There are two main types of hydraulic power transmission systems: hydrokinetic, such as the hydraulic coupling and the hydraulic torque converter, which use the kinetic energy of the liquid; and hydrostatic, which use the pressure energy of the liquid. The hydraulic coupling is a device that links two rotatable shafts.

2. Content
1. Power transmission system
 Introduction of power transmission system
 Functions of Power transmission system
 Components of Power transmission system
2. Hydraulic system
 Introduction of hydraulics
 Basic principles of hydraulics
 Components of hydraulic system of tractor
 Functions & properties of hydraulic fluids
 Advantages & Dis-advantages of hydraulics
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3. • A transmission is a machine in a power transmission system, which
provides controlled application of the power.
• Often the term transmission refers simply to the gearbox that uses
gears and gear trains to provide speed and torque conversions from a
rotating power source to another device.
• Transmission is a speed reducing mechanism, equipped with several
gears.
• The system consists of various devices that cause forward and
backward movement of tractor to suit different field condition.
Introduction of power transmission
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4. • 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.
• To transmit power through right angle drive.
Functions of power transmission system
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5. • Clutch
• Transmission gears
• Differential
• Final drive
• Rear axle
• Rear wheels
Components of Power transmission system
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6. Necessity of clutch in a tractor:
• Clutch in a tractor is essential for the following reasons:
i. Engine needs cranking by any suitable device. For easy cranking, the
engine is disconnected from the rest of the transmission unit by a
suitable clutch. After starting the engine, the clutch is engaged to
transmit power from the engine to the gearbox.
ii. In order to change the gears, the gearbox must be kept free from the
engine power, otherwise the gear teeth will be damaged and
engagement of gear will not be perfect. This work is done by a clutch.
iii. When the belt pulley of the tractor works in the field it needs to be
stopped without stopping the engine. This is done by a clutch.
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7. Essential features of a good clutch:
• It should have good ability of taking load without dragging and
chattering.
• It should have higher capacity to transmit maximum power without
slipping.
• Friction surface should be highly resistant to heat effect.
• The control by hand lever or pedal lever should be easy.
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8. Types of Transmission system
Transmission
Systems
Mechanical
Clutch gear
box and lie
axle
Clutch gear
box and dead
axle
Clutch gear
box and axle
less
Hydraulic
Hydrostatic Hydrodynamic
Electrical and
Electro
Magnetic
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9. Types of clutch
 Friction clutch
• Friction clutch produces gripping action, by utilizing the frictional force
between two surfaces.
 Dog clutch
• It is a simple clutch having square jaws, which are used to drive a shaft
in either
• direction. It is mostly used in power tillers.
 Fluid coupling
• Fluid coupling consists of a driving member and a driven member. An
impeller with radial- vanes constitutes the driving member and runner
with radial vanes constitutes the driven member. 08

10. Transmission gears
Types of gears
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11. Gear ratio
• When two shafts are connected by gears ,the ratio between the
speed of the shafts will be always constant and this constant ratio is
called Gear ratio.
Speed of driver (N1) No. of teeth in driven(T2)
Speed of driven No. of teeth in driver (T1)
= Constant
=
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12. Gear Box
• A Gear Box is an assembly consisting of various gears, synchronizing
sleeves and gear-shifting mechanism fitted in a metal housing.
• The metal housing usually made of aluminum/iron casting
accommodates all the gears in it.
• Gearbox is a part of the ‘transmission’ system as the gears play an
important role in transmitting the engine power to the wheels
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13. Torque converter
• Torque converter is a hydraulic transmission which increases the torque
of the vehicle reducing its speed.
• It provides a continuous variation of ratio from low to high.
• The key characteristic of a torque converter is its ability to multiply torque
when there is a substantial difference between input and output
rotational speed, thus providing the equivalent of a reduction gear.
• There are four components inside the very strong housing of the torque
converter:
1. Pump
2. Turbine
3. Stator
4. Transmission fluid
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14. Differential unit
• 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 differential unit consists of:
i. Differential casing
ii. Differential pinion
iii. Crown Wheel
iv. Half shaft and
v. Bevel gear 13

15. Final drive
• 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.
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16. Rear wheel
• In rear wheel drive vehicles, the rear wheels are the driving wheels,
• whereas in the vehicles with front wheels drive the front wheels are
the driving wheels.
• Almost all the rear axles in the modern cars are live axles, which
mean that these axles move with the wheels, or revolve with the
wheels and are known as live axles.
• Dead Axles are those axles which remain stationary and do not move
with the wheels.
 Semi-Float Axles
 Three-Quarter Floating
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17. Animation for power transmission
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18. Introduction of hydraulic system
 Hydraulics is the branch of physics dealing with the mechanical
properties and practical applications of liquid in motion.
 Hydraulic system transmits power; they do not create power.
Hydraulic system requires an outside source of power to operate.
This outside power source is called the prime mover.
 Oil hydraulic engineering is based on the transmission of forces
and power by static pressure of fluid in tubes and conduits as
already indicated by a French physicist name Blaise Pascal in the
seventeenth century.
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19. Basic Principles of Hydraulics
 In 1653, a French scientist named Blaise Pascal formulated the
fundamental law that explains the operation of hydraulic equipment. The
law, which became known as Pascal's Law, states that:
“Pressure applied to a confined fluid is transmitted undiminished in all
direction, acts with equal force on equal areas, and act at right angle to
the wall of container.”
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20. Components of hydraulic system of tractor
1. Reservoir
2. Pipes, hose & fitting
3. Pumps
4. Valves & distributor
5. Hydraulic cylinder
6. Filters
7. Hydraulic accumulator
8. Hydraulic Fluid
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21. 1. Reservoir
part of any hydraulic circuit is a storage reservoir tank. It contains
sufficient oil to move the piston for lifting the load . On a tractor hydraulic reservoir
is located beneath the driver seat and it may be single type or combined with
transmission.
Functions of reservoir,
• To store hydraulic oil which can be used and reused continually as the
circuit works.
• To dissipates the heat of the oil being hot after passing through the circuit.
• To provide time to settle down the contamination of the oil.
• To provide passage to the oil by incorporating internal oil gallery into its
body.
• To help oil de-aerate by providing space to separate the air from the oil.
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22. 2. Pipes, Hoses & Fitting
• Hydraulic tubes are seamless steel precision pipes, specially
manufactured for hydraulics.
• The tubes have standard sizes for different pressure ranges with standard
diameters up to 100 mm.
• The tubes are supplied by manufactured in lengths of 6m,cleaned, oiled
and plugged.
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23. 3. Pumps
• Mechanical power is converted into hydraulic energy using the flow and
pressure of a hydraulic pump.
• Hydraulic pumps operate by creating a vacuum at a pump inlet, forcing liquid
from a reservoir into an inlet line, and to the pump.
• Mechanical action sends the liquid to the pump outlet, and as it does, forces
it into the hydraulic system.
• There are severs type of pump such as gear pump, plunger pump ,and screw
pump. Gear pump is Widely us in tractor .
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24. Gear pump
• A gear pump is a type of positive displacement (PD) pump.
• Gear pumps use the actions of rotating cogs or gears to transfer fluids.
• The rotating gears develop a liquid seal with the pump casing and
create a vacuum at the pump inlet.
• There are two basic designs of gear pump: internal and external
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25. External Gear Pump
There are three stages in an internal gear pump’s working cycle:
Filling Transfer Delivery
• As the gears come out of mesh on the inlet side of the pump, they create an
expanded volume. Liquid flows into the cavities and is trapped by the gear
teeth as the gears continue to rotate against the pump casing.
• The trapped fluid is moved from the inlet, to the discharge, around the
casing.
• As the teeth of the gears become interlocked on the discharge side of the
pump, the volume is reduced and the fluid is forced out under pressure.
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26. Internal gear pump
• The teeth of one gear project outward while the teeth of the other gear
project inward towards the center of the pump.
• One gear will stands inside the other.
• This type of the gear can rotate or be rotated by a suitably constructed
companion gear.
• An external gear is directly attached to the drives shaft of the pump and is
placed off center in relation in the internal gear.
• The two mesh on one side of pump chamber.
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27. 4. Valves
• In a hydraulic system the pump generates the flow of oil which is to be
fed to the cylinder or other actuator.
• The pressure energy is fed to the actuator through a number of control
blocks called valve.
• Basically valves are expected to control:
a) Blocking or stopping of flow
b) Direction of flow
c) Pressure of flow media
d) Flow quantity
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28. Types of valve
• Based on their function and used in the system a valve are classified
as,
1) Direction control valve
2) Pressure control valve
3) Flow control valve
Relief Valve
• Relief valves are used in hydraulic systems to limit the system pressure
to a specific set level. If this set level is reached ,the pressure relief
valve respond and feeds the excess flow from the system back to the
tank.
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29.  Control Valve
• Control valve is a type of valve ,witch controls the movement of
hydraulic oil to have desired direction , magnitude and speed of
lifting. This helps to determine speed of movement for the
actuators.
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30. 5. Hydraulic cylinders
• Hydraulic cylinders are device that initiate the force used by the
hydraulic system to transfer throughout the hydraulic device.
• These cylinders contain pressurized hydraulic fluids.
• These cylinders have a cylindrical barrel, the piston and piston rod.
• Hydraulic fluids pumped into the hydraulic cylinder create the force
needed to move the piston rod
• Properly functioning hydraulic cylinders regulate the oil flow in the
hydraulic system.
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31. 6. Filters
• Foreign matter and tiny metal particles from normal wear of valve,
pump and other components are going to enter a system.
• Strainers, filters and magnetic plugs are used to remove foreign particles
from a hydraulic liquid.
Surface filters or strainer
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32. 7. Hydraulic Accumulator
• A hydraulic accumulator stores fluid under pressure.
• The fluid is then released when it’s required to perform a specific task
in the hydraulic system
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33. 8. Hydraulic fluid
• Hydraulic fluids, also called hydraulic liquids, are the medium by which
power is transferred in hydraulic machinery.
• Common hydraulic fluids are based on mineral oil or water
• The primary function of a hydraulic fluid is to convey power.
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34. Functions and properties of Hydraulic fluids
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35. Properties of hydraulic fluid
• Good lubricity
• Stable viscosity characteristics
• System Compatibility
Oil hydraulic system :
• Good heat dissipation
• High Bulk Modulus
• Adequate low- temperature properties
• Flash point
• Low foaming tendency
• Fire resistant
• Prevent rust formation
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36. Hitch system in tractor
• Design of three-point hitch systems used with agricultural tractors is
quite evolved and is governed by an established standard.
• Freedom within the standard, though, can be exploited to tailor the
individual hitch performance.
• The primary benefit of the three-point hitch system is to transfer the
weight and resistance of an implement to the drive wheels of the
tractor.
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37. 36

38. Advantages and Disadvantages of Hydraulics
Advantages
• Increased flexibility
• Infinitely variable speed
• Multiplication of force
• Reduced wear
• Increased automation potential
• Decreased equipment damage
• Reversibility
• Similar than mechanical linkage systems
• A good range of speed operation is possible
• Power can be engaged or disengaged using a simpler valve 37

39. Disadvantages
• Use of high pressure
• Need for cleanliness
• Safety hazards
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40. Animation for hydraulic system
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