In this article we will discuss about:- 1. Farm Tractor Development 2. Classification of Farm Tractor 3. Selection 4. Power Transmission System 5. Estimating the Cost of Power 6. Repair, Maintenance and Storage.
Farm tractor is a self-propelled power unit having wheels or tracks for operating agricultural implements and machines including trailers. Farm tractor engine is used as a prime mover for active tools and stationary farm machinery through power take-off shaft (PTO) or belt pulley.
Farm Tractor Development:
The present tractor is the result of gradual development of machine in different stages.
History of tractor development is given below in chronological order:
1890 – The word tractor appeared first on record in a patent issued on a tractor or traction engine invented by George H. Harris of Chicago.
1906 – Successful gasoline tractor was introduced by Charles W. Hart and Charles H. Parr of Charles City, Iowa (48A).
1908 – First Winnipeg tractor trials were held.
1911- First tractor demonstration was held at Omaha (Nebraska).
1915-1919 – Power take-off was introduced.
1920-1924 – All-purpose tractor was developed.
1936- 1937 – Diesel engine was used in tractor and pneumatic tires were introduced.
1937- 1941- Hydraulic controls and three point linkage were developed.
1950-1960 – Manufacturing of diesel tractors on extensive basis throughout the world was taken up.
1960-1961- Tractor manufacturing was started in India by first manufacturer M/s Eicher Good Earth.
1962-1970 – Manufacturers like Tractor and Farm equipment Madras, Hindustan tractors at Baroda, Escorts tractors at Faridabad and International Harvester in Bombay started work during this period.
1971- Escorts tractor Ltd. started producing ford tractor.
1973 – Manufacture of HMT tractor was started.
1974 – Pitti and Kirlosker tractors were started.
1975 – Harsha tractors were established.
1981 – Auto tractors were started.
1982- Universal tractors were established.
Between 1983 to 2003, GTCL tractors, M.M. Tractors Sonalika, VST, L & T, PTL, Bajaj.
Classification of Farm Tractor:
Tractors can be classified into three classes on the basis of structural design:
1. Wheel tractor
2. Crawler tractor (track type or chain type)
3. Walking tractor (power tiller)
1. Wheel Tractor:
Tractors, having three of four pneumatic wheels are called Wheel tractors. Four wheel tractors are most popular everywhere.
2. Crawler Tractor:
This is also called Track type tractor or Chain type tractor. In such tractors, there is endless chain or track in place of pneumatic wheels.
3. Power Tiller:
Power tiller is a walking type tractor. This tractor is usually fitted with two wheels only. The direction of travel and its controls for field operation is performed by the operator, walking behind the tractor.
On the basis of purpose, wheeled tractor is classified into three groups:
(a) General purpose
(b) Row crop and
(c) Special purpose
(a) General Purpose Tractor:
It is used for major farm Operations such as ploughing, harrowing, sowing, harvesting and transporting work.
Such tractors have:
(i) Low ground clearance,
(ii) Increased engine power,
(iii) Good adhesion and,
(iv) Wide tyres.
(b) Row Crop Tractor:
It is used for furrow crop cultivation. Such tractor is provided with replaceable driving wheels of different tread widths. It has high ground clearance to save damage of crops. Wide wheel track can be adjusted to suit inter row distance.
(c) Special Purpose Tractor:
It is used for definite jobs like cotton fields, marshy land, hill sides, garden etc. Special designs are there for special purpose tractor.
Selection of Farm Tractor:
Selection of farm tractor depends upon following factors:
1. Land Holding:
Under a single cropping pattern, it is normally recommended to consider 1 hp for every 2 hectares of land. In other words, one tractor 20-25 hp is suitable for 40 hectares farm.
2. Cropping Pattern:
Generally 1.5 hectare/hp has been recommended where adequate irrigation facilities are available and more than one crop is taken. So a 30-35 hp tractor is suitable for 40 hectares farm.
3. Soil Condition:
A tractor with less wheel base, higher ground clearance and low overall weight may work successfully in lighter soil but it will not be able to give sufficient depth in black cotton soil.
4. Climatic Condition:
For very hot zone and desert area, air cooled engines are preferred over water cooled engines. Similarly for higher altitude, air cooled engines are preferred because water is liable to be frozen at higher altitude.
5. Repairing Facilities:
It should be ensured that the tractor to be purchased has a dealer at nearby place with all the technical skills for repair and maintenance of machine.
6. Running Cost:
Tractors with less specific fuel consumption should be preferred over others so that running cost may be less.
7. Initial Cost and Resale Value:
While keeping the resale value in mind, the initial cost should not be very high, otherwise higher amount of interest will have to be paid.
8. Test Report:
Test report of tractors released from farm machinery testing stations should be consulted for guidance.
Power Transmission System of Farm Tractor:
Transmission is a speed reducing mechanism, equipped with several gears. It may be called a sequence of gears and shafts, through which the engine power is transmitted to the tractor wheels. The system consists of various devices that cause forward and backward movement of tractor to suit different field condition. The complete path of power from the engine to the wheels is called Power train.
Function of Power Transmission System:
i. To transmit power from the engine to the rear wheels of the tractor.
ii. To make reduced speed available, to rear wheels of the tractor.
iii. To alter the ratio of wheel speed and engine speed in order to suit the field conditions.
iv. To transmit power through right angle drive, because the crankshaft and rear axle are normally at right angles to each other.
The power transmission system consists of:
(b) Transmission gears
(d) Final drive
(e) Rear axle
(f) Rear wheels
Combination of all these components is responsible for transmission of power.
Estimating the Cost of Farm Tractor Power:
The cost of operation of farm tractor is divided under two heads known as fixed cost and Operating cost.
I. Fixed Cost:
Fixed Cost includes:
2. Interest on the capital
4. Insurance and
It is the loss of value of a machine with the passing of time.
D = C-S/L × H
D = depreciation per hour
C = capital investment
S = salvage value, 10% of capital
H = number of working hours per year and
L = life of machine in years.
2. Interest on the Capital:
Interest is calculated on the average investment of the machine taking into consideration the value of the machine in first and last year.
I = C+S/L×H × i/H
I = interest per hour
i = % rate of interest per year.
Housing cost is calculated on the basis of the prevailing rates of the locality but roughly speaking, the housing cost may be taken as 1% of the initial cost of the machine per year.
Insurance charge is taken on the basis of the actual payment to the insurance company but roughly speaking, it may be taken as 1% of the initial cost of the machine per year.
Taxes are calculated on the basis of the actual taxes paid per year but roughly speaking, it may be taken as 1% of the initial cost of the machine per year.
II. Operating Cost:
Operating Cost Includes:
3. Repairs and maintenance, and
1. Fuel Cost:
Fuel cost is calculated on the basis of actual fuel consumption in the tractor.
Charges for lubricants should be calculated on the actual consumption, but roughly speaking the lubricants cost varies between 30 to 35% of the fuel cost.
3. Repairs and Maintenance:
Cost of repairs and maintenance varies between 5 to 10% of the initial cost of the machine per year.
Wages are calculated on the basis of actual wages of the workers.
Repair, Maintenance and Storage of Farm Tractor:
Some of the causes and remedies are as follows:
A. Trouble- Engine Does Not Start:
1. Cause – Battery not fully charge. Remedy- Charge the battery fully
2. Cause – Starter pinion jammed. Remedy- Adjust the pinion
3. Cause – Faulty switch. Remedy- Repair or change the switch
4. Cause – Battery terminals not connected. Remedy- Connect the terminals
5. Cause – Starter out of order. Remedy- Check the starter and repair it
6. Cause – Engine too stiff. Remedy- Use lubricating oil of low viscosity
7. Cause – Air lock in fuel system. Remedy- Bleed the fuel line
8. Cause – Fuel pump faulty. Remedy- Repair it in specialised shop
9. Cause – Fuel filter blocked. Remedy- Clean the fuel filter
10. Cause – Water in fuel line. Remedy- Change the fuel oil
11. Cause – Pump timing not correct. Remedy- Check up the timing
12. Cause – Injectors faulty. Remedy- Check it on injector testing machine
B. Trouble – Engine Gives Out Black Smoke:
1. Cause – Air cleaner choked. Remedy- Clean it well
2. Cause – Engine over loaded. Remedy- Reduce the load from the engine
3. Cause – Excess fuel injected. Remedy- Check the injection pump and injector in specialized shop
4. Cause – Unsuitable fuel. Remedy- Use the correct fuel
5. Cause – Imperfect cooling. Remedy- Check the cooling system machine
C. Trouble – Engine Gives Out Blue Smoke:
1. Cause – Worn out oil rings. Remedy- Replace the oil rings
2. Cause – Lubricating oil of low viscosity used. Remedy- Use oil of correct viscosity
3. Cause – Lubricating oil level too high. Remedy- Maintain correct level of oil
D. Trouble – Engine Does Not Take Sufficient Load:
1. Cause – Valve clearance incorrect. Remedy- Adjust the correct gap
2. Cause – Valve spring broken. Remedy- Replace it
3. Cause – Head gasket damaged. Remedy- Replace it
4. Cause – Ring stuck or worn. Remedy- Change it
5. Cause – Decompression mechanism incorrectly adjusted. Remedy- Adjust it correctly
6. Cause – Fuel filter partially chocked. Remedy- Clean it well
7. Cause – One or more injectors faulty. Remedy- Check it on injector testing machine
8. Cause – Injection timing incorrect. Remedy- Check it & correct it
9. Cause – Fuel injection pump defective. Remedy- Repair it in specialised shop
10. Cause – Faulty governor. Remedy- Repair it in specialised shop
11. Cause – Air cleaner choked. Remedy- Clean it well
12. Cause – Exhaust pipe blocked. Remedy- Clean it well
13. Cause – Cylinder worn. Remedy – Rebore or resleeve the cylinder
E. Trouble – Engine Runs in Idle Condition but does not Run on Load:
1. Cause – Air in fuel system. Remedy- Bleed the fuel line
2. Cause – Fuel lift pump faulty. Remedy- Repair in specialized shop
3. Cause – Fuel filter blocked. Remedy- Clean the filter
4. Cause – Fuel tank vent blocked. Remedy- Clean the vent
5. Cause – Faulty injector. Remedy- Check the injectors on injector testing machine
6. Cause – Valve clearance incorrect. Remedy- Set the clearance
7. Cause – Ring stuck or worn. Remedy- Change the rings
8. Cause – Cylinder worn out. Remedy- Rebore or resleeve the cylinder
F. Trouble – Engine Runs on Load but does not Run in Idle Condition:
1. Cause – Valve clearance incorrect. Remedy- Adjust the clearance
2. Cause – Injection timing incorrect. Remedy- Check the timing and set it
3. Cause – Decompression mechanism faulty. Remedy- Check and adjust it
4. Cause – Governor adjustment faulty. Remedy- Set the governor in a specialized shop
5. Cause – Injectors faulty. Remedy- Check it on injection testing machine
6. Cause – Injection pump faulty. Remedy- Repair it in a specialised shop
7. Cause – Ring stuck or worn. Remedy- Change the rings
8. Cause – Cylinder worn. Remedy- Rebore or resleeve the cylinder
G. Engine gets Overheated very Soon:
The reasons for overheating may be due to following causes:
1. Faulty Cooling System:
(a) Cause – Leakage in cooling system. Remedy – Check the leakage
(b) Cause – Dirt and scale on cooling surface. Remedy – Check it thoroughly
(c) Cause – Defective water pump. Remedy – Repair the pump
(d) Cause – Thermostat valve not opening properly. Remedy – Adjust the valve
(e) Cause – Fan belt loose or broken. Remedy – Change the belt
(f) Cause – Radiator choked. Remedy – Clean the radiator
(g) Cause – Mud on crankcase. Remedy – Clean it
2. Inefficient Combustion:
(a) Cause – Injection timing wrong. Remedy – Check the timing
(b) Cause – Engine overloaded. Remedy – Reduce the load on the engine
(c) Cause – Exhaust pipe choked. Remedy – Clean the exhaust pipe
(d) Cause – Faulty injectors. Remedy – Test the injectors on injector testing machine
3. Improper Lubrication:
(a) Cause – Oil filter choked. Remedy – Clean it thoroughly
(b) Cause – Lubricating oil dirty. Remedy – Replace it
(c) Cause – Air cleaner out of order. Remedy – Check it and repair it
(d) Cause – Oil viscosity too high. Remedy – Use correct grade of oil
(e) Cause – Lubricating pump defective. Remedy – Repair in specialised shop
H. Trouble – Clutch Slips:
1. Cause – Repair in specialised shop. Remedy – Adjust the play
2. Cause – Burnt or worm clutch lining. Remedy – Repair or replace the lining
I. Trouble – Clutch Does Not Disengage:
1. Cause – Clutch lining rusted. Remedy – Repair at the repair shop
2. Cause – Clutch pedal not properly adjusted. Remedy – Adjust the play
J. Trouble – Poor Braking:
1. Cause – Excess play of the brake pedal. Remedy – Adjust the play
2. Cause – Oil leakage in brake chamber. Remedy – Check the leakage
3. Cause – Seized or worn brake lining. Remedy – Replace the lining
4. Cause -Acting stroke of the right and left pedal different. Remedy – Stroke should be made same.
K. Trouble – Brake Pedal does not Return Smoothly:
1. Cause – Broken return spring. Remedy – Replace it
2. Cause – Grease runs short at each sliding section. Remedy – Remove rust and apply grease
L. Trouble – Hydraulic System does not Lift:
1. Cause – Lack of hydraulic oil. Remedy – Fill it up to mark
2. Cause – Pipe sucks air. Remedy – Remove the leakage
3. Cause – Filter clogged. Remedy – Clean the filter
4. Cause – Hydraulic pump defective. Remedy – Repair at specialised shop
5. Cause – Broken control valve. Remedy – Repair at specialised shop
6. Cause – Broken cylinder. Remedy – Replace the cylinder
7. Cause – Pipe leakage. Remedy – Remove the leakage
8. Cause – Cracked pipes. Remedy – Replace the pipes
M. Trouble – Hydraulic Pressure does not Drop:
1. Cause – Control valve is out of order. Remedy – Repair at the shop
2. Cause – Broken cylinder. Remedy – Repair at the shop
Periodical Maintenance of Tractors:
(A) At 8 to 10 Engine Working Hours:
1. Tractor and implements should be cleaned.
2. Check oil level in crankcase and hydraulic oil chamber and if necessary, top up.
3. Remove sediments from the air pre-cleaner bowl. Clean the oil bath of the air cleaner if the tractor operates in dusty conditions.
4. Top up the fuel tank if necessary, preferably in the evening, after day’s work.
5. Clean the radiator. Remove dust and dirt, accumulated in core and top up the water in the radiator. Use clean water.
6. Check the tension of the V-belt.
7. Check the tightness of the fuel pipes, oil pipes, water pipes, hoses and drain plugs to avoid leakage.
8. Check the air pressure in front and rear tyres, and maintain recommended pressure.
9. Check that the ends of the cables are properly connected to the terminals.
10. Check the level of the electrolyte in the battery and if necessary top up with distilled water.
11. Grease all the points recommended by manufacturers.
12. Check the ball joints of the steering linkage. Tighten the balls of the front axle and wheel hubs.
13. Start the engine and check, (а) whether the oil pressure gauge is showing sufficient pressure or (b) whether dynamo is generating proper current.
B. At 50 to 60 Engine Working Hours:
1. Carry out all the operations given in (A)
2. Clean the filters.
3. Check the clearance between clutch thrust bearing and disengaging levers.
4. Make sure that the brakes are in good working condition.
C. At 100 to 120 Engine Working Hours:
1. Carry out all the operations given in (B)
2. Disconnect the cables of the electrical equipment from the terminals, apply grease and connect it.
3. Make sure that there is no leakage in the water pump.
4. Lubricate the dynamo, by putting a few drops of engine oil in each of the oil caps.
D. At 200 to 250 Engine Working Hours:
1. Carry out all the operations given in (C).
2. Drain oil from oil sump and flush with flushing oil. Refill with new engine oil up to mark.
3. Lubricate the throttle control linkage and ball joints.
4. Check the clearance of the front wheel hub bearing.
5. Check the toe-in of the front wheel.
E. At 480 to 500 Engine Working Hours:
1. Carry out all the operations, given in (D).
2. Add rust removing compound to the radiator and flush the cooling system.
3. Interchange the tyres of the front wheels to secure uniform wearing.
4. Flush the fuel tank.
5. Clean the self-starter and dynamo of the tractor.
6. Check the injector and adjust if necessary.
F. At 960 to 1000 Engine Working Hours:
1. Carry out all the operations given in (E).
2. Check the oil in the gear box, steering housing, power take-off case and hydraulic system of tractor.
3. Clean and adjust the brake lining.
4. Check the compression pressure of the engine and if necessary overhaul the engine.
A. Cooling System:
1. Never rim the tractor without water up to desired level.
2. Never fill water when the engine is hot, always use clean water.
3. Never remove the radiator cap abruptly when the engine is hot.
4. Never lubricate the fan bearing when the engine is running.
B. Lubrication System:
1. Use clean oil of proper grade.
2. Use flushing oil for flushing the engine.
3. Drain the crankcase only when the engine is hot.
4. Never check the oil level while the engine is running.
5. Never use cotton waste for cleaning the components.
6. Metal type oil filter element should be cleaned with diesel or petrol with the help of a brush.
C. Air Cleaner System:
1. Never try to remove the oil cap when the engine is running.
2. Refill only clean oil of the proper grade.
3. Always clean the filter with jet of compressed air.
D. Fuel System:
1. Use only clean fuel of proper grade.
2. Handle the fuel filter very carefully.
E. Transmission and Wheel System:
1. Avoid riding over the clutch pedal.
2. Never overload the engine.
3. Never over lubricate the bearings.
4. Release the clutch slowly to avoid jerks.
5. Drain the transmission case only when the engine is warm.
6. Always keep recommended inflation of the tyre.
F. Hydraulic System:
1. Use only cleans hydraulic fluid of the proper grade.
2. Maintain the oil level as prescribed by the manufacturer.
G. Electrical System:
1. Never touch concentrated electrolyte.
2. Never add concentrated electrolyte in the battery.
3. Never let the terminals of the battery to corrode.
4. Never drive the tractor if the dynamo is not functioning.
5. Never touch bare wirings.
Storage of Tractor:
If the tractor is to be stored for more than 30 days, the following steps should be taken:
1. Store the tractor in a dry, well protected place.
2. Wash and clean the tractor thoroughly.
3. Clean all unpainted parts and apply suitable grease on those parts.
4. Lubricate the chases thoroughly.
5. Drain the crankcase oil from the engine and flush it with flushing oil. Refill the crankcase with fresh lubricating oil.
6. Remove the storage battery from the tractor and store in accordance with manufacturer recommendation.
7. Drain the cooling system of the tractor.
8. Place blocks under axles to take weight of the tyres and to prevent them from touching the ground.
9. If water is filled in tyres, drain the same.
10. Plug the crankcase breather pipe and exhaust pipe, if covers are not provided.