AGRICULTURE • HOME ECONOMICS • 4-H • DEVELOPMENT

C O O P E R A T I V E E X T E N S I O N S E R V I C EU N I V E R S I T Y O F K E N T U C K Y • C O L L E G E O F A G R I C U L T U R E

4CB-02PO

Petroleum Power Program Tractor ProjectUnit 2

Assuring Safe & EfficientTractor Operation

Welcome to the second unit in the 4-H tractor project series. This year mytwin sister Carla and our farm friends join me in guiding you through

this manual to help ensure safe tractor operation and maintenance.Unit one helped you get acquainted with the tractor. You studied the

history of the tractor; safety practices; basic information about tractor sys-tems; and minor maintenance and service. You also should have become fa-miliar with the operator’s manual, instrument panel and controls, and start-ing and stopping the tractor in preparing yourself to drive. The underlyingtheme was safety. The next step, in this unit, is operation, care and mainte-nance.

We challenge you to more in-depth study of tractor systems, fuels andlubricants, servicing the tractor, keeping operating cost records, and learningmore about tractor operation and maintenance, including universal handsignals for communicating with tractor drivers.

As always, “Learning-by-Doing” is the key to 4-H success. So rememberto complete the suggested activities and answer the quiz questions suppliedat the end of each lesson. Both will help round out your knowledge and skillsin tractor safety, operation and care.

Wishing You Good Luck!

Careful Carl & Carla and Friends

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AcknowledgementsThis educational material has been

prepared in consultation with the Na-tional 4-H Tractor Task Force comprisedof representatives of Extension Service,United States Department of Agricul-ture, the Cooperative Extension Serviceof the State Land-Grant Universities andNational 4-H Council.

Special thanks are extended toAmoco Foundation, Inc., donor for theNational 4-H Petroleum Power Awardsprogram, for financial assistance. Specialthanks are also extended to Deere &Company for use of the technical illustra-tions used throughout this publication.Illustrations shown are from the follow-ing Deere publications:

FMO Agricultural Machinery SafetyFMO Preventive MaintenanceFOS Electrical SystemsFOS EnginesFOS HydraulicsFOS Power Trains

This material is published by Na-tional 4-H Council, 7100 ConnecticutAvenue, Chevy Chase, Maryland, 20815.National 4-H Council is a not-for-profiteducational organization that utilizesprivate resources to help expand andstrengthen the 4-H program. 4-H is theyouth education program of the Coopera-tive Extension Service of the State Land-Grant Universities and the U.S. Depart-ment of Agriculture.

Programs and educational materialssupported by National 4-H Council areavailable to all persons regardless ofrace, color, sex, age, religion, nationalorigin or disability. Council is an equalopportunity employer.

©1986

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ContentsI. Safe Tractor Operation ................................................... 3

The Tractor, Safety and You ...................................... 3Thinking and Acting Safely ........................................ 3Begin With Safe Equipment ....................................... 3Safety Practices to Know and Use ............................. 3Universial Hand Signals ............................................ 5

II. Record Keeping ............................................................... 8Servicing Forms .......................................................... 8Recording Fuel, Oil and Repairs ................................ 9Operating Costs .......................................................... 9

III. Fuels and Lubricants .................................................... 10Fuels .......................................................................... 10Engine Oils ................................................................ 10Lubricants ................................................................. 11

IV. Fuel Systems ................................................................. 13Diesel Fuel System ................................................... 13Spark-Ignition Engines ............................................ 14Engine Air Supply and Cleaners (Filters) ............... 15

V. Lubricating the Tractor ................................................ 18Engine Lubrication ................................................... 18Oil Filters and Systems ............................................ 18Servicing the Lubrication System............................ 19Greasing the Tractor ................................................ 19Lubricating Other Systems ...................................... 20

VI. Electrical System .......................................................... 22The Battery ............................................................... 22Starting Circuit ......................................................... 23Charging Circuit ....................................................... 23Ignition Circuit ......................................................... 24

VII. Cooling System .............................................................. 27Water-Cooled Systems .............................................. 27Air-Cooled Systems ................................................... 29

VIII. Hydraulic System .......................................................... 31The Hydraulic Principle ........................................... 31Hydraulic System Maintenance ............................... 32

IX. Drive Train .................................................................... 34The Clutch ................................................................. 34Transmissions ........................................................... 35Differentials .............................................................. 36Final Drives............................................................... 36Maintenance .............................................................. 37

X. Glossary ......................................................................... 39

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SAFE TRACTOR OPERATIONtractor accidents. You can become a safe tractoroperator by forming two important safety habits:(1) Be sure the equipment you operate is safe, and(2) Keep a proper attitude — one that lets youthink safety and act safely so you can avoid haz-ardous or accidental situations.

Begin withSafe Equipment

Every time you get ready to start your tractormake sure it is mechanically safe to operate. Thatgoes for all other machines, too. You can give yourtractor a complete daily maintenance and safetycheck in less than five minutes. Use a method thatlets you start at one place on the tractor and movecompletely around it. Include the seat, steering,breaks, clutch, platform, wheels, tires, hitch andPTO in your check. You can add other items asnecessary.

Seats on tractors have several adjustments.Adjust the seat to your size and weight. You needto be able to reach and operate all controls from acomfortable sitting position. Check all the boltsand screws. If any are loose or missing makerepairs immediately.

Good brakes are important, too. Brakes wearwith use. For this reason they must be checkedregularly. Form the habit of stopping your tractorby slowing down the engine. Don’t jam on thebrakes to make a stop unless it is necessary toavoid an accident!

Safety Practicesto Know and Use

Safe handling and storing of fuels: If nothandled properly, petroleum products can causefires and explosions. The explosive force of onegallon of gasoline, vaporized and mixed with air, isequal to 87 pounds of dynamite.

Where underground storage is not feasible,safe fuel storage may be provided by a goodaboveground tank. Locate it as far as practicalfrom buildings. (Forty feet is considered a mini-mum.) A shutoff valve between the hose and thetank is a must. The valve should be one that willstop the flow of fuel in case of fire. Never refuel a tractor while it is running oreven while the engine is hot. It’s the fuel vaporwhich burns, and a hot manifold or spark could

The Tractor, Safety & YouYou have learned several reasons why it is

important to maintain a tractor properly. Goodtractor care results in longer tractor life, morepower and lower operating costs. If you learn howto do small but important maintenance jobs your-self, you will get better production from yourtractor while helping to reduce the need for majorrepairs and high maintenance costs.

While learning to care for your tractor, youshould also be learning safe operating procedures.‘Thinking’ safety and ‘acting’ safely around thefarm can help save lives.

Thinking andActing Safely

“I was in a hurry.” . . . “I got careless” . . .“I thought I could get out of the way in

time.”

How many times have you heard these excusesfrom persons who have had accidents? Why?Because we become hurried, careless, preoccupiedand try to do more in a given amount of time thancan be done safely. When we get behind in ourwork we take too many chances. That results inaccidents!

Did you know that the tractor is involved inmore accidents than any other farm machine? Onesource reports that when an accident occurs due tohuman error it is usually because someone failed toobey a safety precaution and made one or more ofthese mistakes:

1. Forgot an operating function—such as notsetting the brake or not placing the gearshiftinto “park” position before dismounting.

2. Took a shortcut—such as trying to operatetractor controls from the ground.

3. Took a safety risk—such as stepping over arotating power take-off (PTO) shaft or refuelingwhile smoking.

4. Ignored a warning—such as “Disengage powerand shut off engine before adjusting or lubricat-ing the machine.”

5. Failing to recognize a hazard.

As a member of the 4-H tractor program youshould make a commitment to helping reduce

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ignite it. If fuel spills, always let it evaporatebefore starting the engine.

Never allow smoking or an open flamenear fuel storage areas.

Fire Extinguishers. Do you have a fireextinguisher on your tractor? Do you have one inthe shed where the tractor is stored? You need tohave fire extinguishers in these areas and knowhow to use them. Use only extinguishers that areapproved for use on petroleum fires. Carbondioxide (CO2) and dry chemical extinguishers areapproved extinguishers. (See Fig. 1-1.)

Figure 1-1KEEP A FIRE EXTINGUISHER ONHAND IN THE TRACTOR SHED.MAKE SURE IT IS APPROVED FORUSE ON PETROLEUM FIRES.

Radiators. If the radiator has a pressurecooling system let it cool before removing theradiator cap. The water in this system quicklyturns to steam when the cap is removed and thepressure is suddenly released. When removing theradiator cap, first place several layers of cloth overthe cap as a precaution against being burned bythe steam. Then turn the cap slowly, letting out alittle steam at a time, and remove.

Exhaust gases contain carbon monoxide (CO),a deadly poison. It can kill! You can’t smell it orsee it so you have no way of knowing when adeadly amount is present. Always run an engineout of doors so the fumes can escape. If you mustrun an engine inside, keep the doors open for goodventilation.

Tractor OverturnsFive out of ten tractor-related deaths occur

when the machine rolls over on someone. There aremany ways a tractor can overturn. Let’s look atthree common causes.

A tractor can tip over sideways if a wheel dropsinto a hole or hits an obstruction. It can also tipover when making turns. The greater the speed themore likely the tractor will tip over. Slow down. Becareful to avoid obstructions or holes and becareful when making turns.

When working in hilly or sloping fields becautious of sideways or backward upset. Have therear wheels adjusted to a wide position when

working along a slope to help protect from asideways upset. Also, be very careful when drivingor pulling a load up a hill. The chance of a tractorupsetting backward increases when the front endis higher than the back end. Let the clutch out veryslowly when starting up a slope. Keep the hitchpoint at standard level, which is 13-21 inchesabove the ground depending on tractor size.Pulling a heavy load with the drawbar too high willcause a tractor to upset backward.

Tractors can even upset in level areas. Beespecially careful when working along deep ditchesor streams. Keep the tractor back from the edge fora distance at least equal to the depth of the ditch.

Tractor Run OversTwo out of every ten persons (20%) killed by

tractors are run over. About half are run over afterfalling from their tractors.

Some important rules to remember:1. The operator should be the only person on the

tractor any time it is in motion.2. Operate the tractor only when in the tractor

seat.3. Fasten your safety belt if your tractor is

equipped with a roll-over protection device, butdon’t use the belt if your tractor has no suchdevice.

4. Be sure you know where all helpers or bystand-ers are at all times. Make sure they are not inthe tractor’s path.

Following these rules will help protect you andothers from run-over situations.

Power Take-Off DevicesEven though the PTO shaft is almost always

well marked as a danger point, one out of tendeaths from tractor operation occur at the powertake-off. An unguarded shaft is dangerous at anyspeed. It can quickly catch loose clothing, twine,rope or chains you might be wearing or holding.Once caught, you are helpless against the power ofyour tractor.

Never operate a tractor unless the power take-off is covered with a shield (Fig. 1-2). One type ofshield covers the top and sides of the shaft. An-other is fastened to the PTO. It will rotate slowlywhen the PTO is in use but will stop if it istouched. You can’t always tell whether a PTO shaftis guarded by a loose shield while operating. To besafe, treat it as an unguarded shaft and stay awayfrom it.

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Figure 1-2SHIELDS MUST BE USED TO PROTECT PERSONSFROM ROTATING PTO SHAFTS.

The PTO stub should be protected when it is not inuse (Fig. 1-3). This can be done with a stub shield.Some tractors also have front PTO shafts. Theseshould be shielded for protection the same as arear PTO.

Figure 1-3A SHIELD AND GUARD SHOULD COVER THEPTO SHAFT STUB.

Universal Hand SignalsYou probably know what it’s like to try to talk

to your mom or dad when the water’s running orwhen household appliances are in use. It is difficultto hear for the noise. Well, the same principleapplies when the tractor is in use. When the noiselevel is high you can’t always hear what anotherperson is saying, so hand signals have been devel-oped to assist in giving directions while working inthe field.

There’s a universal set of hand signals that youand others should learn. These are helpful in noisysurroundings or when working at some distancefrom another person. Take time to learn them. Youcan start at home in front of the mirror. Graduateto in-person drills with a friend. Practice them inthe field at every opportunity. Figure 1-4 showshow Careful Carl and Carla practice in front of themirror.

Learn by Doing1. Check to make sure all protective devices (PTO

shields, canopies, seat belts, etc.) are availableand in working order on a tractor. You shouldalso check over implements, such as powerlawnmowers and garden tractors, to determinewhether required protective shields and guardsare in place.

Find recent statistics on tractor-relateddeaths and accidents in your state or the UnitedStates. (National Safety Council publications inthe library or local Extension agents are goodsources.) What are some preventive measuresthat could have avoided certain accidents?

2. Do some research. Give a report on a tractor-related accident. Point out ways the accidentcould have been avoided.

3. Learn and practice the set of universal handsignals used to communicate with the tractoroperator. Team up with a partner and taketurns calling out conditions requiring the signalsso you can learn to use them comfortably whenneeded.

4. Liquid fuel cannot burn. It must be vaporizedand mixed with air. You can demonstrate thiswith a candle.

Light the candle and watch it burn for afew seconds. Notice how the paraffin first meltsfrom a solid to a liquid and then is vaporized bythe heat from the flame. When the candle issnuffed, the vapors that continue for a fewseconds can be relighted some distance from thewick.

5. Sometimes it’s difficult to know what to do in anemergency. In many instances, people tend tofreeze and do nothing at all or make the wrongmove. Here’s an easy way to demonstrate thisfact. Hold one end of a broomstick and askanother 4-H’er to grip the other end tightly withone hand and pull. Tell him to let go when hefeels you jerk on the broom. After a second ortwo give a quick jerk on the handle. Chancesare, your friend only tightened his hold andcould not let go. A person’s natural reaction is totighten his grip and hold on. This is why somany people get caught in machinery or running

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equipment. The machine suddenly unclogs itselfand the operator can’t let go, so the hand goesinto the machine, or they wait too late to let go

and their clothing gets caught, pulling them intothe machine.

Figure 1-4THESE UNIVERSAL HAND SIGNALS ARE FOR COMMUNICATING UNDER NOISY CONDITIONS ANDIN OTHER SPECIAL CASES.

Start the Engine: Move arm in acircle at belt level.

Come to me: (Can also be come tome because I need assistance). Liftyour arm vertically over your headwith the back of your hand to therear and turn your arm in largehorizontal circles

Move Toward Me or Follow Me:Look toward person or vehicleyou need to move. Hold one handin front of you with the back of the handtoward the vehicle and move your arm.

Raise Equipment: Point upwith one finger and at the sametime, move your hand in a circleat head level.

Increase Speed: Lift your handto shoulder.

Stop the engine: Move yourright arm across your neck fromleft to right.

Move out: Face in the neededdirection of movement. Put yourarm straight out behind you.Then, swing your arm over yourhead and forward until your armis straight out in front of youwith the back of your hand up.

This far to go: Put your hands infront of your face with the back ofyour hands outward. Move yourhands in or out as an indicationhow far to go.

Lower equipment: Point to theground with one finger and at thesame time move yourhand in a circle.

Decrease speed: Put your arm outhorizontally with the back of your handup and then move your arm down about45 degrees minimum many times. Keepyour arm straight and do notmove your arm above yourshoulder.

Stop: Raise your arm fully up withthe back of your hand to the rear.Keep this position until the signalis understood.

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Checking up on Safe Tractor Operation1. What three conditions cause the most deaths attributed to tractor operations? State at least one

measure for preventing each unsafe condition.

A. Condition: ______________________________________________________________________________

Preventive Measure: ____________________________________________________________________

B. Conditions: _____________________________________________________________________________

Preventive Measure: ____________________________________________________________________

C. Conditions: _____________________________________________________________________________

Preventive Measure: ____________________________________________________________________

2. If the operator is cautious, a tractor may be started slowly while standing onthe ground, as long as there are no implements attached. T F

3. All tractors should be equipped with seat belts and the operator should use themwhen in the tractor seat. T F

4. As a general rule, the tractor’s PTO shaft does not become dangerous until ithas developed at least one-half its rated power. T F

5. (A) Carbon dioxide (B) Carbon monoxide in exhaust gases can kill you.

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RECORD KEEPINGIt is extremely important that you service a

tractor regularly and according to the operator’smanual. Keeping records is a way of verifyingservices performed.

Records help guard against forgetting toperform services on time and they provide informa-tion to help you figure operating costs. Records donot have to be complicated. You simply write downthe services performed when they are done and thecost of the supplies used.

The sample record forms in this unit aresimplified but complete. They provide a record ofoperation and services performed and a record offuel, oil and repair expenses. You can use these orany others which allow you to keep similar infor-mation. Facts you always want to note include: thedate, number of hours operated, services per-formed, and any other notes or observations youwish to make.

Your operator’s manual is an important guideto record keeping. Refer to the maintenance andservice schedule. If you study the instructionscarefully and keep those records faithfully, you’llbe well repaid by savings in repairs, time andlonger tractor life.

Servicing FormsThe first form (Fig. 2-1) contains a list of

tractor services and the normal periods for doingthese. Note that the services are grouped by howfrequently they must be done. Below the listing ofthe services, spaces are provided for checking offthe hours the tractor is used. Each square repre-sents one hour of operation and there are 10 blocksor hours in each vertical line. The date should beinserted for the first hour of use.

Moving down the first column of blocks, enter acheck mark for each hour of operation. On the nextday of operation, begin a new series of blocks byentering the date in the next square.

Whenever a group of services is performed,that day insert the code letter for that group. If youlook at the sample form here, you see that thetractor was used five hours each day on October 31and November 1. The “A” services (10 hours) wereperformed. The next day, November 2, the tractorwas used nine hours and, for the sake of conve-nience, it was serviced before being taken out forthe next day’s work.

From the chart you can see that for conve-nience the 50-hour check-up and servicing were

given at 49 hours. At this time all the serviceslisted for the 50-hour or “B” periods were com-pleted, as well as those for the 10-hour “A” service.The same applies to the other service periods. Eachtime you do the “C” services you do the “A” and “B”services, and so on.

Figure 2-1A SERVICING RECORD FORM AND SAMPLEENTRIES FOR A TRACTOR.

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Preparing the Service ListWhen preparing a list of services for your

tractor, refer to your operator’s manual and selectthe jobs that should be done at stated intervals.The most common intervals are daily (or usuallyevery 10 hours) and at 50, 100, 200, 500, 750 and1,000 hours. If no definite time is listed for aservice, ask you local dealer. Some services are seton a seasonal basis. These should be listed to fitthe hours of annual operation.

List the services for your tractor at the top ofthe blank form as shown in Fig. 2-1. These servicesare examples and may not apply to your particulartractor. However, this form can be easily adaptedto apply to any tractor.

Also, don’t let normal service intervals take theplace of common judgment. Intervals are calcu-lated for average operating conditions. Underdusty conditions, check and service the air filtersmore frequently. Change the engine oil for cold orwarm weather operation when the weatherchanges.

Recording Fuel,Oil and Repairs

A record that shows the amount of fuel and oilused for each job is of great benefit in determiningthe cost of tractor operations. It also is of value indetermining charges for custom work, that is,renting out your tractor to do work for someoneelse. The record form in Fig. 2-2 is designed toprovide such information.

Figure 2-2A USEFUL FORM FOR RECORDING EXPENSESAND REPAIRS FOR A TRACTOR.

Operating CostsYou can use the Record of Fuel, Oil and Re-

pairs to determine simple operating costs for yourtractor. Operating costs consist of fuel, oil, tires,batteries and repair expenses. If you were to keepaccurate records of these expenses for one year,you would know the annual operating costs foryour tractor.

In this unit you should keep records for at leastone month. On the basis of the expenses for thisperiod you can estimate the annual costs. Thelonger you keep complete records the more accu-rate will be the estimate of annual costs.

Operating costs are only part of the expenses ofowning and operating a tractor. Operating costsalso can include monies paid to the operator. Thereare “fixed” costs, too. These include depreciation,insurance, taxes, housing and interest on money.You will learn more about these costs and how theyare determined in the next 4-H tractor manual.

Learn by Doing1. Modify a set of records for an actual farm

situation and keep 3-6 months of records.2. Compute the cost of materials (filters, oil, etc.)

for the machine used in number 1 above.3. Visit an implement dealer and compare the

service costs with the cost to replace damagedparts.

4. Determine the cost per hour for operating atractor. Add costs of fuel, oil, grease, etc anddivide by hours used.

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FUELS AND LUBRICANTSforces which the pistons, valves and bearings arenot designed to absorb. If knocking continues, itcan seriously damage internal engine parts.

Gasohol is a mixture of 90 percent unleadedgasoline and 10 percent ethanol (grain alcohol). Itis available in some areas as a substitute forgasoline. Ethanol contains less energy per gallonthan gasoline. An engine will develop more powerfrom ethanol only if it is designed and tuned for ahigher octane fuel.

LP-Gas is available for use in farm tractors.However, it is not very popular because it requiresspecial equipment to transfer it into the tractorfuel tank. It is a clean burning fuel and LP enginesrequire fewer repairs than gasoline or dieselengines.

Engine OilsMany engine oils are available to the con-

sumer. It may seem difficult to choose the correctone for your tractor. But if you know the standardsystem of classification you can be sure you arealways using the proper oil.

After motor oils are refined, they are givenmany tests so that manufacturers know they aremaking a uniform product.

Viscosity Classifications: The viscosity testis one of the most important ones for the user.Viscosity tells how well the oil flows at differenttemperatures. You have probably heard peoplespeak of a “light” or “heavy” oil. They are referringto viscosity.

Figure 3-1MULTI-VISCOSITY OILS REPLACE SEVERALSINGLE-VISCOSITY OILS.

Oils with additives to provide good low tem-perature properties and prevent too rapid thinningwhen heated are classed as multigrade oils (Fig. 3-1).Such oils are listed as 5W-20, 10W-30, 10W-40 or20W-40. These are well suited to start-and-stop

A tractor won’t run without fuel, oil and otherlubricants. And it won’t operate properly andefficiently unless the correct products are used.Let’s look at how these products are classified andwhen to use them.

When you use the correct fuel in a properlymaintained engine, you can help ensure that yourtractor will produce all the power for which it wasdesigned. Greases and oils enable the tractor tooperate efficiently, and they help prolong enginelife by cutting down on wear.

It is important for you to know which fuels andlubricants are well suited for certain operatingconditions. Review your operator’s manual forspecifics.

FuelsDiesel. Reliable suppliers provide diesel fuel

formulated for high-speed diesel engines, such asthose in tractors, other farm machinery andindustrial engines.

Your operator’s manual specifies that anyrecommended diesel fuel have a minimum “cetane”number. This is a measure of the fuel’s ability toself-ignite. The higher the cetane number, thebetter the fuel self-ignites when heated. Rememberthat the diesel engine has no spark plug. The fuelmust self-ignite from heat of compression immedi-ately after it is injected into the cylinder.

Most modern diesel engines for tractors andother heavy equipment are designed to operate onfuels with cetane numbers between 40 and 60.Even a good diesel fuel still may not self-igniterapidly in cold weather. Ether, with a cetanenumber of perhaps up to 95, is sometimes used toassist in cold weather starting. However, do notuse ether for starting diesel engines unless it isrecommended by your tractor manufacturer.

Gasoline is available in many mixtures:“regular,” “unleaded,” “premium,” and “superpremium.” Your operator’s manual will tell youwhich grade to use in your tractor.

The major differences (except for adding lead)between the gasoline grades mentioned depend onthe octane number of the fuel. The octane ratingmeasures the ability of the fuel to prevent “knock-ing.” Lower octane fuels will knock in high com-pression engines because they are not formulatedto be compressed so much. Knocking occurs whenfuel ignites unevenly in the combustion cylinder.Instead of burning evenly, the fuel mixture, ineffect, explodes. This causes excessive and uneven

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operation. They are especially useful for seasons inwhich extremes of warm and cold temperaturesoccur.

The SAE grade of oil to use in your tractordepends on crankcase temperature and enginedesign. An oil with a low SAE number is a thinneroil and an SAE 40 is a thicker oil.

Service Classifications: Engine oils also areclassified according to the suitability of service.These classifications, which tell the “quality” of theoil, have been developed by the American Petro-leum Institute (API).

Current API classifications have either theprefix “S” for service station engine services or “C”for commercial and fleet engine applications. It’seasy to remember that S categories are mainly forspark-ignition engines while C categories are fordiesel engines.

A second letter denotes the sequence of perfor-mance tests a motor oil has passed. The simplestservice categories are SA and CA. Motor oilsmeeting specifications for these categories offerlittle more than basic lubricating properties. Suchmotor oils would offer little protection in today’smodern, high-performance engines. As perfor-mance requirements become more complex, motoroils are improved to meet or surpass engine protec-tion needs (Fig. 3-2).

Figure 3-2NEWER MOTOR OILS ON THE MARKETUSUALLY MEET OR EXCEED MORE THAN ONEAPI SERVICE CLASSIFICATION.

Each time a new series of tests is developed,the second letter is changed in the API classifica-tion. Thus, motor oils passing the SF and CD testsequences are the “best” oils available, in terms of

protection they offer the engine (Table 3- 1).Always use a grade carrying the same or higherAPI classification of oil specified for your tractor.For example, CD quality oil may be used to replaceCC quality.

Table 3-1API Service Designations for Engine Oils

SAE Letter API IdentificationDesignation of Engine Service

SA Utility Gasoline and DieselEngine Service

SB Minimum-Duty Gasoline EngineService

SC 1964-67 Gasoline Engine War-ranty Service

SD 1968-71 Gasoline Engine War-ranty Service

SE 1972 Gasoline Engine WarrantyService

SF 1980 Gasoline Engine WarrantyService for many AutomotiveApplications

CA Light-Duty Diesel Engine ServiceCB Moderate-Duty Diesel Engine

ServiceCC Moderate-Duty Diesel and Gaso-

line Engine ServiceCD Severe-Duty Diesel Engine

Service

LubricantsGear lubricants are classified in the same

way as engine oils — by viscosity and serviceclassification. While they resemble the thickerengine oils, they perform different jobs in thetransmission, differential, final drive units orpower take-off.

Gear oils range from the simple, for use inolder systems, to hydraulic-type lubricants for usein newer machines. These newer gear systemsusually have smaller, stronger gears able to with-stand tremendous loads that produce high pres-sures and friction between the moving parts.

Grease is a solid or semi-solid lubricant,usually a lubricating oil with a thickener andsometimes other additives. The thickener is often atype of soap.

Different greases were needed to lubricatevarious parts of the tractor years ago. The newermulti-purpose greases usually are suitable foralmost any tractor application.

Synthetic Lubricants. Ordinary lubricantsare produced by refining mineral (petroleum) oilsto the desired quality and adding any other com-pounds to meet specific performance requirements.

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In recent years, many manufacturers have intro-duced “synthetic” lubricating products. These fluidlubricants and greases are made by building up orsynthesizing a product (usually petroleum product)for a specific purpose.

Manufacturers claim that the greatest advan-tage of synthetics is their longer service life. Asynthetic oil, for example, may perform effectivelyfor four times as long as a mineral-based oil. Thesenewer oils also remain viscous at much lowertemperatures than a mineral oil of the same SAEnumber.

Synthetic products carry the same SAE andAPI classifications as mineral-based products.Check with your tractor dealer to be sure syntheticproducts can be used on your tractor. This isespecially important when systems are under amanufacturer’s warranty.

Learn by Doing1. Visit your local service station, farm supply

outlet or tractor dealer. Make a list of the

various lubricants available. Compare your listwith the lubricants recommended in your tractoroperator’s manual. How many of those availablemay be substituted to meet the tractor’s require-ments? Which ones are unsuitable and why?

2. Obtain some automobile or tractor engine partsthat have been replaced because they are badlyworn. Try to determine whether poor lubricationwas a major contributor to their failure. Youmight want to obtain an estimate on the cost ofreplacing the parts, if you can. Make a display soothers can see how important proper lubricationis.

3. Tape record an engine “pinging” and use it in apresentation at your club meeting.

4. Take a sample of oil and divide it into threesamples. Place one in a deep freezer, warm onein an oven, and leave one at room temperature.Punch a hole in a can. One at a time, comparethe time necessary for an ounce of each to dripthrough the hole in the can.

Checking up on Fuels and Lubricants1. Why is ether sometimes recommended for helping start a diesel tractor in very cold weather?

___________________________________________________________________________________________________________________________________________________________________________________________________

2. Match the lubricants in the left column with the characteristics in the right column which bestdescribe their viscosities.

SAE 10-40 engine oil Does not flow at normal temperatures.SAE 120 gear oil Flows well over a wide range of temperatures.SAE 50 engine oil Not viscous enough for cold weather engine operation.No. 5 lubricant Similar to slow-flowing engine oil.

3. You have just purchased a new diesel tractor. Your operator’s manual would specify an enginehaving at least the ________ service designation.(A) CA (B) SF (C ) CD (D) SD

4. An engine oil carrying the SA specification willlast longer than one having the CD specification. T F

5. So-called synthetic lubricants last longer in an enginebecause they contain special nonpetroleum chemicals. T F

6. “Regular,” “unleaded,” and “premium” are terms used to distinguish between types ofA) ethanol, B) gasoline, C) natural gas?

7. Always use a grade of oil carrying A) higher/same, B) lower/same API classification, as specified inyour operator’s manual?

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FUEL SYSTEMSYou will remember from your earlier tractor

studies that gasoline, LP-Gas and diesel enginesget their names from the fuels they use and allhave different fuel systems. But there are basicsimilarities. A tank stores the fuel, one or morepumps transfer the fuel, and the injectors (dieselengines) or carburetors (spark-ignition engines)atomize the fuel so it burns easily. Fuel systemsalso include lines and filters to transport and cleanthe fuel, and serve as a means of providing largequantities of clean air for mixing with the fuel.(See Fig. 4-1.)

Figure 4-1BASIC FUEL SYSTEM.

Diesel Fuel SystemsInjection Pump. Most diesel engines on farm

tractors have two fuel pumps. A fuel transfer pumpforces fuel under low pressure from the tank to theinjection pump. The injection pump puts the fuelunder high pressure (from 1,900 to 5,000 poundsper square inch) and distributes it to each injector.The transfer pump delivers fuel to the injectionpump.

Many makes of diesel tractors use a distributorinjection pump (see Fig. 4-2). It features an engine-driven driveshaft which imparts rotary motion topump components. The fuel transfer pump at oneend of the shaft supplies fuel under low pressurethrough the rotor. Fuel is pumped to the injectionnozzles by two pistons or plungers working towardeach other.

A diesel engine does not have a choke to assistwith cold starts. Some diesel tractors have a meansfor injecting a starting fluid during cold weather.Starting fluids often are ether, which volatilizes toa gas and ignites easily. These fluids are highlyexplosive and only work at temperatures down to0°F. At temperatures below O°F an electric supple-mental heater mounted in the cooling system isneeded.

Figure 4-2MAIN COMPONENTS OF A DIESEL FUEL SYSTEM (DISTRIBUTOR TYPE SHOWN).

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Do not use ether unless recommended by yourtractor manufacturer. If recommended, follow theinstructions carefully. Consult your operator’smanual.

When the plunger mechanism increases thefuel pressure to the injector, the additional pres-sure overcomes the spring force and the valveopens. Fuel is injected into the combustion cham-ber until the fuel pressure inside the nozzle be-comes lower than the spring’s.

The governor operates the injection pumpcontrol valves and varies the amount of fuelsupplied to the engine. This control helps maintaina constant engine speed once the speed is set bythe operator. In most diesel fuel systems thegovernor is part of the fuel injection pump and isnot serviceable.

MaintenanceWater and dirt are the enemies of any fuel

system — especially the diesel system. Fuel sys-tems on tractors have one or two places to removewater and two or three places to remove dirt orother solids. Check your operator’s manual so youwill know where and how often to service these.

You have already learned how to store fuelcorrectly to help keep out water and dirt. Never-theless, water can still condense in the fuel tank, ifthe tank is not kept full during cool weather. Mosttanks, therefore, have a drain valve underneath soany water (and dirt) can be removed. The fueltransfer pump normally has a second water trapand a strainer filter to stop any larger pieces of dirt.

Most diesels have two more filters between thetransfer pump and the injector pump. They areoften called the primary and secondary fuel filtersand are usually canister-type.

Your operator’s manual has details for servic-ing the transfer pump filter and any additionalfilters in the fuel lines. Be sure to tighten themsecurely during reassembly to prevent air, waterand dirt from entering the system later.

Bleeding theDiesel System

The diesel fuel system cannot operate with airin the fuel lines. Air can get into lines in severalways: (1) if the tractor runs out of fuel duringoperation; (2) when fuel filters are changed; (3)when any part of the system is repaired. Any airinside the lines must be removed by “bleeding.”

Bleeding procedures vary for each dieselengine (Fig. 4-3). Your operator’s manual showsthe steps necessary for your tractor. To bleed thefuel system, work from the fuel tank toward the

engine. Generally, you must first ensure that thefuel tank contains clean fuel. Then open one ormore bleeding screws or ports (often located on ornear the filters) until no air bubbles show in theescaping fuel.

Figure 4-3ONE TYPE OF ARRANGEMENT FOR BLEEDINGA DIESEL FUEL SYSTEM ON A TRACTOR.

Spark-Ignition EnginesIn spark-ignition systems, both fuel and air are

metered and supplied together to the combustionchambers (see Fig. 4-4). The carburetor is theprecision part of the spark-ignition fuel systemwhich mixes the fuel and air and supplies thecorrect amount for combustion.

If too little fuel is supplied, it’s called a “lean”mixture. A lean mixture burns slowly and does notgive full power. The exhaust gas temperature of alean mixture due to slow burning is so hot that itcan cause valve trouble. On the other hand, if toomuch fuel is allowed to enter the engine a “rich”mixture results. This wastes fuel and causesdeposits on the spark plugs and other engine partsbecause of incomplete combustion.

The carburetor works like an insect spray gun.As you pump a spray gun, air passes over a littletube that leads up from the insecticide can. Thespeed of the air over the tube creates a vacuum andliquid comes up from the can. The force of the airthen breaks the liquid into a fine mist, atomizing it.

In the engine, the piston intake stroke creates avacuum in the cylinder. Air rushes in. The incomingair goes through the air cleaner and through thecarburetor to the combustion chamber of the engine.

If the carburetor is properly adjusted, youshould not need to change the settings. If you thinkthe engine is not operating correctly, check thetroubleshooting section of your operator’s manual.Many problems blamed on the carburetor actuallyare caused in the ignition system or are the fault ofa poor supply of fuel or air.

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Figure 4-4ARRANGEMENT OF COMPONENTS IN A GASOLINE FUEL SYSTEM — SPARK-IGNITION ENGINE.

You may be able to adjust the idling speed, theidling mixture and the load mixture by carefullyfollowing the steps outlined in the operator’smanual. But remember, if you are not experiencedin working on carburetors, have an experiencedperson help you, or have a trained person make theadjustments.

The governor (see Fig. 4-5) on a spark-igni-tion engine acts in much the same way as the oneon a diesel. The governor is used to regulate enginespeed and rotation.

The engine turns weights on the governor. Asthe weights rotate they tend to fly outward. Be-cause the weights are connected to the throttlevalve of the carburetor, the throttle closes as theweights move outward. Tension on the governorspring controls the distance the weights can move.If the spring is tight, the engine must run faster tothrow the weights out the same distance. Increasingthe spring tension, by advancing the throttle lever,thus makes the engine run faster. By balancing thepull of the weights against the spring, the engine iskept running at whatever speed it is set to run.

Engine Air Supply andCleaners (Filters)

Just as engines must have clean fuel, so mustall of the air used in combustion be cleaned care-fully. Several types of filters can be used to cleanthe air for tractor engines. Maintaining the filtersso they do their jobs correctly is an important task.Once again, an adult or dealer-mechanic would beyour best bet the first time you tackle this task.

Most older tractors use an oil bath cleaner(see Fig. 4-6). It has a screen that is automaticallywashed with oil. The air coming down through the

air intake stack passes over the surface of the oilheld in the small cap. Some of the oil is carried up

Figure 4-5GOVERNOR SPRING & LINKAGES.

Figure 4-6OPERATION OF AN ENGINE OIL BATH AIRCLEANER.

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into the separating screen; then it drains back intothe cup. This process keeps the separating screenoiled and washes the dirt back into the cup. Thefine dust not trapped when the air passes over thesurface of the oil will be caught by the oil film inthe separating screen. The cleaned air flows oninto the engine.

Most late model tractors have dry-type aircleaners which use a paper element in place of anoil bath for removing the dust. The element ismade of special paper and must be replaced peri-odically so that air flow to the engine is not re-stricted. A restricted air intake causes power lossand increased fuel consumption. On a dieselengine, a restricted air cleaner will cause smokingand loss of power. A severe restriction will alsocause a gasoline engine to smoke.

One dry-type air cleaner has an automatic dustunloader and pre-cleaner to continually removelarger dust particles (see Fig. 4-7). Another type isbuilt like an oil bath cleaner. It collects the dust ina cup which must be emptied as the dust builds toa given level.

The aspirated air cleaner is a newer type ofdevice used as a pre-cleaner. The pre-cleanerconsists of a swirl chamber that is connected to themuffler or on the exhaust pipe. Suction pulls thedirt from air in the swirl chamber and out throughthe exhaust pipe.

Figure 4-7TWO METHODS OF REMOVING DUST WITH PRE-CLEANERS AND DRY-ELEMENT AIR CLEANERS.

Servicing Air CleanersTo check an oil bath cleaner, remove the oil

cup and look at the oil. If it is very dirty, clean andrefill it. Be sure to use the oil specified in yourmanual and to fill the cup to the correct level.While you have the cup off the air cleaner, examinethe wire mesh or separating screen. Make sure thebottom of that screen is not covered with trash orchaff. Clear the air passage from the pre-cleanerinto the oil cup periodically. Oil bath air cleanersshould be checked daily, or more often, whenoperating under dusty conditions.

Be sure all hoses and connections in the intakesystem are in good condition and tight. Leakinghoses and clamps let in enough dirt to ruin anengine.

Knowing when to service a dry air cleaner isimportant. Underservicing can cause engine wearand loss of power. Overservicing can let dirt enterthe engine each time the filter is removed. It alsocan damage the elements. Most tractors have anindicator to show when the filter should be ser-viced. The indicator may be located on the intakesystem or it may be a light located on the instru-ment panel. Check your operator’s manual for howand when to inspect and service the dry element.

Some paper elements are cleaned by gentlytapping the filter element with the heel of yourhand. Then apply low pressure compressed air tothe element, using a filter cleaning adaptor on theair hose. In other cases, it may be best to wash theelement in special detergent. Then let the elementdry thoroughly before installing.

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Learn by Doing1. Describe the steps required to bleed air from a

diesel fuel system. If a tractor is available, askan adult familiar with the procedure to help youbleed the system.

2. Fuel a tractor. Review operator’s manual thenactually fuel a diesel and a gasoline engine. Howare they similar? Different?

3. How do you know when it is time to service theair cleaner system on a tractor? Perform thismaintenance procedure. Ask an adult to bepresent in case you have a problem.

4. Clear the fuel storage area. Bury or burn oldrags and other dangerous items that can cause afire.

All tractor fuels burn readily. Clean up allspilled fuel immediately after refueling.

Checking up on Fuel Systems1. How do dirt and water affect the parts of a diesel fuel system? ___________________________________

_______________________________________________________________________________________________________________________________________________________________________________________________________

2. What is one possible cause of smoking from a diesel and a gasoline engine?How can the condition be corrected?_____________________________________________________________________________________________________________________________________________________________________________________________

3. The injector on a diesel engine is comparable to the carburetor on a gasoline engine;both provide the proper air/fuel mixture to the engine. T F

4. A high-speed stream of air flowing through the carburetor is used to pick up andvaporize fuel in a spark-ignition engine. T F

5. Oil bath cleaners on tractors use lubricating oil from the engine to help filter the air. T F

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LUBRICATING THE TRACTORRegular lubricating with proper lubricants is

necessary for long life and trouble-free operation ofyour tractor. Your operator’s manual will showsome type of lubrication guide for your tractormodel. The manual will also specify the properlubricants to use and how to check and apply them.

Engine LubricationModern engines use an oil pump to circulate

the oil. The most common pump has a small set ofgears which picks up the oil from the oil panreservoir and puts it under pressure. A screen onthe suction side of the pump removes large par-ticles that might otherwise damage the pump.Much more oil is pumped than is needed and thesurplus flows through a bypass valve or pressureregulating valve back to the crankcase.

An oil pressure gauge or light on the instrumentpanel indicates whether the pump is putting the oilunder pressure in the line. In fact, some of the linescould be plugged and you would not know the differ-ence by looking at the gauge. It would merely showpressure. This is one reason why it is so importantto service the engine oil and filters on time.

Some engines have small pipes and holes in thecrankshaft which lead to all bearings. Such anarrangement is called a full-force feed system (seeFig. 5- 1). With this system, if the bearings becomeloosened or worn, the oil pressure may drop.Lowered pressure is most likely to be noticed if theengine is operated at slow speed. Loose bearingswill let more oil escape and this oil will be thrownup on the pistons. Such a condition is a commoncause of high oil consumption.

Figure 5-1A FULL-FORCE FEED LUBRICATION SYSTEMFOR A TRACTOR ENGINE.

Another oiling system popular in older, smallertractor engines is the circulating splash system (seeFig. 5-2). Oil is pumped to a dip trough or squirtedthrough holes in an oil line to the rod bearings.

Figure 5-2A CIRCULATING SPLASH LUBRICATINGSYSTEM.

Oil Filters & SystemsThe most common type of filtering system

found on modern tractors is the full-flow oil filter.This filter receives all of the oil as it leaves the oilpump and filters out contaminants before the oilreaches the bearings. Oil and filters must bechanged regularly at the intervals specified in theoperator’s manual to avoid clogging the filter.Many oil filtering systems contain a filter bypasswhich allows oil to flow past a clogged filter andstill lubricate engine parts. However, if the oil isdirty enough to clog the filter, it is too dirty toeffectively lubricate engine parts.

Filters usually are changed with each oilchange. Always use the type specified for yourengine. Some filters are mounted inside a canisterand secured with bolts. Spin-on type filters also arecommon. To mount a spin-on filter, put a thin filmof clean engine oil around the rubber gasket on thefilter face and turn the filter onto the mountinguntil you feel the gasket just making contact.Tighten the filter by hand an additional amountspecified in your instructions (usually one-half tothree-quarters of a turn). Do not over-tighten byusing a filter wrench; this could damage the gasketand its seal.

After changing the oil and replacing the filter,always run the engine a short time. Check forleaks around the crankcase drain or the filter.

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Servicing theLubrication System

It’s not difficult to service the lubricationsystem. The important thing is to service it ontime, according to your operator’s manual.

The oil level is always checked daily. This is donewith the “dipstick” (see Fig. 5-3). If checked at the endof the day, be sure all the oil has drained back intothe crankcase after the engine has been shut off.When adding or changing engine oil, always use thetype specified for your engine and the local operat-ing conditions. You should change the engine oilimmediately following a daily operation, while theoil is still warm and impurities are in suspension.

Figure 5-3THE DIPSTICK IS USED TO CHECK THE ENGINEOIL LEVEL DAILY.

Greasing the TractorYour tractor has several points equipped with

grease fittings which must be serviced regularly (seeFig. 5-4). The most common locations are around thefront and rear axles. Follow the detailed diagramsand instructions in your operator’s manual.

Always be sure to wipe off the fitting beforeattaching a grease gun. Hold the gun as much in linewith the fitting as possible so a good seal is made.Remove the gun by moving it through a slight arc.Be careful not to apply too much pressure or greaseto any bearings having seals; you might break theseal. This will allow grease to escape and waterand dirt to get in the bearing. A few strokes with a

large hand gun are usually enough. Finally, greaseat the end of the working day. Fittings are stillwarm and take the grease better.

Be especially careful in handling greases.Always keep the grease indoors so dirt and watercan’t get in.

When greasing ball or roller bearings (such asfront wheel bearings) by hand, remember that it isthe grease within the bearing that will actuallylubricate it. A typical wheel bearing assembly isshown in Figure 5-5.

Figure 5-5BEARINGS ON A SPINDLE WHEEL ASSEMBLY.

Before packing the bearing, clean it carefullyby washing it in solvent, then allow it to dry. Thendip the bearing in oil and allow it to drain for ashort time. A film of oil in the bearing makes iteasier to get the grease into it. The oil soon mixeswith the grease.

Follow these steps to pack a ball or rollerbearing. First, place about one-half cup of clean,fresh grease in the palm of your hand. Hold thebearing by one side and “bite” it into the grease toforce the grease upward through the bearing

Figure 5-4THE OPERATOR’S MANUAL SHOWS WHEREALL GREASE FITTINGS ARE LOCATED AND TIMEINTERVALS FOR LUBRICATION.

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retainer and inner cup (see Fig. 5-6). Rotate thebearing and continue to take bites of grease untilyou have worked all the way around the bearing.The new grease should be squeezed up through thebearing and out the top between the rollers.

Figure 5-6WHEEL BEARINGS MUST BE CAREFULLYPACKED WITH GREASE.

Lubricating OtherSystems

The transmission, the final drives and thehydraulic system are some other systems requiring

regular lubrication. These will be discussed inLessons 8 and 9 in this manual. Meanwhile, don’tforget to check and service these systems asindicated in your operator’s manual.

Learn by Doing1. Review the manufacturer’s instructions for

checking and changing the engine oil in yourfarm or garden tractor. If you are not sure of theprocedures, ask a knowledgeable adult to helpyou. When you have mastered the procedures,ask if you can be responsible for regularlychanging the oil.

2. Take an inventory of the lubricants required forany machinery around your farm or home.Estimate the quantities needed for a givenperiod (monthly, etc.). Purchase lubricantsahead of time so that they are available whenneeded.

3. Greasing the tractor is an excellent activity for a4-H member. Follow the operator’s manual andwrite down the date and engine hours for futurereference.

4. Drain a sample of engine or transmission oil andpass a magnet through the sample. Inspect formetal filings. Send a sample into a testinglaboratory and review the results with theowner and with a mechanic.

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Checking up on Lubrication1. The engine oil level of the tractor should be checked

(A) every 15 operating hours (C) whenever the oil pressure warning light comes on(B) daily (D) under any of the above conditions

2. A new oil filter should be tightened to the manufacturer’s recommendations by using(A) a torque wrench (B) a special filter wrench (C) your hands

3. The oil pressure warning light or gauge on the tractor indicates whether(A) the oil level is adequate (C) oil pump pressure is adequate(B) oil pressure is adequate throughout the system (D) all of the above

4. When a hand-operated gun is used to lubricate grease fittings,(A) a few strokes usually provide enough grease(B) grease until you can see the old grease pushed out around the sealed area(C) grease until you feel a definite resistance within the fitting

5. Describe briefly when, during the operational day, the following procedures should be done for bestresults.(A) lubricating grease fittings _________________________________________________________________(B) changing an oil filter ______________________________________________________________________(C) changing engine oil _______________________________________________________________________(D) checking oil level after oil pressure light has been on during operation ________________________

_____________________________________________________________________________________________

6. List any other systems which require lubrication on your tractor _____________________________________________________________________________________________________________________________

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ELECTRICAL SYSTEMThe electrical system makes it possible for the

engine to start. This system consists of threeimportant circuits — the starting circuit, theignition circuit and the charging circuit. Thestarting circuit converts electrical energy from thebattery into mechanical energy needed to crankthe engine. The ignition circuit creates the sparkwhich ignites the fuel-air mixture to power gaso-line or LP-Gas engines. The charging circuitrecharges the battery and generates currentduring operation. How do all these things happen?Yes, through electrical circuits.

A simple electrical circuit consists of a conduc-tor (a wire or some other body through whichelectricity can pass) and a source of electricalenergy (a storage battery, for example). If theconductor is connected to the two terminals of thebattery, electricity will flow from one terminalthrough the wire to the other battery terminal. Ifdevices, such as motors or light bulbs, are placedwithin the circuit by properly connecting them tothe conductor, useful work is done. If a switch alsois wired into the circuit, it can be used to controlwhen and for how long the work is done.

The component of the electricity doing thework is called “current,” the charge itself. Currentis forced through the conductor by electricalpressure or “voltage.” All along the circuit thecurrent meets “resistance,” which attempts torestrict current flow.

In this lesson we will be concerned with threemain circuits—starting, ignition and chargingcircuits. You will find many other circuits on mosttractors. Some of these include the lighting cir-cuits; certain controls, sensing devices and gauges;and even circuits for radios and air conditioners.However. let’s begin with the battery.

Figure 6-1INTERNAL CONSTRUCTION OF A WET-CELLSTORAGE BATTERY.

The BatteryThe battery is the heart of the tractor’s electri-

cal system. A battery has a number of positive(lead) and negative (lead oxide) plates held apartby thin strips called separators (see Fig. 6-1). Eachgroup of plates is called a cell. The cells are con-nected and held together in a hard rubber orplastic box. Each cell in this type of battery pro-duces a little more than two volts of electricalforce. A six-cell battery can produce a little morethan 12 volts. Connecting two six-volt batteries inseries also gives 12 volts. Twelve-volt electricalsystems are common on modern tractors. Somelarge tractors have two 12-volt electrical batteriesin series or in parallel to provide 24 volts for thestarting circuit (see Fig. 6-2).

Figure 6-2BATTERIES MAY BE CONNECTED TO PROVIDEADDITIONAL ENERGY.

Caring for the BatteryA few simple measures will help ensure that

the battery lasts for at least as long as it wasdesigned. First, older batteries must have water. Inhot weather when the tractor is used heavily,water evaporates from the battery fluid (electro-lyte). The water level should be checked frequently(at least every 50 hours). Add only clean, soft water(if you have it, distilled water is ideal).

Some batteries are sealed and do not requirethe water to be checked.

The battery cable connection should be keptclean of dirt and corrosion. Clean connections willhelp provide good contact with the battery posts.Dust and dirt can be wiped from the battery with adamp cloth. Be sure, however, to keep the cap on thecells to prevent dirt from getting inside the battery.

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To clean dirty battery connections, sprinkle alittle baking soda on the corroded area and mixwith a small amount of water (just enough to makea paste). Brush the mixture around until thefizzing stops, then flush the grime off gently withwater. When replacing the cables, a little grease orpetroleum jelly spread over the connections willhelp prevent more corrosion.

Finally, be sure connections are tight. Check tosee that the battery is clamped firmly in its carrierframe. Don’t fasten the bolts too tightly—you couldcrack the battery case.

Charging the BatteryDuring normal operation of the tractor, the

charging circuit keeps the battery charged. It ispossible, however, for the battery to becomedischarged. This could happen if the chargingcircuit is defective, if the battery is used for a longcranking period in trying to start the tractor, if it isleft in the cold for a long time, or if a short circuitdevelops.

A discharged battery in good condition can berecharged. This is done by a commercial batterycharging unit. Both terminals of the battery shouldbe disconnected during recharging. The positivelead from the charger connects to the positive postof the battery and the negative lead to the negativepost. Between 12 and 24 hours may be needed torecharge the battery. Follow the charger instruc-tions carefully to prevent further damage to thebattery and to prevent a possible explosion. Alwaysremove the caps from the cells, except on mainte-nance-free batteries, so all gases formed canescape. Keep sparks and open flames away fromthe battery at all times. Do not allow a battery tobecome completely discharged in freezing weatheror the battery may break open.

Starting CircuitThe starting circuit consists of the battery, the

starter (or ignition) switch, the starter solenoid andthe starter motor. Arrangement of these compo-nents is shown in Figure 6-3.

To start an internal combustion engine, anelectric starting system engages the engine’sflywheel and turns it until the engine starts. Thesolenoid opens and closes the circuit switch whichtransmits electric current from the battery to themotor. Electricity causes the smaller gear locatedon the motor shaft to turn and mesh with the teethon the flywheel, which cranks the engine. Withthese parts working together, when the fuelignites, the engine begins to run.

Figure 6-3COMPONENTS OF AN ENGINE STARTINGSYSTEM.

The Charging CircuitThe charging circuit restores the electrical

energy lost from the battery during starting.During normal operation of the tractor, this circuittakes over from the battery to supply current forignition, lights and most other accessories. If alarge amount of current is needed to operateelectrical devices, the battery will supply enough tomake up the deficiency.

The charging circuit includes the battery, avoltage regulator and a generator or alternator(see Fig. 6-4). The latter two devices convertmechanical energy from the engine to electricalenergy for the battery and other circuits.

Generators produce a type of pulsating directcurrent (DC) and alternators generate alternatingcurrent (AC). The AC is converted to DC for use inthe charging circuit. Alternators deliver moreelectrical energy at low speeds than do generators.Alternators require less maintenance so they arealmost always found on newer equipment. Theyare driven from the engine crankshaft by a V-beltwhich also may drive the cooling fan.

A meter or warning light on the tractor instru-ment panel indicates whether the alternator orgenerator is charging at the correct rate. If thelight stays on or the meter shows discharging afterthe engine has run for a short time, shut off theengine and find out why no charging is takingplace. A loose drive belt is the most common cause.The operator’s manual will show how to adjusttension on the belt.

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Figure 6-4COMPONENTS OF AN ALTERNATINGCURRENT (AC) CHARGING CIRCUIT.

Alternators need no lubrication; older genera-tors may need a few drops of light oil, according toinstructions in the operator’s manual. Theirbrushes also may need attention if the generator isnot charging properly.

The voltage regulator in the charging circuitcontrols the amount of current flowing through thecircuit and protects the battery from overcharging.No maintenance is required on the voltage regulator.

The Ignition CircuitThis circuit is found only in spark-ignition

engines. It actually involves two circuits — theprimary and secondary ignition circuits. The twocircuits are shown in Figure 6-5.

The primary circuit is a low-voltage circuitoperating through the battery, the ignition switch,primary windings of wire in the coil, and thecondenser and breaker points in the distributor.The primary circuit acts to induce or create thehigh voltage of the secondary circuit (ignition coil);it is this high voltage which produces the spark toignite the fuel mixture in the cylinder.

The breaker points open and close by riding ona cam, which has as many lobes as there arecylinders in the engine (see Fig. 6-6). The distribu-tor cam is connected directly to the engine crank-shaft. When the ignition switch is on but theengine is not running, the breaker points may beclosed. This is why the battery may discharge if theswitch is accidentally left on. The simple primarycircuit is from the positive side of the battery,through the switch, through the primary coilwinding, and through the points to ground andback to the negative side.

However, when the engine is turning over —even slowly — the distributor cam is rotating,

opening and closing the points. Each time thepoints open, the current flows into the condenserfor a brief moment, then discharges back into theprimary wiring.

The condenser acts as an electrical “shockabsorber.” As the current flow is halted throughthe primary circuit, the magnetic field around theprimary windings in the coil breaks down. Anytime one magnetic field collapses near another,voltage is induced in the second field. In this case,the second field is in the secondary windings.There are many more wires in the secondarywinding so the voltage produced there is muchgreater. The normal voltage in the primary circuitis 12 volts. In the secondary circuit it can be up to25,000 volts.

This powerful surge is led into the top of thedistributor. It then passes through the rotor whichdistributes the charge to the proper spark plug. Atthe spark plug, the high voltage enters the termi-nal at the top of the plug, flows down to the centerelectrode and jumps the gap to the side electrodegrounded against the engine (see Fig. 6-7). The highvoltage is needed so the spark will cross this space.

The spark jumping the gap between the elec-trodes ignites the air-fuel mixture in the top of thecylinder.

Figure 6-5COMPONENTS OF PRIMARY ANDSECONDARY SPARK-IGNITION CIRCUITS.

Servicing theIgnition SystemSpark Plugs

Look in your operator’s manual for instructionson checking and changing spark plugs. Use a sparkplug socket wrench of the correct size to removeplugs for inspection. There is less danger that thewrench will slip and crack the porcelain insulator.

Have someone go over the plugs with you todetermine whether they should be replaced or only

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cleaned. Cleaning should be done in a sand-blast-ing machine. Wash or use compressed air to removesand particles from within the plug after cleaning.Do not use a powered wire brush to clean plugs. Ifplugs are badly fouled, it is best to replace them.

The gap between the center and side electrodesmust be set precisely, according to themanufacturer’s recommendations. Setting the gaptoo narrow may cause poor idling. A gap that is toowide may cause missing under full load.

Always use a round feeler gauge to check thegap of a used plug (see Fig. 6-8). A round gauge

will fit the burned electrodes which are no longerflat. When adjusting the gap, bend the electrodeattached to the shell or outside of the plug.

Some spark plugs have copper or steel gasketswhich seal them to the engine head to make themgas tight. When replacing these plugs, it is impor-tant to use new gaskets. Always tighten the sparkplug enough to crush the gasket somewhat. Besure the threads are clean. Use a wire brush toclean the threads if necessary, but don’t let anydirt get into the cavity around the electrodes andinsulator. Tighten the cleaned plug snugly, untilyou feel it draw against the gasket. Then give itabout another half turn. Some plugs do not usegaskets but are sealed with a tapered fit.

Figure 6-8CHECKING THE SPARK PLUG GAP WITH AWIRE GAUGE.

Keep Wires CleanThe wires leading from the distributor to the

spark plugs carry high voltage. Therefore, they areheavily insulated. If the insulation cracks, thespark may arc across to the engine block and fail toreach the spark plug. Keep these wires wiped cleanand keep dirt away from the spark plugs. Also wipedown the coil and distributor. Dirt around thehigh-voltage wires or spark plugs may collectmoisture and “short out” the spark. Moisture on adirty engine is a common cause of hard starting,especially in high humidity.

Checking Breaker PointsThe breaker point gap should be checked

periodically. Your operator’s manual will tell youhow often and will indicate proper spacing.

Use a flat feeler gauge to check the spacing. Besure the engine has been turned until the pointsare wide open. The proper gap is provided whenthere is a slight drag on the feeler gauge as youpull it between the contact points.

Figure 6-6DISTRIBUTOR BREAKER POINTS OPENED BYTHE BREAKER CAM. (HOW MANY CYLINDERSDOES THIS ENGINE HAVE?)

Figure 6-7CUTAWAY VIEW OF A SPARK PLUG.

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If the points are set too close they will burnand pit rapidly. If the points are set too wide theymay cause a weak spark at higher engine speeds.Be sure the breaker points fit together squarely. Ifthey make only partial contact there will be burn-ing, pitting and uneven wear.

When you finish working with the breakerpoints, run a strip of clean paper between thecontact surfaces to remove any grease or dirtparticles. Grease or dirt on the points will causeburning and pitting.

Learn By Doing1. Recharge a battery. Obtain a discharged battery

in otherwise good condition. Have an adult help

you hook the battery charger to the battery. (Becareful not to get the battery acid in your eyes oron your clothing.) Use a hydrometer to check theelectrolyte before starting, then check it againperiodically during charging.Did all the cells recharge equally?Do you think that after charging for a sufficienttime the battery is usable? Why or why not?How does a low-maintenance battery differ?

2. Clean a corroded battery and return to service.3. Price several batteries at two or more stores.

Why are they different prices? Which is thebetter buy?

4. Collect used parts and make a display of astarting circuit.

Checking up on the Electrical System1. What is the difference between fouled and corroded spark plugs? Which is caused by too much

heat? Too little heat? ________________________________________________________________________

2. What maintenance procedures are required on a liquid storage battery? A maintenance-free bat-tery? _______________________________________________________________________________________

3. Draw lines representing battery cables to show how the circuits below are to be hooked up.

12-volt 12-volt 12-volt 12-voltsystem series parallel battery

system system charger

4. List the proper sequence of steps used to hook up cables between a booster battery and a deadbattery during jump starting. Be sure to list the connection points for each step.A. __________________________________________________________________________________________B. __________________________________________________________________________________________C. __________________________________________________________________________________________D. __________________________________________________________________________________________

5. Name the three components of the charging circuit and their primary functions.A. __________________________________________________________________________________________B. __________________________________________________________________________________________C. __________________________________________________________________________________________

6. What kind of electrical system problem do you think a poor connection between the negative (-) postof the battery and the tractor engine or frame would cause? Which circuit(s) would be affected?_____________________________________________________________________________________________

7. Match these words to the proper definitions:A. Ammeter E. Voltmeter ___ describes the force behind the electron flow in a conductor.B. Voltage F. Resistance ___ instrument used to determine if a battery is beingC. Current G. Electrolyte charged or discharging.D. Hydrometer H. Electric Energy ___ battery fluid mixture of sulfuric acid and water.

___ describes opposition to electron flow in a conductor.

8. The direction of current flow through a battery during charging and discharging is the same. T FWhy? _______________________________________________________________________________________

27

COOLING SYSTEMWhat would happen if you left an empty pan on

the stove with fire under it? It would get hot,eventually start smoking, and maybe even crack orburn a hole in the pan. However, if you discoveredthe pan getting hot and poured water into it, thewater would pick up the heat thus cooling the pan.Tractor engines can be cooled in a similar manner.Internal combustion engines cooled by pumpingwater through them are “water-cooled” engines.

Another way to cool the heated pan would be toblow cool air over it. To do so requires a fan. Sometractor engines also are cooled with a fan. Theseare “air-cooled” engines.

The engine’s cooling system has two functions.It must keep the engine from overheating and itmust maintain a uniform temperature in theengine. Up to one-third of the heat from the burn-ing fuel released in an engine must be removed bythe cooling system.

Engines can be damaged from overheating, butmuch damage also can be caused by operatingthem at temperatures too cool. Operating anengine too cool causes parts to wear rapidly andreduces power output. It also may cause spark plugfouling and a waste of fuel.

Tractor engines are built with large coolingcapacities so, if properly maintained, the coolingsystem should help prolong the life of your tractor.

Water-Cooled SystemsSince few tractors have air-cooled engines we

will devote most of this lesson to the water-cooled

systems. The water-cooled system consists of aradiator, fan, water pump, thermostat, hoses andwater passages in the engine block.

Engine manufacturers recommend using acoolant mixture of clean, soft water and permanentantifreeze (ethylene glycol). This mixture containsthe necessary rust inhibitors to protect the insideof the cooling system. This coolant mixture also hasa higher boiling point than water, so the enginecan be built to operate at a higher temperature.

The term “permanent” means the ethyleneglycol can be used in the system all year. However,the coolant mixture still should be changed periodi-cally, according to the instructions in youroperator’s manual.

The correct ratio of ethylene glycol and waterwill depend upon how much winter protection youneed for the engine. Freezing water can crack theengine block or cylinder head. Where little or nowinter protection is needed the usual coolant ratiois half water and half ethylene glycol. More anti-freeze and less water protects against lowertemperatures. Ethylene glycol should not be usedalone in the cooling system; it must be mixed withwater. Usually a mixture of 50% water and 50%antifreeze is adequate for most climates.

Coolant filters are found on all new engines.Change them as recommended.

The RadiatorIn a water-cooled engine, water soon would boil

away if the heat was not removed (see Fig. 7-1). To

Figure 7-1A COOLING SYSTEM MUST REMOVE LARGE AMOUNTS OF HEAT.

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remove some of the heat, water is passed through aradiator. Air passes around the fins and tubes,picks up the excess heat and carries it away. A fankeeps a large amount of air moving through theradiator. So, in a water-cooled engine both waterand air are used for cooling.

On some engines, oil from the transmission orhydraulic system is circulated through a coil infront of the radiator. This helps cool the oil.

Never add very hot or very cold water to theradiator. Inspect radiator hose connections often tomake sure there are no leaks. A leaky radiatorhose or leaky radiator causes you to keep addingcoolant. Check the inside of hoses, too. Rubberwears off with age and small pieces can plug theradiator.

Pump and ThermostatThe water pump circulates the coolant through

the cooling system (see Fig. 7-2). The pump drawshot coolant from the engine block and forces itthrough the radiator for cooling. If the pump failsto circulate the coolant, heat is not removed fromthe engine and overheating will occur.

The thermostat provides automatic control ofengine temperature. This heat-controlled valveregulates the flow of water between the cylinderblock and the radiator. During engine warm-up thethermostat remains closed, stopping water circula-tion until the engine warms up to operating tem-perature. Once the engine is warmed the thermo-stat opens and hot coolant flows from the engine tothe radiator and back.

Figure 7-2LIQUID COOLING SYSTEM ON A MODERNENGINE.

An engine operating at a temperature lowerthan recommended will use more fuel, have lesspower, and have increased cylinder wear. Be surethe thermostat on your cooling system worksproperly. And, never operate an engine without athermostat.

Here’s how to check a new thermostat or one thatyou have removed from your tractor (see Fig. 7-3).

Use a string to suspend the thermostat in a canof water. Place an oven thermometer in the water.Heat the can of water on a stove or hot plate. Asthe water heats up you can watch the thermostatto see if it opens at the correct temperature. If thethermostat is working properly it will open whenthe water reaches the same temperature indicatedon the thermostat.

Figure 7-3TESTING A THERMOSTAT.

Pressure SystemOn most engines the radiator cap seals the

radiator. It contains one valve that admits air to keepthe radiator tubes from collapsing and another thatlets liquid escape from the system when the inter-nal pressure reaches a predetermined level (seeFig. 7-4). We call this a pressure cooling system.

If your engine has such a cooling system makesure that the gasket used to seal the radiator capfits tightly and that it doesn’t leak. Also, be sure theengine has cooled before you remove the radiator cap.If it must be opened, cover with rags and release thepressure slowly. If you remove the cap while theengine is hot and the system is still pressurized,you could be burned. Pressurized systems typicallyoperate at temperatures of 200°F or higher.

It is important not to overfill the radiator ofyour engine. Some space must be left for coolantexpansion. If there is too much liquid, the excesswill drain off in the overflow pipe. Coolant runningfrom the overflow pipe usually means the coolantlevel is too high, not that the engine is overheating.New tractors have containers attached to theradiator to catch and recirculate coolant forced outfrom overfilling.

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Figure 7-4THE RADIATOR CAP MAINTAINS A PRE-SETPRESSURE WITHIN THE COOLING SYSTEM.

Figure 7-5MAINTAIN PROPER TENSION ON THEFANBELT.

Fans and BeltsEngines are equipped with a V-belt to drive the

fan. It should be adjusted for the proper tensionbetween the pulleys (see Fig 7-5). Correct tensionis important so the fan, water pump and otheraccessories driven by the same belt operate asdesigned. Your operator’s manual will tell you theproper tension.

Allow Engine to Cool Before StoppingA gasoline engine may be so hot after pulling a

hard load that it will keep on running after youturn off the switch. This happens when red-hotcarbon in the combustion chamber ignites the fuel.The best way to prevent it is to allow the engine toidle for about five minutes at one-half to three-fourths throttle until it cools somewhat. Then,when you turn off the switch, the engine will stop.Turning off a hot engine without first allowing it tocool is a common cause of sticking valves.

Newer tractors may have gauges to tell youwhen the engine is cool enough to shut off.

Air-Cooled SystemAir-cooled engines are used in small and large

tractors. They also are used as power units onmany machines.

Since air-cooled engines are often operated industy areas you must be especially careful to keepthe air inlet screen clean. The engine must havesufficient air for cooling. On air-cooled engines youwill find a metal shroud to direct the air flow. Themetal keeps the air near the engine. Be sure dirt,leaves and trash do not collect in the shroud andbetween the fins around the cylinders. Restrictedair flow may allow overheating and cause burnedpistons or valves. Some engines have a section ofthe shroud which can be removed for cleaning butshould be replaced before restarting the engine.

Learn by Doing1. Change the coolant in a tractor following the

operator’s manual.2. Change the filter on a tractor engine cooling

system. Report or illustrate the results to yourclub.

3. Survey 3-4 farms in your community. Note thetype of engine and cooling system for eachtractor you find. Have the cooling systems beenserviced regularly?

4. Price a water pump at an implement dealer.Were you surprised at the cost?

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Checking up on the Cooling System1. Briefly describe the two functions of a tractor’s cooling system.

A. ____________________________________________________________________________________________B. ____________________________________________________________________________________________

2. Why is a special coolant solution used in the water-cooled system? __________________________________

3. What are three main causes of radiator leakage? __________________________________________________

4. What two maintenance checks do you think should be made daily on a tractor’s water-cooled system?A. ____________________________________________________________________________________________B. ____________________________________________________________________________________________

What should be checked daily on an air-cooled engine?_______________________________________________________________________________________________

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HYDRAULIC SYSTEMYou learned in your first year of the tractor

project that hydraulic systems provide the“muscles” for controlling various tractor opera-tions. This is possible because an efficient hydrau-lic system multiplies a small amount of appliedforce to do a great amount of work.

The brakes on a vehicle are a simple exampleof hydraulic power. Slight force on the brake pedalslows or stops the vehicle’s movement. Likewise,only a light touch of the hand on the tractor’shydraulic control lever is needed to lift implementsweighing several hundred or thousands of pounds.

The most common hydraulic functions found onmodern tractors involve: steering, brakes, trans-missions, implement control, remote cylinders andhydraulic motors (see Fig. 8-1). These functionsmay use a common hydraulic fluid supply or eachmay have its own reservoir where oil is stored.

The fluid in a hydraulic system serves not onlyas the power-transmitting medium but also as thesystem’s lubricant and coolant. You must, there-fore, carefully follow your operator’s manual forselecting the recommended fluid and servicing anyhydraulic system on the your tractor.

The Hydraulic PrincipleFigure 8-2 illustrates the principle of hydraulic

power in a simplified system. A scientific principlediscovered by the French physicist Pascal governswhat happens in the hydraulic system. Pascal’sLaw states that “pressure applied to a fluid in aclosed container is transmitted with equal inten-sity throughout the liquid and at right angles(perpendicular) to the surface of the container.”Any force applied to the drive piston is transmittedthrough the liquid to the driven piston. You can seein the bottom part of Fig. 8-2 that one piston isdriving four others.

Other components are needed to build apractical system. A reservoir supplies the fluidneeded (see Fig. 8-3). A pump moves the fluid fromthe reservoir through the system. A control valveregulates the direction of fluid flow, and some typeof cylinder or hydraulic motor does the work (seeFig. 8-4.)

Figure 8-1A MODERN TRACTOR WITH A COMPLETE HYDRAULIC SYSTEM.

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Figure 8-2A HYDRAULIC SYSTEM MULTIPLIES FORCEMANY TIMES.

Figure 8-3A SIMPLE HYDRAULIC SYSTEM.

Using theHydraulic System

The tractor operator’s manual should bestudied carefully so that functions and operation ofall segments of the hydraulic system are under-stood. Special attention should be directed to thehydraulic load-sensing controls, hydraulic differen-tial locks, and controls for remote operations.Proper settings for load-sensing controls willdepend upon the implements being used and thedegree of sensitivity desired. Operation of differen-tial locks will be discussed in Lesson 9.

Remote cylinders or motors are connected tothe main hydraulic system, usually by special

flexible lines. Tractors may have only one or asmany as three or four sets of ports for attachingthese lines. It is important to know how the linesare to be connected. This information will be in theoperator’s manual.

Figure 8-4BASIC OPERATION OF A HYDRAULIC MOTOR.

Hydraulic SystemMaintenance

A well-maintained hydraulic system seldomgives the operator any trouble. Check the oil levelregularly. Changing the oil and filters regularlyand keeping the fluid lines tight help preventproblems and are necessary maintenance on thehydraulic system.

Hydraulic fluid is a special petroleum oilrefined to meet the demands of the system. Itcontains additives which help prevent rust, corro-sion, oxidation and foaming, and which helpwithstand extreme pressures as well. However, oilin the hydraulic system can become contaminatedjust like engine and transmission oil. Dust, rust,moisture and metal particles will damage thehydraulic system. When checking fluid levels andchanging filters be especially careful to clean thesurface around the dipstick, filler cap and filter sodirt does not enter during checking or filling. Also,clean remote cylinder hose ends.

Follow the manufacturer’s recommendationsfor the type of fluid to use in your tractor’s hydrau-lic system. Proper selection of oil is mandatory forsatisfactory performance and life of your hydraulicsystem. One survey indicates that about three outof every four problems in hydraulic systems arecaused by using either the wrong or contaminatedfluid. Manufacturers’ warranties on the hydraulicsystem become voided if the wrong fluid is used

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and the system fails. Fluid for hydraulic brakesystems must not be used in the tractor’s mainhydraulic system. Brake fluid is not petroleumbased and could ruin the system.

Do not look for leaks with your hand. Use apiece of cardboard or paper. Oil under

pressure can penetrate the skin and causeserious injury.

Routine checks for oil leaks will preventexcessive loss of fluid and possible overheating. Airleaks will cause the oil to oxidize rapidly formingharmful gum and sludge.

Remember, hydraulic systems on newertractors are an integral part of the entire tractor.When the hydraulic system fails the tractor isinoperable and expensive to repair.

CAREFUL CARL’S SAFETY RULES FORHYDRAULICS• Always lower implements before working on

them.• Park equipment where children cannot reach.

• Block up hydraulic implements if you must workon them in the raised position.

• Never service a hydraulic system while theengine is running, unless absolutely necessary,such as while bleeding the system or looking forleaks. Use a piece of cardboard to check forleaks.

• Do not remove cylinders until the implementsare resting safely on the ground or blocked upsafely. Make sure the engine is off and the key isremoved.

Learn by Doing1. Change the filter on a hydraulic system. How

much did this cost (filter, oil, etc.)?2. Clean the area of a tractor where hydraulic

hoses are connected.3. Obtain a used oil pump. Take it apart to learn

how it works. Describe and illustrate at a clubmeeting.

4. Make a list of how hydraulics are used on afarm.

Checking Up on the Cooling System1. Name the basic parts of a tractor hydraulic system. ________________________________________________

___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. List three maintenance problems commonly associated with hydraulic systems. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. Give one safety rule which you should follow to avoid injury from the hydraulic system. _________________________________________________________________________________________________________________________________________________________________________________________________________________

4. Explain the difference between a hydraulic pump and a hydraulic motor. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________

5. What is the most common cause of premature hose failure? ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6. How do you relieve hydraulic pressure before servicing the tractor hydraulic system? _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

34

DRIVE TRAINand forefinger. Have someone try to turn the half-dollar. What happens? Then loosen your gripslightly. What happens? The person can turn thehalf-dollar easily.

Figure 9-2 shows the parts of a simple, single-disk clutch and what happens when the clutch isengaged and disengaged. While the clutch pedal isout, strong springs force the pressure plate andclutch disk against the spinning flywheel. Torquefrom the flywheel is transmitted through theclutch and into the transmission. When the pedalis depressed, a throw-out bearing pulls the clutchplate back from the clutch disk breaking powertransmission.

Figure 9-2PARTS OF A SIMPLE DISK CLUTCH.

The multiple-disk clutch works in much thesame way as the single-disk, except that severaldisks are used to obtain more frictional area in themultiple-disk type.

Disk clutches may be either of the “dry” or“wet” type. Dry means that the clutch operates andis cooled by air. Wet means that the clutch oper-ates and is cooled in oil. On the wet-type, the oillevel must be checked and the oil and filterchanged regularly.

Dry types may occasionally require greasing atthe bearings but be careful! Too much grease canget into disk faces and cause poor operation,including slipping, grabbing and dragging. Followthe instructions in your operator’s manual forservicing each.

Caution: Do not “ride” the clutch; that is,leave your foot on the pedal while it isengaged. This causes clutch slippage,

overheating and excessive wear.

The power that the engine develops can betransferred to implements either through thewheels, the PTO or hydraulic pressure. On newertractors, all these systems are connected into adrive train which transmits power from the engineto the wheels.

Beginning at the engine and tracing the flow ofpower along the train are these components: theclutch, transmission, differential and, just beforereaching the wheels, the final drives. These compo-nents are shown in relation to each other in Figure9-1.

Figure 9-1LOCATION OF COMPONENTS OF THE POWERTRAIN IN A TRACTOR.

The ClutchThe clutch links the engine to the transmis-

sion. Power is transmitted from the clutch to thetransmission. If the engine were coupled directly tothe transmission, power would be transmittedcontinuously, as long as the engine is operating.The clutch enables power transmission to occursmoothly when starting out, to be interruptedmomentarily to shift between speeds, and to behalted for stopping tractor movement.

Clutches may be either mechanically or hy-draulically actuated. Clutches on older tractors andsmaller models are mechanical. Those on newertractors, especially larger models, are hydraulicallyoperated. Some newer tractors which use torqueconverters in fluid drives do not have clutches.

The Mechanical ClutchA good way to demonstrate how a disk clutch

works is: Place a half-dollar between two quartersand pinch the quarters tightly with your thumb

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TransmissionsThe turning force developed at the crankshaft

of the engine is called torque. Torque and speedtogether give power. When more torque is neededfor pulling heavy loads, reduce speed. Reducing thespeed increases the tractor’s pulling ability withthe same power. Likewise, increasing the speedreduces torque.

Gear TransmissionsGears are used to change speed in a tractor

and are the basic components in the power train.They transfer power from one shaft to another.Basically, the gears apply the twisting force(torque) to the rotating parts. Torque varies withrelative gear size and a small gear driving a largergear gives less speed and more torque and viceversa (see Fig. 9-3 and 9-4).

Figure 9-3TORQUE VARIES WITH RELATIVE GEAR SIZE.

Figure 9-4OUTPUT SPEED DEPENDS ON RELATIVE GEARSIZE; SMALL GEAR ALWAYS TURNS FASTER.

Gears are usually classified by type of teeth.Meshing gears, as illustrated, must have teeth ofthe same size and design and at least one pair ofteeth in contact at all times.

There are several types of gear teeth andarrangements. Three major types are straight cut,helical cut and planetary. Figure 9-5 illustratesthese.

Straight-cut teeth gears enable speeds to bechanged directly by sliding the gears togetheralong a shaft. Helical spur gears are very common

in transmissions because they are quieter at highspeeds and are more durable. Planetary gear setsalso are popular because each set can have morethan one speed change and the work load can bespread over several gears, reducing wear and tearon any one gear.

Figure 9-5THREE TYPES OF GEARS COMMONLY FOUNDIN TRACTOR TRANSMISSIONS.

Mechanical TransmissionsGear shifting in a mechanical transmission is

done with the clutch and shifting lever. Afterdisengaging the clutch, the operator uses the leverto reposition gears in the transmission. Gearrepositioning may be accomplished by sliding gearsalong shafts or by locking freely rotating gears todriving shafts by means of shifting collars. Ifsynchronizers are added to the transmission, theoperator can shift between certain gears withoutstopping the tractor. A synchronizer matches thespeeds of two gears so they engage or meshsmoothly.

Hydraulic-Assist TransmissionsHydraulic assisted transmissions are common

on modern tractors. They provide the advantage ofbeing able to shift them while “on-the-go” and theflow of power is not interrupted. Shifting is accom-plished by routing fluid to hydraulic clutches insidethe transmission. The operator doesn’t actually

36

select gears but instead selects clutches to engagecertain gears which are in constant mesh.

Hydrostatic TransmissionsHydrostatic transmissions use a fluid at high

pressure but relatively low speed to transmitpower. A pump connected to the engine pumpshydraulic fluid through a number of circuits in aclosed system to a motor. The power output fromthe hydraulic motor is directed to the drive wheels.Because the rate, direction and pressure of oil inthe system is easily controlled, many combinationsof speed and torque are available. However, hydro-static transmissions are not very energy efficient.

Hydrodynamic TransmissionsThis fluid-type system uses fluids at high

speeds but relatively low pressure; another namefor this drive is a torque converter. It offers smoothshifting between an endless number of speeds andis usually coupled with a gear train to allow moreefficient operation.

The torque converter functions by pumpinghydraulic oil at high pressure against blades of aturbine causing it to spin. The speed of the oil canbe varied to change the torque obtained from theturbine. The converter automatically increases ordecreases torque so only a few gear ratios areneeded.

DifferentialsPower from the transmission goes to the

differential. A differential takes power “aroundthe corner” from the drive shaft to the drivewheels. It also makes one wheel speed up as theother slows down in turning. If you make a shortturn by stopping the inside wheel, the outsidewheel will go twice as fast.

You may compare the action of the differentialto marching soldiers. When soldiers make a turn,the one on the inside slows or stops and waits forthose on the outside to come around. In a differen-tial, there is a small gear on the end of each axle(see Fig. 9-6). Each axle turns a wheel. Two orthree small bevel pinion gears connect to these twogears. The bevel pinion gears are attached to a casewhich is bolted to a larger gear called the ringgear. When the tractor is traveling straight ahead,the gears on the ends of the axles turn with thering gear. The bevel pinion gears do not turn. Theyare carried around by the carrier.

Now, if the tractor is turned, one wheel slowsdown and the small bevel pinion gears turn, thusmaking the outside wheel speed up. The outsidewheel speeds up at the same rate the inner oneslows down. If you should turn a sharp corner andstop the inside wheel, the bevel pinion gears cause

the outside wheel to turn at twice the speed re-quired for moving in a straight line.

Differential LocksA differential lock is used when power must be

delivered equally to both wheels. If a tractor losestraction on one wheel, which begins to spin becauseof differential action, locking out that action willhelp regain traction.

Figure 9-6THE TRACTOR DIFFERENTIAL.

Differential locks may be either mechanical orhydraulic. Both types may be engaged while thetractor is in motion. Differential locks should neverbe left engaged when the tractor is turning becausethey force both wheels to turn at the same speed.

Final DrivesThe final drive is the last link carrying the

power of the engine to the wheels. Its primaryfunctions include providing the final gear reductionfor slowing down the tractor and increasing torqueat the drive wheels. The most common types offinal drives on tractors are the pinion drive and theplanetary drive.

37

Pinion final drives consisting of a pinion gearand a spur gear are sometimes mounted within thedifferential case (see Fig. 9-7). In this older design,all final gearing is kept within one case for a morecompact unit with a single lubrication system. Thisdesign allows a straight axle shaft to be used,providing space for wheel tread adjustment. Piniondrives may be located at the outer ends of the finaldrive shafts.

Figure 9-7A PINION GEAR ASSEMBLY FOR SPEEDREDUCTION LOCATED IN THE DIFFERENTIAL.

Planetary drive sets are smaller and morecompact than pinion type. They also are sturdierbecause stresses are distributed over several gears.Like pinion drives, they also may be placed next tothe differential or at the outer ends of the finaldrive shaft (see Fig. 9-8).

MaintenanceBecause of the many possible types of designs

in power transmission systems, it is impossible togive specific instructions for maintenance. There-fore, it is very important that you follow youroperator’s manual.

All components are essentially sealed unitsbuilt of strong steel. Gears are assembled on shafts

which turn on large ball or roller bearings. Goodlubrication is critical to the proper functioning andlong wear of these parts. Be sure to keep enough ofthe recommended lubricant in the transmissionand gear cases. Also, be sure oils are kept clean byadding them regularly and changing oil and filtersas recommended.

Repairs to drive train components can be verycostly. So it’s worth your time and effort to performthe specified maintenance in order to preventcostly and time-consuming repairs.

Figure 9-8A TRACTOR FINAL DRIVE WITH PLANETARYGEAR ASSEMBLIES AT OUTER ENDS OF FINALDRIVE SHAFTS.

Learn by Doing1. Check the fluid level of a tractor’s transmission.

Add oil if necessary.2. Review the cost of overhauling the transmission

on a tractor.3. Review the specifications of a sample transmis-

sion oil.4. Review how a differential works and why some

machines have differential locks.

38

Checking up on Drive Trains1. Name four functions of power trains. ___________________________________________________________

___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Name three basic parts of a power train. ________________________________________________________________________________________________________________________________________________________

3. A small gear driving a larger gear will deliver (more/less) torque to the driven shaft? _______________

4. Define “Torque.” ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

5. What is the purpose of the clutch in the drive train? ______________________________________________________________________________________________________________________________________________

6. Name and describe two types of gear transmissions. _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

7. What two jobs does the differential perform? ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

8. Can the differential lock be engaged while the machine is moving? Yes / No

9. List two advantages of planetary gears compared to pinion-type drives. _______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

10. List three common causes of final drive failures. ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

39

THANKS FOR JOINING US!This concludes Unit 2 in the 4-H tractor project

series. You should have learned many new thingsabout tractor operation, care and maintenance,especially about tractor systems, fuels and lubri-cants, servicing the tractor, and the importance ofkeeping operating cost records.

Of course, safety is always a concern whenworking with machinery. So, remember to followthe rules and safety practices provided by Carlaand me and our farm friends.

To reinforce learning-by-doing, don’t forget tocomplete the activities and quizzes supplied ineach section of this manual. They will help expandyour knowledge of the tractor and give you achance to gain practical experience in everydayoperations. If you forgot to do the activities as youwent along, now’s the time to catch up. Once you’redone, you’ll be ready to move on to Unit 3.

GLOSSARYACCUMULATOR A container in a hydraulicsystem which stores energy as fluid pressure foruse as needed to maintain system pressure. It mayalso act as a shock absorber to protect the system.

ALTERNATING CURRENT (AC) The flow ofcurrent which reverses its direction of flow atregular intervals, from positive to negative andvice versa.

ALTERNATOR A device which converts mechani-cal energy into electrical energy, producing alter-nating current. The AC is then changed to directcurrent (DC) by diodes in the alternator.

BATTERY (STORAGE) A device which produceselectricity through chemical reactions and whichcan be recharged by reversing those same reac-tions.

BLEEDING Removal of unwanted air in a fuel orhydraulic system.

BREAKER POINTS Electrical contacts in anignition distributor which control the flow ofcurrent into the ignition coil.

CETANE NUMBER The measure of a diesel fuel’sability to self-ignite when heated by compression.The higher the cetane number, the faster self-ignition occurs.

CHOKE A device to temporarily enrich a fuel/airmixture by increasing the amount of fuel in it. Thechoke is used to help an engine run smoothly untilit reaches its normal operating conditions.

CLUTCH A device which connects or disconnectsengine power output from a transmission or driveshaft.

CONDENSER A component in the primaryignition system which protects breaker points fromburning as they open and close.

CURRENT The flow of electrodes through aconductor. Current is denoted by the term “am-pere” and is the component of electricity whichproduces work.

DIRECT CURRENT (DC) The flow of electricalcurrent in one direction only, from the positive tothe negative side of a circuit.

DISTRIBUTOR A switch-like device in a spark-ignition engine which directs electrical current toone spark plug at a time.

ELECTROLYTE A solution capable of conductingan electric current. The sulfuric acid and water ina storage battery is an electrolyte.

GENERATOR A device for converting mechanicalenergy into electrical energy. The energy producedis smoothed out to direct current for use in thecircuits of the tractor.

HYDRAULIC MOTOR A motor whose motionand power are produced by fluid flowing throughgears or vanes.

HYDRAULIC PRESSURE A force produced byflowing liquid.

HYDROMETER An instrument for measuring thespecific gravity of a liquid.

IGNITION COIL A type of electrical transformerwhich increases the normal voltage of an ignitionsystem to a very high voltage for igniting the fuelmixture.

OCTANE NUMBER The measure of the anti-knock quality (resistance to pre-ignition or unevenignition) of a fuel.

PINION (GEAR) The smaller of two gears mesh-ing together.

PLANETARY (GEARS) A set of gears with onegear in the center (sun gear) surrounded by pinions(planet pinions) and all encased within a ring gear.Each pinion rotates on its axis while all rotatearound the sun gear. Each pinion meshes with theinside of the ring gear.

RADIATOR A part of the liquid cooling systemthrough which hot water passes for cooling.

REMOTE CYLINDER A hydraulic cylinderlocated away from the source of hydraulic power. Itis usually connected to the system with flexiblelines.

RESISTANCE Restriction of the flow of electricalcurrent through a conductor. Resistance is pro-duced by wires, light bulbs or other devicesthrough which current must travel.

SERVICE CLASSIFICATION Two-letter codesdeveloped by the American Petroleum Institute(API) to define the “quality” of engine lubricatingoil. They enable oils from different manufacturersto be classified by their engine protection qualities.

SOLENOID An electromagnetic device whichconverts electrical energy to linear motion.

SPARK PLUG The electrical device which pro-duces the ignition spark in the cylinder of a spark-ignition engine. It ignites the fuel-air mixture.

SPECIFIC GRAVITY (SG) The ratio of thedensity of a liquid to the density of pure water. Ifwater has the arbitrary SG of 1.0, a liquid with theSG of 2.5 is two and one-half times as dense.

STARTER A part of the electrical system. A motorattached by gears to the engine’s flywheel. Themotor converts electrical energy to mechanicalenergy for cranking the engine.

SYNTHETIC LUBRICANT Petroleum-basedlubricants which have been synthesized or built upto meet one or more special lubrication needs.Ordinary lubricants are produced mainly throughrefining processes which break down crude petro-leum. Synthetics are created by building up prod-ucts from basic constituents.

THERMOSTAT A heat-controlled valve used inthe cooling system of an engine to regulate the flowof water between the cylinder block and the radia-tor.

TRANSMISSION A group of gears or othercomponents which provide a selection of speeds forincreasing or decreasing the output speed from anengine.

VISCOSITY RATING A numerical rating devel-oped by the Society of Automotive Engineers(SAE). Defines the flow rate of lubricating oils.

VOLTAGE The force or pressure which moveselectrical current through a conductor.

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, C. Oran Little, Director of CooperativeExtension Service, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort.Issued: 9-86; Last Printed 1-97, 1200 copies.