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Special feature

April 2007 Classic Tractor 43

Designers of Challenger’s MT700Band MT800B Series put considerablethought into making sure theworkplace was as comfortable andproductive as possible.

Anyone who has spent time operating acontemporary agricultural tractor will knowthat the ergonomics of the machine have

become as important as the quality of its engine,transmission, or hydraulics.

This was not the case decades ago when keymechanical components were not particularlyreliable, and just getting the machine to do its jobfor the duration of the day was foremost in the mindof the operator.

With today’s high degree of engineeringsophistication and manufacturing quality,mechanical systems have become so reliable thatother factors now contribute to overall productquality and success in the marketplace.

As the design discipline focusing on matchingthe characteristics of equipment with thecharacteristics, requirements and limitations ofhuman users, ergonomics has played a major role inthe evolution of tractor technology during the pasthalf century. Also, the importance of this designspeciality to this industry continues to grow in leapsand bounds.

Modern tractors possess all of the requisiteelements that call for a high level of ergonomicdesign involvement. These machines must operate inharsh environments that subject the operator tovibration, noise, dust and extreme temperatures. Themyriad functions performed by tractors requirenumerous control inputs to drive the machine and

guide it through its paces, which can be surprisinglycomplex.

The ever-expanding capabilities of electronics,computers and displays require careful attention toevery detail of the operator interface to ensure thatthey are easy to operate and safe to use.

In many respects the ergonomic milestones ofthe past 50 years parallel developments in theaviation industry – albeit with a slight time lag.

Efforts to standardise the operation, functionand shape of aircraft controls, for example, were ofparamount importance in reducing pilot error in the1940s and 1950s. Some forward-thinking tractormanufacturers recognised the benefits of controlcoding and standardisation, and began to reflect this

CONTROLLINGINFLUENCEDo the controls of your tractor fall easily to hand, with the minimum of effort? If so, it’s not a coincidence – it’s because of good ergonomics. This is the design discipline of matching the characteristics of the machine to the operator. Steve Casey, a leading specialist from the United States, looks at how ergonomics have, over the past 50 years, become increasingly important in tractor design.

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ergonomic practice in their products in the 1950sand 60s.

A few decades later, the aviation communitywas developing multi-function displays to handlethe growing volume and complexity of informationprovided to pilots. These same technologies beganto work their way into tractors a decade or two afterfor similar reasons. And today tractor manufacturersare wrestling with the same issues associated withfly-by-wire control and significant levels ofautomation that the aviation industry faced 10 or 20years ago.

The American industrial designer HenryDreyfuss, through his work with John Deere, isrightly credited as the first to apply human factors,engineering and ergonomic principles to the designof tractors. Although his work with John Deerestarted in 1937 and focused largely on styling, by the1950s Dreyfuss and Deere were busy improving theoperator’s workspace through improved controllayout and design.

Inspired by British and American human factors,and engineering work applied to aircraft cockpitsduring and soon after the second world war,Dreyfuss and his associates developed, among otherthings, shape and colour-coded control handles and

standardised them across the John Deereagricultural product line. Like an aircraft pilot, atractor driver could identify a control by the way itfelt. It was no longer necessary to look at the controland its label to see what it was. Shape coding alsoaided operations at night.

The 1950s also witnessed rapid advances in thearea of tractor seating, and again, Dreyfuss and histeam were at the forefront of activity in this area.

Dreyfuss associates Alvin Tilley and WilliamPurcell, along with Dr Janet Travell, had a prototypetractor seat developed in 1955. Among its featureswere improved suspension, a broad seat pan with aslight ‘waterfall’ off the front for leg comfort, backand arm rests, and most notably, a full range ofvertical and horizontal adjustability from a singlecontrol handle.

Now operators of different proportions couldadjust the seat to accommodate their owndimensions, and there was no longer a need for toolsto do something as simple as moving the seat foreand aft.

By 1960 the yellow Deere & Co tractor seat wasin production and setting a new standard forfunctionality and comfort. Unlike the old cast orstamped metal tractor seats of the past, the new

Deere & Co seat, and others like it, were designed tomeet the needs of the range of users – not only themythical 50th percentile man.

Dr Richard Hornick, who was the human factorsresearch chief at the Bostrom Research Laboratoriesin Milwaukee, Wisconsin, in 1960, recalls how muchof his own work on tractor seating and vibration wasan extension of work originally conducted in theaviation field.

Vibration frequencies were most certainlydifferent for tractors and aircraft, but extendedexposure times, the vibration response of the humanbody, and accommodating the range of users withone seat were common to both settings.

Bostrom was particularly active in the area ofvibration isolation research and biodynamicamplification – a situation in which parts of the bodycan actually amplify a frequency.

It was work such as this that helped to definedesign requirements for the new generation oftractor seats. Numerous university researchprogrammes in North America and Europe, as wellas other seating and tractor manufacturers, alsoadvanced the science of seating for tractors duringthis period. The results were improved health, safetyand comfort for countless thousands of operators.

Credit for our third ergonomic milestone intractor technology must be given to Scandinaviaand, in particular, Valmet (now Valtra) for thedevelopment and serious promotion of cabs toprotect operators from roll-overs as well as theelements.

Although crude cabs could be found on tractorsused in special applications in the 1940s, and solidcab structures became somewhat common,especially in Europe, during the 1960s, it was theintroduction of the Valmet 900 in Finland in 1967that marked the significant shift from cab-lesstractors to tractors with cabs.

Engineers at Valmet’s Tourula facility decidedthat the tractor driver was just as entitled toprotection from the elements as a truck or lorry

driver, and the benefits for safety and protectionduring roll-overs were obvious. The result was theValmet 900 which, because it now had a cab, couldbe even friendlier to the operator with car-likecontrols, a heater and inside lights.

The growing prevalence of cabs in NorthernEurope was quickly reflected in reduced accidentrates, especially from roll-overs, and cabs weremandated by law, first in Scandinavia, then inEurope, and later in the United States. Literallythousands of lives have been saved worldwide dueto the presence of cabs on tractors.

Cabin ‘real estate’ – or lack of it – was the initial

driving force behind the development of multi-function displays in aircraft. A look inside the cockpitof most commercial airliners or military aircraft ofthe 1960s revealed a mind-boggling array ofseparate controls and displays. As the number ofsystems grew, so did the need for space within thecockpit for associated display information andcontrols.

The answer, of course, was the multi-functiondisplay, a single display screen that could be used forany number of functions. CRT and, later, flat paneltechnologies provided the means for displaying allmanner of graphics and text.

It took the development of low-cost, high-contrast flat panel displays before multi-functiondisplay technology worked its way into the tractorcab. In addition to basic questions of display layoutand legibility in high ambient light, ergonomistsconcerned themselves with developing interfacesthat were intuitive to use.

One clever approach for allowing the operatorto quickly move between a dozen main displayfunctions with a single motion was employed in theClaas Lexion combine of the late 1990s. Much likean old television channel control, the desiredfunction could be displayed by turning a rotaryselector control to the appropriate ‘channel’.

This metaphor was also used in the Challenger

rubber-tracked tractors and proved to be vastlysuperior to tedious step-by-step keyboard control ofthe interface.

Ergonomists continuously ask “How can wemake this as easy as possible for the user?” In sodoing they create challenges and, on occasion,headaches for engineers. In the end, though, aninterface that can be readily learned by the operatorand operated reliably will be more successful in the

Above: Research carried out by Bostrom Research Laboratories inMilwaukee in 1960 helped to shape thedesign of tractor seats for the next decade.

Above Left: Deere & Co’s yellow cushion‘posture seat’ went into production in 1960and immediately set a new standard forfunctionality and comfort.

Left: Positioning of the controls on the JD10 and 20 Series tractors was influenced bythe work of legendary American industrialdesigner, Henry Dreyfuss.

Above: Scandinavia – and Sweden inparticular – was pushing for roll-overprotection long before the implementationof safety cab legislation in 1970.

Above Right: Early weather cabs put a roofover the driver but that was about all. ThisFritzmeier look-a-like was offered by Pekoof Germany during the mid-1960s.

Right: Bird’s-eye view of the integral cabinfitted to the Valmet 900. Note the use ofpadding, car-like instrument panel andside-mounted gear levers.

Main Picture: Introduction of an integralsafety cab on the Valmet 900 in Finland in1967 marked a significant shift from cab-less tractors to tractors with cabs.

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marketplace.Traditional manual hand and foot controls link

the operator to the controlled elements of themachine via rods, cables, valves and levers. Withelectronics and computers, it is possible to de-couplethe control from the machine and place the controlalmost anywhere relative to the operator. This de-coupled control can move in ways that may not havebeen possible before and operate in almost anyfashion because its output is electric.

From the operator’s point of view, however, thecontrol must still provide necessary positional,kinesthetic, proprioceptive, visual and auditoryfeedback.

The fly-by-wire control must move in a logicaland easy-to-understand manner. The naturalfeedback provided by a traditional control mustoften be replaced or deliberately re-engineered,especially feedback like detents and spring loading.

Electronically-controlled powershift trans-missions were one of the earliest examples of fly-by-wire controls in agricultural tractors. The Ford 30Series and, later, Ford/New Holland Genesis 70Series tractors of the late 80s and early 90s were

among the first to have electronically-controlledpowershift transmissions with 16 forward and ninereverse speeds.

Recognising the importance of ergonomics andthe opportunities presented by a fly-by-wiretransmission control, Ford/New Holland obtainedergonomic design assistance for the system. Aftercareful analysis of numerous interface designalternatives, a logical fore/aft layout with asecondary bump feature for up-shifts and down-shifts was developed and put into production. Thissuccessful design carried on for over 15 years andwas typical of the shift pattern layouts developed forpowershift transmissions.

Our trip back in time ends, appropriately, withthe present, where we are now witnessing the latestround of ergonomic design activity in agriculturaltractor design. Once again, it is a matter of trying tomake the best use of the latest advances intechnology to aid the operator and make farmingmore efficient.

‘Automation’ is the key word nowadays. Withthe combined power of on-board computers, theCANbus, sensors, memory, reliable actuators, andGPS systems, all manner of automation has becomepossible. Systems such as Challenger’s OneTouchautomation aid allow an operator to ‘record’ and‘playback’ complex sequences of control inputs thatare often repeated. For example, the many changesin speed, transmission, implement position andimplement status that occur with each cycle at theheadland at the end of a field.

GPS sensing has provided all manner of datacollection possibilities, as well as square metre bysquare metre control over seed and fertiliserapplications.

Automatic steering systems – such as JohnDeere’s AutoTrac and Fendt’s Auto-Guide paralleltracking system – have become surprisingly popularand are proving not only to unburden the operatorbut bring about improvements in fuel usage and

materials by eliminating overlaps.From seating and cabs, from basic controls and

displays and, now, to fly-by-wire interfaces and taskautomation, each advance in tractor technology hasrequired a commensurate advance in ergonomicsand the science of designing for human use.

Each of our milestones represents an attempt tomake the latest technology not only productive forthe owner, but also make the common agriculturaltractor easier and safer to use. With regard to thefuture, perhaps the most important thought to takeaway from this tour through the ergonomicmilestones of tractor technology is that there willalways be a user interface regardless of thetechnology that is developed and applied.

‘Fly-by-wire’ control, computers, GPS andautomation will not result in the user being removedfrom the system, as is sometimes believed. As witheach of our six milestones of the past, themilestones of the future will simply see the role ofthe user change, perhaps from that of a real-timecontroller to that of a programmer, monitor andmaintainer.

Above: Features such as armrests ontractor seats were still in their infancywhen Bostrom launched its ‘Argus de luxe’seat in the mid-1970s.

Above Right: Ford’s 30 Series tractor range(8630, 8730 and 8830) was one of the firston the market with an electronically-controlled powershift transmission.

Right: Challenger’s Tractor ManagementCentre (TMC), top, is a good example of amodern control system. Operators canmonitor performance, perform repetitivetasks with the One-Touch managementsystem and also interface with GPS-basedsystems such as the optional Auto-Guide.

ABOUT THE AUTHORSteven Casey is president of Ergonomic SystemsDesign in Santa Barbara, California. For over 25years he has provided ergonomic designconsulting for numerous tractor manufacturers,including Ford, New Holland, Versatile, JohnDeere, Case-IH, Massey-Ferguson, Agco,Challenger and Valtra.