POWER TRANSMISSION SYSTEM
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:
to transmit power from the engine to the rear wheels of the tractor,
to make reduced speed available, to rear wheels of the tractor,
to alter the ratio of wheel speed and engine speed in order to suit the field conditions and
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: (a) Clutch (b) Transmission gears (c) Differential (d) Final drive (e) Rear axle (f) Rear wheels. The Combination of all these components is responsible for transmission of power.
CLUTCH AND FLUID COUPLING CLUTCH: Clutch is a device, used to connect and disconnect the tractor engine from the transmission gears and drive wheels. It transmits power by means of friction between driving members and driven members.
TRANSMISSION GEARS AND TORQUE CONVERTER GEAR: A tractor engine runs at high speed, but the rear wheel of the tractor requires power at low speed and high torque. That's why it becomes essential to reduce the engine speed and increase the torque available at the rear wheels of the tractor because
BHP = 2πNT/4500
Where T is torque in kg-m and N is rev/min.
If the engine hp is constant, it is obvious that for higher torque at wheels, low speed is required and vice versa. So the gearbox is fitted between engine and rear wheel for variable torque and speed. This is done by suitable design of gear and shafts. Speed varies according to the field requirements and so a number of gear ratios are provided to suit the varying conditions. Gears are usually made of alloy steel. As the tractor has to transmit heavy torque all the time,-best quality lubricants free from sediments, grit, alkali and moisture, is used for lubrication purpose. SAE 90 oil is generally recommended for gearbox.
DIFFERENTIAL UNIT AND FINAL DRIVE
Differential unit is a special arrangement of gears to permit one of the rear wheels of the tractor to rotate slower or faster than the other. While turning the tractor on a curved path, the inner wheel has to travel lesser the tractor to move faster than the other at the turning point. The output shaft coming from the gear box is provided with a bevel pinion at the end of the shaft. The bevel pinion is in mesh with a large bevel wheel known as crown wheel. The main functions of crown wheel assembly are:
To transmit power through right angle drive to suit the tractor wheels.
To reduce the speed of rotation.
Differential lock: Differential lock is a device to join both half axles of the tractor so that even if one wheel is under less resistance, the tractor comes out from the mud etc as both wheels move with the same speed and apply equal traction.
Final drive: Final drive is a gear reduction unit in the power trains between the differential and the drive wheels. Final drive transmits the power finally to the rear axle and the wheels. The tractor rear wheels are not directly attached to the half shafts but the drive is taken through a pair of spur gears. Each half shaft terminates in a small gear, which meshes with a large gear called bull gear. The bull gear is mounted on the shaft, carrying the tractor rear wheel. The device for final speed reduction, suitable for tractor rear wheels is known as final drive mechanism.
STEERING SYSTEM AND BRAKE STEERING SYSTEM: The system, governing the angular movement of front wheels of a tractor is called steering system. This system steering wheel minimizes the efforts of the operator in turning the front wheel with the application of leverages. When the operator turns the steering wheel, the motion is transmitted through the steering shaft to the angular motion of the pitman arm, through a set of gears. The angular movement of the pitman arm is further transmitted to the steering arm through the drag link and tie rods. Steering arms are keyed to the respective kingpins which are integral part of the stub axle on which wheels are mounted. The movement of the steering arm affects the angular movement of the front wheel.
BRAKE: Brake is used to stop or slow down the motion of a tractor. It is mounted on the driving axle and operated by two independent pedals. Each pedal can be operated independently to assist the turning of tractor during the fieldwork or locked together by means of a lock.
HYDRAULIC CONTROL SYSTEM: It is a mechanism in a tractor to raise, hold or lower the mounted or semi-mounted equipment by hydraulic means. Working principle: The working principle of hydraulic system is based on Pascal's law. This law states that the pressure applied to an enclosed fluid is transmitted equally in all directions. Small force acting on small area can produce higher force on a surface of larger area.
Principle of operation: Brake works on the principle of friction. When a moving clement is brought into contact with a stationary element, the motion of the moving element is affected. This is due to frictional force, which acts in opposite direction of the motion and converts the kinetic energy into heat energy.
REFERENCES:
Transmission systems of agricultural prime movers. Transmission system of tractor. Retrieved from http://www.hillagric.ac.in/edu/coa/agengg/lecture/243/Lecture%208%20Transmission.pdf
Transmission systems of agricultural prime movers. Transmission system of tractor. Retrieved from
https://patents.google.com/patent/US4262768
Here's my first article for today. Let us all be familiar with transmission system. Good evening!
It's very tough for me to understand every point, every word. Cause I have no idea about this topic.😣 So, I translate it in my native language for understand it.