Testing and evaluation
of agricultural
machinery and equipment 110
Principles and practices
Trang 2Testing and evaluation AGRICULTURAL
of agricultural BULLETIN
machinery and equipment 110
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FOREWORD
Formal testing of agricutual machinery was instigated during the industrial revolution atthe turn of the century, but it was only with the wide adoption of engine powered equipment that testing began to make & ‘Serious and valuable contribution to manuficturers and users of agricultural machinery Testing, im which the ‘ogincring parameters of a machine ae determined, as, without doubt, received the greatest stenton, The ‘valuation of machines, in whch heir characteristics of handling and performance, their economic impact, 8 well a ther enginering paameter, are determined, came a a auc ltr stage in development, despite thề tater potential benefits provided to the user and manufacturer by these activites, There is no universal terminology which can beusd to distinguish the sctvities of súng and evaluation
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ACKNOWLEDGEMENTS,
“This Manual isthe fait of an enterprise that was initiatd in 1950 withthe prpartion and delivery of « practical course on farm machinery evaluation for scientists of the Mexican National Forestry and Agricul Research Insitute (INIFAP) Since 1990 the material has been developed further during similar practical workshops in Cuba, Honduras and Chile Financial help from the UK Government's Overseas Development ‘Adminisirtion and the British Council enabled these workshops to take place and is gratefully acknowledged
{A penultimate version ofthe Test Procedures presented inthe second pat ofthe Manual was prepared forthe Eleventh FAO Panel of Experts on Agricultural Eagineeing vhịch met in Rome in October 1992 At chat smocing it was recommended that the Procedures be edited und supplemented and that practical guidelines should be included, This commendation was adopted by FAO and resulted inthe preseat document
Many collegues hive reviewed drafts and have made valuable comments which have enhanced our Understanding of the project Among these we would like to single out for special hanks
Frank Inns; Ulrich Vihigs Derek Suton; Jim Elit-Jones; Steve Twomlow:; Graeme Rained: Adianus Rik: Terry Lester We owe «special debt to Sue Robinson who bated with manuscripts and typed many drafts of the fn text We also recognise the cheerful and consrictve efforts of Rosemary Bras; Maria Koaggs; Bob Wardell and Roger Cover of Slsoe Research Institute Graphics Deparineat who produced the illustrations
Despite the contributions fom al thse sho have collaborated the views contained inthe Manval ae those of the authors: likewise we are responsible forall omissions und ecrors
November 1993
Trang 6CONTENTS 2's Temgerture 3 Feel Consumption 23 Rate of appisation 3
Trang 743 Measurement of power 0 43.1 Rotary power „ 35:1 Engine m 4# — Aimalpedonmanee “ £6 Machine performance 4 446.1 Cultivators (vimary and secondary) a S611 General a 4612- DatmaamaMBBE ‘4621.3 Machine capacity and Gal efficieny a rm Sod Sal venion GUS Sushae evennass
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(62 — Partial Budgets mm 61 — Nu Beehi ValnsaniTuie ii BaaeS 64 Variability isk and sensitivity analysis =8 a7 S_——Eauiibrium point partial budget sĩ
ANNEX | INSTRUMENTATION AND EQUIPMENT: 269, SEX 2 CONVERSION FACTORS TO SI UNITS "
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SECTION A: PRINCIPLES AND PRACTICES 1 INTRODUCTION
Farm mechanisation i one component of agricultural enginering which canbe describe asthe application of Al aspects of engineering technology to rural wd agricultural development In many industrialised countries the fruits of research in agricultural cence have made poasiblefor agricultural production to exceed nations food requirements, and complementary advances in agricultural engineering (especially farm mechannation) have helped to make the eppliation ofthese frat achaical reali
‘The situation in too many developing counts is quite he reverse Million of impoverished farmers labour near subsistence lve and do not have accest tothe technical improvements which would allow thm to Jimprove land and labour productivity and raise net farm incomes,
a the last few decades considerable effort has been expended by many research groups both national and intemtional on the design and development of “improved” equipment for small und medium sized farms Unfortunately farmer adoption, ad therefore the impct on standards of living, hasbeen well below the level, hoped for The numerous “improved” plougs; tol carr; equipment powered by pals, steam, biogas, ‘wind, solar energy or animal: driers sbllrs and trehers; pumps and mich more at wll a “Wactorstion” projects, either with conveationl actors or specially desigoed sll farm model, have failed in many cases Im spite ofan impeccable programme oftechacal developmeat of the technology
‘A farm mochansation innovation wll nly be acept by farmers if it provides «solution thatthe farme i Actively soking, to» problem Kenly fl by the fare al Thic means that it ust be compatible with he farming system andthe needs ofthe farm fay taking technical, socal and economic factors int account ‘Wilt recognising this comple of factors, the sim ofthis manual sto focus on prosdres which have heen developed for testing and evaluating farm machinery, and on the criteria for testing small farmer onened technology
Improvement in the quality of equipment evaluation procedre in national or regional tating programmes will eof benefit to various groups These may include the following’
loại agricultural implement manufacturers
2 extensonist iru development projects decision makers in rural cet hanks tat extend credit linet to small sale producers * programmers and decision makers inthe agricultural and industrial sector
dition the fundamental ingredient of discipline i scene evaluation develops an apitule for observation and precise measurement, important aspects i taining agricultural engineers
‘TESTING AND EVALUATION
‘The term “testing ie unsly used in connection with an analysis of the behaviour of x mache compared with well defined suadards under ideal and epeauble conditions Vohason, 1985)
Trang 10‘Testing
‘Test procedures and standards for agricultural tractors have been established in several industrialised countries for many yeats, The evenval coincidence of North American (ASAE, 1980) and European (OECD, 1970) test procedures and the universal adoption ofthe International Standards Organisation code (GSO, 1983 wil mean inlermational standardisation and wil aoid the need to perform a tractor test n more thân one country
(ficial tractor tests are designed to prose reliable and repeatable informatio, they donot include tests ‘under agricultural condition as these would be impossible to reproduce precisely In consequence the olf tess only cover measurement of parametcts which are not affected by ground conditions, for example
= complete tractor specifications © engine power and fuel consumption
power and capacity of the hydraulic stem turning area and turning cree
smoke emission centre of gravity noe levels drawbar power
brake performance
resistance of protective structures (safety cabs),
In order to enable test results from differen tes sites tobe compared, drawbar power is measured on 4 special concrete track, The drawbar pulls achieved are, therefore, greatly in exces of those that eould be ‘apected under normal fed coodiiame
In addtion to tractor performance test procedures, several counties ave defined standards fora wide range of technical aspects of specifeations (materials, dimensions and geometry) for actors and agricultural implements (e4, Society of Automotive Engincersin the USA and British Standards inthe UK) Adherence torthese standards (eg drawhar height and thee poat linkage geomet) allows compatibiliy of common parts and attachments Again the move is towards world wide homogencity with the publication of ISO ‘Sandards for tractor and may agricultural machinery component spesifiations (ISO, 1983)
Evaluation
‘The purpose of obtaining information by testing sto compare a device or machine with the requirement which it as developed be lon and tests may not be as valuable to users as other methods of asessment Ac has been discusced, to full (Crossley and Kilgour, 1983, In the inert of comparability this im may tess performed under ideal conditions may be irrelevant to agricultural situations (eg dravbar pull of 2 tractor on concrete trac)
Although tractor testing has the potential of being vniform internationally, the dilering working eeairoements and level of sophistication of grcultural implements mean that standard te procedures are “cult to produce tan international level With few exceptions (eg fetlserdsibutors; potato pan rape harvesters - ISO, 1983) litle has heen achieved
‘National organisations (notably the British Nationa Insitute of Agricultural Engiacering - NIAE - before 1969, and the Canadian Paste Agricultural Machinery Insitute - PAMI, amongst many others) have produced test codes adapted to their local conditions The relatively sophisticated procedures ofthe industrialised counties usually require expensive equipment and instrumentation and are often inappropriate for developing country test centes
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In practice all asessment procedures for agricultural equipment include asction done under controlled and repeatable conditions (less); and a section of Geld gvalustions For the remainder of this paper the term “est procedure” i taken lo ned both ypes of assessment
Categories of Tests
“The type of test procedure selected as appropriate wil be influenced by- = the stage of development of the equipment to be tested = the potemtial henefciaries of the test report
8) The Stage of Development
‘Whether the tess required atthe design, prototype development or manufacturing stage will affect the ype of procedure that should be applied
A the design stage, even before engineering drawings have been made, i is very important t justify the proposed inoration ‘The procedure involves the Mentifation and quanifeation of the aced forthe Innovation ia echnical, social and economic terms Any native effets (eg on the labour demand or the need for new inputs oF processes) must be inluded inthe anal
The stage of prototype development wil include practical tests of the prototypes and their componcats, smcchanisms nd processes, under laboratory and field coniions The iit Verily whether the prototype functions as expedted, effectively, ecosomicallyandsafes Almost always this process results ia modiiations which must, intra, be tested
Testing and evaluation atthe manufacturing stage are aimed at measuring the quality ofthe product its <orahiity and elcincy They also permit comparsons between different models or makes of tke machine [AU this stage user experience surveys ca be insued which wll yield additional information ox reliability, ‘durability andthe epost common causes extension purposes of breakdown, This formation i generally very valuable or
Frequenlly in industrially developing counties, the quality of fabrication is ot always uniform between manufacturers, Series tet, in which several makes of « machine type are tested under similar conditions tenable the most appropriate machine to be selected from the alternatives available, Matthews (1%) Aeseribes the advantages of series test in India where they served asthe fist step in improving the "breed ‘ofa machine pe, Research areas were denied more easly and it was possible to draw othe attention ff manufacturers those snpocs of mediocre equipment which could be improved
»
‘An appropriate test procedure can only be selected ifthe ue ofthe information to be produced is well defined There i a range of possible ‘Test reports can help potential users of ä machine to compare the performance of alternatives and select the model most suited to their needs (Stevens, 182) Nevertheless, as Jason (1985) points out, in mest, ‘countries where this typeof information i asl it generates very litle intrest, The mos important Tuetr for potential atc the reputation of the manuladturer or đtibor
Information from tess canbe used to cones imports of tractors and implements with view to assuring gual ad service forthe ser, One of the frat examples was the Nebraska tractor tess (Barger sta, 1963) Since 1920 thas been state legal requirement To all tractors forsale in Nebraska to have been oficial tested and that replacement parts ae avaiable
‘The fundamental goal of OECD tests has ben to provide reliable information for governments and wsers in all the member countics to rodMe hamier to nternaiomal trade (Manby and Matthews, 1973) The Same authors mcaton a series of secondary sms and underline the importance of presenting th information inan ection om ene aes andiuclstownertnd the portance: ope in of tractors and implements,
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4
One of the motives frequently put forward by developing country goveraments to justly a ational testing programme isto protect the economy against a misuse of foreign exchange Its maintained that, by means ff atest programme, only machinery approptate tothe country’s conditions is made avalable to farmers ‘This strategy has often proved to be inpratical as machinery manufacturers change specifications inthe normal course of product developmcot and sot may aot be possible to supply machinery tothe speciation “as tested" Johnson, 1985) However, evaluation to asese 8 machine's suitability to local conditions is potentially beneficial both to the user and tothe national economy if modifications can be incorporated before widespread dissemination
Increasingly important are tests for safety and environmental impact Certain features of a machine which affect the user's comfort and health, or that may contribute to environmental degradation, ean be measured objectively (Matthews 197), Examples ar:- Poteetiveeab tests; operator vibration; nose; smoke and txie fumes (180, 1989 Confidential and impartial testing canbe of henefit to manufacturers for product development A test centre ‘may have the capital equipment and the expertise 1o carry out tests more cheaply than individual manufacturers
OPE OF THE MANUAL
‘The aim ofthis manuals to give a guide tothe sepecs of a machine's performance that ean be evaluated and the procedures given in Seton B give ths inforenation fora range of equipment
‘The am isnot to offer inflexible test procedures, quite the opposite Whilst the procedures include many ofthe characteristics which could be tested its comphassed thatthe user ofthe test information must only ‘cect for test those aspects of the procedure which are of particular fterest nd which wil ycld usable information,
In many situations, acces toa fll rage of testing facts isa varity and test personnel may no aways have the depth of experience required to interpret fly the procedures given Therefore the manual also ves guidelines (in Section A) on how to apply them in practice
In some eases (or example: engine speed and torque; sound pressure lewk implement drat forex) some instrumentation is necessary and in these cases the corret aplication of available equipment is deseibed together with sources to design adequate equipment with frequently salable resources without prejuicig the quality of the of supply In other cases where the priaciples are clearly understood it wil be possible information gathered Examples could he: "Patterators”for sprayer dtibuion assessment; engine fuel ‘consumplion messurcmen; stil properties assessment “Two topes not dealt wit in detail in Section B ate eegonomic and economic evaluation of farm equipment “The themes ate developed in Section A tothe extent that a general coverage of the principles involved is sven forthe respective appraisals twill be appreciated that each of the topics could merit a complete ‘manusl, the sim here isto emphasis the need for a complete appraisal of farm equipment from the tedhnieal, ergonomic and economic viewpoint and aot to foster the notion that a machine need only he technically efficent and effective to be asteptable to potential adopters
POTENTIAL USERS
Trang 132 MEASUREMENTS
‘An essential part of any procedure for the mechanical evaluation of an itm of farm equipment isthe ‘measurement of parameters which will dctermine the performance characteristics Th lve of accuracy of the measurements wil depend on the panicular procedure used andthe sophistication ofthe measuring egwipmen sealuble, For example, it is generally trve that the smaller the measurement (0 be made, the treater accuracy required of the measuring equipment (eg the length of a sed compared with the length ‘of Geld po),
To compare results of tests on similar models and types of machine itis useful to ave the data presented in consistent units The use of Sjtéme International (St) units has now been universally aecepted and has ben used throughout the test procedures in Section B, However, other unit are often used and where this the case, they have been incorporated into the te procedures Annex ites tales of conversion factors for Stuns,
Tn many eases, the desired parameters are expressed in basi units, however, fequeaty aber units devived from these The following paragraphs give details of the asie units used and those which are ‘derived ‘The more wseful multiples and sub-muliples of the units of measurement are formed by the following refines, Pasar ie Prefs Symbol 190 000 ¬ M 000 ito ` 10) hen, ụ 0 deca a a đế 4 m mi m" dã HBalc measurements 3Á Time
Short periods of time are measured in seconds (5) and are generally used with other functions such as evolutions, distance, volume and pulses, Calfrated mechanical stap-watches have the required accuracy for this fonction, however electronic quartz based timers are generally inexpensive, very accurate over log, petiods and canbe incoeporated ito other mulsfuntional measuring isruments,
For loger period of time such a when eaeyng out ld tests, durability rials and tials om farmers Fields, the times are measured in hours (h) If the tests are not under constant supervision, some wpe of hour recorder should be ured Electronic versions ate avalale for fing to power unite and tractors wally *anajng (rom the hattry charging crits,
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Figure 2 Vibvation type time recorder stacked to a manually operated sprayer 212 Mas
‘The basic uit of mass measurement isthe gram (g) whichis generally sed for test samples of gain, sed, er, etestera, The weighing of such samples usally takes plac i the laboratory where Yer) are hold (Fig 22) Spring type balances may be used for Feld work i lower levels of Sccuracy can be tolerated Where greater quantities of material or machines requite to be weighed, the ‘multiple unt ofthe gram the Klggram (kg i used whichis the SI unit Por weights of materials such as bulk quantities of seed, fetiser oF grain, spring type balances, eleeeonic strain gauged tendoa links oF Portable platform weighing machines may be used Large fixed weighing platforms will be required for lwactors and field machinery Portable electronic sain gauged wheel or anleweighers are avalale and are useful When testing machines or wails in the Fld
213 Dimensions
‘The metre (m) oF its multiples are the hase units used for dimensional measurements, Rules and eliprs fraduated in millimctes (a1) and centimetres (em) are sed for accurate measurement of machine details, ges of adjustment and materials (Fig 23) Field measurements of working width and depth of soi ‘engaging implements can be eatied out acurstly by using a specially made graduated rule (Fig 2), travel Gistances are marked by pegs and measured by suitable measuring tapes The Setting up of markers for ‘caveling speed measurement and for defining working plot arcas is also usually carried out using measuring
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Gracustes with sae ngu depth ese ‘Bae ine for recingdenth
tư
Figure 24 Graduated rule for measurement Source: RNAM, 1983 of furow width and depth
The marke (Fig 25) made of wood or light tube, is one metre between the tps and is swung around while walking allowing metre distances toe marked off quickly
1 metre
Figure 25 Pace marker for measuring plot size Source: Crosley and Kilgour, 1981 214 Revolutions
Trang 17245 Temperature
‘The measurement of temperatures may also require equipment to cover a wide range fom ambient at values to those ofthe exhaust gasses from itera combustion engines The Sl unt of temperature is the Kelvin (K), degree Celsius (0) is also recognised for use in conjunction with the SI and has the sume datum and vale as
the Kelvin Measuring equipment is usally graduated in degrees Celis
Mercuryinglans thermometers may be adequate for some ambient and fuel measurement, however, the ‘thermocouple typeof mearuring device hat a large temperature range and x commercially available and widely ‘wed The electrical device can be bul iat «hand-held unit (Fig 2.6) oF coupled to additional monstoiag recording equipment
Figure 2.6 Handheld electeicl thermometer 216 Bletrical
During tests of machines incorporating electrical equipment, it soften nscesty to measire the units eesti potential (vot), current (ampere) and esistance (ohm) ‘Standard commercial instruments are available with meters adequacy covering ranges and units suitable for iret current (DC) and alternating curent (AC) supplies Its recommended that measurements on electrical quipmeat should only he made hy experienced personnel
22 Derived Measurements 221 Are
“The square metre (m) isthe recommended unit of area and is usd for calculation of pot size, Measurement isby calibrated tapes or pace markers asin Section 2.1.3 Larger field areas are usualy quoted in hstaes (bt) qua to 10:0 suare metres Smuller multiples such asthe squresentinete (cm) are used for plot sampling seas sucha stra eoleton for combine tts or wed area for culation work, Sizes of small components ‘sch as pump pistons are expres in Square ailimetres(r
Trang 18222 Volume
ard ui of yume is he eaic mete (a) wih smaller mips ofebicceatimere (em!) and cubic millet (om?) However, the ize () with alu of 100 ex? bsg common ws or siedĐjng the volume of gus and granular material eg hopper capac)
‘ylindrs of known volume required for th field sampling of sis ean be manufactured from steel tubes of various sizes (Fig 27) When checking specifications, the volume of tanks and containers on machines such as sprayers, seeders and spreaders can be calculated from ternal dimensions or by filing with measured quanties During performance tess, dhe (tal output ofthe distribution of sprayer aozlee measured sing propictary made calibrated eyinders either sng) (Fig 28) or in a row asin the distribution measuring “Paternator” described ia Section 44 Larger volumes can be measured using previously calibrated buckets or tans, L °———>'` Volume of eyinder = =P x
Figure 27 Construction of stel einer for sil density determination
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Figure 2.8 Sprayer nozzle output measured with graduated cylinder 223 Fore
‘The newton (N) i the SI unit of force whichis defined atthe force Which, when applied l a ody of one ‘ilogram mas, gives tan acceleration of one metre per sevnd squared (kgm), The Kilogram force (kg) ithe force that when applied to body of mas of one kilogram give the standard acceleration đạc o gray (6.8067 ale) Therefore 1 kg = 9.8067 km? = 9.8067 NI can be seen, therefore, that tis possible to calculate forces fom results obtained by using the same equipment as that used for measuring mas (Section 312)
Spring type blancs may be used for measurement of force on hand ols ad ight implements drawn manually ‘ory annals However, under Fld conditions because of lack of damping, they may be dificult ead with secure,
Deaf forces of tractors and machines may be considerably greater an the capacity of these weighing units and Figure 2.9 shows an arrangement wing a system of levers which could he we
Hydraulic dynamometers using calibrated pressure gauge indicators (Fig 210 are avaiable to measure heey ‘rat Toads but these have generally hee superseded by electronic stain gaged teasion links (Fig 211) These ‘units, with thee indicators canbe purchased in various die to measure deft forces ofthe smallest manual Imachine to those af the ages tractor of fel machine The units are easily calibrated, portable and can be Iter powered for fel ut They can alo be connected to sable recording or analyzing equipment In ‘he cue of machines with ined dra poles sone rodietion may be necenary to sccm the menting device, Fig 212 gives tu examples,
Trang 21
Draw pole
Force transducer 4 Fred ring
Sliding ngs Irmplement it lever
Trang 22224 Pressure
Pressure measurements are reuited tobe made in tests of power units, tractors, prayers and wat
‘These cover a wide range and can be positive or negative pumps
Lower levels such as depressions in engine inlet manifolds and in water pump sueton pipes can be measured ‘sing simple water or mercury fled manometers In this ease, the pressure in the stem is aleulated using the diference in height ofthe liquid column,
Pressore and vam gauges are manufactured in various ranges and grated and scaled in units such as bars, hlograms force per square centimetre (kgf/em?),Pascals (Pa) oF Newtons per square metee (N/a), this latter unit being preferred bythe SI Eledronic sjnems using pressure sensors may be obtained together wid thei asocated display and recording equipment
225 Sped
‘The SI uit of speed of rotations radians per second (ea/s), this unit i used fo calelation of power trom machines suchas engines ad tractors Test meastrements are made in evaluations Qn radians) fora given lime, per minute (ev/min) or per second (re¥/),
“Mechanical revolution counters and totalisces will require time to be measured by stopwatch, Eletrical and slecronie units automaticaly cunt the mumber of revolutions aver a period of time and the ress are splayed and continually updated (Fig 213)
Figure 213 Range of mechanical and electronic revolution cousters
The unit of near sped isthe metre per second (m/s) However, the unit normally used when presenting the travelling speed of tractors and machines is the Kilometre per hour (km/b) which is derived by calculation,
Trang 23—n:.: #E— Hee cm Tae Figure 2.14 Field measurement of forward speed Source: RNAM, 198
\When drawbar tess and sip measurements are being made inthe fel he distance for atractor or machine to trae! fora numberof whe! revolutions femeasuted If the travel ime is leo recorded, the travel speed say be caleulated (Fig 215),
Figure 215 Fick! measurement of tractor whecllip during forward travel 226 Torque
Trang 24“6
Selected org values may be appli tothe driveshaft by variation of he intra loading In mos propitary ‘machines the length of the arm i designed to give constants of whole numbers inthe power calculations
‘Transmission dynamometer: that canbe fied into an enginelmachine or tractor power take-offimachine rive line (Fig 2-16) ae available to cover large range of torque and speed requirements These units are portable sod comprise an intemal strain gauged shaft or tube with suitable monitoring and read-out equipment, they an ‘be mains or batery operated
Figure 2.16 Torgue meter fit into the driveline between an engine and water pump 2.2.7 Work and Power
“The ST dt of energy and work is the jole (1) whichis defined a the work done when a free of one newton ste through a distance of one mre i the direction ofthe force, Th joule () is equivalent to ane neon ‘etre (Nm) The unit of power i the wat (W) which is equal to one joule per Second (is) or one newton ‘mete per second (Nas) The uit mest commonly used isthe EW which sequal to one kilo newton mete per second (KN)
For measurement of linear power, fora actor drawhar test for example, the following equation i ws Force (AN) x distance (a)
Trang 25„ For rotating mechanisms such as engines,
Power (W) = Torque (Nm) x Speed of rotation (rad/s)
If the speed of rotation is measured in revolutions per minute (R) and since there are 2x radians i one revolution then: Ni x Speed of rotation 2k Power (kW) = Torque ¬ For measurement of power of tractor hyraulic stems, the fllowing formula is use N 1 Power (kW) Flow x Presure (——} x —— về 100) However, a frmola in common we i
Power (kW) x Pressure (bar) —— oo
For water pups the equation is again modified to include the suction and pressure head (se section 467) and density ofthe liquid to give the pressure futon
"`
For machines driven by electric motors, power requirement may he established hy iting a torque measuring device in the drive line and measuring speed of rotation,
If this not possible, «good approximation ca be obtained by measuring the input voltage (V) and eurent (A) tothe motor and ealeulating the average power in watts (W)
For this the relationship powcr (W) = vollge (V) x curren (A) i used However, is possible to obtain ‘rious iypes of wat meters which when connected betwen the supply ad the motor wil give dret power dings (Figs 2.17 and 2.18) The diagram gives connections for ects upto approximately 5A, higher power rang re required, transformer is needed inthe current measuring crcit and should be wired fe accordance withthe meter manufactures instructions
1 should be understood that measuring the power inthe drive fine will give the exact requirement of the ‘machine The watt meter measures the electrical power input tothe motor ad the efiency ofthe motoe to transit that power tthe machine shouldbe taken ito secount, The motor efcioncy valves wll pend fon the level of loading and will range from approximately 70% to 90%
228 Rate of Work
This measurement is concerned wih the output of machines i Field evaluations, Rate of work is defined as atca worked in square metres (?) for Unit of ime, say on hor (b), ivng the equation:
sea (a
Rate of Work = time (8)
Trang 27339 Rate of Flow
Volume of flow is measured 10 establish he fuel consumption of peeol and desl engiaes, and the output of sprayers and pumps ‘The basic funtion for fow rat, volume per unit of time is used in each ease
Trang 28Start level Calibrated] scale =: Measuring system —-— Original system Mounting board £ ——+r OCF Tmesway | engine tank Nave LE———— Uo ae Tank valve v Figure 220, Construction of fuel measuring apparatus for petrol or diesel engines
Trang 30n
Propriotary meters ising direct read-out of lw rat are wed forests on hydraulic systems, Fig 2.23 shows how meters fied into the Naw line ofa eator hydraulic sytem In ease of tractors wth “sedi systems, the meter must be of pe to withstand the pressure of the boost pump supply ino which the ‘eturn ow is connected, Before iting est equipment to ths type of tritorBydraule cut, information fon testing methods shouldbe Sought from the Wactor manufacture Temperature gauge gauge Press Tee OA Pump: mẻ ẢNme ấu ——— ae lÌ } tggng — Trưng Fw meter fer
Figure 223 Arrangement for power test of tractor hydraulic system
Suitable Now meters may also be fed ito water pump outlets in preference to measuring the time to fil tanks of know volume A farther technique for measuring larger amounts ofigid lw ito we a°V notch ited into the Mow channel (Fig 2.24) Tis consists ofa plate wth a 90 'V" notch actos the line of flow through whch the liquid lows, There isa relationship between the height of the iui level above the lowest pat of the ate and the tp sce ofthe liquid Dow, "The expression fora rue 9 notch x
Rate of fw, Q = kx /3gx —— xÊS whore Q = rate of flow (o/s) f= aeccleration dục to ghi (28067 m/s)
HL = height of liquid lve en) = plate coufcent
Trang 31se 224 V-notch for rate of ow measurement 8 Am x TH Not - kx xg x 6 xBeHts 22.10 Fuel Consumption
When considering the fuel consumption of engines the ability of an engine to convert fel into useful work wll vary with engine type and design and wth speed and loading The measured fuel consumption should be seated to the power output and expressed as “specifi fuel ecasumplion” ia lies per Kilowatt hour ayewy, Fig 225 gives an example of cures of torque covering the operating speed range of an engine on to which have been added ins of constant power and specific fuel consumption, 1 can he seen that for the same power output, the specific fuel consumption, and hence the fuel consumption, decreases wth speed For example, at 75% of maximum power, the consumption wil all shout 7% when the speed is als reduced to 75% of rated speed At 50% power, fll a coasumption of shout 15% is achieved witha speed of 759% of rated speed
‘This ical example shows bow measurement of specific fuel consumption can be used to highlight areas ot higher fel efficiency in terms of power and speed It shows, generally, tat for tractor operation, iis ‘more economical to work nthe highest gear ratio posible, adjusting the tote to maintain the required load and forward speed,
2211 Rate of application
Trang 32120 — : rob 1o g sof 5 100 Š Š£ s0} ì Sự Dị ge mE a By 38 Sẽ s0Ƒ se sẽ Hy eS sol 3S 88 35 Sẽ 4oL 80 Be š sof a5 ỗ zo} ỗ = 10 0.582 1/kWh Fe ee ° 10 20 30 40 50 60 70 80 90 100 110 120 Engine speed / rated engine speed, %
Figure 225 Fuel economy measured over operating range of an engine Source: Crosley and Kilgour, 1983 22.12 Output
Trang 33% 3 CALIBRATION OF TEST EQUIPMENT
‘The reliability of data fom measurements made during tests and evaluations wil depend on the accuracy ofthe instruments used This supposes thatthe use of such equipment is understood by testing personnel and operated correctly with accurate data recording ‘The level of accuracy wil depend on the purpose of| the text greater accuracy i generally required for smaller quantities (og engine fuel consumption oF Aimensions of small components) Such accuracy i not required for larger quaniis, og Geld ize Tnsruments with high levels of acaracy wil generally be more expensive,
‘The range ofthe measuring equipment used shouldbe consistent with the range expected during the test (a expected drat ores of up t0'5 KN should be measured witha tense nk of § BN rated Toad), All proprietary measuring equipment wil be produced and supplied calibrated to known standaeds and Fits ‘of accuracy oer suitable meastring ranges, Instrument accuracy wil depend on such actors a: hysteresis ron-lincariy, repeatability, creep and temperature, Simple measuring devices such as rules apes, and fraduated eslndces and thermometers will not requice regular ealibation as changes dv to damage and ‘rear wil be obvious andthe units are relatively inexpensive to replace,
Much of the mechanically based test equipment has now been superseded by electric and electronic measuring devices which can be mains or battery operated and are suitable for laboratory or field ws Testing engineers without stable knowledge to wndertand al the basic processes of the new systems wl reed to have total reliance on the continued accuracy ofthe equipment, Because of this reliance on accuracy, all test measuring equipment should have periodic calibration checks especial if there are any ‘doubts about the results of measurements, Manufacturers may include standards fo cllration within the ‘ipment sch asa standard noise source fr sound level meters and means for measuring frequency of light for revolution counters
Many checks can be made within the testing organisation using “standard” equipment for comparison, uated einders maybe ued to check the volume oF ouput of fuel measuring devices andthe capacity ‘of various containers, pressure gauges, balances and timers ean be checked agaist further units ofthe same type However, these should only he used for spot” cheeks and instruments should be returned tothe
‘manufacturer of to suitably equipped standard test laboratory
Fig 3.1 shows a laboratory set-up for testing a pressure gauge where the pressure in the system is provided by known standard weights acting on avery accurately machined piston and elinder The reservoir and ‘mp ae ited to ensure thatthe stem i AI an thatthe piston is supported by the Higuid column when measurements are made
Strain gauge devies used on engines, teactoes and machines inthe Fld are particulary vulcrabe to damage ‘and adverse conditions and will require more frequent checks A well equipped laboratory may have a Specially designed machine for calbating compression of tension links However, standard weights of Sulcient quantity may be used as shown in Fig 32 for calbating a teason link used for drat free
‘A set-up for applying loads when clbrating sft attached tothe test stand anda torque am is atached to the other A weight tray and weights are a torque meters shown ia Fig 33 One end of the meter drive ded to the arm ata suitable distance which is accurately measured and defined For accuracy, the torque Sem shouldbe a light as posible and balanced hefore weighs are added
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4 [APPLICATION OF MEASUREMENT TECHNIQUES TO TESTING PROCEDURES an Selection of material fr tests
During evaluations, machines are asessed on their ability o meet certain design criteria Fediler lstribotors, seeders, planter, tresbers and harvesters are specially designed to proces particular types ‘of bulk material The material selected or the tests should e in accordance withthe design eter ofthe ‘machine and should be adequately checked and specified inthe test report This is particularly important
‘where varios tyes of machines are being compared for performance
Granular fertiliser should be specitid by name, type and shape The flow of material inthe hopper and the passage through the clements ofthe machine willbe affected by the size distribution of the granules and the e content The density of the material will be related tothe volume applied by the machine per
and hence the capacity of hoppers and feed mechanisms,
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“The metering and feed components of any seed dill or planter will be designed for seeds of particular shape, dimension and weight Bulk seed for tests should be sampled for measurement and the weight of 1000 grains (standard grain specification weight) established Damage to the sced when pasing through the machine {Sone ofthe important aspects tobe assessed The sample used for tests should not contain any damaged seeds so that any damage caused bythe machine can be measured Where a germination method is used to assese machine performance, the germination rate ofthe original sample wil ced to be established
‘Threshers and shellers ae asessed on their ability to separate grains from straw or cobs without damage Im addition to specifying the type and varity, moisture content, size and density ofthe original materi the average ratio of grain/straw and grain/eob should be established
The type and condition ofthe crop will considerably affect the performance of combine harvesters The rain output test should be made With cops in “average to good coniton which means thatthe majority ‘standing with a minimum amount of weeds and atthe desired moisture content, Where investigations ae ‘made under poor condition (id or weedy crops), these should be adequately specified,
2 Soll conditions
For tests on soil engaging implements and machines, there are parameters which can be established to Aeseibe soil conditions before and after work has been cariel out These parameters wil enable ‘sessment ofthe quality ofthe work andthe ably ofthe implement or machine to satisfy deste criteria 421 Soiltexure
Particle size analysis, leo referred toss mechanical analysis, determines the percentage of he three mineral feactions sand, stand clay in the soil and hence is textural lass The texture of s ơi it most permanent characterise and deel influences a number of other sail properties (see Table 4.1) suchas Staucure, soil water regime, permeability, inflation rte, eur rate erodibility, workability, root penetration and fet ee ad as such itis a asie parameter which should always be determined
Measurement of sil particle size distribution requires very accurate equipment and is normally undertaken ina suitably equipped sil laboratory The method i by sedimentation (Brsh Standard Institution, 1973) Figs shows percentages of clay (below 0.002 mm), sit (0.002 - 206 mm) and sand (0.06 - 2.0 mm) inthe Ina wil textural clases The subdivisions reflec he various combination of particles present
4211 Field Estimation
Trang 37” ‘Table LA Average Soil Physical Characteristics (ranges shown in parentheses) fr undisturbed sites nan Thư nnnn nh ‘oD mee om ‘ae footy aerty “me a) ARE awa usttsy any quần " io)
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deal, samples for tillage studies should be taken at intervals of 0.1 m oF less, throughout the culation layer eg srface (140.05 m), 05.0.1 m, 0150.25 m and possibly to 0.10 m below the layer of intended depth of elation, The minimum sample size taken at each depth 200g and should be replicated al ae tree times throughout the fest area toe a representative estimate of sil txture forthe area
‘A ball of about 2.5m diameter is formed of fine soil Water i slowly dripped onto the soil unt it proaches the sticky point ithe point at which the silos starts to sick fo the hand The extent to which {he moist soil can be shaped by hind is indicative of is texture
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¬ Iam, hgh hi can been in Ut oa, ih ring
‘When dry, loam or silt wil gve of fine powdery dus ifseratehed or Blown upon, but a clayey sil will not; alts exeemely powdery hecause of i very low clay content A loam when wet fel soapy and mote or Tess plastic, when rubbed etwecn the Finger wai dey t leaves dust om the skin ely docs ot
‘When ploughed of augured clay that has slighty moist condition displays a shining surface, loam does 422 Bulk Density
“The dry bulk density ofa soil gives an indication ofthe si’ strength and thus the resistance presented to Ullage implements or plan roots a they penetrate the si Soi bulk dent x defined asthe mass po wnt volume of di soi ints undisturbed state Fora sol ofa given article density (eypicaly 2.65 Mg m"), bulk density is deel related to total porosity, the space avalable i the sol for gas and water movement and ‘oot development, Less directly bulk density is also elated to si strength and permeability Soils witha high total pore space have alow bulk density and conversely low porosity leads to high bulk density Bulk densities in exces of 16 Mm can restrict root growth and result in very low levels of water movement ‘into and within the so Some typical values for diferent soil textures are given in Table 4.1
422.1 Field estimation of bulk density 42211 Core sampling
“This method consists of taking a core sample of soil using a coring ender of a known volume which is Acven into the sit and then carefully dug out (Fig 43) ‘The cyiner, which should be numbered for easy reference, is esally about 005 m long with « 005 m diameter If he sample doesnot completly fil the ‘liner (ee some scl may be los if x dry) the void should be measured as accurately as posible, to establish the actual dimensions ofthe sample One suggested method of establishing the actual dimensions ‘ofthe sample would be to fill the voids with fine dry sand, and then empty out the sand and measuring its ‘lume, “An alerts, approach f time allows and water content snot bing determined, sto thoroughly ‘wet the sampling ste porto the taking of the sample
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Figure 43 Sol core sampling for bulk density measurement
Each sample shouldbe taken othe laboratory in a sealed container, After weighing the samples are oven Arid at 108°C for 8 hours and then cooled in a desiccator before te-weighing
M (Oven dred bulk density (Dy) Tel Mi Mass ofthe dried sample
Re Radius (internal) of elinder
Length of elindrcal sample corrected for any less of sil a above 4222
Sampling strateyy for hulk density measurements
[Atleast four replicate determin increments from the soil surface t0 010m below the estimated depth of tillage work, Pos! <illge ions are normally made at each ste prior to any tillage work at 005 m ‘measurements require more precise determinations to characterise the degree of soi disturbance which will, ‘ary withthe implement sed For general clvation implements, such as plowghs and eliatos, i Fecommended that atleast tem replicate determinations he made pee ste at 008 m inrements from the oil, Surfaee to 0.10 determinations should he made at leat thee literal ponitions, 0, O10 and 0.20 m a right angles tothe m below the depth of tlle work Where tined implements are used for single passes pasta ofthe ine Figure tt shows how dy lke density vies with increasing distance from the passage fa tne
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Figure 44 Variation in dey bulk density with depth for thece positions (0 0.1 and 0.2 mộ at eight angles to the passage of eltivator tine 4223 Dey bulk density and porosity
The relationship between dry bulk density and porosity is
ry bulk: density
Porosity (Vp) = 100-( particle density (2.65) )x 100 433 Moisture Content
Within the soiater stem water occurs in thee phases, s a sold (le), a Tiqud and a vapour Under semi-arid conditions, is the liguid phase that sof paticular interest as it feflecs the physial properties ‘ofthe soi their natural state a affected by le, Soi holds water ia two ways as free moisture in Pores and spaces that occur between the solid particle; and a adhesive or swelling moisture, by adsorption fon the solid surface of clay and organic particles, Free water is of most interest in tillage studies a sil Strengih is diecly related to sil water content
4281 Measurement method