AGRICULTURAL MACHINERY TESTINGby

J. T. KyleMember C.S.A.E.

Director, Saskatchewan Agricultural Machinery Administration, Regina, Sask.

This paper will deal only with thetechnical aspects of the testing offarm machinery, with an introductionto the complex problems associatedwith the scientific measurements ofvarious phenomena, as experiencedby the Testing Branch of the Saskatchewan Agricultural Machinery Administration.

The most difficult and vexing problem that the Agricultural MachineryAdministration is faced with in farmmachinery testing is the developmentof a suitable test technique for thelair and adequate evaluation of theperformance characteristics of a farmmachine. The testing of farm machinery on a scientific basis is a comparatively recent science and becauseof this, there exists very little in termsof "ready made" testing instruments.It is therefore necessary to design newinstruments of measurement or adaptinstrumentation designed primarilyfor the aircraft or automotive indus

tries.

It is rather distracting to note thatup until very recent years, the designing of farm machinery with the exception of tractors, has been carriedout by manufacturers on a very general basis. The primary objective ofdesign engineers has been to improvean acceptable product, while placinga comparatively small amount of emphasis on the investigation of new deigns.

The technique employed is comparatively straight forward, involving the performance comparison of anewly designed component with acomponent that has already provenacceptable in use by the purchaser.New designs are regarded as superioronly if they perform in the field in amanner superior to the componentthey are replacing.

Manufacturers in the past year ormore have come to depend more onthe specific measurement of the fieldloadings of various component partsand are basing their design calculations on this data.

Time is always pressing in the testing of farm machinery, and personnelare constantly faced with the problemof where to strike the balance between

prolonged and detailed testing tosecure adequacy and full informationon one hand, and on the other, perfunctory observation for the sake of aquick opinion.

It must also be noted that unlessthe test conditions can be defined insome repeatable way, it is difficult toassess the merits of a particular machine or to make comparisons betweenthe performance of any two machinestested on different dates or in different seasons. Because of this difficulty,it is necessary to introduce such devices in a technique as "comparison"or "Standard machines", or "Seriestesting." These two techniques developed originally by the National Institute of Agricultural Engineering inthe United Kingdom represent difficult problems in themselves. However, they can usually be relied uponto supplement the brief descriptions,photographs and whatever scientificmeasurements are feasible to presentan unbiased and factual report.

The comparison or standard machine technique involves the use ofsome particular machine that is fairlywell accepted on the market in thearea, as a "baseline" unit againstwhich one may compare the functional performance of the machine undertest, thus minimizing the problem ofvariation in conditions year afteryear.

The series testing of machines involves the concurrent testing of anumber of different makes of mach

ines of the same general type. Thistechnique represents more field problems since a number of machines are

being handled at one time as well asthe various allied equipment that isrequired. It is also more costly inasmuch as a good deal of the instrumentation must be duplicated on eachmachine.

These problems are compensatedhowever, by the ability of the observerto evaluate the performance characteristics of a number of machines un

der identical field conditions at thesame time and under the same field

loadings.

Although it is necessary to developa test technique for each type of ma

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chine that is to be tested, there are anumber of general factors that shouldbe included in all techniques whichmay be generally stated as follows:

(1) An assessment of the quality ofthe work done by the machine.

(2) An assessment of the quantity orrate of doing work which will usually involve some measurementof the machine's capacity inter-pretable by the user.

(3) A measurement of the power requirements in terms of horsepower, including that requiredto power the integral parts of themachine as well as the traction

drives if applicable. This very often includes a measurement of

the fuel consumption. Thisshould also include the P.T.O.

horsepower requirements.

(4) An assessment of or observationswith regard to, the labour requirements of a machine withsome measurement of the effort

required to operate the variouswork centres of more than one.

(5) An evaluation either measured orobserved, of the handling characteristics or ease of operation ofthe machine including the effortrequired to operate mechanismssuch as the clutch, brake and central levers. This usually includesan assessment of the normal time

required for service and adjustment.

(6) A recording of the structural history during the time the machinewas on test. This will includebreakage, distortion and fatiguefailures, and these will always beassociated with hours of use.

(7) An evaluation of the safety features of the machine includingthe protective devices for the machine itself as well as the operator. This will also include a determination of the center of gravityof each machine to determine itssafety on slopes of 20%.

In the interests of uniformity, thehours of use employed for A.M.A.tests on farm machinery involves anestimated one-half lifetime. This usecan be obtained very readily on tillage machines that can be worked from

early spring until late fall. However,it is impossible to obtain half-lifetimeuse of a harvesting machine in anyone individual fall due to the extreme

shortness of the harvesting season. Aproving track composed of steef obstacles is used to accelerate the hours

of use placed on any one individualmachine.

'̂I'lJI'iUMmttM^

Figure !. The proving track provides controlledconditions as well as an economical methodto accelerate the test work.

A concrete strip five hundred feetlong is used, on which is bolted obstacles with lifts of one and a half andthree inches. The obstacles may beclamped in place with various spac-ings and with various intervals, andvarious arrangements.

An accelerometer is used as a trans

ducer on the machine in the field andthe traces are recorded showing themagnitude and frequency of the acceleration to which the machine isnormally subjected. When the machine is placed on the track, an attemptis made to vary the forward speedand the tire pressure as well as thenumber of obstacles to simulate thefield gravitations. The frequency atwhich the various gravitation classifications occur, is increased on the proving track to accelerate the test approximately 3:1 while keeping theamplitudes the same as those occurring in the field.

During the time machines are operated on the track, as many of the component parts as possible are loadedwith simulated loadings determinedby actual strain gauge measurementsof the loadings during the time themachine was actually operating in thefield. A program of cycling of tablelift, reel lift, clutch, etc. is arranged.

Although it is possible to acceleratethe number of hours with a provingtrack in terms of fatigue loading, it isnot possible to accelerate wear of thevarious bearings, components partsand so on, on the same basis. It istherefore necessary to make up thedifference between the acceleratedhours and the normal hours by operating the machine on a stationarywear test in the laboratory. The machines are set up in the laboratory

and simulated field conditions againattempted by loading the various component parts with absorption units.The magnitude of the loadings are obtained by actual field measurementstaken in the field.

Although it is never possible to include in any one test all of the different conditions that a machine is like

ly to meet in field operation, a reasonable knowledge of the end user'srequirement, combined with previousfarm machinery testing experience,can be relied upon to suggest a realistic range of practical conditions under which the machine should be

tested to obtain a worth while esti

mate of its performance capabilities.

MmMmmFigure 2. The mobile laboratory is recording the

horsepower input to the cutting mechanism andihe vertical accelerations of tne frame.

When a machine is being tested, themanufacturer of the unit should beencouraged to participate in early discussions of the technique that will beemployed for evaluation, primarily tosee that the machine is not subjectedto conditions beyond that which itwas designed to operate in, and further, to develop a common trust between the Test Engineers and themanufacturer's staff.

A test technique usually calls forthe evaluation of a machine performing on a variety of soil conditions suchas textures, stones and topography ifit is a tillage machine, and operationin certain crop conditions such asyield, height and topography if it isa harvesting machine.

Figure 3. The direct writing instrument used bythe Machinery Testing Branch.

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Finalization of the technique isnecessary before a test should be undertaken, and the crop and soil conditions set out in the technique shouldthen he located and agreements madewith local farmer co-operators to operate the test machine on their particular crops or land during the testing procedure.

Engineering students, technicians,or agricultural engineers are with amachine throughout the time it isbeing operated in the field. Performance measurements are taken as prescribed in the agreed upon technique,as the machine is being operated inthe various sets of conditions throughout the operational area.

The evaluation of farm machineryis not an exact science. Many performance characteristics are not measur

able in any scientific manner. It isimportant, so that considered judgments can be made on performancecharacteristics with some degree otaccuracy.

Even when rather complicated instrumentation is used to measure and

obtain certain data on a machine, itis important that the results are in-terpretable by the end users of farmmachinery. Further, no data need beobserved and recorded which is not

of a material benefit to the farmer.

To carry out adequate farm machinery evaluation, certain instrumentation is necessary, as was indicatedearlier in this paper, a good deal ofthe instrumentation is not available

as such and requires adaptation fromthe automotoive and aircraft indus

tries. Figure (3) indicates some ofthe instrumentation used in farm ma

chinery evaluation.

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In order to have the support ofmanufacturers and users, and becauseit is a specialty requiring special staffand associated research and instru

mentation development, testingshould be carried out by a specificorganization and not dispersedthrough the universities. Yet performance testing cannot be divorced fromresearch and is, in fact, an essentialform of research.

This as the major and concludingpoint. Performance testing of existingdesigns and methods inevitably leadsto further applied or fundamental research concerning questions which arepushed out into the daylight by theresults or execution of a test. In some

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