, experience, skill, and incentive to do the

best possible job.

From two to seven workers may be needed for

hand sorting to remove tare material including

clods, stones, vines, culls, cut potatoes, and potatoes damaged by frost. Hand sorters should be

nimble fingered; many operators prefer women

because of their manual dexterity. As some work

positions on the machine are more tiring than

others, it is a good i^ractice to rotate workers to

different positions each time across the field or

each round.

Capacity of Potato-Handling Equipment

The capacity of the handling equipment should

be keyed to the anticipated harvesting rate with a

very liberal margin. Unloading equipment should

BN-SJ61-X

FIGURE 4.—This blade is much shorter than the common

single-pointed blade. It is intended for use in heavy

soils. Note also the bridge plate inside the apron and

just to the rear of the cone rollers. This is used when

needed to prevent excessive undersweep or "boiling."

BN-,S4.53-X

FIGURE .5.—Two-piece or open-center blades similar to

these are often preferred for conditions where tough

root material tends to accumulate uncut on one-piece

blades.
INCREASING POTATO-HARVESTER EFFICIENCY

have a capacity from 50 to 100 percent greater than

the average harvesting rate because its operation

IS less continuous. High capacity for quick unloading can sometimes reduce by one the number of

trucks required, without unduly delaying the operation of the harvester. Älaximum eflicíency and

economy depend on coordination of operations as

well as on efficiency of the individual operations.

Preventing Unplanned Interruptions

Systematic periodic inspection and general preventive maintenance, including lubrication, adjustment, and general care of the harvesting

machinery, are especially important because of

the interdependence of the different operations.

Interruptions of harvester operation causecl by

machine failures that require repairs result in

idle time for the trucks, the harvester crew, and

the storage-house crew. Such idle time may cost

from $10 to $15 per hour. Excessive interruptions

in harvester operation have caused even greater

losses where they have resulted in significant

acreage ieft unharvested with the coming of

freezing weather.

Maturity Acceleration and Other Preharvest

Precautions

Preharvest precautions, incbiding maturity acceleration by timely vine killing, can conti'ihute

substantially to harvesting success by making the

work easier and the crop less vulnerable to damage.

Growers should keep this in mind during ]:)lanting,

cultivating, and other production operations.

They should avoid soil compaction when it would

aggravate the clod problem.

When neither frost nor natural maturity is

adequate, mechanical mutilation or a recommended chemical treatment should be used to kill

the vines and accelerate maturity. The action

should be taken early enough to allow for 2 to 3

weeks of warm weather before harvest. In irrigated areas, it is advisable to withhold irrigation

about 3 weeks prior to the planned harvest date.-

SPECIFIC DETAILS OF OPERATION

Blade Control and Performance

The performance and depth control of the blade

are of major importance in the operation of a

potato harvester. For each half inch of average

depth of the blade, about 75 tons of soil are lifted

per acre of operation. In muck-type soils, the

weight is less. An extra soil load of about 1 ton

per minute, resulting from operating the blade

one-half inch deeper than necessary, may overload

the aprons beyond their operating capacity. When

this occurs, it may be necessary to reduce either

the travel speed or the depth until one of the following occurs: (1) An occasional potato is cut;

(2) the separating capacity is adequate; or (3)

the soil blanket on the primary aprons becomes

inadequate for pi'otection against damage.

The blade should be polished enough to permit

it to scour freely. Failure of the blade to scour

freely, especially in certain types of soil, is a common problem. This failure may be caused by

paint, rust, inadequate polish, too steep an angle

with respect to horizontal, loose soil condition, or

uncut material accumulated over the cutting edge.

(See later discussion under "Reducing Spill-Out

Losses.")

If unsatisfactory scouring persists, one or more

of the following should be tried: (1) Deeper operation; (2) blades with smaller surface area (see

fig. 4) ; (3) faster travel speed of harvester and

truck; (4) open-center or two-piece blades (figs.

5 and 6); (5) a blade substitute—either driven

rotary rod, undriven rotary rod, stationary round

rod, or 1/2-inch pipe slotted on one side and slipped

over the cutting edge of a narrow blade (figs. 7

and 8).

In very heavy soil, uniform accurate depth control at the ideal depth is sometimes difficult to attain. This situation can be corrected by equipping the machine either with rubber-tired wlieels

or with spool rollers located just ahead of the

blades. Without these and with the suction of the

blades carried on the end of a long tractor drawbar, the total deflection in the draAvbar itself, in

the tractor tires, and in the machine frame may

vary enough to make accurate depth regulation

unattainable.

Factors Affecting Separation

Separation of potatoes from extraneous matter

is a complex problem because of the extremely

variable nature of the tare material and the widely

assorted sizes and shapes of potatoes. Constantly

changing soil conditions, temperatures, and crop

characteristics produce problems I'equiring alert-

- For further details ou maturity acceleration, the

following reference.s ou vine killing are suggested :

HOUGIILAND, G. V. C. POTATO VINIC KILLIXO. DiV, Veg.

Crops and Diseases, Bur. Plant Ind. and Agr. Engin.,

Agr. Res. Admin, unnumbered rpt., 5 pp. IJIimeographed.j 19.J2.

KUNKEL, R., EDMUNDSON, W. C, and BISKLKY, A. M.

HESULTS WITH POTATO VINE KII.LEES IN COLOIiADO. Cohj.

Agr. Expt. Sta. Tech. Bui. 46, 36 pp., illus. 1!).":^.

SCIIOEXE.MANN, .JOHN A. BETTEI! QUALITY POTATOES

THEOUGl-l TIMELY VINE KILLING. Ill I'otato Handliook, Machinery and Equipment Issue S: ;"JI-.j2. Potato Assoc.

Amer. 195S.
6 AGRICULTURE HANDBOOK 171, U.S. DEFT. OF AGRICULTURE

FiGTRE G.—These two-piece blartes have a modified mirtdlel)nster design. The unter luoklboard on eaeh uuit Is iuteuded to reduce the clod pitihleiu by dellectluK packed

soil from the shoulders of the ridge outward so that

fewer clods are delivered onto the aprons.

ness and keen judgment on the part of the harvester operator.

The operator has several choices of combinations to meet tlie specific situation. Damp soil on

api'ou rods may build up to a diameter of threefourths to 1 inch, Avhich greatl}^ reduces the soilseparating capacity of the apron. At the same

time, this provides excellent padding to reduce

damage to the tubers. It may be practical to use

higher apron speeds to offset partially the loss of

separating capacity resulting from the reduced

space between the heavily coated rods. Aprons

Avith Avider pitch and sprockets to match may be

needed; or aprons "svith smaller rod size (threeeighths instead of seven-sixteentlis inch) can be

substituted advantageously until drier soil conditions prevail.

Pitch of Aprons

Pitcli is the length of each individual link from

hinge point to hinge point. Average pitch is the

total leng-th of an apron in inches, divided by the

number of links. (Net distance between apron

rods is sometimes erroneously referred to as

"pitch.") Aprons with 1.56-inch pitch have been

most conuiion.

Use of aprons having wider pitch is often the

best means of increasing separation. Pitches of

1.63, 1.76, 1.88, or even 2 inches, with suitable

sprockets, may be used instead of 1..56-inch pitch.

An apron of wider pitch, with sprockets to match,

is recommended for use in adversely wet conditions (fig. 9).

When drier conditions prevail and reduce soil

buildup, too many of the small potatoes are likely

to fall through the apron. "VVlien this occure,

these small potatoes can be saved by applying rubber digger tubing to the apron rods. This also

protects the tubers from damage. Aprons with

wide pitcli are more suitable for round varieties

than for long or flat types.

Magnitude and Frequency of Agitation

Agitation of the apron can be expensive when

it is too severe. Its severity depends on its magnitude and also on apron speed and the amount of

soil padding on the apron at the point of agitation.

Tlie term "magnitude" as used here refers to the

distance the apron rods are lifted in passing over a

pair of idler rollers or a pair of agitator sprockets.

The term ''frequency" as used here indicates the

number of times per minute the apron is lifted by

any given pair of idler rollers or agntator sprockets. Frequency depends on the number of links

passing for each lifting action, the apron operating speed (generally in terms of feet per minute),

and the pitch of the apron. The frequency over

round idlers is equal to the number of links passing per minute; thus, aprons with wide pitch have

slower frequency than those with narrower pitch

oi)erating at the same number of feet per minute.

This change in relationship is often an advantage

for the apron with the wider pitch because the

same frequency of agitation is reached at slightly

higher apron speeds, which produces more thinning action in a given volmne of soil. (See also

the discussion under "Thinning the Flow and Increasing the Scatter.")

Agitator sprockets with varying magnitude and

frequency are shown in figure 10.

All smooth idler rollers give the same frequency

with a given apron speed and pitch. The smaller

the roller with respect to the chain pitch, the

greater the magnitude of agitation.

Plain round idler rollers under aprons may be

considered as mild agitators of low magnitude and

high frequency. Their frequency is equal to the

BN-S-459-X

FIGURE 7.—Under unfavorable soil conditions, a stationary 1-inch round rod with flattened ends bolted under

the regular blade brackets, as shown here, has sometimes been more satisfactory than conventional blades.

This unit is subject to further improvement in method

of mounting.
INCREASING POTATO-HARVESTER EFFICIENCY

JS .-'

BX-S404-X

FIGURE S.—The rotary rod blade-substitute shown here is power-talveoff driven at very low speed, as in rod weeders.

Basically similar units have been produced by five or more manufacturers. Research, testing, and development

are being continued.

number of chain links passing per unit of time.

Their magnitude and degree of agitation depend

on the material of which they are made and the

relation between their diameter and the pitch of

the ajoron. Large-diameter rubber idlers under a

closely pitched apron would give the softest type

of agitation. Idlers as small as 2 inches in diameter have been used. These require special

mounting brackets. (See fig. 10.)

Rubber Covering for Apron Rods

Eubber covering should be used on apron rods

to reduce damage to the potatoes if they are to be

dropped from a height of 6 inches or more. This

covering may be applied in the form of tuliing, or

it may be applied by dipping or by molding.

The tubing used for this purpose is often called

"potato-digg'er tubing." It is manufactured in

solid-wall type for rod diameters of •%(;, %, and V^ß

inch. The respective outside diameters of this

tubing are 11/32, i%2, i"ic^ -%2 inch.

Sponge-rubber tubing Avith %-incli niside diameter and with outside diameters of three-cparters and 1 inch are also used in some harvesters,

but this type is less readily available at present.

Applications of rubber coating to apron rods

by dipping and molding processes require special

manufacturing facilities.

Relation of Pitch to Rubber Covering

A wide-pitch apron with rubber covering can

be used for gentle handling of tubers without the

loss of soil-separating capacity that would result

from the application of rubber covering to a

standard-pitch apron. Sprockets of matched specifications are required.

"Undersweep" and "Boiling"

"Undersweep" is a term used to describe the soil

action of that part which is sifted tlirougli tlie

front of the liai'vester apron and dragged forward

by the lower side of the apron. (This soil is actually reoircuhited over the front of the apron.)

It is important to understand this action and to

take full advantage of it in the operation of both

digger and harvester. This action makes possible
8 AGRICULTURE HANDBOOK 171, U.S. DEPT. OF AGRICULTURE

;C'ÍÍR'í"i^^*f*i'

BN-84G0-X

FiGiTRE 9.—Severe soil Imilclnp on aprons, a.s shown here,

greatly reduces separating capacity when heavy soil is

very clamp. Aprons with wider pitch are suggested for

u.se in such conditions; they can he aprons whose pitch

has been increased signiflcautly by wear. There is need

for development of a good apron cleaner.

the gentle lifting of potatoes onto the priniafy

apron of an indirect harvester. It is also nsefnl

in the performance of diggers or direct harvesters.

The amount of undersweep varies with soil conditions, depth of operation, apron design (dimensional specification), accumulated wear (which

has increased the pitch), apron adjustment

(which determines the amount of sag behind the

front idler rollers), and the location of lower

apron-return idlers with respect to the front pair.

Either the height or the distance of span between

the front pair and the next pair of apron-return

idlers to the rear may atfect the amount of undersweep.

"When undersweep action is excessive to the extent of being troublesome, it is often referred to as

"boiling."' This ma}' be reduced by one or more

of the following measures:

1. Removing one or more apron-chain links to reduce

slackness of apnm.

2. Relocating one or two iiairs of apron-return idlers to

change their height, length of span, or length of contact where underside of the apron drags soil forward.

3. Changing the position of the front idler rollers ( cone

rollers or cylindrical face type) vertically witli respect

to the blade.

4. Changing the spacing between rear edge of the t)lade

and the front of the apron by fore-and-aft positioning

of front idler rollers (same rcillers as in suggestion 2

above lint in different direction ).

5. Changing the tilt of the l)lade in combination with suggestion 2 or without other change.

6. Increasing the depth of operation.

7. Inserting a bridge phite 10 to IS inches wide close under the apron and just l)ehind the cone rollers. (See

fig. 4.) This reduces the amount of soil that falls

through the front part of the apron.

Means for readily adjusting undersweep have

been used experimentally, but manufacturers have

not provided for such adjustment except by the

means just listed.

Thinning the Flow and Increasing the Scatter

Thinning the flow or increasing the scatter of

the potatoes and soil reduces bridging of the soil

and increases the capacity for sifting material

through the aprons. Witli pulled-type harvesters

that have independent power units, or potato-harvesting machines with variable-speed drives, the

depth of material carried on aprons and conveyor

belts can be reduced by increasing apron speeds

or by reducing travel speeds of the liarvesters.

Two advantages can be gained by these means.

On tilted conveyor belts or ajjrons where separation is accomplished by lateral rolling—that is,

crosswise to the direction of conveying—adequate

scatter is a jirerequisite to tlie most effective separation. This principle of increasing or decreasing scatter by changing relative speeds sliould be

utilized to full advantage to increase separation

under some conditions (wet, heavy soil; weedy

fields; heavy vine growth) and to facilitate gentleness of handling and reduce rollback mider intermediate and drier conditions.

"With some harvesters, it is optional either to use

a long, continuous primary apron, or to use acBN-8457-X

FIGURE 10.—A wide assortment of apron idler rollers and

agitator sprockets offers a choice of different magnitudes and frequencies of agitation. The small 2-incli

roller at the upper left requires a special mounting

bracket, as shown at the lower left. The 4-inch roller

at the lower right gives very soft, high-freiiuency a°-itation with approximately Vs-inch magnitude. " The

second roller from the left in the top row gives a fre-

()uency half that of a round idler roller. Others shown

give frequencies %, %, %, and l/io of plain-roller frequency. The agitator sprockets in the top row are

represented in mesh with 1.56-inch chain pitch and in

the second row with 1.63-inch pitch.
INCREASING POTATO-HARVESTER EFFICIENCY 9

BN-84G5-S

riGUEE 11.—In the two-row direct harvester shown here, tilted-apron separation is featured in both the rear cross

conveyor and the long donble-hine conveyor on tlie left where most of the hand sorting is done. The right (upper)

side of the conveyor on the left delivers tare material back onto the ground. Double lateral-roll fractionization,

of which this machine provides an example, is now featured in several makes of harvesters popular in the Red

River Valley.

cessories to convert this to the split-apron arrangement by dividinff the long apron into two.

In the latter alternative, the drop from the first

section to the second is a partial snbstitute for

agitation. This arrangement increases soil separation to meet wet conditions; but under dry

conditions, increased depth of operation (undesirably deep) may be required in order to supply

enoug'h soil padding to protect the potatoes

against the drop. The split-apron arrangement is

not recommended for inclirect operation because of

the extra drop, generally without adeciuate soil

padding on the apron.

Tilted-conveyor separation is probably the most

widely used method of separating stones and clods

larger than the smallest potatoes to be saved. (See

fig. 11.) The degree of tilt in most of these is

adjustable.

Belts and rubberized rod aprons are both used in

these units. Belts require from 8° to 12° of tilt.

Aprons require more tilt than do belts to produce

an equivalent rolling action. Their tilt may range

from 10° to nearly 30°. It is necessary to maintain scatter and avoid overloading these elements

in order for them to operate effectively. If rodtype conveyors are used, it is important to keep

them well rubberized. (See fig. 12.)

Eubber-roller table separators, which are most

highly developed in Idaho (fig. 12), have a very

high soil-separating capacity and are adapted to

certain conditions. Their successful use has been

limited to lighter soils and to soil conditions dry

enough so that soil buikUq) on the rollers is not

too troublesome. A full-capacitj^ flow of potatoes

over the rollers should be maintained to avoid

continuous rolling without forward movement of

individual potatoes, as this tends to increase

skinning.

Vine Elimination

Vine removers, often called deviners, differ

widely in design. Most of them can be classified

under four general types: (1) Double wringerroller with belts; (2) single-roller type, operating

against the underside of an apron at delivery end;

(3) wide-mesh apron (or strainer) type, some of

which have stripper rollers; (I) airblast type.

Each type has limited adaptation to si^ecific conditions. The two most widely used are types 1

and 3. (See figs. 11,13. and 14.)

Vine elimination by the use of an airblast is

featured in machines employed wliere vines are

likely to be completely dead and dry at harvesttime. The airblast type has become popular

enough for use on dry Annes to be considered a

standard feature on some harvesters built chiefly

for local distribution in Idaho.

Other types of mechanical vine removers that

are still in the experimental stage do not fall under

any of the classifications just mentioned.
10 AGRICULTURE HANDBOOK 17 1, U.S. DEFT. OF AGRICULTURE

EX-S454-X

FIGURE 12.—This two-row direct liarve.'iter, built in Idaho, is representative of those featuring multiple rubber-roller

separation. The resilient rubber rciUer.s, are usually about 3 inches in diameter and all turn in the .same direction.

They are most popular where harvest conditions are dry and soil buildup on rollers is not troublesome.

Eecommendations applicable to all vine removers, or deviners, are to keep protective shields and

safety devices in fiood condition, to avoid overloading, ito keep drives and tension springs correctly

adjusted, and to clean otf accmnulatious of vines

frequently.

Reducing Spill-Out Losses

It is essential to watch for spill-out losses that

are only partly visible. Losses of this type are

frecinent, variable, and ditlicult to measure accurately. Losses of 15 bushels per acre are not uncommon, and losses up to HO bushels per acre liaA-e

been observed in some soils when blades were not

scouring finely. Corrective measures include

the following:

1. Cleaninsraml reiiolishins the lilade.

1'. <!'ban.!iing to different Idade style (jr shape, or to a blade

nf smaller soil-contact area.

3. Substituting' open-center or two-piece blade for single

blade. ( See figs. •"> and G. )

4. Sharpening the blades if they fail to cut root material

satisfactorily.

.5. Increasing the operating depth of the blade.

6. Trying (jne of the blade substitute.s—a stationary round

rod (see flg. 7) : a rotary rod weeder (see flg. .S) : or a

r(]und-edged bar or a length of i4-inch pipe, slit on one

side and slipped over the cutting edge of a narrow-type

blade. In many instances, a positively driven, slowly

rotating rod has been the most satisfactory accessory

for handling old alfalfa roots or other material too

tough to be effectively cut by blailes. This accessory

lias been produced by three or more manufacturers of

potato harvesters. It is well suited for use in inuck or

peat soils.

No satisfactory method has been found for

keeping the aprons continually clean or for solving the problem of soil and root Ijuiklup which

increases the working diameter of aiiron rods

(See fig. 9.)

Reducing Clod Problems

Clod problems resulting from wheel packinoduring seedbed preparation, cultivation, chemical

application, or vine mutilation can best Ite reduced or minimized at their source. Surface

clods resulting from hilling can be substantial!v

reduced by the pressure of spool rollers ahead of

the blade. Soft pneumatic rollers located on har-
INCREASING POTATO-HARVESTER EFFICIENCY 11

BN-S458-X

riGURE 13.—This closeup view shows the double vine-remover belts in the machine illustrated in figure 11 and also the

rubberized cross conveyor. Note that the location of the aiiron-.sui)iiorting idler rollers is good. The single roller

at the upper side of the apron is not directly under the point of delivery of the potatoes from the vine-remover belts

to the apron. The delivery of potatoes onto the apron rods not directly supported by paired idler rollers tends to

reduce the severity of impact.

Tester aprons have been used with partial success

where clods were not too hard, but they have not

been satisfactory for severe clod conditions.

Clods from positions below the potatoes can be

minimized at harvesttime by using shortened

blades and operating as shallowly as feasible.

Clods from shoulders of ridges can be minimized

by more careful tractor driving during vine beating and by the use of harvester blades similar to

those shown in figure 6.

For clods lifted by the harvester aprons and

not readily reduced by agitation, there are three

principal methods of elimination on the harvester :

(1) lateral roll on tilted-belt or tihed-apron conveyors; (2) use of resilient rubber-roller tables;

(3) hand sorting (as a supplement to mechanical

separation). (See figs. 11 and 12.)

EfiFicient Hand Sorting

Efficiency in hand sorting can often be improved

by proper coaching and pract ice. It has been demonstrated that hand sorting of materials carried

on a conveyor in front of the workers is more

efficiently done when the workers toss the materials

to the opposite side of the conveyor with a rotary

arm movement than when they toss it behind

them with a swinging arm movement.

When clods are soft enough to crush readily by

hand, they can be eliminated more efficiently by

pressing them through a rod apron than by grasping the clods and tossing them elsewhere.

Transferring the Potatoes Into Hauling Equipment

Careless transfer into hauling containers can

cause considerable damage to the potatoes. However, little danntge will occur if the bulk loader is

continually adjusted so that the potatoes do not

fall more than -l to 6 inches.

Bulk handling from field to storage is adapted

for very high capacity and maxinnun economy

and requires no arduous labor. With power hydraulic controls on harvester bulk loaders, an alert

operator can deliver potatoes very gently into selfunloading hopper truck boxes with almost negligi-
12 AGRICULTURE HANDBOOK 171, U.S. DEPT. OF AGRICULTURE

BN-8462-X

FIGURE 14. The wide-mesh apron (or strainer) type of vine remover is shown in this machine. This illustrates an

idea that has been widely used since about 1948. It is best adapted for use on unmutilated vines (vines that have

not been partly destroyed' with mechanical shredders), especially where the potatoes are mature enough so that they

are not still clinging too tightly.

ble damage. The chief requirements are an alert

and conscientious harvester operator, who should

be reasonably experienced and skilled, and a similar qualified truckdriver. The truck should be

equipped with a low-gear transmission, and it

should be in good mechanical condition so that it

will be responsive to the operator and will facilitate coordination of travel speeds of truck and

harvester.

One manufacturer features a swingable bulk

loader that is intended to reduce the risk of accidental damage to the equipment caused by lack

of coordination of travel speed. Swingable bulk

loader booms may be featured in future models by

other manufacturers.

Crew Communication and Coordination

Commmiication between the harvester operator,

the tractor driver, and the driver of the truck being loaded should be by simple and easily understood signals. Hand signals seem to be effective

and practical. The harvester operator should be

within easy reach of all controls and should be in

position to observe and direct operations and

maneuvers.

It is good practice to begin by filling a truck

box about two-thirds of the way forward and to

rio-ht of center, to Avork fore and aft evenly, and

to complete the filling by working from the far

side to the near side.

Heavy log chains have been used between truck

and harvester to equalize the rate of travel and

thereby protect the harvester bulk loader against

damage from lack of travel coordination between

drivers. Tractor and truck drivers should be

alert for visible signals from the harvester operator. When the truck is nearly loaded, the tractor driver should be especially alert to truck stalling. Many operators select only one truckdriver

to drive each truck in turn while it is being

loaded. With this arrangement, it is necessary to

train only one truckdriver to respond to the operator's signals and coordinate the truck speed with

the harvester movement.

Safety of Workers

Workers' safety should be guarded by proper

maintenance of all protective devices, especially

guards over chains, sprockets, and power-drive

shafts. Alert, supervision and an alert crew contribute to individual safety and to the productivity of the team. A warning signal just before a

travel clutch or a machine clutch is engaged is

good practice. Goggles and respirators may be

needed for dusty conditions.
INCREASING POTATO-HARVESTER EFFICIENCY

SUMMARY OF PRACTICAL SUGGESTIONS

13

T-lie following suggestions, if carried out, will

result hi more proñtable, safe, and efficient operation of potato-harvesting machinery and methods

used under conditions set forth in this handbook.

1- Take all possible precautions before harvest

to minimize the problems of,oversize and immature potatoes as well as clods, weeds, and vine

elimination.

2. In very stony soil, effoi'ts to completely mechanize may be economically unsound except with

some stone clearing. Stone clearing may be feasible on much of the acreage, but on steep slopes

erosion may be serious enough so that it would be

better to put the land to other use than for potatoes or any other root crop.

3. Choose the harvesting method and equipment most suitable to your particular requirements.

4. Have all equipment available and ready to

operate in anticipation of requirements. Select

ecpiipment with adequate capacity to avoid bottlenecks during operation.

5. Select harvesting equipment, with enough

capacity to insure completion of harvest before

tuber temperatui-es fall below 40° F. If necessary

to operate at low temperatures, use loAver apron

speeds and more gentle handling in order to offset the increased vulnerability of the potatoes to

bruisino-.

6. Choose an alert, capable operator for the

harvester.

7. Ti-ain the crew to wor-k as a team and to aim

at fully coordinated operations.

8. Control depth of operation for minimum

damage to and maximum recovery of potatoes,

and for regulation of the quantity of soil to be

separated.

9. Regulate the travel speed to keep the quantity of soil lifted within the capacity of the aprons

for separation without using severe or tuber-damaging agitation.

10. Regulate the apron speed and agitation in

accordance with the natural soil padding or with

the rubber covering on the apron rods. Use of

low-magnitude agitation will give a wider practical range in apron speeds than is obtainable with

high-magnitude agitator sprockets. Try to solve

separation problems by thinning the flow of material rather than by increasing agitation.

11. Keep apron rods well rubberized where potatoes drop 6 inches or more.

12. Control tlie bulk loader for minimum drop

and gentle delivery of potatoes into the truck box.

13. Use as wide a pitch as possible in diggerwindrower and harvester aprons, consistent with

the varietal shape and size of the potatoes being

harvested.

U.S. GOVERNMENT PRINTING OFFICE: I9S9