chuyên đề hệ thống truyền lực bản tiếng anh

TABLE OF CONTENTS
LIST OF TABLES...................................................................................................5

IMAGE BIBLIOGRAPHY......................................................................................6

TABLE OF CONTENTS.........................................................................................7

LIST OF TABLES.................................................................................................10

IMAGE BIBLIOGRAPHY....................................................................................11

PART 1. BEGIN....................................................................................................12

1.1. Reasons for choosing the topic..................................................................12

1.2. Objectives of the project............................................................................12

PART 2. RESEARCH RESULTS..........................................................................14

2.1. Overview of mechanical gearboxes...........................................................14

2.1.1. The history of the development of mechanical gearboxes in cars:........14
2.1.1.1. Basic changes of mechanical gearbox:..........................................14
2.1.1.2. The development of mechanical gearboxes and its role in the
powertrain:................................................................................................. 15
2.1.1.3. Development stages of mechanical gearboxes:..............................16
2.1.1.4. Common types of mechanical transmissions in cars:.....................17
2.1.1.5. The development of components and mechanisms in mechanical
gearboxes:.................................................................................................. 18

2.1.2. Basic elements of a mechanical transmission in a car:..........................20
2.1.2.1. Principle of operation of mechanical gearbox:..............................20
2.1.2.2. Main and auxiliary functions of mechanical gearboxes:................21
2.1.2.3. The relationship between revolutions, gear ratio and torque in
mechanical gearboxes:...............................................................................22
2.1.2.4. Impact of mechanical transmission on driving mode and vehicle
performance:.............................................................................................. 23
2.1.2.5. Advantages and limitations of mechanical gearboxes:..................24

2.1.3. New features and technologies in mechanical gearboxes:....................25
2.1.3.1. Clutch systems and actuators in mechanical gearboxes:................25
2.1.3.2. Mechanical gearbox and performance enhancing technology:......25
2.1.3.3. Automatic and semi-automatic gear shift systems:........................26
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2.1.3.4. Advanced technologies in mechanical gearboxes:.........................27
2.1.4. Developments and trends in mechanical transmissions in cars:............27

2.1.4.1. Improved performance and fuel efficiency in mechanical
gearboxes:.................................................................................................. 27
2.1.4.2. Integration of intelligent and connected technologies in mechanical
gearboxes:.................................................................................................. 28
2.1.4.3. Direction of mechanical gearbox technology in the future:...........29
2.2. Force to choose the design plan and design the calculation of the
gearbox.............................................................................................................. 29

2.2.1. Selection of design plan........................................................................29
2.2.2. Gearbox calculation design...................................................................31

2.2.2.1. Calculation of the gear ratio...........................................................31

2.2.2.2. Determine the No. 1 hand transmission ratio.................................32
2.2.2.3. Calculation of the basic parameters of gears..................................33
2.3. Gearbox wheel durability..........................................................................38

2.3.1. Payload mode.......................................................................................38
2.3.1.1. Gear durability...............................................................................39

2.3.2. Calculation of the gearbox shaft...........................................................41
2.3.2.1. Choosing shaft material.................................................................41
2.3.2.2. Preliminary calculation of gearbox shaft dimensions....................41
2.3.2.3. Axial strength................................................................................41

2.3.3. Rolling bearing calculation...................................................................47
2.4. Durability of the No. 2 gear pair on the Inventor....................................49

2.5. Check maintenance and repair of gearbox...............................................55

2.5.1. Repair inspection..................................................................................55
2.5.1.1. Check the gearbox housing............................................................55
2.5.1.2. Check the tooth surface of the gears..............................................55
2.5.1.3. Inspection of bearings....................................................................55
2.5.1.4. Check the accelerator mechanism..................................................55
2.5.1.5. Check the gear lever......................................................................55
2.5.1.6. Check the lever fork......................................................................56

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2.5.1.7. Check the positioning mechanism and the two-digit anti-mounting
mechanism................................................................................................. 56
2.5.2. Attention when disassembling..............................................................56

2.5.2.1. Attention when removing..............................................................56
2.5.2.2. Attention when mounting..............................................................56
PART 3. CONCLUSIONS AND LESSONS LEARNED......................................57
3.1. Knowledge..................................................................................................59
3.2. Skills............................................................................................................59
3.3. Attitude.......................................................................................................59
3.4. Lessons learned..........................................................................................60
BIBLIOGRAPHY.................................................................................................. 61
BIBLIOGRAPHY.................................................................................................. 62

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LIST OF TABLES
Table 2.1: Working states of gearbox..............................................................................30
Table 2.2: Calculation data table......................................................................................31
Table 2.3: Number of teeth of active and passive gears...................................................34
Table 2.4: Correct gear ratios in gear handles..................................................................35
Table 2.5: Precision shaft spacing at gear arms................................................................35
Table 2.6: Table of coefficient of adjustment of each pair of gears.................................37
Table 2.7: Basic dimensions of forward gears.................................................................37
Table 2.8: Basic dimensions of reverse gears...................................................................38
Table 2.9: Force acting on gears......................................................................................39
Table 2.10: Bending stress value at each gear..................................................................40
Table 2.11: Contact stress values at each pair of gears....................................................41
Table 2.12: Distance of force setpoints (N)......................................................................43
Table 2.13: Jets at support pillows (N).............................................................................44
Table 2.14: Moment at force setpoints (Nmm)................................................................45
Table 2.15: Equivalent torque at force setpoints (Nmm) and diameter selection
calculation d (mm)...........................................................................................................46
Table 2.16: Glass guide load (N).....................................................................................48

Table 2.17: Rtd equivalent force (N) and calculated dynamic load capacity C (kN).......49

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IMAGE BIBLIOGRAPHY
Figure 2.1: Diagram of a 5-speed gearbox.......................................................................20
Figure 2.2: Number hand.................................................................................................21
Figure 2.3: Diagram of a 5-speed 2-axis gearbox............................................................30
Figure 2.4: General force laying diagram for number hands from 1 to 4.........................42
Figure 2.5: General force laying diagram for hand 5.......................................................42
Figure 2.6: Axis torque chart 1(left), axis 2(right) hands 1 to 4.......................................44
Figure 2.7: Axis torque diagram 1(left), axis 2(right) hand No. 5....................................45

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TABLE OF CONTENTS
LIST OF TABLES........................................................................................................... 5
LIST OF IMAGES........................................................................................................... 6
PART 1. INTRODUCTION............................................................................................. 7
1.1. Reason for choosing topic........................................................................................ 7
1.2. Objectives of implementing topic............................................................................ 7
PART 2. RESEARCH RESULTS.................................................................................... 9
2.1. Overview of mechanical gearboxes......................................................................... 9
2.1.1. History of development of mechanical transmissions in cars:................................. 9
2.1.1.1. Basic changes of mechanical gearbox:................................................................. 9
2.1.1.2. The development of the mechanical gearbox and its role in the power
transmission system:....................................................................................................... 10
2.1.1.3. Stages of development of mechanical gearboxes:.............................................. 11
2.1.1.4. Common types of mechanical transmissions in cars:......................................... 12
2.1.1.5. Development of components and mechanisms in mechanical gearboxes:.......... 13

2.1.2. Basic elements of mechanical transmissions on cars:............................................ 15
2.1.2.1. Operating principle of mechanical gearbox:....................................................... 15
2.1.2.2. Main and auxiliary functions of mechanical gearbox:........................................ 16
2.1.2.3. Relationship between number of revolutions, gear ratio and torque in mechanical
gearbox:.......................................................................................................................... 18
2.1.2.4. Impact of mechanical transmission on driving mode and vehicle performance: 18
2.1.2.5. Advantages and limitations of mechanical gearboxes:....................................... 19
2.1.3. New features and technologies in mechanical gearboxes:..................................... 20
2.1.3.1. Clutch and transmission systems in mechanical transmissions:......................... 20
2.1.3.2. Mechanical transmission and performance enhancing technology:.................... 21
2.1.3.3. Automatic and semi-automatic transmission systems:....................................... 21
2.1.3.4. Advanced technologies in mechanical gearboxes:.............................................. 22
2.1.4. Developments and trends in mechanical transmissions in cars:............................ 23

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2.1.4.1. Improved performance and fuel efficiency in mechanical transmissions:.......... 23
2.1.4.2. Integrating smart and connected technologies in mechanical gearboxes:........... 23
2.1.4.3. Future direction of mechanical gearbox technology:.......................................... 24
2.2. Force for selecting design options and designing and calculating gearbox........ 25
2.2.1. Select design option.............................................................................................. 25
2.2.2. Design and calculation of gearbox........................................................................ 26
2.2.2.1. Calculate gear ratio............................................................................................. 27
2.2.2.2. Determine the 1st gear ratio............................................................................... 27
2.2.2.3. Calculate basic parameters of gear..................................................................... 29
2.3. Durability of gear box............................................................................................ 34
2.3.1. Load mode............................................................................................................. 34
2.3.1.1. Gear durability................................................................................................... 35
2.3.2. Calculate gearbox shaft......................................................................................... 37
2.3.2.1. Select shaft material........................................................................................... 37

2.3.2.2. Preliminary calculation of gearbox shaft size..................................................... 37
2.3.2.3. Axial durability.................................................................................................. 37
2.3.3. Bearing calculation................................................................................................ 43
2.4. Check the durability of the number 2 gear pair on the Inventor....................... 45
2.5. Check, maintain and repair gearbox.................................................................... 51
2.5.1. Check and repair................................................................................................... 51
2.5.1.1. Check box number............................................................................................. 51
2.5.1.2. Check the tooth surface of gear.......................................................................... 51
2.5.1.3. Check bearings................................................................................................... 51
2.5.1.4. Check the synchronizer mechanism................................................................... 51
2.5.1.5. Check gear lever................................................................................................. 51
2.5.1.6. Check the lever................................................................................................... 52
2.5.1.7. Check the positioning mechanism and the two-digit anti-engagement mechanism

...................................................................................................................................... 52
2.5.2. Pay attention when disassembling......................................................................... 52
2.5.2.1. Pay attention when removing............................................................................. 52

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2.5.2.2. Pay attention when installing.............................................................................. 52
PART 3. CONCLUSION AND LESSONS LEARNED 53
3.1. Knowledge............................................................................................................... 55
3.2. Skill ......................................................................................................................... 55
3.3. Attitude. .................................................................................................................. 55
3.4. Lessons learned....................................................................................................... 55
REFERENCES.............................................................................................................. 56

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LIST OF TABLES
Table 2.1 Working states of gearbox.............................................................................. 26
Table 2.2 Calculation Data Sheet................................................................................... 26
Table 2.3 Number of teeth of active, passive gears........................................................ 30
Table 2.4 Precision gear ratios in gear hands................................................................. 30
Table 2.5 Precision shaft spacing at the number arms.................................................... 31
Table 2.6 Table of translation coefficients for each pair of gears................................... 33
Table 2.7 Basic dimensions of forward gears................................................................. 33
Table 2.8 Basic dimensions of reverse gears.................................................................. 34
Table 2.9 Force acting on gears...................................................................................... 35
Table 2.10 Bending stress values at each gear................................................................ 35
Table 2.11: Contact stress values at each pair of gears................................................... 37
Table 2.12 Force setpoint distances (N)......................................................................... 39
Table 2.13 Jets at Pillows (N)......................................................................................... 40
Table 2.14 Moment at force setpoints (Nmm)................................................................ 41
Table 2.15 Equivalent torque at force setpoints (Nmm) and diameter selection calculation
d(mm)............................................................................................................................. 42
Table 2.16 Glass Guide Load (N)................................................................................... 44
Table 2.17 Rtd equivalent force (N) and calculated dynamic load capacity C
(kN)................................................................................................................................ 45

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IMAGE BIBLIOGRAPHY

Figure 2.1: Diagram of the 5-speed 20 gearbox Figure 2.2: Hand No. 21 Figure 2.3:
Diagram of the 30-speed 5-axis 2-axis gearbox Figure 2.4: General force laying diagram
for numbers 1 to 4 42 Figure 2.5: General force laying diagram for hand number 5 42
Figure 2.6: Axis torque diagram 1(left), axis 2(right) hands No. 1 to 4 44 Figure 2.7:
Axis torque chart 1(left), axis 2(right) hand No. 5 45

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PHẦN 1. BEGIN
1.1. Reasons for choosing the topic

In Group 1, we chose the research topic on mechanical gearboxes for the following
purposes:

-In order to apply knowledge about the structure, the principle of movement of
mechanical gearboxes to apply and calculate and analyze.

-Present the principle of operation, structure, details and assemblies of
mechanical gearboxes.

-In order to analyze, evaluate and compare the development trend of
mechanical gearboxes compared to automatic or stepless automatic transmissions.
With the strong development of informatics in the leading role, automation has
penetrated deeply into manufacturing industries and their products, one of which is
automobiles, not only making users feel comfortable, close to their cars, Show the style
of the person who owns them. But automation also improves the safety factor in use.
This is why automatic systems are always equipped for high-end cars and gradually
applied to popular vehicles. Therefore, with the chosen topic of research, survey of
mechanical gearboxes, we hope that this topic will better consolidate the knowledge that
has been passed on so that when we graduate, we can participate in Vietnam's
automobile industry, contributing to the overall development of the industry.
The content of the big exercise consists of 3 parts:

-PART 1: PROLOGUE
-PART 2: RESEARCH RESULTS

-PART 3: CONCLUSIONS AND LESSONS LEARNED.
The content of the big exercise was completed under the guidance of Mr. Bui Van
Hai, Faculty of Automotive Technology, Hanoi University of Industry

1.2. Objectives of the project
Surveying mechanical gearboxes helps us equip more about the structure and

working principle of a specific mechanical gearbox in terms of gear ratio creation
mechanism. In addition, the topic also helps us see the repair inspection process of

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vehicles equipped with mechanical transmissions, from how to receive complaints from
users to the vehicle testing process to identify the area where the failure occurs and parts
that may occur. This helps us not only understand the features and principles of a
mechanical transmission but also help us repair it and pay appropriate attention when
using vehicles equipped with mechanical transmissions.

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PHẦN 2.RESEARCH RESULTS
2.1. Overview of mechanical gearboxes
2.1.1. The history of the development of mechanical gearboxes in cars:
2.1.1.1. Basic changes of mechanical gearbox:

The mechanical gearbox (also known as mechanical transmission, hydraulic
gearbox or mechanical gearbox) has undergone many changes and improvements
throughout its development history. Here are some important fundamental changes:

- Gear level: Initially, the mechanical gearbox had only a single gear level,

meaning that it could only switch between two states: forward and backward. However,
over time, the gearbox has been improved to be able to switch between many different
gear levels. The gearbox number is usually represented by a number, for example 4, 5 or
6 gear levels, depending on the type of gearbox.

- Internal mechanism: The mechanism inside the mechanical gearbox has
undergone many changes to both improve performance and durability. The design of
components such as serrations, gears, drive shafts and clutches has been optimised to
provide smooth and precise transitions between gear levels.

- Synchronization mechanism: Synchronization is an important component in
mechanical gearboxes. It helps the gears and drive shafts to be connected consistently,
ensuring smooth transmission and avoiding slipping or sucking each other. The
synchronization mechanism has been improved to increase accuracy and durability.

- Improved performance: New technologies have been applied in mechanical
gearboxes to improve performance and save energy. For example, using lightweight and
high-quality materials in gearbox manufacturing can reduce weight and increase
accuracy. The lubrication and cooling systems have also been improved to increase the
life and performance of the gearbox.

- Integrated electronic technology: Electronic technology has been integrated in
the mechanical gearbox to provide automatic functions, mode selection, electronic
control system

- Dual gearbox: Some advanced mechanical gearboxes have been equipped
with dual transmissions. Instead of having just one pair of gears, dual gearboxes use two

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pairs of parallel gears to provide additional gear level. This allows for smoother
transitions and increased gearbox flexibility.

- Load balancing system: Today's mechanical gearboxes are often equipped
with a load balancing system, which distributes the load force evenly to the gears and
components in the gearbox. This increases the service life and durability of the gearbox,
while improving performance and smooth transmission.

- Automatic transmission: Another major improvement of mechanical
transmissions is the appearance of automatic transmissions. Automatic transmissions use
a power or electronic system to automatically switch between gear levels, reducing
driver intervention and providing an easier driving experience.

- Smart technology integration: Some modern mechanical gearboxes are
integrated with intelligent technology, including automatic control systems, sport driving
modes and fuel economy modes. These technologies help customize performance and
driving experience according to driver preferences.
2.1.1.2. The development of mechanical gearboxes and its role in the powertrain:

The mechanical transmission has undergone significant development through the
stages and plays an important role in the vehicle's powertrain. Here's an overview of the
evolution of mechanical gearboxes and their role in powertrains:

- Classic mechanical transmission: Initially, cars used simple mechanical
transmissions with one forward and one reverse gear levels. This gearbox allows power
to be adjusted from the engine to the wheels through gears, rollers and tapers. It plays a
major role in driving from the engine to the active drive system (main drive shaft or rear
axle).

- Increased gear levels: With the development of technology and operating

requirements, mechanical gearboxes have been improved by increasing gear levels.
Increasing gears in mechanical transmissions provides a wider speed range and helps
optimize engine performance under different driving conditions. This can be achieved by
adding the right actuators and gears.

- Other innovative technologies: In addition to increasing gear levels,
mechanical gearboxes have also undergone other improvements such as improved
material quality, increased machining accuracy, fuel-efficient design, and reduced

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friction. This boosts the overall powertrain performance and reduces the vehicle's fuel
consumption.

- Integrated electronic technology: Electronic technology has been integrated in
the mechanical gearbox to provide automation functions and increase the intelligence of
the system. Functions such as automatic mode, intelligent driving mode and electronic
control system have been added to the mechanical transmission to enhance performance
and driving experience.

The mechanical transmission plays an important role in the car's powertrain. Its
main role is to drive from the engine to the active drive system (main or rear drive shaft)
and regulate the power transmitted to the wheels. Here are the main roles of mechanical
gearboxes in the powertrain:

- Torque and power adjustment: The mechanical gearbox allows adjustment of
torque and power from the engine to the wheels. By selecting the right gear level, the
transmission can increase or decrease the torque and power transmitted from the engine
to the active drive, depending on the operating conditions and driver requirements.

- Provides a wide speed range: The mechanical transmission allows to provide
a wide speed range for the vehicle. By having multiple gear levels, the gearbox provides
speed adjustment and provides optimum power in different road situations. The wide
speed range makes it possible to move from low speed to high speed efficiently.

- Provides reverse gear: The mechanical transmission provides a reverse gear,
allowing the vehicle to move in reverse. Reverse gear makes parking or moving in the
opposite direction easy and convenient.

- Increased efficiency and fuel economy: Mechanical gearboxes can be
designed to optimize performance and fuel economy. By adjusting the gear level
accordingly, the gearbox keeps the engine operating in the optimal velocity and load
range, increasing efficiency and reducing fuel consumption.

2.1.1.3. Development stages of mechanical gearboxes:
Mechanical gearboxes have gone through important stages of development in the

evolution of the automotive industry. Here are some notable stages of development of
mechanical gearboxes:

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- First stage: Early mechanical transmissions were simple gearboxes with
limited gear levels, usually 2 or 3 gear speeds. During this period, mechanical gearboxes
were used mainly in the first types of cars and were not fully optimized for performance.

- Stage of increasing gear levels: As technology and operating requirements
have evolved, mechanical gearboxes have been improved by increasing gear levels.
Instead of only having 2 or 3 gear speeds, the mechanical transmission has been
upgraded to 4, 5, 6 and possibly more. The increase in gear increases the speed range and

improves performance and fuel economy.

- Electronic technology integration stage: Another important development of
mechanical gearboxes is the integration of electronic technology. Electronic technology
is used to improve the performance and performance of gearboxes. Modern mechanical
gearboxes often integrate electronic control systems, intelligent driving modes and
automatic modes. Electronic technology enhances the driving experience and improves
the responsiveness and performance of the transmission.

- Stage of optimizing performance and driving experience: Car manufacturers
continuously research and develop mechanical gearboxes to optimize performance and
driving experience. They focused on improving material quality, reducing friction,
increasing machining precision, and improving the overall design of gearboxes. The goal
is to create lightweight, efficient and smooth mechanical transmissions to provide the
best driving experience.

- The next stage in the development of mechanical gearboxes is to optimize
performance and driving experience. Automakers are focusing on improving various
aspects of gearboxes to meet the increasing demands of users.

- Improved material quality: The manufacturing technology and materials used
in the gearbox have been enhanced to increase durability, reduce weight and ensure
smooth operation throughout the life of the gearbox. Using materials such as high-
strength steel, aluminum alloy and carbon fiber has improved the mechanical properties
and bearing strength of the gearbox.

- Reduced friction: The elements inside the gearbox are designed to reduce
friction and energy loss. Using anti-friction materials, precision-machined parts and
effective lubrication use reduce friction and increase gearbox performance.

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- Increased machining accuracy: The machining and assembly processes of the
gearbox have been improved to achieve high precision. This ensures a perfect match
between components and minimizes vibration and noise during operation.

- Overall design improvements: The overall design of the gearbox is optimized
to increase powertrain, reduce size and weight, and provide a smoother driving
experience. Using technologies such as streamlined cutting gears, a good clutch
mechanism and a precision gear lever system has contributed to the improvement of
performance and driving experience.

2.1.1.4. Common types of mechanical transmissions in cars:
Depending on the criteria, mechanical gearboxes are classified as follows:
- According to the state of the gearbox shaft during work
+ Gearbox with fixed shaft
+ Gearbox with mobile shaft (planetary gearbox)
- According to the axis of the gearbox (excluding the reverse axis)
+ Two-axis gearbox
+ Three-cylinder gearbox
- By number of tiers
+ 2-speed gearbox
+ 3-speed gearbox
+ 4-speed gearbox
- According to the gear structure
+ By sliding gears
+ By accelerator
+ By brake and clutch (for hydromechanical gearbox)

2.1.1.5. The development of components and mechanisms in mechanical gearboxes:

Likened to the heart of the powertrain, the transmission transforms the torque, the

working speed of the engine to suit the working conditions of the wheels on the road.
Since George Selden's famous invention of front-wheel drive combined with a
horizontally placed 3-cylinder engine became a car design, few new ideas have fit.

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Introduced in 1894, the first sketch of the modern gearbox by two French
engineers, Louis-Rene Panhard and Emile Levashor, did not bring them glory but instead
received criticism.

The presentation was unsuccessful, the model car stalled, the content was truncated
to be presented only on the blackboard. One newspaper wrote that "the charlatan used
many tricks to deceive the public with the new car." Perhaps inventors should skip the
tech talk and use the description just enough. What they did was gross.

At that time, the drive structure was quite simple with a belt transmission or tapered
gear transmission. The car can only run at a maximum speed of 32 km/h. When
encountering obstacles on the road, the driver must stop in low gear.

F. W. Lanchester, one of the pioneers of automobiles in England, described his car
as consisting of two belt transmission levels, one for low speeds, requiring large torque
and one for high speeds, small torque.

A year after the infamous press conference, the famous Panhard and Levassor
returned not only with the transmission itself, but also the entire powertrain. This time,
they had their first car ready to run when stepping on the accelerator. Besides, they have
also made a lot of changes in ideas. In fact, it is a model that has met most of the
requirements of cars built in the 90s and also in later years.

Unlike the current model, the new design has an engine located along the front,
transmitting power to the rear axle via a clutch and a 3-speed sliding gearbox and chain-
driven bridge. It is almost the same as the powertrain on modern cars, but without an
active differential and semi-axle. However, in 1898, this became a reality when
millionaire Louis Renault successfully connected power from the longitudinal engine,
through the gearbox to the "live" rear axle using a metal shaft.

The "live" rear axle, or rear differential, was something Renault did in line with the
idea developed by an American named C. E. Duryea in 1893. Since it overcame the
problem of tire wear, this invention was adopted by most automakers. The differential
consists of an articular gear assembly that is responsible for dividing power between the
two wheels of the rear axle. It allows the outer wheel to spin faster than the wheel while
the car rotates.

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In 1904, the manual transmission of the slip shift of Panhard-Levassor was realized
by most automakers. Whether they exist in one form or another, they are still in use until
recent times. Obviously, there have been improvements, the most important change
being the synchronization system that allows the process of matching the gear way
smoothly, without shocks. Gearboxes equipped with accelerators were first used by
Cadillac in 1928. After being developed by Porsche, this invention has become popular
to this day.

The period between the appearance of the manual transmission and the moment of
the invention of the accelerator, there was another attempt to simplify the process of
shifting gears. It is a gearbox made of a planetary gear transmission, which first appeared
on the 1908 Ford Model T.

The planetary gear transmission consists of a central gear or also known as a solar
gear, several planetary gears that fit around. Today, planetary transmissions are used
more on automatic transmissions than on manuals.

Several types of complex manual gears using planetary gears have been introduced,
the Wilson Preselector being one such transmission. It used to be used in the 30s. The
system uses 4 separate planetary gear transmissions, allowing the driver to pre-select a
gear ratio by moving the small joystick next to the steering axle.
2.1.2. Basic elements of a mechanical transmission in a car:
2.1.2.1. Principle of operation of mechanical gearbox:

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